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The Effect of Slip on Sanitary Pump Performance

August 26, 2014

This post will touch on a topic we’ve discussed a few times in the past- the low slip design the Waukesha Universal series of sanitary positive displacement pumps. Previous posts have talked about how the external circumferential piston design of the Waukesha Universal series makes it nearly perfectly positive and efficient at viscosities over about 250 cps, but why is this important? Outside of efficiency, the low slip design of the Universal series pump allows us to accomplish four useful things- it allows us to pump low viscosity fluids in low NIPA systems, it allows us to pump from vacuum vessels, self-prime, and meter fluids. This post will look at each of these four benefits and why they are important to system performance.

Waukesha Univeral Pumps can be Run at Slow Speeds, Minimizing Shear

Waukesha’s Unique ECP Rotor is More Efficient than Lobe or Bi-wing Designs, Resulting in Less Slip

To begin, the low slip design of the Waukesha Universal series of pumps allows us to efficiently pump low viscosity fluids when net inlet pressure available (NIPA) is also low. When pumping low viscosity fluids in low NIPA systems, slip can greatly reduce pump capacity and increase energy requirements. At low pump speeds this generally isn’t an issue, but if pressure differential across the pump causes excessive slip, little or no flow may result. At higher speeds, internal pump losses may be high enough to limit flow. In a high slip, low efficiency pump design, high velocities of fluids within the chamber can create localized areas of low pressure. If this pressure drops below the vapor pressure of the fluid being pumped, flashing can occur and vapor will fill the pump cavities, destroying the ability to sustain uniform flow.

The next thing the low slip design of Waukesha pumps allows us to do is pump out of a vacuum vessel. Pumping from a vacuum vessel is an example of an extremely low inlet pressure system. Vacuum chambers are typically used to evaporate fluids to hold and process liquids at extremely low temperature. This means we’re going to be operating at or near the fluids vapor pressure in these applications. Because of this, we need to use a pump that is as efficient as possible to allow us to run the pump as slowly as possible. High speeds will create an area of low pressure at the inlet of the pump which can lead to flashing and cavitation, crushing system efficiency and greatly reducing pump life.

As we’ve talked about in previous posts, the clearances in Waukesha pumps are so tight that at higher speeds the pump can even move air. What that means is that the pump can be used to dry prime or actually evacuate the air in the inlet line, reducing pressure, and drawing fluid up the line and into the pump chamber where normal pumping can begin. While not suggested, Waukesha PD pumps can run dry long enough to draw fluid into the pump chamber and begin standard processing. Care should always be taken to ensure the maximum available pressure at the inlet of the pump. Contact a Holland sales engineer for help determining the amount of lift your Waukesha pump can generate.

A low slip Waukesha pump can also be used to meter fluids. If the slip is low, a pump will deliver nearly its theoretical displacement in each revolution. By counting or controlling the revolutions per minute of the pump, we can measure the amount of liquid displaced. In any metering application, it’s important to operate in the metering range of the pump- i.e. the range at which the relationship between change in speed and displacement is linear. System conditions should also be kept constant. We want to maintain constant suction head and minimize the pressure differential across the pump. By coupling this with the efficient design of a Waukesha Universal pump, we can reduce the effect of slip and meter effectively.

To conclude, the low slip design of Waukesha Sanitary PD pumps has further reaching implications than just increasing system efficiency. The low slip design of the Waukesha Universal series of pumps allows us to pump low viscosity fluids with low inlet pressures, it allows us to pump out of vacuum vessels, it allows us to dry prime, and it allows us to meter. If you have more questions about your next Waukesha pump application, contact a Holland Sales Engineer today.

What is a Sanitary Surface Finish?

August 13, 2014

This blog was created to answer common questions about sanitary and high purity process equipment. One question we ask customers every day is, “What surface finish do you require?”. Many of our customers know what they use or what they need, but few understand what an Ra, grit, or micron rating means in terms of surface finish. Not knowing what you need can lead to unnecessarily expensive fittings with extended lead times. This post will focus on what a sanitary surface finish is and specifically the relationship between Ra, micron, and grit.

