The team initially conducted mercury transfer as part of the Spallation Neutron Source (SNS) project and later the MERcury Intense Target (MERIT), a high-energy physics collaboration for demonstrating a flowing mercury-jet target in an intense magnetic field. More recently, ORNL researchers investigated the structural integrity of decades-old mercury storage flasks which required transferring mercury into new flasks.

Far-reaching implications

ORNL is a US Department of Energy (DOE) facility that delivers technical breakthroughs in clean energy and global security. As the largest DOE science and energy laboratory, ORNL’s research and development in neutron science, materials science and engineering, and nuclear science and technology have far-reaching applications. ORNL’s examination of the properties of materials at a subatomic level, using the SNS, may ultimately lead to improved medicines, metals, plastics, and ceramics.

Yet, mercury transfer can be a risky business. The project’s engineers and technicians don side-shield goggles, nitrile gloves, lab coats, and safety shoes according to ORNL’s safety standards. With precautionary respirator training and the use of snorkels and fume hoods to mitigate vapors, scientists are relatively well-protected. However when using centrifugal and/or vacuum pumps to transfer the substance, the pump mechanics became contaminated. The team needed a better solution.

“At the time, we investigated ‘blood pumps’ which are used in the medical and food industry,” explained Philip Spampinato, an ORNL senior engineer. “That search led us to peristaltic pumps, which led us to the Masterflex® pump.”

The right technology for the task

The Remote Systems Group has used Masterflex pumps for fluid transfers since 1999. More recently, when it came to transferring 76 pounds of mercury from a standard storage flask into containment vessels, the Masterflex I/P® Precision Brushless Drive with Analog Remote proved to be advantageous on many levels. Along with the Masterflex I/P Easy-Load® pump head and compatible Tygon® long-life tubing, the pump system solved several of the group’s dilemmas at one time.

“The quantity of mercury flow can be controlled by varying the pump speed and occlusion,” said Spampinato. “The mechanical components of the pump do not become contaminated. The mercury only comes into contact with the tubing. This decreases the risk of exposure to elemental mercury and its vapors. We only need to be concerned about safely discarding the tubing when it becomes necessary to replace it. Finally, because the tubing is clear, the operator can visually observe the transfer. This provides an added level of confidence that the process is working well.”

It also automates a process that might have otherwise been handled manually, a prospect that is both ineffective and potentially hazardous.

“The Masterflex pump system is a significant advantage compared to pouring mercury out of a flask that weighs about 80 pounds,” said Spampinato. “While the viscosity of mercury is similar to water, its density is 13.6 times that of water and it is a nonwetting liquid. Therefore, controlled pouring is virtually impossible.”

——-

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Saver Suggestion #2: Use an advanced bioreactor with one control interface

Bioreactors simulate an environment for photosynthetic organisms, especially algae, to grow and chemically convert. They are used for biodiesel and medical research, fermentation, and various applications within the production of nutraceuticals, pharmaceuticals, cosmetics, food, and more. Many, if not most, bioreactors require external lighting systems and peristaltic pumps to operate. Yet, newer, more advanced models combine these elements into one compact system that also takes up less space in the lab.

IKA® BR 10 Bioreactor

Doug Stark, IKA Manufacturing Engineering Manager, along with his colleagues worked with marine scientists to develop a unit that contains these efficiencies and more. “The IKA^® BR 10 Bioreactor is a self-contained automated unit that optimizes cell growth,” he explained. “The interior of the vessel is chemically inert, with no exposure to metal. It contains six compact double-fluorescent lamps which can be timed to simulate day or night. A digitally controlled overhead stirrer gently agitates the contents to assist with oxygen transfer while also preserving fragile cells. A variable-speed peristaltic pump provides the flow. One interface controls all of the variables―lighting, motion, pH value, and temperature.”

Because of the automation, users spend less time adjusting and monitoring the variables and can concentrate on other lab work. Also, with an integrated compact system such as this, labs can save more than twice their counter space as compared to traditional units.

According to Bob Hardin, Director of Manufacturing/Industrial Engineering, IKA, they can realize other savings as well. “Traditional bioreactors typically cost in the $50,000 range. With these newer, more progressive units, the price point is about half that even though users are getting more advanced features,” he said.

Some systems are also versatile. For example, as a 10-liter system, the IKABR 10 Bioreactor can also be put to use as a lab reactor. “Simply turn off the lighting system and this unit is equal to many lab reactors,” said Hardin.

The savings accumulates―less time to operate, less lab space, lower price point―to deliver enhanced efficiency.

More efficient options are available, including automating these tasks or outsourcing them. Instead of diverting scientists’ time from critical procedures or analyses, recapture it. Here’s how in part one of a two-part series:

Saver Suggestion #1: Use an automatic glassware washer rather than hand-washing

According to Labconco Product Manager Jenny Sprung, labs can realize multiple savings by using an automatic glassware washer. While the upfront costs of purchasing an automatic glassware washer will likely run several thousand dollars, the ROI is significant.

“For labs that are washing more than 25 flasks per day, the automatic glassware washer will pay for itself within two to two-and-a-half years,” said Sprung.

Labconco® FlaskScrubber® Laboratory Glassware Washers

At the same time, the water and energy conservation also adds up. “While the hand-washer expends 20 gallons of water―a conservative estimate―to wash 30 items of glassware, machine washing requires only 13.6 gallons to wash these same items. This amounts to saving 1,664 gallons of water per year,” she said.

Because less water is heated throughout the cycle, the machine washer is also more energy-efficient. “The scientist has the option to not use the drying cycle at all,” said Sprung. “If the delayed start option is activated, he or she can set the machine washer to run eight hours later, during off-peak hours.”

Automatic glassware washers clean all types of lab soil, from light to heavy. To remove waxes, agar, and other media, a high-heat washer works best; to scrub general solvent soil, high heat is not needed. To protect flasks, graduated cylinders, and other narrow-neck glassware, a spindle rack in the washer holds the glassware.

In comparative studies, machine washing eliminated far more total surface counts (TSC) of contaminants when compared to hand washing. “Our studies indicate machine washing removed more surface residue. When residue is left on glassware, it can impair or prevent the growth of bacteria and cell cultures. It has the potential to cross contaminate. Traces of residue can catalyze or make chemical syntheses impossible. And, glassware can become etched or corroded from residue alkaline,” said Sprung.

Of course, the immediate savings is the time that the scientist no longer spends scrubbing glassware at the sink.

Determining Flow Rate at Various Points on a Golf Course

A groundskeeper at a large golf course needs to measure the flow rate in the watering system at more than 30 different points throughout the course. With several miles of pipe, the diameters vary from 2 to 4 inches. The groundskeeper also indicated they want to monitor the flow continuously for 10 minutes at each point of measurement. They have a budget of less than $10,000. Which flowmeter and process would be ideal for this application?

A: Install spring-loaded flowmeters at each point around the course. Take readings every 15 seconds and record them in a notebook.

B:  Install tee-fittings with paddle wheel sensors at each monitor point, and carry a battery powered meter around the course. Take readings every 15 seconds and record in a notebook. 

C:  Use a Handheld Doppler Flowmeter and take readings every 15 seconds and record them in a notebook.

D:  Use a Portable Transit-Time Flowmeter and program the datalogger’s sample rate for one reading per second.

Check to see if you are right.

Cole-Parmer IFT 2001 Gift Pack

Not only is June National Dairy Month, but one of the largest food shows in the industry begins in just a few days. The Cole-Parmer booth at IFT® in New Orleans will feature efficient new products for food scientists and processors:

• The breakthrough picoSpin™ Benchtop NMR Spectrometer from Cole-Parmer is the world’s first miniature NMR spectrometer. The 45-MHz picoSpin spectrometer is affordable, portable, and easy to use.
•  The new Atago® Programmable Digital Refractometers with Touch Screen have a built-in thermomodule to ensure accuracy while also eliminating the need for a water bath circulator. Use this fully featured device to determine the refractive index of citrus, animal, or vegetable oils, and more. Take precise Brix measurements of fruit and concentrated juices, canned syrups, liquid sugars, and glucose with a Brix range of 0.00 to 100.00%.
• The Oakton® Benchtop pH 700 Series Meters offer a compact footprint more than 40% smaller than similar benchtop meters―saving valuable space in the research lab. Visit the booth to see their oversized LCDs, with optimal visibility even at a distance. Instruments for food quality and safety testing will also be available, including viscometers, thermometers, and more.

What’s in it for you? Each day one raffle winner will receive a New Orleans Gift Pack valued at more than $200. The bags include a variety of “survive and thrive in New Orleans” items including a cooler, water bottle, gift certificate, and more. Register to win.

According to Nate Kogler, Division Product Manager for the Bradley Corporation, the new technologies provide enhanced washdown coverage and improved cleanliness. For an eye-opening article describing  this next generation of products, read more.

Challenge: Research Labs has a mixed culture of streptococcus, staphylococcus, and enterococcus bacteria. For their current project, they would like to research the effects of their new drug on staphylococcus only.

Which media should they use so they can selectively look at the staphylococci alone?

