In the high purity fluid handling industry, there is no such thing as a “typical” plant. Layouts and installations vary from plant to plant, company to company. That being said, certain pieces of equipment, such as pumps, sanitary diaphragm valves, gaskets, and flexible hose assemblies are ubiquitous throughout all facilities. We’ve talked extensively about those on this page before. One piece of commonplace equipment we haven’t spent as much time emphasizing are tanks. This post will take a closer look at pharmaceutical storage tanks, specifically tank vents and common considerations that go in to selecting the right one for your application.
To begin, why do we need a tank vent filter? Well, let’s start by thinking about why we’re using a tank in the first place. Tanks are expensive, so it makes sense that they are commonly used to store valuable product or utilities- such as water for injection or buffer media. And the whole point of having a sanitary, clean system is protecting this valuable product form microbial or particulate contamination. Seems easy enough, right? Let’s just seal the tank, don’t let anything in or out, and call it a day- no problem. Well not so fast.
When liquid is added or removed from a tank, air must move in or out of the tank to fill or adjust to the changing airspace above the liquid. Unlike solids and liquids, gases can expand and compress easily. This means that as we pump into a tank and fluid takes up a larger part of the tank, the gas will compress, increasing the pressure of the tank. And when we pump out of the tank, we will create a vacuum, assuming there is no airflow in or out of the tank. Remembering the ideal gas laws, we also know that temperature swings can affect the volume of gas in a tank. During an SIP cycle, for example, cool down following 140 C steam can result in a huge temperature swing and the rapid collapse of the volume of gas/fluid within the tank. This can lead to problems ranging from a rupture disc blowing, to a catastrophic collapse of the tank if the vacuum created exceeds the vacuum rating of the tank.
So if sealing the tank is not going to work, we need to figure out how to allow air to flow in or out of the tank without contaminating the contents. So how do we accomplish this? Usually it’s done with the use of a 0.2 micron hydrophobic sterilizing grade filter cartridge. As the name implies, hydrophobic filters don’t like water. Hydrophobic filters will not “wet out” like hydrophilic filters that are used for liquid filtration. Because of this hydrophobic filters will readily let gas pass through the membrane. Usually made of Teflon, these hydrophobic filter membranes eliminate significant microbial contamination risk.
When sizing a vent filter, there’s usually several unknowns, but there are a few pieces of information to focus in on and that we can use to a make educated guess at the correct size. The first is to identify the air inflow rate. If this is not available, it can be determined by using the liquid flow rate (gpm), multiplied by the conversion factor of 7.81. This will give you CFM, or cubic feet per minute of air flow, a standard measurement used in the sizing of tank vent filters. Next, we want to identify the maximum vacuum rating of the tank. All ASME pressure vessels will have this stamped on the side of the tank. Other bulk storage tanks won’t carry the ASME stamp, indicating it is not a rated vessel.
Finally, we want to identify the maximum operating pressure of the tank. In tanks that contain fluid at an elevated temperature, the fluid has a higher vapor pressure, resulting in water “carryover” with air at the top of the tank during fill. Why is this important? Well if the temperature of the vent filter is not maintained, this water vapor can condense on the membrane of the filter. This results in blinding, decreasing the available membrane filter area and the possibility creating of a vacuum during tank drawdown. For this reason, it is common to see sterile vent filter housings equipped with steam jackets or electrically heat traced to not only keep the temperature of the housing elevated, but also maintain and control the temperature at the filter, extending membrane life.
So there you have it- why tank vent filters are so important and why it is important to heat them. For your next sanitary vessel application, keep in mind that when liquid is added or removed, we need to allow air to move in and out of the vessel to compensate. If you have any additional questions about your next tank venting application, contact a Holland Sales Engineer today.
At Holland, we understand the importance of quality assurance. Whether we’re manufacturing a vessel or an adapter, using the assurance that you’re using the material you think you’re using is critical. While previous posts have focused on the importance of PMI for quality assurance, in this post we’re going to take a closer look at what a mill test report is, what information they provide, and why they are so important in the high purity processing industry.