A profilometer is an instrument that measures the actual metal surface by dragging a stylus across the metal a predetermined length, measuring the distance between the peaks and valleys of the surface.

A profilometer is an instrument that measures the actual metal surface by dragging a stylus across the metal a predetermined length, measuring the distance between the peaks and valleys of the surface.

To begin, when we say “surface finish” what we really mean is surface “roughness”. Surface roughness is a component of a surfaces overall texture. The most common measure of this roughness is a measurement known as the arithmetic roughness mean, or Ra. The Ra value of a surface reflects the average height or irregularities on a surface from a mean line. Think of this as the measurement of the heights of peaks and valleys along a line. The lower the Ra, the smoother the surface.  These values can be measured using a profilometer.  It moved a stylus across the surface of the metal and records the differences between the peaks and valleys.

Most commonly measured in microninches, Ra provides a simple value for us to make accept/reject decisions. We measure the Ra of a sanitary surface with a profilometer. Traditional profilometers use a diamond stylus that is moved along a surface for a specified distance with a specified contact force. This allows the profilometer to measure small surface variations across the sample.

A corollary to the micro inch is the micron. One micron is equivalent to about 39.37 micro inches. Ra values in both micron and micro inch are interchangeable as they both reflect the arithmetic mean of the average centerline deviations of a surface.

One thing that is not necessarily equivalent to Ra? Grit. Grit is a measure of abrasive grains per given area. The specification of a grit reference does not necessarily equate to a consistent surface finish. A specific grit is used by a mechanical polisher to achieve a desired Ra. In order to achieve that finish, the right tool needs to be chosen and utilized properly. Selecting and using the right tool is much more an art than a science and is a skill that takes years of practice to acquire- that’s why Johnny Polish gets paid the big bucks.

So why is surface finish important? Smooth, crevice and pit free surfaces, i.e. ones with low Ra readings, are essential to ensure there are not entrapment areas where product can build up and grow nasty things. Entrapment areas can be difficult to clean, allowing bacteria to accumulate. This is obviously undesirable in high purity applications.

Historically, 32 Ra has been the standard sanitary surface finish for the high purity industry. With the advent of stricter regulation of the pharmaceutical and biologics markets, and subsequently process components, increasingly smoother surfaces are being required. Now, process equipment used in a pharmaceutical application will generally need to comply with ASME BPE standards that dictate a maximum surface roughness of 20 Ra or better, depending on the application.

Standard Grit (Reference Only) Ra (uin) Ra (um) Common Name
60 985 6.3 Mill Finish
180 32 0.8 Sanitary Finish
220 20 0.51 Pharma/Biotec Finish
320 10 0.25 Ultra High Purity

Hopefully this post serves as a good refresh on what a sanitary surface finish is. If you don’t want to read all of my typos, check out the table below for an overview or contact a Holland Sales Engineer today about any of your sanitary process component questions.

How to Size a PD Pump for a Range of Viscosities

August 7, 2014
Waukesha Universal 2 Pump Side Mounted on a Stainless Steel Frame, with Motor, Gear Reducer and a Variable Frequency Drive

Waukesha Universal 2 Pump Side Mounted on a Stainless Steel Frame, with Motor, Gear Reducer and a Variable Frequency Drive

At Holland, we size pumps for sanitary applications every day. We also work with many customers who are having issues with pumps someone else sized for them. This experience has made us well aware of many common oversights made when selecting a rotary positive displacement pump. One of the most common errors made when sizing an ECP pump, such as the Waukesha Universal 1 or Universal 2 series pump, is failing to take into consideration the range of product viscosities the pump will handle. This post will focus on that issue and what steps we can take to ensure adequate drive speed range is selected to handle a variety of products.