A. Blood agar 5%

B. Lauryl tryptose broth

C. Mannitol salt agar

D. Baird Parker agar

E. XLD agar

See the answer

This app leverages years of research on chemical compatibility for plastics, metals, Elastomers and ceramics. It contains more than 24,528 entries, covering 584 chemicals, and 42 materials. It is the single most comprehensive Chemical Compatibility Database in the world―and it is now available for your iPhone and iPad.

The database’s easy-to-use interface allows you to search in a variety of different ways to get the results you need for your project. If you can’t find the chemical or material you’re looking for, just use the included call button to contact our FREE applications specialists for help.

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Read the scenario below, determine your answer, then click on the link to see if you are right!

Luigi, a process engineer, currently uses a 20% hydrofluoric acid in his etching process. He is considering using a higher concentration of this acid in order to speed up his operation. Currently, he stores the acid in a 40-gallon double-wall tank made of high-density polyethylene (HDPE). He pumps the acid out of this tank using an air-operated pump with wetted materials of Kynar® PVDF and PTFE.

What concentration of hydrofluoric acid can Luigi safely use given his current equipment?

A. He needs to stay with his current 20% concentration there is no way to speed up the operation.

B. He can increase to a 50% hydrofluoric acid to improve his process.

C. He can increase to a 75% hydrofluoric acid to improve his process.

D. He can increase to a 100% hydrofluoric acid for maximum speed.

See the answer.

VS

Glassware washing techniques vary from lab to lab and can depend on the soil type inside the glassware, types of glassware and technique required by the laboratory’s standard operating procedure.

The three types of glassware washing we’ll look at are hand washing, residential dishwashers and laboratory glassware washers.

Hand WashingHand washing requires an acid or base wash, rinse or soak which can be performed in plastic tubs. This method requires appropriate disposal of both acids and bases after washing is complete. Hot, soapy water can also effectively clean soiled glassware. A final rinse in purified water or tap water usually completes the process. In most cases, hand-washing water will reach 120ºF maximum, requiring sanitization or sterilization to be done in an autoclave. For drying, the glassware can be hung on a drying rack, placed in an oven, or dried manually. This process is time consuming and sometimes requires a dedicated person to hand wash the glassware.

Automatic Residential DishwashersAutomatic residential dishwashers are another option sometimes employed when washing lab glassware. The initial investment is much less than an instrument designed for lab use and its features are not as durable or as flexible. The interior is generally plastic or stainless steel designed to handle basic food, soil and beverages, not chemicals and contaminants found in a laboratory. The baskets are designed for domestic plates, cups, bowls, glasses, pots and pans, rather than narrow neck glassware, culture tubes, flask, beakers, and other specialized glassware used daily in the laboratory. Basket inserts for lab utensils are also not available. Expect the manufacturer’s warranty to be void when used for purposes other than residential settings.

Automatic Laboratory Glassware WashersAutomatic laboratory glassware washers are designed to clean all types of lab soil, from light to heavy, and offer features and accessories for a broad range of lab glassware and contaminants. A washer with a high heat option is best for cleaning heavy and difficult to remove soil such as waxes, oil or agar. For more soluble soil, high heat is not required. If flasks, graduated cylinders and other narrow-neck glassware are to be washed, a spindle rack option should be considered.

The interior of a lab washer must be designed to prevent damage to the washer from residual exposure to basic laboratory chemicals. Stainless steel chambers withstand traces of the every day chemicals used in a laboratory. Internal components, including the detergent cup, seals, pumps and other plastic and rubber components, have been carefully chosen to withstand chemicals as well as the high heat conditions inside the washer.

Another feature usually incorporated into a laboratory glassware washer is an optional purified water rinse. If pressurized purified water is not available, a separate pump may be required. Some washers include a separate pump to introduce purified water into the chamber, eliminating the need to buy it separately.

HEPA filtered forced air drying, which traps dirt, lint and other particulate contaminants from the air, should be considered if your research is sensitive to this type of contamination. Also, an RS232 port, to communicate wash conditions to a printer or computer, is available on some models if validation is required.

Pipette inserts allow the effective washing of pipettes in various sizes. The attachment forces water and detergent deep inside the pipettes assuring cleanliness. Other inserts for specific types of glassware such as culture tubes, media plates, DNA sequencing plates, and BOD bottles are readily available.

Automatic washer detergents formulated specifically for laboratory washers can meet specific needs. There are a wide variety of detergents — phosphate-free, chlorine-free, surfactant-free and non-ionic or ionic. These detergents leave no residue on the glassware so they are safe for sensitive applications such as tissue culture or instrumental analysis. Some laboratory washers automatically dispense liquid detergent and weak acid neutralizing rinse solutions. This eliminates the need to manually fill the detergent cup and rinse dispenser before each use. Using a built-in pump, the washer automatically meters the precise amount of detergent and acidic rinse solution into the washer at the appropriate cycle.

To determine the best washing system for your lab, an analysis should be done to calculate your potential daily cost of hand-washing vs. the cost of buying and using an automatic glassware washer. Information such as the amount of time spent per day hand-washing glassware, costs of labor, electricity, water, and detergent, types of glassware and how much of it — all should be included in the analysis. Once all the costs are calculated and compared, you can decide if the purchase of an automatic glassware washer provides a logical payback and consistent results. It’s working hard or working smart.

Published with permission from Jenny Sprung, Senior Product Specialist, Labconco Corporation

View our complete selection of laboratory glassware or laboratory glassware washers.

Full article can be found at http://www.coleparmer.com/techinfo/techinfo.asp?htmlfile=glass-handVSmach.htm&ID=934&referred_id=5618

Our Method
We begin our discussion of freeze drying for the laboratory by examining the three steps in the process: prefreezing, primary drying and secondary drying. Next, we examine a typical freeze drying cycle and the methods available to facilitate the freeze drying process using equipment designed for use by laboratories. Finally, suggestions to optimize successful results are discussed, including determination of end point, contamination, backfilling of dried samples and product stability. A glossary of terms used throughout this booklet to explain the freeze drying process follows the text, along with a bibliography.

Introduction
Freeze drying has been used in a number of applications for many years, most commonly in the food and pharmaceutical industries. There are, however, many other uses for the process including the stabilization of living materials such as microbial cultures, preservation of whole animal specimens for museum display, restoration of books and other items damaged by water, and the concentration and recovery of reaction products.

Specialized equipment is required to create the conditions conducive to the freeze drying process. This equipment is currently available and can accommodate freeze drying of materials from laboratory scale projects to industrial production.

Freeze drying involves the removal of water or other solvent from a frozen product by a process called sublimation. Sublimation occurs when a frozen liquid goes directly to the gaseous state without passing through the liquid phase. In contrast, drying at ambient temperatures from the liquid phase usually results in changes in the product, and may be suitable only for some materials. However, in freeze drying, the material does not go through the liquid phase, and it allows the preparation of a stable product that is easy to use and aesthetic in appearance.

The advantages of freeze drying are obvious. Properly freeze dried products do not need refrigeration, and can be stored at ambient temperatures. Because the cost of the specialized equipment required for freeze drying can be substantial, the process may appear to be an expensive undertaking. However, savings realized by stabilizing an otherwise unstable product at ambient temperatures, thus eliminating the need for refrigeration, more than compensate for the investment in freeze drying equipment.

Principles of Freeze Drying

The freeze drying process consists of three stages: prefreezing, primary drying, and secondary drying.

Prefreezing: Since freeze drying is a change in state from the solid phase to the gaseous phase, material to be freeze dried must first be adequately prefrozen. The method of prefreezing and the final temperature of the frozen product can affect the ability to successfully freeze dry the material.

Rapid cooling results in small ice crystals, useful in preserving structures to be examined microscopically, but resulting in a product that is more difficult to freeze dry. Slower cooling results in larger ice crystals and less restrictive channels in the matrix during the drying process.

Products freeze in two ways, depending on the makeup of the product. The majority of products that are subjected to freeze drying consist primarily of water, the solvent, and the materials dissolved or suspended in the water, the solute. Most samples that are to be freeze dried are eutectics which are a mixture of substances that freeze at lower temperatures than the surrounding water. When the aqueous suspension is cooled, changes occur in the solute concentrations of the product matrix. And as cooling proceeds, the water is separated from the solutes as it changes to ice, creating more concentrated areas of solute. These pockets of concentrated materials have a lower freezing temperature than the water. Although a product may appear to be frozen because of all the ice present, in actuality it is not completely frozen until all of the solute in the suspension is frozen. The mixture of various concentration of solutes with the solvent constitutes the eutectic of the suspension. Only when all of the eutectic mixture is frozen is the suspension properly frozen. This is called the eutectic temperature.

It is very important in freeze drying to prefreeze the product to below the eutectic temperature before beginning the freeze drying process. Small pockets of unfrozen material remaining in the product expand and compromise the structural stability of the freeze dried product. The second type of frozen product is a suspension that undergoes glass formation during the freezing process. Instead of forming eutectics, the entire suspension becomes increasingly viscous as the temperature is lowered. Finally the product freezes at the glass transition point forming a vitreous solid. This type of product is extremely difficult to freeze dry.