To begin, a Mill Test Report (MTR) in the world of sanitary process is a quality assurance document that records the chemical and physical properties of the stainless steel (or other alloys) used in the fabrication of hygienic process components and equipment. MTRs go by a variety of names, including Certified Mill Test Report (CMTR), Mill Certification, or Metallurgical Test Report. When a heat (lot) of steel is generated at the mill, it is assayed. The results of that assay are recorded and an MTR is generated. Whether the lot of steel is then processed into plate used to manufacture vessels, strip used to make fittings and tubing, or larger shapes to be used in machining valves or pumps, that heat number and its accompanying MTR are tracked throughout the manufacturing process.
Finished products normally have the heat number (or numbers) stamped onto the outside surface to maintain the traceability of the part. This process is followed for all 316L stainless material and higher grade alloys. Normally the heat numbers of 304 stainless steel are not tracked. At Holland, it is our receiving and quality control groups’ responsibility to inspect and match received goods to their corresponding MTR to ensure that the components received meet the purchase specifications.
To begin understanding the information that an MTR provides, we need to start by understanding how material is labeled for identification. There are a variety of ways that material manufacturers can do this, but they all usually loop back to a Heat Number. When matching an MTR to its raw material, all accompanying paper work, and in most cases markings on the part itself, must match the heat number on the MTR.
So now that we know how to match a part with its MTR, what information does it provide other than the basic material type? First, the MTR provides the specific material grade of a material (316 or 316L). The MTR will also certify that parts meet appropriate ASTM and ASME specifications. Compliance with ASME guidelines is especially important when fabrication pressure vessels that are to receive an ASME stamp.
The MTR will also identify the dimensions of the raw material. For most fittings, this is the tube or bar stock thickness and width. While this information is important, the part that most stands out are the actual measured properties for the material. In order to comply with the material the cert says it is, these properties must fall within the range limits of that materials specification. The carbon, sulfur, chromium, and nickel contents of the material are all listed in this section. This detail is similar to what our x-ray fluorescence analyzer spits out when we zap a piece of steel that isn’t properly marked. Finally, the MTR is certified with the signature of a responsible employee of the foundry or mill producing the raw material.
At Holland, we maintain MTR records of virtually every piece of traceable material that we supply. If you need more help understanding what’s on your MTR, or even retrieving the MTRs from a component you purchased previously, contact a Holland Sales Engineer today.
At Holland, we’ve built our business around being flexible and catering to the exacting needs of the high purity process industries. We’ve been successful doing this by not only catering to our customer’s current requirements, but also anticipating their future needs. We’ve talked a lot on this blog about the dichotomy between stainless and single use processing equipment that is developing in the high purity process industry. Today we’re going to highlight a new capability we are now offering and how it can help solve common problems our single use customers have every day.
Due to recent customer demand, Holland is now offering pre-cut single use tubing made to our customer’s exact specifications. How can this benefit you? Let us explain.
Most coils of single use tubing these days come in lengths of either 25 or 50’. So what do you do if you use 10’ or 20’ lengths of tubing? Well, for many of our customers we found this meant they would have to order standard lengths, cut it to length in house, and then pitch the excess. This can lead to a lot of wasted time and material if you can only get a couple of pieces of tubing out of each coil.
To help address this need, Holland recently acquired and implemented into our quality program an Azco PC-25 automated tube cutter. Coupled with our on hand single use tubing inventory, we’ve been able to help customers reduce on hand inventory requirements, eliminate down time, and better mitigate the risk of process interruption. As a distributor for Saint Gobain, and with access to almost any other material you could ask for, we’re able to purchase your specific size and formulation in bulk and cut it to length as you request. We’re able to cut a variety materials, including platinum cured silicone, C Flex, Tygon, Pharmed, StaPure, and even PTFE tubing.
Taking this a step further, we found that many of our customers wanted their tubing to come kitted, or a single package with a variety of different lengths. By automating the tube cutting process, we’re able to offer this service as well. Again, by providing tubing cut to a variety of lengths and prepackaged as a kit with a single part number, we’re able to help our customers reduce inventory requirements and keep their operators doing what they do best- making high value product.