To begin, a sanitary process system may require that the same pump handle both viscous and thin products. A simple example could be a shampoo process- imagine a facility wants to transfer shampoo from one tank to another and then follow the transfer with a system water flush. An excellent pump for this application is the Waukesha External Circumferential Piston pump. The Universal 1 and Universal 2 pump, utilizing Waukesha Alloy 88 rotors, have long slip paths compared to other PD pump types, allowing them to handle both thick and thin fluids. Initial pump selection, however, must consider the RPM required for both thick and thin products.

Why do we need to consider both products? As products become thinner, or less viscous, the fluid tends to “slip” back through the pump. While the U1 and U2 series pumps are nearly perfectly efficient with fluids over 300 cps, some “slip” does occur with thin fluids. This “slip” must be compensated for with additional motor RPM. Optional pump features, such as front face or hot clearance rotors and CIP features only exacerbate this problem. Other challenges, such as high pressure conditions that also increase slip should also be considered.

Additionally, pump condition and wear should be considered as well. The tolerances on brand new pumps tend to be much tighter than used pumps. This wear opens clearances and increases slip, decreasing displacement capacity. We will need to increase pump speed to compensate for this.

To avoid these issues, it is critical to ensure we are able provide enough speed for the low viscosity product and enough torque for the high viscosity products. PD pumps are driven by motors coupled to gear reduction units. A gear motor uses a series of gears to increase torque, resulting in decreased shaft speed. We want to avoid using a drive that is “maxed” out when running the thick product and can’t spin fast enough to move our thin product. If we don’t have a large enough gear reduction, however, we will be unable to generate the torque to move the high viscosity product.

So how do we solve this problem? It’s actually not that difficult. First, we size a pump and motor that will spin faster enough to move the high slip product. Then we check that the torque the higher speed motor can generate against the torque required to move the high viscosity product. Finally, we’ll utilize a variable frequency drive and a motor with at least 10:1 constant torque turndown (we need to avoid motor slip as well), which will allow us to effectively adjust speed of the pump to handle the complete range of product viscosities and displacement requirements. Finally, an over speed safety factor will should be considered to compensate for pump wear over time.

To recap, when sizing a sanitary pump for multiple products, it is critical to take into account the viscosities of all products the pump will hand. At Holland, we use our over 60 years of experience sizing sanitary pumps to dictate how much speed compensation is required for a given set of conditions. For help with your next sanitary pump application, contact a Holland Sales Engineer today.

Waukesha Single Seat Valves- An Overview of an Industry Leader

August 6, 2014
Picture of a Waukesha W60 Series Valve Manifold We Fabricated in our Shop

A Waukesha W60 Series Valve Manifold We Fabricated in our Shop

Throughout the past 10 months, we’ve dedicated many posts and countless hours to conveying the advantages the Waukesha Universal series of positive displacement pumps have over other brands in the hygienic market. Today’s post will focus on another best in class product offered by Waukesha Cherry Burrell- the W60/80 line of seat valves and 5 specific benefits they offer over the competition.

First and foremost, all Waukesha valves are designed specifically for the sanitary and high purity market. Waukesha valves are cleanable, featuring 316L wetted parts, minimal cracks and crevices, free draining in multiple positions are 3A and FDA compliant, as well as EHDGE tested. They have options for surface finish upgrades (all the way to 15 Ra w/ EP), as well as a variety of stem seals and seat options to allow for optimal performance in applications with particulate that can challenge valve cleaning. MTRs are also an available option.

The next staple of Waukesha seat valves are heavy duty construction. All bodies are machined from bar with thick walls and laser welded ports. Valve stems are ¾” of an inch and feature multiple bearing support. This rugged design allows Waukesha valves to perform at pressures up to 1220 psi through the use of heavy duty clamps and high pressure adapters.

Waukesha valves are also flexible and have a modular design. The WCB valve line offers a variety of body and port orientations to match up with sometime complicated piping designs. Bodies are usually one piece or two piece clamped. The standard body MOC is 316L, but AL6XN is all available for application with extremely corrosive products. Custom port lengths and center to center bodies are also available to allow drop in replacement of legacy series valves such as Tri-Clover and Sudmo valves.