Primary drying: Several factors can affect the ability to freeze dry a frozen suspension. While these factors can be discussed independently, it must be remembered that they interact in a dynamic system, and it is this delicate balance between these factors that results in a properly freeze dried product.

After prefreezing the product, conditions must be established in which ice can be removed from the frozen product via sublimation, resulting in a dry, structurally intact product. This requires very careful control of the two parameters, temperature and pressure, involved in the freeze drying system. The rate of sublimation of ice from a frozen product depends upon the difference in vapor pressure of the product compared to the vapor pressure of the ice collector. Molecules migrate from the higher pressure sample to a lower pressure area. Since vapor pressure is related to temperature, it is necessary that the product temperature is warmer than the cold trap (ice collector) temperature. It is extremely important that the temperature at which a product is freeze dried is balanced between the temperature that maintains the frozen integrity of the product and the temperature that maximizes the vapor pressure of the product. This balance is key to optimum drying. The typical phase diagram shown in Figure 1 illustrates this point. Most products are frozen well below their eutectic or glass transition point (Point A), and then the temperature is raised to just below this critical temperature (Point B) and they are subjected to a reduced pressure. At this point the freeze drying process is started.

Figure 1

Some products such as aqueous sucrose solutions can undergo structural changes during the drying process resulting in a phenomenon known as collapse. Although the product is frozen below its eutectic temperature, warming during the freeze drying process can affect the structure of the frozen matrix at the boundary of the drying front. This results in a collapse of the structural matrix. To prevent collapse of products containing sucrose, the product temperature must remain below a critical collapse temperature during primary drying. The collapse temperature for sucrose is -32° C.

No matter what type of freeze drying system is used, conditions must be created to encourage the free flow of water molecules from the product. Therefore, a vacuum pump is an essential component of a freeze drying system, and is used to lower the pressure of the environment around the product (to Point C). The other essential component is a collecting system, which is a cold trap used to collect the moisture that leaves the frozen product. The collector condenses out all condensable gases, i.e; the water molecules, and the vacuum pump removes all non-condensable gases.

It is important to understand that the vapor pressure of the product forces the sublimation of the water vapor molecules from the frozen product matrix to the collector. The molecules have a natural affinity to move toward the collector because its vapor pressure is lower than that of the product. Therefore, the collector temperature (Point D) must be significantly lower than the product temperature. As can be noted in Table 1, raising the product temperature has more effect on the vapor pressure differential than lowering the collector temperature.

Table 1

A third component essential in a freeze drying system is energy. Energy is supplied in the form of heat. Almost ten times as much energy is required to sublime a gram of water from the frozen to the gaseous state as is required to freeze a gram of water. Therefore, with all other conditions being adequate, heat must be applied to the product to encourage the removal of water in the form of vapor from the frozen product. The heat must be very carefully controlled, as applying more heat than the evaporative cooling in the system can remove warms the product above its eutectic or collapse temperature.

Heat can be applied by several means. One method is to apply heat directly through a thermal conductor shelf such as is used in tray drying. Another method is to use ambient heat as in manifold drying.

Secondary drying: After primary freeze drying is complete, and all ice has sublimed, bound moisture is still present in the product. The product appears dry, but the residual moisture content may be as high as 7-8%. Continued drying is necessary at the warmer temperature to reduce the residual moisture content to optimum values. This process is called isothermal desorption as the bound water is desorbed from the product.

Secondary drying is normally continued at a product temperature higher than ambient but compatible with the sensitivity of the product. All other conditions, such as pressure and collector temperature, remain the same. Because the process is desorptive, the vacuum should be as low as possible (no elevated pressure) and the collector temperature as cold as can be attained. Secondary drying is usually carried out for approximately 1/3 to 1/2 the time required for primary drying.

How Freeze Drying Works

Refer to the phase diagram (Figure 1) and a typical sublimation cycle (Figure 2). The product is first cooled to below its eutectic temperature (Point A). The collector is cooled to a temperature approximately 20° C cooler than the product temperature, generally around -50 to -80° C. The product should be freeze dried at a temperature slightly lower than its eutectic or collapse temperature (Point B) since the colder the product, the longer the time required to complete primary drying, and the colder the collector temperature required to adequately freeze dry the product.

After the product is adequately frozen and the collector temperature achieved, the system is evacuated using a vacuum pump (Point C). At this point, primary drying of the product begins and continues until the entire frozen matrix appears dry. Heat input to the product may be achieved by several means such as increasing the shelf temperature in the case of tray drying, or using a liquid bath for manifold drying. While the collector and vacuum pump create the conditions for allowing sublimation to occur, heat input is really the driving force behind the whole process.

Heat input to the sample can be enhanced by controlling the pressure in the system at some level above the ultimate capability of the vacuum pump. Some freeze dryers incorporate vacuum control systems that automatically regulate the pressure to the preset level. This allows additional gas molecules to reside in the system thereby improving the conduction of heat to the sample. This improves the sublimation rate, reducing process time and associated energy costs. Care must be taken to prevent the pressure within the system from exceeding the ice vapor pressure of the product or melting of the sample may occur.

Figure 2

Heat input to the product must be very carefully controlled especially during the early stages of drying. The configuration of the product container and the volume of the contained product can affect the amount of heat that can be applied. For small volumes of material, evaporative cooling compensates for high levels of heat and drying is accelerated.

The volume and configuration of the suspension to be freeze dried often determines how the material is freeze dried. For example, the greater the ratio of the surface area to the volume of the suspension, the faster drying occurs. This is because a greater area for the water molecules to leave the product exists compared to the distance they have to travel to reach the surface of the frozen matrix. Drying occurs from the top of the product and initially the removal of water molecules is efficient. However, as the drying front moves down through the product, drying becomes more and more difficult. The water molecules must now travel through the dried portions of the product which impedes their progress. As the drying front moves farther and farther down the matrix, the application of heat to the product becomes more important (Figure 3).

Figure 3

Shell freezing as a method of prefreezing the product can increase the surface area to volume ratio by spreading out the frozen product inside the vessel (Figure 4). Shell freezing is accomplished by rotating the vessel in a low temperature bath causing the product to freeze in a thin layer on the inside surface of the vessel. The thickness of the frozen suspension depends on the volume of the product in comparison to the size of the vessel. Shell freezing is primarily used in conjunction with manifold drying.

The vacuum system is very important during freeze drying because the pressure must be maintained at a low As drying proceeds product level to ensure adequate water vapor flow from the temperature remains below shelf temperature product to the collector. A pressure gauge (commonly called a vacuum gauge) is used to monitor the pressure in the system during the drying process. Pressure can be expressed in several different units which are compared in Table 2. Some gauges measure condensable gases, while others do not. Those gauges that do not measure the condensable gases give an indication of the total pressure in the system. Gauges that do sense the condensable gases indicate a change in pressure during drying. These sensors can be used as an indication of the rate of drying, as well as the endpoint of the drying process.

Figure 4

Table 2

Freeze Drying Methods

Three methods of freeze drying are commonly used: (1) manifold drying, (2) batch drying, and (3) bulk drying. Each method has a specific purpose, and the method used depends on the product and the final configuration desired.

Manifold Method. In the manifold method, flasks, ampules or vials are individually attached to the ports of a manifold or drying chamber. The product is either frozen in a freezer, by direct submersion in a low temperature bath, or by shell freezing, depending on the nature of the product and the volume to be freeze dried. The prefrozen product is quickly attached to the drying chamber or manifold to prevent warming. The vacuum must be created in the product container quickly, and the operator relies on evaporative cooling to maintain the low temperature of the product. This procedure can only be used for relatively small volumes and products with high eutectic and collapse temperatures.

Manifold drying has several advantages over batch tray drying. Since the vessels are attached to the manifold individually, each vial or flask has a direct path to the collector. This removes some of the competition for molecular space created in a batch system, and is most ideally realized in a cylindrical drying chamber where the distance from the collector to each product vessel is the same. In a “tee” manifold, the water molecules leaving the product in vessels farthest from the collector experience some traffic congestion as they travel past the ports of other vessels.

Heat input can be affected by simply exposing the vessels to ambient temperature or via a circulating bath. For some products, where precise temperature control is required, manifold drying may not be suitable.

Several vessels can be accommodated on a manifold system allowing drying of different products at the same time, in different sized vessels, with a variety of closure systems. Since the products and their volumes may differ, each vessel can be removed from the manifold separately as its drying is completed. The close proximity to the collector also creates an environment that maximizes drying efficiency.

Batch Method. In batch drying, large numbers of similar sized vessels containing like products are placed together in a tray dryer. The product is usually prefrozen on the shelf of the tray dryer. Precise control of the product temperature and the amount of heat applied to the product during drying can be maintained. Generally all vials in the batch are treated alike during the drying process, although some variation in the system can occur. Slight differences in heat input from the shelf can be experienced in different areas. Vials located in the front portion of the shelf may be radiantly heated through the clear door. These slight variations can result in small differences in residual moisture.

Batch drying allows closure of all vials in a lot at the same time, under the same atmospheric conditions. The vials can be stoppered in a vacuum, or after backfilling with inert gas. Stoppering of all vials at the same time ensures a uniform environment in each vial and uniform product stability during storage. Batch drying is used to prepare large numbers of ampules or vials of one product and is commonly used in the pharmaceutical industry.