The next natural request our customers have is, “well can you just put the kit together for me and ship it to me complete?”. The answer to that is yes. While we’ve been offering custom single use tubing assemblies for several years now, with the addition of an automated tube cutter, we’ve been able to drastically increase throughput and minimize the cost passed along to our customers. The same engineering capabilities that have made us successful with our stainless customers allow us to customize assemblies for your specific needs and requirements. And our business relationships with almost every component supplier in the industry allows us to incorporate almost an endless combination of tubing and fittings to meet your exact specifications.
The linchpin of all these offerings is the robust quality system we’ve developed in our 60+ years catering specifically to the high purity process industry. We understand our customer’s unique needs and have skilled sales engineers that know what questions to ask upfront to prevent problems down the road. In accordance with standard operating procedures and written work instructions, we keep detailed documentation of each job and any maintenance performed on our equipment, including machines dedicated to single use components like our automated tube cutter and pneumatic assembly tools. As a critical component supplier to so many large pharmaceutical customers, we don’t have a choice but to continuously improve our quality systems to meet our customer’s increasingly high expectations.
So whether it’s 1500 pieces of one tubing length, or 10 assemblies, at Holland we are now equipped to help you with your precut tubing needs. We’re able you reduce inventory requirements and better manage your inventory. Whether its cut tubing lengths, kits, or even assemblies, Holland can help solve your single use challenge. Contact a Holland sales engineer today for more information.
We sell a lot of sanitary pumps and almost all of those pumps have some type of mechanical seal. We’ve talked a lot about seals on this blog in 2014. The mechanical seal in a sanitary pumps separates the “clean” process from the “dirty” outside world. Failure of the mechanical shaft seal is the most common cause of pump downtime. The shaft seal is exposed to a wide variety of conditions and it can be quite difficult to identify why a seal failed. This post will take a look at the most common costs of seal failure and readdress how we reduce the frequency of seal failure.
Running Dry/Lubrication Failures
The first cause of failure we’d like to highlight in this post is what we call “lubrication failures”. Proper functioning mechanical seals use hard seal materials that depend on lubrication provided by the fluid being pumped. Obviously, if you don’t have any fluid in the pump, that’s not good and your seal will fail. But dry running is not the only time seals can be insufficiently lubricated. At high temperatures or near a fluids vapor pressure, the fluid does not always act as a good lubricant. Lack of lubrication again will lead to friction and heat generation and ultimately seal failure.
The easiest fix for lubrication challenges is to use a mechanical seal with a flush. By using a flush fluid that is compatible with the product, seal life will greatly increase in these challenging applications. Seals are essential for high temperature or vacuum applications.
Another common problem that leads to seal failure is buildup of product on the mechanical seal faces. Sanitary pumps are subject to large swings in temperature, pressure, and velocity. These constantly changing conditions increase the risk of sedimentation in or near the sealing gaps between seal faces. This is a common problem when pumping fluids that tend to solidify quickly and scale on seal faces. As the deposits accumulate on the seal faces, the sealing gap opens further. The result is a leaking seal. This leaking can start slowly at first and increase with time. Accumulation of abrasive particles can also lead to seal face damage, making a bad situation worse. To combat this, exceptionally hard seal faces are recommended for these abrasive applications.
Again, the fix here is to use a mechanical seal with a flush. The flush fluid helps not only to lubricate the seal faces, but also keep them “clean” and prevent product from getting into the seal gap.
There are two primary sources for operator error that results in seal failure. The first is damage during seal removal or cleaning. Carbon, a common material for mechanical seals, is very brittle. Mishandling can easily chip seal faces which quickly leads to a problem. When servicing a pump, care should always be taken to ensure the seals are handled carefully and the seal faces are adequately cleaned.
The second source of operator error is also from improper cleaning. When a pump is taken off line, if it is not properly cleaned, product can solidify on the seals and essentially “lock” the seal faces together. When the pump is brought back online, the high motor starting torque can damage the stuck seals. It is critical to ensure the pump is cleaned properly and product is not left in the product zone. This means CIPing your Universal 2’s and pulling the rotors out and cleaning your Universal 1’s.
Chemical and Physical Degradation
This is the most obvious source of seal failure. If you are pumping an abrasive product, make sure you select compatible seal materials. As a seal wears, the originally smooth seal face becomes worn and pitted, resulting in leaks. And while much emphasis is placed on seal face material selection, it’s also important to ensure that the elastomers used are compatible as well. Swelling and failure of the elastomers can also compromise the seal chamber ,leading to failure. For more information about seal face or elastomer compatibility, refer to our previous posts on the topic.