Continually, the major valve components- the body, stem, adapter, and actuators- are modular in design and all for quick and easy assembly and maintenance. There are a variety of actuators compatible with all Waukesha W60 valves, ranging from fully maintainable to maintenance free actuators. A complete line of control tops is offered as well, including the low cost APV CU4 and the industry leading Burkert 8681- see one of our previous post for more information relating to the Waukesha control top offerings.

All of these benefits- hygienic design, robust construction, and modularity and flexibility- endow all Waukesha seat valve with an exceptionally low total cost of ownership. Their heavy duty design maximizes service life. Waukesha’s extensive distribution network allows for regular preventive maintenance and immediate end user support, while part commonality reduces stocking requirements. The valves modular design results in several multi-use parts and easy training for new operators, again minimizing spare part stocking requirements.

Finally, all Waukesha seat valves are manufactured and supported domestically. Waukesha seat valves are made in Delevan, Wisconsin. They’re so close to us at Holland Applied that we pick up our orders at the factory twice a week. This proximity has allowed Holland and SPX to build a value-added distributor relationship through face-to-face representation and training. At Holland, we are able turn around most spare parts orders in 24-48 hours as well as perform on-site repairs and maintenance. This cohesive relationship between manufacturer and distributor goes a long way to minimizing total cost of ownership for the end user.

So for your next seat valve application, we strongly encourage you to consider Waukesha. At Holland, we can work with you to identify and size the right valve technology and specifications for your application- we do this every day. Contact a Holland Sales Engineer today for more information.

What do the Physical Properties of Single Use Tubing Mean?

July 31, 2014
Sani-Tech Ultra Silicone Tubing

Sani-Tech Ultra Silicone Tubing

One thing that is on the marketing literature for every bioprocessing tubing on the market are the typical physical properties of the product. These are things like durometer, tensile strength, ultimate elongation, tear resistance, specific gravity, and tensile modulus. While these properties fill space on a piece of literature, it’s important that we understand what they each mean. This blog post is the first in a series that will try to give a concise overview of the properties relevant properties for single use tubing and connectors.

To begin, let’s take a look at Saint Gobain’s latest generation of platinum cured silicone tubing- SaniTech Ultra. On Saint Gobain’s marketing brochure, they list the following properties:

  • Durometer Hardness Shore A, 15 Sec
  • Tensile Strength, psi
  • Ultimate Elongation
  • Tear Resistance (kN/m)
  • Specific Gravity
  • Tensile Modulus

Along with these properties, they also list sterilization methods, which have been a focus of previous posts and we will continue to address in the future. Let’s take a look at each of the aforementioned properties one by one:

Durometer

The first property is durometer. Durometer is the measurement of the hardness of a material. This is usually tested via the standard defined in ASTM D2240. Durometer is based on the resistance to penetration of a specific indenter into the material under controlled conditions. It is reported on using the shore scale, with Shore A hardness typical for silicone and other thermoplastic elastomers. This property is tested on a lot release basis. Lot release is a representative sampling from a lot of tubing that is tested as a requirement for product release.

Tensile Strength

Tensile strength is the measure of the force (stress) required to stretch a material to its breaking point. Tensile strength is usually tested in accordance with ASTM Method D412 and a lot release basis. Tensile strength testing is performed by placing the tubing into a device known as a tensiometer and stretching to its breaking point. The load required to do this, measured in psi or MPa, is the tubing’s tensile strength.

Ultimate Elongation

Ultimate elongation is the elongation at the moment the tubing breaks during tensile strength testing. This indicates how far tubing can be stretched prior to breaking. Results are determined by comparing the distance tubing was stretched at the time of break to its original state and reported as a percentage.

Tear Resistance

Tear resistance, or tear strength, measures the resistance to propagation of a rip or tear once the rip has been initiated. Measure in accordance to ASTM D624, tear resistance testing is usually done on a qualification basis during design or process qualification. ASTM D624 outlines a procedure where a tear is made in the tubing and a controlled force is used to pull the tubing apart.