Bulk Method. Bulk drying is generally carried out in a tray dryer like batch drying. However, the product is poured into a bulk pan and dried as a single unit. Although the product is spread throughout the entire surface area of the shelf and may be the same thickness as product dried in vials, the lack of empty spaces within the product mass changes the rate of heat input. The heat input is limited primarily to that provided by contact with the shelf as shown in Figure 5.

Bulk drying does not lend itself to sealing of product under controlled conditions as does manifold or batch drying. Usually the product is removed from the freeze dry system prior to closure, and then packaged in air tight containers. Bulk drying is generally reserved for stable products that are not highly sensitive to oxygen or moisture.

Figure 5

Determining Drying Endpoints

Several means can be used to determine the endpoint of primary drying. The drying boundary in batch drying containers has moved to the bottom of the product container and inspection reveals that no ice is visible in the product. No visible ice indicates only that drying at the edges of the container is complete and gives no indication of the conditions in the center of the product. An electronic vacuum gauge can be used to measure condensable gases in the system. When the pressure indicated by the electronic gauge reaches the minimum pressure attainable by the system, as measured by using a McLeod vacuum gauge or as determined previously, no more water vapor is leaving the product.

As the heat input to the product is increased, evaporative cooling keeps the product temperature well below the temperature of its surrounding atmosphere. When primary drying is complete, the product temperature rises to equal the temperature of its environment. In manifold systems and tray dryers with external collectors, the path to the collector can be shut off with a valve and the pressure above the product measured with a vacuum gauge. If drying is still occurring, the pressure in the system increases.

Contamination in a Freeze Dry System

Two types of contamination can occur in a freeze dry system. One results from freeze drying microorganisms and the other results from freeze drying corrosive materials.

The potential for contamination of a freeze drying system by microorganisms is real in any system where microorganisms are freeze dried without a protective barrier such as a bacteriological filter. Contamination is most evident in batch tray dryer systems where large numbers of vials are dried in a single chamber. Evidence for contamination can be found by sampling the surfaces of the vials, shelves and collector. The greatest degree of contamination is usually found on the vials and on the collector. Some vial contamination can be due to a bit of sloppiness in dispensing the material originally, but contamination on the collector is due to microorganisms traveling from the product to the collector through the vapor stream.

The potential for contamination must be considered every time microorganisms are freeze dried, and precautions must be taken in handling material after the freeze dry process is completed. Recognizing that the vials are potentially contaminated, the operator should remove the vials to a safe area such as a laminar flow hood for decontamination. Decontamination of the freeze dry system depends upon the type of freeze dry system used. Some tray dryer systems are designed for decontamination under pressure using ethylene oxide sterilization. Ethylene oxide is considered hazardous, corrosive and detrimental to rubber components. Its use should be carefully monitored. Coupled with the risk of contamination in a freeze dry system is the risk of cross contamination when freeze drying more than one product at time. It is not a good practice to mix microbiological products in a freeze dry system unless some type of bacteriological filter is used to prevent the microbial product from leaving the vial itself.

While freeze drying of corrosive materials does not necessarily present a risk to the operator, it does present a risk of damaging the freeze dry system itself. Freeze dry systems are designed using materials that resist corrosion and prevent the build up of corrosive materials. But care should be taken to clean the system thoroughly following each use to protect it from damage.

Backfilling

For many freeze dried products, the most ideal system of closure is while under vacuum. This provides an environment in which moisture and oxygen, both detrimental to the freeze dried material, are prevented from coming in contact with the product. In some cases, vacuum in a container may be less than ideal, especially when a syringe is used to recover the product, or when opening the vessel results in a rush of potentially contaminating air. In these cases, backfilling the product container with an inert gas such as argon or nitrogen is often beneficial. The inert gas must be ultrapure, containing no oxygen or moisture.

Backfilling of the product container is generally useful in a batch tray dryer type system. The backfilling should also be carried out through a bacteriological filter. It is important that the gas flow during backfilling be slow enough to allow cooling of the gas to prevent raising the collector temperature. Backfilling can be carried out to any desired pressure in those tray dryers that have internal stoppering capability, and the vials then stoppered at the desired pressure.

Stability of Freeze Dried Products

Several factors can affect the stability of freeze dried material. Two of the most important are moisture and oxygen.

All freeze dried products have a small amount of moisture remaining in them termed residual moisture. The amount of moisture remaining in the material depends on the nature of the product and the length of secondary drying. Residual moisture can be measured by several means: chemically, chromatographically, manometrically or gravimetrically. It is expressed as a weight percentage of the total weight of the dried product. Residual moisture values range from less than 1% to 3% for most products.

By their nature, freeze dried materials are hygroscopic and exposure to moisture during storage can destabilize the product. Packaging used for freeze dried materials must be impermeable to atmospheric moisture. Storing products in low humidity environments can reduce the risk of degradation by exposure to moisture. Oxygen is also detrimental to the stability of most freeze dried material so the packaging used must also be impermeable to air.

The detrimental effects of oxygen and moisture are temperature dependent. The higher the storage temperature, the faster a product degrades. Most freeze dried products can be maintained at refrigerator temperatures, i.e. 4-8° C. Placing freeze dried products at lower temperatures extends their shelf life. The shelf life of a freeze dried product can be predicted by measuring the rate of degradation of the product at an elevated temperature. This is called accelerated storage. By choosing the proper time and temperature relationships at elevated temperatures, the rate of product degradation can be predicted at lower storage temperatures.

________________________________

Glossary

• Accelerated Storage: Exposure of freeze dried products to elevated temperatures to accelerate the degradation process that occurs during storage.
• Batch Freeze Drying: Freeze drying multiple samples of the same product in similar sized vessels at the same time in a shelf tray dryer.
• Bulk Freeze Drying: Freeze drying a large sample of a single product in one vessel such as the bulk drying pans designed for shelf tray dryers.
• Collapse: A phenomenon causing collapse of the structural integrity of a freeze dried product due to too high a temperature at the drying front.
• Collapse Temperature: The temperature above which collapse occurs. Collector: A cold trap designed to condense the water vapor flowing from a product undergoing freeze drying.
• Internal Collector: A collector located in the same area as the product. All water vapor has a free path to the collector.
• External Collector: A collector located outside the product area connected by a small port through which all water vapor must pass. Allows isolation of the product from the collector for drying end point determinations and easier defrosting.
• Ethylene Oxide: A colorless, odorless gas used for gas sterilization of tray dryer systems.
• Eutectics: Areas of solute concentration that freeze at a lower temperature than the surrounding water. Eutectics can occur at several different temperatures depending on the complexity of the product.
• Eutectic Temperature: The temperature at which all areas of concentrated solute are frozen.
• Evaporative Cooling: Cooling of a liquid at reduced pressures caused by loss of the latent heat of evaporation.
• Freeze Drying: The process of drying a frozen product by creating conditions for sublimation of ice directly to water vapor.
• Glass Transition Temperature: The temperature at which certain products go from a liquid to a vitreous solid without ice crystal formation.
• Isothermal Desorption: The process of desorbing water from a freeze dried product by applying heat under vacuum.
• Lyophilization: The freeze drying process.
• Manifold Freeze Drying: A freeze drying process where each vessel is individually attached to a manifold port resulting in a direct path to the collector for each vessel.
• Prefreezing: The process of cooling a product to below its eutectic temperature prior to freeze drying.
• Pressure Gauge (Vacuum Gauge): An instrument used to measure very low pressures in a freeze drying system.
• Thermocouple Gauge: A pressure gauge that measures only the condensable gases in the system. This gauge can be used as an indicator of drying end points.
• McLeod Gauge: A mercury gauge used to measure total pressure in the system (i.e. condensable and non- condensable gases.)
• Primary Drying: The process of removing all unbound water that has formed ice crystals in a product undergoing freeze drying.
• Residual Moisture: The small amount of bound water that remains in a freeze dried product after primary drying. Residual moisture is expressed as the weight percentage of water remaining compared to the total weight of the dried product. The amount of residual moisture in a freeze dried product can be reduced during secondary drying.
• Secondary Drying: The process of reducing the amount of bound water in a freeze dried product after primary drying is complete. During secondary drying, heat is applied to the product under very low pressures.
• Shell Freezing: Freezing a product in a thin layer that coats the inside of the product container. Shell freezing is accomplished by swirling or rotating the product container in a low temperature bath.
• Sublimation: The conversion of water from the solid state (ice) directly to the gaseous state (water vapor) without going through the liquid state.
• Vapor Pressure: The pressure of the vapor in equilibrium with the sample.