The life span of a mechanical seal is directly affected by shaft movement. Vibration can cause carbon face chipping and seal face opening. Seal face opening can result in contaminants to penetrate between the seal faces causing premature wear. There are a host of causes for excessive vibration including, bent or warped shafts, pump and drive misalignment, worn or loose bearings and unbalanced rotating components.
To conclude, mechanical seal failure is often a combination of a variety of factors. The mechanical seal is a dynamic area of the pump that experiences both temperature and pressure swings. Running dry, operator error, and compatibility issues can all lead to premature seal failure. For help troubleshooting your pumps mechanical seal, contact a Holland Sales engineer today.
If you call Holland Applied Technologies to speak with a customer service representative and ask for a 316 stainless steel fitting, you’ll likely be asked “Do you require BPE compliant fittings?” Previous posts to our blog have spent some time talking about BPE fittings and other parts of the ASME BPE Standards, but it occurred to us that a lot of people don’t know what the ASME BPE is. This post will go into some more detail.
ASME BPE is an abbreviation for American Society of Mechanical Engineers – BioProcessing Equipment Standards.
The ASME BPE Standards Committee is a collection of the both manufacturers and end users that set out to develop a guideline to cover the design, materials, construction, inspection, and testing of BioProcessing equipment.
The BPE standards committee is broken down into a series of subcommittees that allow industry experts to collaborate and utilize their expertise to develop a comprehensive approach to all aspects of bioprocessing equipment the subcommittees are:
- General Requirements
- Systems Design
- Dimensions and tolerances for Process Components
- Material joining
- Process Contact Surface Finishes
- Sealing Components
- Polymeric and Other Nonmetallic Materials
- Metallic Materials
- Process instrumentation
As new types of technology come to market, additional subcommittees are developed to address them. Updated standards are published bi-annually. The most recent revision to the standard, published in 2014, covers new topics ranging from hygienic supports to weld discoloration acceptance criteria and dynamic seal performance.
The Standard developed by the ASME for bioprocessing equipment is the leading standard used to design and build equipment for the bioprocessing market. The Standard incorporates current best practices that help equipment manufacturers and end users alike, maximize product purity and safety. By developing a standard, the ASME has allowed companies to improve communication and become more efficient, which results in lower development and manufacturing costs.
To conclude, the question is not so much as to who is the BPE, but what is it. The ASME BPE is a standard developed by ASME members specifically for the bioprocessing market. Holland Applied Technology personnel actively participate in the BPE meetings. One of our engineers at Holland is a member of the Systems Design and Certification sub-committees. If you should ever have questions regarding ASME BPE compliant equipment please contact us at 800-800-8464 or our website www.hollandapt.com
Since we re-launched this blog, we’ve hit on most of the types of sanitary process equipment we deal with at Holland. One category of equipment we’ve overlooked, however, is sanitary strainers. Today’s post will take a look at sanitary perforated sheet and wedgewire strainers inserts and some of the advantages and disadvantages of each.
To begin, the most common type of sanitary filter insert used in the industry today is a perforated sheet type strainer with a wire mesh overscreen. Perforated inserts will commonly use 14 gauge sheet metal perforated with 60 degree staggered 1/8” or ¼” holes. The 60 degree stagger pattern is preferred because of its superior strength and large open area ratio, increasing filter capacity. Wire mesh linings are often used with the perforated sheets for finer filtration and take advantage of the reinforcement provided by this thick material perforated sheet material. Mesh screens are generally available in both stainless and cloth bag versions. The perforated type of insert is economical.
A common alternative to perforate filter inserts with mesh over screens are wedgewire inserts. Wedgewire inserts have a unique set of advantages that make them ideal for the high purity processing industry. A wedgewire insert is made by welding specially shaped wire to support rods, thereby creating a continuous slot. The wedged shaped profile of the wire allows for fine filtration. With hole sizes as small as 0.005”, filtration as fine as 100 mesh is possible with a wedgewire insert.