Specific Gravity

This one is pretty simple. Specific gravity is a products density relative to water. But while the concept is simple, you may be wondering why it’s important for silicone tubing. Well, changes in density can reflect absorption and other physical changes in the tubing after processing. This is important when considering extractables and leachables.

Tensile Modulus

Also known as Young’s modulus, the tensile modulus describes the tendency of an object to deform along an axis when opposing forces are applied. It is the ratio of tensile strength to tensile strain or the stress at a given strain. In more simplified terms, this is a measure of rigidity. Tensile modulus should not be confused with strength, stiffness, or hardness. Because the tensile modulus is a measure of force per unit area, it has pressure units, like PSI or MPa

So there you go- more excruciating details than you’d ever want to know about a piece of silicone. It’s probably not critical that everyone understands exactly how each of these are tested, but it is important that you have a general idea of what each means, especially when you are comparing two different materials. For more information about elastomeric properties, contact a Holland Sales Engineer today.

Good Sanitary Pump Piping Practice- things to keep in mind for you next install

July 29, 2014
Waukesha U2 Pump with Water Jacket Mounted on a Skid.  Note the Extended Length of Straight Piping on the Inlet Side of the Pump

Waukesha U2 Pump with Water Jacket Mounted on a Skid. Note the Extended Length of Straight Piping on the Inlet Side of the Pump

One thing people will often lose sight of when going through the process of specifying a pump for a sanitary application is what to do after they get the pump on site. The reality is that there are several good piping practices that should be kept in mind when designing your next system that will help maximize pump service life and return on investment. This post will focus on good sanitary pump piping practices and things you should keep in mind for your next sanitary PD pump install.

Straight Lengths

When installing a sanitary pump, it is of the utmost importance to allow 4-6 tube diameters of straight inlet tubing into the pump. This continuous length of inlet allows for laminar flow to develop into the pump. By preventing choppy, turbulent flow- which greatly increases air entrainment in product- we reduce the risk of pump cavitation. As we’ve discussed in the past, cavitation is a killer of pump efficiency in both sanitary centrifugal and PD pump applications. We have similar recommendations for flow meters- just remember, the smoother the flow, the less transition, the better the performance.

Support

Here’s an obvious one we’ve touched on in previous posts- piping support. When sanitary tubing is full of fluid it can be pretty heavy. Ten feet of 3” sanitary tube can hold about 4 gallons of fluid. Based on water, that’s about 33 pounds. That’s a lot of weight to hang off the end of the pump. It’s important that we distribute this weight and strain independently of the pump through the use of hangers or other supports. The use of hangers will also come in handy for some of our other tips as well. All of this weight can cause misalignment of the motor and pump shafts. This can lead to shaft deflection and catastrophic pump failure. Excess strain can also compromise system seals, allow air into the process.

Slope

Piping slope is important in a sanitary system for a few reasons. The first is to help systems drain when we run a cleaning cycle. The second is to prevent air pockets in the suction line. Again, mixing of fluid and air can lead to pump cavitation and a loss of efficiency. For this reason, while horizontal lengths are acceptable, it’s important to minimize line high points where air can accumulate and to slope piping upward toward the inlet of the pump.

Strainers and Traps

Strainers and traps not only protect the product, they also protect the pump. Inlet side strainers and traps can be used to prevent pump damage from foreign matter. When specifying a mag trap or strainer for the pump inlet, be cautious- clogging or restricting the pump inlet can cause cavitation and flow stoppage.

Pressure Gauges

As we’ve talked about in previous posts inlet and discharge gauges are helpful in identifying and diagnosing pump problems. Gauges are the easiest way to identify changes in pump, product, or system condition. See our post in pump pressure gauges for more on this.

Valves

There are three primary types of valves we like to see in a good pump set up- check or foot valves on the inlet side to maintain a liquid leg in the suction side of the pump, isolation valves, and relief valves. Check valves help us to keep the pump primed and prevent backflow. Isolation valves allow us to maintain and safely remove the pump from the system without emptying the entire line. And relief valves, as we have also discussed previously, protect the pump and piping system again excessive pressure.