Bibliography

1. Barbaree, J.M. and A. Sanchez. 1982. Cross-contamination during lyophilization. Cryobiology 19:443-447.
2. Barbaree, J.M., A. Sanchez and G.N. Sanden. 1985. Problems in freeze-drying: I. Stability in glass-sealed rubber stoppered vials. Developments in Industrial Microbiology 26:397-405.
3. Barbaree, J.M., A. Sanchez and G.N. Sanden. 1985. Problems in freeze-drying: II. Cross-contamination during lyophilization. Developments in Industrial Microbiology 26:407-409.
4. Flink, J.M. and Knudsen, H. 1983. An Introduction to Freeze Drying. Strandberg Bogtryk/Offset, Denmark.
5. Flosdorf, E.W. 1949. Freeze-Drying. Reinhold Publishing Corporation, New York.
6. Greiff, D. 1971. Protein structure and freeze-drying: the effects of residual moisture and gases. Cryobiology 8:145-152.
7. Greiff, D. and W.A. Rightsel. 1965. An accelerated storage test for predicting the stability of suspensions of measles virus dried by sublimation in vacuum. Journal of Immunology 94:395-400.
8. Greaves, R.I.N., J. Nagington, and T.D. Kellaway. 1963. Preservation of living cells by freezing and by drying. Federation Proceedings 22:90-93.
9. Harris, R.J.C., Ed. 1954. Biological Applications of Freezing and Drying. Academic Press, New York.
10. Heckly, R.J. 1961. Preservation of bacteria by lyophilization. Advances in Applied Microbiology 3:1-76.
11. Heckly, R.J. 1985. Principles of preserving bacteria by freeze-drying. Developments in Industrial Microbiology 26:379-395.
12. King, C.J. 1971. Freeze-Drying of Foods. CRC Press, Cleveland.
13. May, M.C. E. Grim, R.M. Wheeler and J. West. 1982. Determination of residual moisture in freeze-dried viral vaccines: Karl Fischer, gravimetric, and thermogravimetric methodologies. Journal of Biological Standardization 10:249-259.
14. Mellor, J.D. 1978. Fundamentals of Freeze-Drying. Academic Press, London.
15. Nail, S.L. 1980. The effect of chamber pressure on heat transfer in the freeze-drying of parental solutions. Journal of the Parental Drug Association 34:358-368.
16. Nicholson, A.E. 1977. Predicting stability of lyophilized products. Developments in Biological Standardization 36:69-75.
17. Parkes, A.S., and A.U. Smith, Eds. 1960. Recent Research in Freezing and Freeze-Drying. Charles C. Thomas, Springfield.
18. Rey, L.R., Ed. 1960. Traite de Lyophilization. Hermann, Paris.
19. Rey, L.R., Ed. 1964. Aspects Theorique et Industriels de la Lyophilisation. Hermann, Paris.
20. Rowe, T.W.G. 1970. Freeze-drying of biological materials: some physical and engineering aspects. Current Trends in Cryobiology: 61-138.
21. Seligman, E.B. and J.F. Farber. 1971. Freeze-drying and residual moisture. Cryobiology 8:138-144.

An Industry Service Publication
reprinted with permission from Labconco Corporation

http://www.coleparmer.in/techinfo/techinfo.asp?htmlfile=guide-freezdrying.htm&ID=1034&referred_id=5618

While standard centrifugal pumps are typically used for mixing, blending and transporting product from points A to B, moving product with minimal shearing requires a positive-displacement (PD) pump. PD pumps can move food and beverages with a minimum of shear because the product is moved, in the case of a rotary PD pump, within the rotor pockets from the inlet to the outlet.

Shear, the relative motion between adjacent layers of a moving liquid, affects different liquids in different manners. Paint thins in viscosity as it is stirred; but cornstarch and water thicken when sheared. With a low-shear pump, delicate soups can be transported from the kettle to the filler, keeping food particles intact, and yogurt can be moved in a dairy without subjecting it to shear that may cause it to separate later after packaging.

Peristaltic pumps use rollers that pinch a tube, providing pumping action. Pumped product does not come in contact with the pump body, and the tube can be cleaned in place like piping. Source: Watson-Marlow.

Popular PD pumps for low-shear applications, according to Chuck Lewis, marketing specialist at Moyno Inc., include rotary types such as peristaltic, lobe, and eccentric disk pumps. In addition, diaphragm pumps belong to the reciprocating family, but like the three rotary types, are able to move product safely without shear. Other PD types include gear, progressive cavity, sinusoidal plate (sine) and rotary vane pumps. While you may want to leave the shearing to a controlled environment such as a Breddo Liwifier rather than a pump, for high shear applications, Lewis suggests using pumps that include grinders and other similar equipment meant to masticate product into smaller pieces that are then conveyed or pumped. He says the violent action of high-shear grinders is designed to help with the disposal process of many waste products of less value.

“If you want a pump for high-shear applications, the best pump technology would be centrifugal,” says Eric Nofziger, Cole-Parmer product manager. “There are specific designs that can accommodate the chopping and grinding of particulates in the system water,” he adds. The key item to take into consideration is the size of the suspended particles. Depending on the size constraint, the pump’s impeller can be either a traditional closed or an open one—and if open, the geometry is adjusted to take the size into consideration.

A gentler, kinder pump

Enlarge this picture Two pumps are compared for slip. The pump on the left has a tight performance band and shows a slip of 4.2 gpm, while the pump on the right has a wide or loose performance band and produces a slip of 28.2 gpm. Source: Pump Solutions Group.

When processors have a viscous product or a product that needs to be transferred gently, PD pumps are the pumps of choice, says Chuck Treutel, Watson-Marlow food & beverage division sales manager. Typically, PD pumps are used in applications where product integrity is paramount. They run at slower speeds and handle higher viscosities than centrifugal or rotary pumps. The most common type of PD pump found in the food industry is the rotary lobe or circumferential piston. These pumps have two shafts and two rotors that turn opposite each other where the meshing rotors create a vacuum at the inlet pulling product in, carrying the product through and discharging it.

Lobe pumps are not great for metering duties because fluid slips between the lobes and the case, explains Treutel. While lobe pumps are low-shear devices, peristaltic pumps are better PD devices as they use a pinched-tube principle to move product, resulting in lower slippage and shear. Another option, says Treutel, is the sinusoidal pump, which has a single sinusoidal rotor that’s capable of powerful suction with low shear, low pulsation and gentle handling.

Treutel points to a leading poultry processor that used two sinusoidal pumps in its marinated boneless breast application, replacing vacuum and air pumps that were previously used to transfer the product into a drop hopper to meter product onto a conveyor. The drop hopper was also replaced, and the sinusoidal pumps were set up to meter boneless products through end-user-supplied spreader horns. Two pumps and two horns were arranged to feed two 16-in.-wide, half-inch sheets of boneless breast meat onto the conveyor, creating an almost-labor-free roasting line.

While perhaps similar in concept to a peristaltic or sinusoidal pump, Mouvex’s eccentric movement technology produces a peristaltic effect with a disk moving in an eccentric (non-rotating) motion inside an annular cylinder, says Wallace Wittkoff, Pump Solutions Group global hygienic director. Because the pumping elements don’t rotate, but instead move in an eccentric motion, there is no need for a mechanical seal. A rubber boot or metal bellows is used to accommodate this eccentric motion. For very low- or almost no-shear applications, the eccentric pump and an old standby, the air-operated diaphragm pump, both are good choices for delicate food products, adds Wittkoff.

Shear, slip, efficiency and saving energy

This winery pump with a progressing cavity design moves up to 20 tons of must or whole clusters of grapes per hour and includes a built-in auger-feed mechanism. Source: Moyno.

“Since the initial price of a pump is only about 5% of its life cycle costs, I advise customers to look at the total cost of ownership of the equipment,” says Sam Raimond, Fristam Pumps customer service supervisor. “This includes maintenance costs (reliability, CIP-ability), more efficient motors and pump efficiency (energy costs),” he adds.

Processors want to save energy, and one way is to use efficient pumps. Shear and slip are inter-related and can affect pump efficiency. Pumps that are best for low-shear applications typically run at slow speeds, have small-diameter rotating parts, and produce minimal internal slip, says Mike Dillon, president of seepex Inc. By definition, PD pumps have the lowest shear rates, he adds.

In pump design, the higher the pump efficiency, the tighter the performance and the greater the energy savings. “When looking at centrifugal pumps, you want a design that utilizes most of its energy for moving liquid instead of being converted into thermal energy,” says Jim LeClair, SPX Flow Technology global product manager. In the design of rotary PD pumps, the minimization of slip within the rotor and case design maximizes the pump’s efficiency, he adds. Finding the optimum pump size based on pumping efficiency is important in maximizing energy savings.

For PD pumps, it’s assumed that no slip equals tight performance. But in reality, most rotary PD pumps do not attain true positive displacement because of slip. The actual flow produced is subject to product viscosity, back pressure, temperature (large clearances are needed) and wear, which is the most troubling, says Wittkoff. Since the Mouvex eccentric technology has very low slip, it can compress air, thus purging much of the product from the line when the supply tank runs dry, Wittkoff adds.

Fewer moving parts in the design of a pump can save energy. Sinusoidal pumps have only one set of bearings, one shaft and one rotor, compared to two of everything for the rotary lobe design, says Treutel.

“The result is less energy required to drive our pumps. Also peristaltic pumps are unique [because] they are 100% volumetrically efficient. This means zero slip,” he adds. No slip means very low shear is imparted on the product, and if the product is not slipping back from the discharge to the inlet, it means the product doesn’t have to be pumped twice, saving time and energy.