The two primary types of wedgewire insert construction are reverse formed and inverted wrap construction. Reversed formed wedgewire inserts feature external support rods which provide a smooth, unobstructed screen surface on the inside of the strainer. The alternative to reverse formed inserts are inverted wrap inserts. Utilizing internal support rods, inverted wrap elements are used as an alternative when the desired basket diameter is too small. The durable, welded construction, allows for a wedgewire insert to outperform and outlast perforated or woven mesh inserts in high pressure applications.
Wedgewire inserts have a few other advantages perforated inserts other than ease of use. The continuous hole spacing means that total percent open area is much higher in a wedgewire insert than with an equivalent woven mesh screen. This increases filter capacity and reduces pressure drop. This higher percentage of open surface area is also going to mean that these inserts are much more cleanable than traditional perforated tubes with mesh inserts. This is huge in a sanitary application where we need to validate or prove that we’re cleaning something.
One other very important advantage wedgewire inserts have over mesh type screens is increased product safety. Mesh screens can fatigue over time. This can result in individual wire pieces of the stainless steel screen breaking off and migrating downstream into the product. Using wedgewire inserts eliminates this risk.
Overall, we try to steer our customers towards wedgewire inserts. While they are priced at a premium to perforated inserts, the overall performance of wedgewire decreases total cost of ownership and makes these our “go to” in challenging filtration applications. In processes where we need to minimize pressure drop by maximizing percent open area and assure that we are going to be able to clean the system, the wedgewire is our go to. That’s not to say perforated and wire mesh inserts don’t have their place. For simple applications, such as pump protection, an inline perforated strainer will work just fine. If you have any additional questions about which insert type is right for you, contact a Holland Sales Engineer today.
Even at Holland, where we’re all sanitary process experts, occasionally we can get confused. One issue that came up recently is the difference between ITT Pure-Flo’s ZSBT and ZSBBT valve. We’re going to take this post to review the functionality of a zero static point of use diaphragm valve and clarify the difference between the ZSBT and ZSBBT zero static valve.
To begin, zero static use points are some of the most critical valves used in the biopharmaceutical industry. A point of use valve allows fluids to be transferred, sampled, drained, or diverted. Zero static valves help us comply with ASME BPE’s L/D dead leg requirements of 2:1. A dead leg is basically a one way water system. Dead legs result in process system that are difficult to clean. Stagnant fluid can also harbor process compromising bacteria.
While the FDA had historically required dead legs not to exceed 6 diameters of unused pipe, the BPE, finding this rule not sufficient to assure sterility, imposed even more stringent requirements. In 1997 the ASME addressed these problems by strongly suggesting (stopping just short of mandating) that the length of a dead leg shall not exceed two times the pipe diameter.
With these stringent requirements, you can see why putting a valve on the branch of a tee could be problematic. As a response to this requirement, the zero static point of use valve has been widely adopted throughout the pharmaceutical process industry. A zero static point of use valve incorporates the outlet valve weir into the main run. Fluid can then be drawn off the main line in a much “cleaner” fashion.
Several variations of the standard zero static diaphragm valve have also developed, including the zero static sample valve and zero static valve with downstream purge. These block body valves incorporate an integral valve onto the back of the valve assembly that provides access either to fluid upstream of the valve weir (Sample), or access to the process downstream of main valve weir (purge). These integral valve assemblies greatly reduce contact surfaces, hold up volume, and possible dead legs.
So now that we know what a zero static valve does, what is the difference between the ZSBT and ZSBBT valve? The answer is shockingly simple- not much. When ITT originally debuted the ZSBBT valve, they used a faceted body that helped in situations with tight space constraints.
Over time, the market started asking for a more economical zero static valve that could be used in applications without space concerns. To answer this, ITT debuted the ZSBT non-faceted zero static tee. This valve has a squared block body that requires fewer machining steps to make. All other critical dimensions are identical between the ZSBT and ZSBBT valves. All MOC’s and actuation options are the same as well. The only difference are the aesthetics.
So there you have it- the mystery of the ZSBT solved. So the next time you’re looking to replace a legacy ZSBBT valve and you get a quote for a ZSBT, rest assured you are getting a drop in replacement for your legacy valve. For any additional questions about your next sanitary diaphragm valve application, contact a Holland Sales Engineer today.