While the physical appearance of PD pumps has changed little over the years, better materials and improved technology have afforded internal pump changes that save energy, says Lewis. Now smaller drive ends can handle larger elements than in the past, which is both a cost and energy saver. Still the best way to save energy is to apply the right pump to the application. The correctly-sized pump can overcome friction loss, avoid excessive back pressure and still handle the upset condition.

“CIP-ability”

For maximum overall efficiency, a rotary lobe pump can be teamed up with a variable-frequency drive to find the optimum spot on the pump’s performance curves. Source: Cole-Parmer.

The term CIP-ability implies the ability for a device to be compatible with clean-in-place methods—to be able to withstand harsh chemicals and extreme wash temperatures. But several criteria raise concern for processors. For example, how quickly and easily can a CIP-able pump be taken apart to verify cleaning? How can a CIP process in a pump be validated? Do seals and pumps exist that can withstand the CIP process? What approvals show that a pump is CIP-able?

“It seems as though the most desirable trait is ease and simplicity to manually clean,” says Dillon. Even though CIP has gained acceptance, many plants still disassemble pumps and piping for frequent inspection, he adds. This explains the persistence of lobe and centrifugal pumps in some plants when other designs are less expensive, are more CIP-able, have lower shear, and are more efficient, says Dillon.

Lewis says his company’s progressive cavity pumps take about an extra 5 to 10 minutes to disassemble and reassemble. The connections are made through a tri-clamp system that makes disassembly easy. More importantly, he adds, the pump should have regulatory approvals in place such as 3-A Sanitary Standards Inc., which indicate the pump has been rigorously tested to meet sanitary conditions.

Quick disassembly and repairs to CIP-able pumps depend on the design from the supplier, says Nofziger. Some designs have a wing-nut-type release bolt to remove the cover plate, while others require more extensive tools. As for repairs, front seals are easier to replace than rear seals, and working in the gearbox can be problematic, he adds. Gear-box repairs on lobe pumps can be tricky because of the timing issues. And with lobe pumps, Nofziger recommends not turning them on until the head temperature has stabilized to the fluid or product. Otherwise spalling could occur inside, causing slippage.

“Temperature variations, which are common in many food applications, can be very hard on pumps,” says Dillon. Dairy products are pumped cold, yet CIP or SIP (steam-in-place) is really hot. Tolerances can change and excessive wear can take place during CIP. Using thinner cross sections of temperature-sensitive materials—like elastomers—leads to less sensitivity to temperature fluctuations, he adds. seepex introduced a new line of 3-A pumps with thinner cross sections of elastomers in the stators to increase longevity in CIP applications.

Doug Silvey, CSI Designs solution expert, believes processors should spend the time normally spent on disassembling and reassembling pumps on validating the efficacy of CIP process on the pump. Adjusting the CIP time, cleaning chemicals, backpressure and pump speed when cleaning, and validating the pump is free of bacteria, eliminates repeated disassembly/re-assembly steps that can cause rotor alignment problems and damage.

The design of a CIP-able pump should meet all the requirements of the CIP definition as stated in the PMO and 3-A standards, says LeClair. When all equipment in the process line—including the pump—meets these standards, the processor can be assured that CIP will be effective for the entire line. Furthermore, if the pump has been tested to the European EHEDG standard, the processor can be assured that the pump will be clean according to the hygienic standards as outlined in the European Union, he adds.

One thing to keep in mind is that pump costs can be much higher if they have to comply with certain standards like 3-A.

“When a pump is rated 3-A, the pump manufacturer not only ensures the correct material of construction [is used], but also pays special attention to O-ring design (how the pump is connected to the rest of the system) as well as making sure there are no sharp corners in the fluid path,” says Nofziger. This detail ensures that the pump can be cleaned to eliminate the chance of bacteria growth. Additional costs accumulate in the third-party verification step where a 3-A member visits the pump manufacturer’s plant and reviews the engineering drawings, he adds.

Seal or no seal

Seals can be a sticky issue, especially with harsh CIP fluids and temperatures. Lewis suggests it may not be that mechanical seals fail due to undergoing CIP. Rather, it could be that the type of seal is incorrect for the process. Double mechanical seals may need to be considered, or the use of a magnetic drive can replace mechanical seals.

The materials used in seals have improved and the standard material provided has been optimized to fit 80% of applications that are currently on the market, says LeClair. The materials most used for rotary seals are silicon carbide against a carbon face. As new elastomeric technologies have been introduced, the use of new compounds has helped seals hold up against many of the new cleaning agents used today as well as improved their heat resistance, he adds.

“There are many options available for pumps to withstand chemical attack, high temperature and high pressures,” says Raimond. “We offer perfluoroelastomers (ASTM designation: FFKM), which are designed to withstand high temperatures and are compatible with many aggressive chemicals. Hastelloy and AL6XN metals have high chemical resistance,” he adds.

Pump manufacturers have addressed seal problems with exotic materials and designs, seal flushing systems and recommended plant process changes, says Treutel. “But the best way of preventing seal problems, such as leaks and premature wear, is to eliminate the seal altogether.

“If a [processor] is having seal problems and cannot find a solution, try a peristaltic pump…they do not have product seals,” he advises.

In the case of peristaltic pumps, during CIP the rollers or shoes that compress the tube are retracted so the pump becomes nothing more than an extension of the piping, says Treutel. If the piping becomes clean during CIP, then the pump will as well because the product and CIP fluid is contained within the tube at all times. Although the pump has no seals, there is some mechanical wear on the tube itself, but replacing it is generally easy.

Hygienic diaphragm pumps such as Wilden’s typically don’t have a mechanical seal; their diaphragm serves as isolation between product and the outside environment. According to Wittkoff, his company’s 3-A and EHEDG-approved pumps have no counter-moving surfaces, so there is no issue with material buildup or abrasive wear.

Trends and challenges

Most processors ultimately want CIP-able PD pumps, and that has been a focus for many suppliers. In creating a CIP-able PD pump, Fristam designed it such that not only the pump remains in place during CIP, but also all of its parts—covers and rotors, says Raimond. The challenge was to make the pump without modifying or increasing its clearances to accommodate CIP.

Suppliers have also dealt with some interesting applications. For example, Lewis describes a sanitary pump system for cold sausage with a viscosity topping 1,000,000 cp. The pump had to be made of stainless steel and designed for quick disassembly. It has also been used in icing, batter and dough applications.

LeClair describes pumping a mixture of fruit skins and grain husks. The low moisture content of this product made for a very abrasive application that required a rubber lobe pump.

Nofziger suggests that a real challenge is educating the customer in properly specifying a pumping system. Choosing a pump that is operating too close to either end of its performance curve tends to happen when a processor is looking for a pump mostly with a price point in mind.

While it is important to find something that will work within the budget, it is also important to review the performance curve of the pump. If a pump costs a bit more and provides an operating point closer to the middle of the curve, it would be a better choice than one closer to the end of its curve. When choosing a pump with an operational point that is close to the end of its curve, the end user will also be spending more on the operation of the pump versus one that is in the middle of the curve (which should have a better efficiency). If the pump is operating 24/7, this operational inefficiency could add up to many times more than the cost of the original equipment.

For more information:
Chuck Lewis, Moyno Inc., 937-327-3111, chuck.lewis@robn.com
Eric Nofziger, Cole-Parmer, 800-323-4340, enofziger@coleparmer.com
Chuck Treutel, Watson-Marlow, 608-883-6851, chuck.treutel@wmpg.com
Wallace Wittkoff, Pump Solutions Group, 502-905-9169,
wallace.wittkoff@pumpsg.com
Jim LeClair, SPX Flow Technology, 262-728-4912, jim.leclair@apv.com
Mike Dillon, seepex Inc., 937-864-7150, mdillon@seepex.net
Sam Raimond, Fristam Pumps, 608-831-5001
Doug Silvey, CSI Designs, 800-654-5635, dougs@csidesigns.com

Wayne Labs, Senior Technical Editor
labsw@bnpmedia.com

Original article:  http://www.foodengineeringmag.com/Articles/Feature_Article/BNP_GUID_9-5-2006_A_10000000000000795034

To view Cole-Parmer’s pump supply:  http://www.coleparmer.com/catalog/product_index.asp?cls=47660&referred_id=5618

If you bought a Butterball turkey this Thanksgiving, you have particle accelerators to thank for its freshness. For decades now the food industry has used particle accelerators to produce the sturdy, heat-shrinkable film that Butterballs come wrapped in.

“Particle accelerators tie the molecules of plastic together and make the film tougher mechanically. It doesn’t crack or tear,” says Marshall Cleland, a technical advisor at IBA Industrial, an international company that has been manufacturing particle accelerators for commercial use since 1988.

Understanding how accelerators give cross-linked shrink film its unique properties requires a refresher course in chemistry.

Heat-shrinkable film—commonly known as shrink wrap—is made of polyethylene plastic. The plastic molecules, called polymers, are long chains of carbon atoms strung together like pearls. Each carbon atom also connects with two hydrogen atoms, leaving it no room to bond with anything else.

“The fully saturated carbon had its full meal, including dessert, and becomes chemically inert,” Cleland says. “If you heat it to the boiling point of water, it will turn into a syrupy mess.”

However, when hit with a beam of electrons from a particle accelerator, the plastic’s polymer strings become chemically active.

The electron beam knocks hydrogen atoms off the polymer chains, leaving the polymers hungry to fill those vacancies. If conditions are right, the carbon atoms in one chain bond with carbons in neighboring chains—and those carbon-carbon bonds are incredibly strong.

“The whole thing starts to knit together. Instead of being loose threads, it is sort of like a fishnet where everything is tied together,” Cleland says. “It is what we call a cross-linking reaction.”

When fully cross-linked, the plastic “becomes elastic if you heat it to boiling temperature, but it won’t melt,” Cleland says. After electron-beam treatment, the plastic is stronger and more heatresistant. It can be heated and stretched into a thin film without ripping. When cooled to room temperature, the cross-linked plastic retains its expanded shape. Place something inside it, such as a Butterball turkey, and apply heat, and the plastic shrinks back down to its original size, resulting in an air-tight wrapping.

The food industry purchases these cross-linked products from plastic manufacturers in large rolls or bags, depending on how the film will be used. You will find cross-linked shrink film wrapped around many items in the grocery store, such as turkeys, produce, and baked goods, as well as around board games, video games, DVDs, and CDs. “It’s a big business,” Cleland says.

Complete Selection of Chemical Property Testing

Published with permission from Symmetry Magazine, A joint Fermilab/SLAC publication

Quest Technologies® NoisePro Personal Dosimeter DL

SOUND DEFINED
When you blow up a balloon you are using your lungs to force air into the balloon. This causes the balloon skin to expand into its stretched out shape. The air in the balloon is now under pressure. If we squeeze the balloon in the middle, what happens? The balloon bulges out at the ends and the pressure inside the balloon increases. When the balloon is released it pops back to its original shape at its original pressure.

Suppose the balloon were very long and someone squeezed it at one end. What would we observe at the other end? First we would notice that nothing happened for a short period after it was first squeezed, then, just like the small balloon, the pressure would increase. What is happening is that the excess pressure caused by the squeeze is traveling down the tube at a speed of about 1200 feet per second. This excess pressure is the sound wave. If the squeeze were released, a decrease in pressure would travel down the tube in the same manner. To convince your self that these actions actually produce sound waves, burst the balloon with a pin.

How do we describe sound? Consider something that appears not to have anything to do with sound at all: a weight hanging from a spring.

If we pull the weight down a certain distance from the point it naturally hangs, then release it, the weight starts returning toward the rest position. But it goes through the rest position until it reaches a point as high above the rest position as it was pulled below it. The weight then starts down again to a new lowest position, where the process repeats over and over. Since the energy source of the person that initially pulled down on the weight is gone, the weight rises and falls a smaller distance each time, eventually coming to rest once again. The maximum displacement from the “at-rest” position is called the amplitude, and the time it takes to go through one complete cycle (from down to up to down) is called the period of the vibration. The number of periods that occur in one second is called the frequency. The units of frequency were once called cycles per second, but are now called Hertz and abbreviated “Hz”. So what’s the correlation between a weight on a spring and sound in air? Look at a stereo speaker emitting a single tone. As the speaker cone moves forward and backward like the spring, it alternately compresses and expands the air in front of the cone. The compression and expansion then moves out away from the speaker as a sound wave.

Single Frequency Sound
There are a number of common sources of sound that act much like the spring because they cause a single frequency sound to be produced. The keys of a piano are a good example. Pressing the middle C key causes its string to vibrate about 260 times per second. The vibrating string and soundboard cause the air adjacent to it to compress and expand with the same frequency. Just like the balloon, the changing pressure moves outward as a sound wave. Other examples of tones are the hum of a motor (60 Hz) and the sound of a police whistle (3500 Hz).

Random Motion–Noise
Suppose instead of just pulling the spring down and releasing it, there is an invisible hand that randomly either pulls or pushes on the weight at different times. Sound can behave in this random manner as well – think of music. So how would you describe this motion? Certainly there is no single frequency or amplitude with which to describe the motion as in the previous case. Fortunately noise such as this can be shown to consist of many single frequency components, each having its own amplitude.

Sound With Many Frequency Components
As an example of sound with many frequency components, consider motorcycles and automobiles. The amplitude of sound from motorcycles is typically greater than for automobiles. Motorcycle sound also contains components that are higher in frequency than an automobile. These are two reasons why motorcycles annoy people more than automobiles.

The Decibel
How do we describe the volume of sound we hear in everyday life? Because the sound levels we encounter in daily life can vary over such a wide range, talking about sound pressure in units such as pounds per square inch would be unwieldy. To remedy this situation we define Sound Pressure Level (SPL) as:

SPL = 20 x logarithm10 (measured sound pressure / reference sound pressure)

The reference pressure used for environmental noise turns out to be the lowest level sound that a person with normal hearing can detect. The unit of SPL is called the decibel (dB). Does all this complicated jargon mean that an enforcement officer will have to have a degree in mathematics? NO! All enforcement equipment is calibrated directly in decibels, so no calculations are involved.

Sound Level And Distance From The Source
Most people know that noise levels increase as you get closer to a sound source and decrease as you move away. It is important to note that the sound pressure level rises at a faster rate as you move closer and at a slower rate as you move away. Think about what happens when you drop a stone in water. The waves that are created are closer together and higher (amplitude) nearer the point of impact and further apart and lower as you move away from where the stone entered the water. Sound pressure behaves in the same manner. The importance of this observation is that officers should make sure he/she is at least as far away from the source as your ordinance requires when taking sound measurements. It is better to be a little too far than a little too close.

Combining Sound Pressure Levels
Suppose we have two identical sound sources, each alone producing the same dB level. So what is the SPL of the combined sources? It is not the sum of the two. We cannot simply add decibels directly to get the overall effect. The correct answer is obtained by using the following rule: Each time the number of identical noise sources is doubled, the SPL increases by 3dB; each time the number is halved, the SPL is decreased by 3dB. This rule is called 3dB doubling or 3dB exchange rate.

How does the 3dB rule help you? Suppose your noise ordinance has an 80dB noise limit. You cite a violator for causing an 89dB noise level and the case comes to court. The judge asks you how loud 89 dB is. Knowing this rule of thumb, you are able to tell the judge that 89 dB is the same noise level that would be generated by 8 identical vehicles, each producing the maximum allowable sound level of 80 dB. Case closed!! Be sure to apply the doubling rule contained in your particular ordinance.

Effects Of Additional Noise Sources
A third factor to remember when measuring sound involves the contribution to the overall level of all the other noise sources present at the time a violator is cited. This extraneous noise is called the ambient level. The violator might ask, “There were a number of other loud noise sources present when you cited me, so how do you know that they didn’t cause the readings to be too high?” The rule that applies here is: a violator should not be cited unless the level measured when the violation occurs is at least 10dB above the ambient noise level immediately before the violation. If this condition is met, then the additional noise caused by all the other sources producing noise will add less than 0.4dB to the level produced by the violator.

Sound Reflection
The last factor to remember is the effect of large objects on sound reflection. Think of the stone in the water again. If the water waves encounter an obstacle as they move away from where the stone entered the water, you will see part of the wave reflected back in the direction it came from, modifying the height of the waves, which is equivalent to the sound pressure in air. The same phenomenon occurs in air when measuring sound. The rule of thumb is to remain at least as far away from any large reflecting objects as you are from the source being measured. What about reflection from the ground? The noise level limit stated in the ordinance should take into account the fact that the noise heard by the receiver consists of sound that is reflected from the ground to the receiver as well as the direct wave. Normally there should be no concern. The exception is when the sound level meter is close to the ground. All measurements should be made with the microphone at least three feet above the ground.

The Sound Level Meter
The most common device used in noise ordinance enforcement is the sound level meter (SLM). The SLM performs three basic operations. It uses a microphone to convert the energy in the sound into an electrical signal. An electronic circuit then conditions the signal to provide meaningful results. Finally, the SLM communicates the results to the operator in one or more ways.

Before we address the specifics of various kinds of meters, we should address the most basic question of all, “How should I hold the SLM?” Should the microphone be pointed at the noise source or should the face of the microphone be oriented at some other angle such as at a right angle to the sound wave? The answer depends on the type of microphone being used. There are three different types of microphones available: free-field, random incidence and pressure. Free-field microphones should typically be pointed directly towards the noise source. Random incidence microphones should typically be held at a 70° angle to the source. Pressure microphones should typically be held at a right angle to the noise source. The rule here is to follow the manufacturer’s recommendations with respect to microphone orientation. Generally, low frequency sounds are not affected by the microphone orientation as much as high frequency sounds. Again, this depends largely upon what type of microphone element is used in the SLM.

The Basic SLM
Features vary considerably from meter to meter and from manufacturer to manufacturer. Perhaps surprisingly, so can performance and accuracy. No matter what type of SLM is used, at least two requirements of the meter should always be met. These include some method for performing a field calibration of the SLM and an independent certification that the SLM meets Type I or Type II standards of performance and all other applicable SLM standards in your locality. Your noise ordinance should include a statement of standards that must be met by the meter.

In its most basic form, the SLM will provide the operator with an indication of the instantaneous SPL being detected. Often a basic meter will also provide an indication of the maximum SPL encountered as well. Results from a Basic SLM’s are almost certainly limited to presentation through the display of the meter. Rarely are there capabilities for these meters to output results to a printer or computer. There may or may not be provisions in the meter to allow the operator to change certain characteristics of the SLM’s signal conditioning circuits. These characteristics in a basic meter may or may not include the weighting network and the response time constant. Your noise ordinance should include a specification as to which weighting network and response time constant is to be used.

Weighting networks most common today consist of “A”, “C” and “Z” weighting. Each of these weighting networks is a “standard” that dictates how the SLM will recognize the amplitude of the SPL based on the frequency of the sound. For instance, “A” weighting circuits simulate how the human ear responds to sound. We know that humans can hear within a fixed range of frequencies and humans perceive that sound is louder or softer as frequency changes.

Response time constants define how quickly an instrument must be able to recognize and process changing SPL’s. The most common options today are “Fast”, “Slow”, “Peak” and “Impulse” time constants. If it were not for the existence of frequency weighting and response time constant standards, results from meter to meter and manufacturer to manufacturer would almost certainly vary widely and prohibit the effective measurement and enforcement of noise limits.

Integrating SLM’s
Depending upon the requirements of your noise ordinance, you may need an SLM that computes the average SPL over a prescribed amount of time. These types of SLM’s are referred to as Integrating SLM’s because they automatically calculate the average SPL. All Integrating SLM’s calculate this result based on a given doubling or exchange rate, as discussed earlier. Some SLM’s may be fixed for a specific exchange rate at the factory. Others may include provisions for setting the exchange rate in the field. In either event, it is important to note which exchange rate the SLM is using and that it matches the requirements of your noise ordinance. Since it is possible for ordinances to change, it is always more favorable to have an SLM that allows the exchange rate to be changed by the user without requiring factory modification, or worse yet, replacement. Integrating SLM’s may include provisions for printing results or uploading them to computer. Generally speaking, unless the meter also documents the performance of a field calibration in its output, the value of the hard copy results is greatly diminished.

Datalogging SLM’s
After integration, the next mostly commonly sought after capability in an SLM is datalogging. Datalogging SLM’s provide much more detail of the noise-testing event. This can include a minute-by-minute profile of the sound source’s SPL levels. At a minimum, these kinds of meters should provide hard-copy and computer upload of test results correlated to the real-time and date of the event.

Octave Band SLM’s and Real Time Analyzers
At the top end of the spectrum for SLM’s you will find devices that are capable of determining and reporting the SPL and average SPL at various frequencies. These meters are rarely used for noise ordinance enforcement since ordinances rarely specify noise limits as a function of frequency. Generally speaking, once frequency content of the sound is a concern, specialists in acoustics are required to perform these tests.

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Published with permission from Quest Technologies

Full article can be found at:  http://www.coleparmer.com/techinfo/techinfo.asp?htmlfile=Sound_Measurement.htm&ID=1183&referred_id=5618

Temperature is one of the most frequently measured parameters in industrial processes. A wide variety of mechanical and electrical thermometers are used to sense and control process temperatures. Regular calibration of these thermometers is critical to ensuring consistent quality of product manufactured, as well as providing regulatory compliance for some industries.

 

The Basics

Most simply stated, temperature calibration consists of placing a thermometer under test into a known, stable temperature environment. A comparison is made between the actual temperature and the reading indicated by the thermometer under test and the difference is noted.

Adjustments can then be made either directly to the thermometer or to its readout. Electrical thermometers are adjusted by mathematically re-creating the coefficients used by SMART transmitters or other readout devices to translate their electrical output to temperature. Many mechanical thermometers, such as dial gauges can be adjusted by turning a dial or other mechanical device. In some cases, such as liquid-in-glass thermometers, direct adjustments are not possible and offsets must be noted.

In industrial applications, the temperature environment is usually provided by a drywell, or “dry-block” calibrator, or a micro-bath. Both offer portability and a wide range of temperatures. Drywells use high stability metal blocks with drilled wells to accept the reference and UUT. Drywells typically cover ranges from -45°C to 1200°C and micro-baths cover ranges from -25°C to 200°C. Micro-baths are similar in size to drywells but use a small tank of stirred fluid instead of a metal block. Micro-baths offer significant advantages when calibrating short or odd shaped probes.

The “actual” temperature of the bath or dry-well is determined by a reference thermometer, which may be either a thermometer internal to the heat source or an external reference thermometer operating independent of the heat source.

Figure 1: Heat source as reference standard

External or Internal Reference

Micro-baths and dry-wells have a built-in sensor to provide a feedback loop to the unit’s controller and to provide a temperature reading to the user. The manufacturer of the heat source (or a third-party laboratory) can calibrate this sensor so the unit displays a traceable temperature within a stated uncertainty. For some applications, this uncertainty level (typically ±1-2°F) is adequate. Using an internal reference is sometimes preferred because it requires fewer instruments and enhances portability for field applications. This method is illustrated in Figure 1.

The reference system, however, should be more accurate than the process system being calibrated. The generally accepted Test Uncertainty Ratio (TUR) is 4:1 (i.e. the reference should be four times more accurate than the sensor or system being calibrated). Therefore, if a process thermometer is being relied on for correct readings within ±2°F, the test system should typically be ±0.5°F or better at each temperature in question. As a general rule, temperature uncertainties are larger at higher temperatures.

Figure 2: External reference standard

Where uncertainty requirements are more rigorous, external reference thermometers help improve system uncertainty (see Figure 2). These thermometers—usually platinum resistance thermometers (PRTs) or thermistors—can often be calibrated to a few hundredths of a degree and can be read by electronic readout devices that contribute little to total measurement uncertainty. These systems can provide measurements with uncertainties as low as ±0.05°F or ±0.02°F—or better. The reference probe and readout should be periodically re-calibrated, preferably by an accredited cal lab, to assure performance specifications and maintain traceability.

Because external thermometers are more accurate, they increase the relative significance of other components of calibrations uncertainty, such as uniformity and stability. It is, of course, critical in any calibration to account for all sources of uncertainty in the process.

System or Component Calibrations

Most temperature sensors used in processes are read by transmitters, which send a 4 to 20 mA signal to a control panel, which then displays the temperature for process monitoring. Such systems involve three instruments, all of which require periodic calibration. Of these three, the largest errors are often found in the temperature sensor (which is subject to drift for a variety of reasons), so its calibration is of particular concern.

More Details or Order Online: Hart Scientific Field Temperature Dry Wells High-Temperature Field Dry Block Calibrator Industrial Dual-Block Calibrator

Several calibration methodologies are used in the process plant with the most representative method being to calibrate the complete measurement system from sensor through transmitter to indicator or controller; alternatively each component of the measurement system can be individually calibrated.

The temperature sensor can be individually calibrated using a drywell or micro-bath heat source to simulate the process temperature. If the temperature sensor is electrical, a readout device measures its output. Adjustments are then made to the thermometer or its coefficients as discussed earlier.

The transmitter is calibrated using a precision simulator to generate the resistance or voltage output from the temperature sensor and input to the transmitter. The simulator also measures the resulting transmitter current or voltage output. The transmitter is adjusted to ensure that the output follows the input, e.g. for a 4 to 20 mA transmitter with a range of 0°C to 200°C, 4 mA corresponds to 0°C and 20 mA corresponds to 200°C. The simulator provides a wide range of input and output ranges to cover all resistance thermometer and thermocouple types.

The indicator or controller is also calibrated using a precision simulator to generate simulate the resistance or current input from the transmitter. The indicator or controller is adjusted so that the display variable matches the simulated input.

The complete system is calibrated using the drywell or micro-bath to compare the reference probe and UUT. The transmitter is adjusted to ensure that the indicator or controller agrees with the reference probe readout. This calibration method is most representative of the real process, is faster and simpler to perform.

Accredited Calibration Services

Calibration of the thermometer standards used to calibrate industrial thermometers provides traceability, which means that measurements are traceable to national and international standards. Traceability to international standards ensures that measurements made in one country agree with measurements in another country, which is particularly important for companies using similar manufacturing processes at different locations around the world.

More Details or Order Online: InnoCal Calibration Services

More and more calibration labs throughout the U.S. are being accredited to international standards such as the ISO Guide 25. Accreditation ensures that a lab’s quality systems, uncertainty levels, and traceability statements have been examined and independently verified. NVLAP and A2LA are the primary accrediting bodies in the U.S. A recently signed international agreement ensures that accrediting bodies in almost every developed nation also recognize accreditations granted by NVLAP and A2LA.

In summary, process plant temperature calibrations require a good reference thermometer with readout, a drywell and/or micro-bath heat source, and a precision simulator. These instruments, in turn, should be periodically calibrated by a reputable lab, preferably one that is accredited and can prove traceability.

How to Determine Thermocouple System Accuracy
Temperature Controller Features
Temperature Conversion Equations
Temperature Instrument Ranges

View original article.

by Bernard Morris, Vice-President of Sales, Hart Scientific, Inc.
Reprinted with permission of Hart Scientific, Inc.