To conclude, successful sanitary pump application in multifaceted. It starts with identifying the best technology for your specific application. Then we need to properly size and select a motor and drive. Once we get the pump on the base, also a challenge, we need to make sure we install it in a manner that provides system feedback and enables long life. If you have questions about any of these pumping challenges, contact a Holland Sales Engineer today.

Colder AseptiQuick Connectors- What Options are Available Today for Aseptic Connections?

July 24, 2014
The Aseptiquik G Genderless Sterile Connector

The Aseptiquik G Genderless Sterile Connector

Throughout this blog, we’ve highlighted and hit on the corners of every niche in the high purity market. As we’ve hopefully shown, today’s market demand for new, safer, more effective, and cheaper drugs is continually driving process engineers to innovate and develop new ways to make process more flexible, reliable, and robust.

One of the groups pushing the boundaries of conventional high purity processing the furthest are the single-use equipment providers. Innovative single use technologies provide engineers greater flexibility by replacing conventional hard piped systems. The benefits of single-use technologies have been discussed in several of our previous posts. Today’s product-centric post will focus on the Aseptiquik family of sterile connectors and what product offerings are available.

To begin, let’s take a look at the connector that started it all- the original Aseptiquick connector. This gendered fitting creates a sterile flow path through an intuitive three step “click-pull-twist” design. The Aseptiquik’s robust design (including integral lock ring) provides reliable performance and eliminates the need for tube welders or bulky pre-manufactured assemblies. The Aseptiquick connector is made from USP Class VI ADCF Polycarbonate (w/ class VI silicone O Ring) and can be both gamma irradiated (50 kGy) and autoclaved (130 C for 30 minutes). The Aseptiquik connector is available with 3/8” and  ½” barbed terminations as well as 3/4” sanitary TC ends.

Now you may be thinking, “Well, what if my flow path is smaller or larger than ½” or 3/8 and I really don’t like having to match up male and female connectors? Then what do I do?”. Those are the challenges the next three products in the Aseptiquick line will address.

So what if you need to make a sterile connection on your thick walled, ¾” tubing that won’t fit in your tubing welder? Well, then you go with the Aseptiquik X brand of sterile connectors. Available in ¾” and 1” hose barb, as well as 1.5” tri clamp flanges, the Aseptiquik X is ideal for high flow applications. Featuring a “Twist-pull-twist” design, the Aseptiquik X’s integral lock rings allow it for use in applications with up to 60 PSI of process pressure. Again featuring similar MOC’s as the Aseptiquik and Aseptiquik S products, the Aseptiquik X can be both autoclaved and gamma irradiated.

So how do you take the best family of sterile connectors on the market and make it even better? You make it genderless. Rounding out the Aseptiquik product line is the Aseptiquik G line of sterile connectors. Available in ¼”-3/4” barbed and ¾” sanitary terminations, the Aseptiquik G simplifies use by eliminating the need to pair gendered parts. This means the guy selling you your single use bioreactor does not need to coordinate with the guy selling you your single use filling assembly to make sure they are supplying the right gender fitting. This also means fewer components that you need to stock in house. The simple “flip-click-pull” design is quickly making a name for itself as an industry leader, offering a full range of flow solutions with the same quality and market availability the Colder name has become synonymous with.

And finally, what do you do if you need to make a sterile connection outside of a laminar flow hood with a line size smaller than three eighths? Well, you could buy a $20,000 tube welder, which doesn’t always work great on those small fluid paths, or you could use the Aseptiquik S connector. Designed for 1/8”, ¼”, and 3/8” flow paths, the Aseptiquik S is a genderless sterile connector designed specifically for small line applications. Featuring an intuitive “flip-click-pull” design, the Aseptiquik S expands on the proven advantages of the standard Aseptiquik. Available with both barb, sanitary clamp, and MPC terminations, the Aseptiquik S is made from the same materials as the standard Aseptiquik connectors enabling the same robust process performance.

To conclude, there are many ways by which drug manufacturers can create a sterile connection. The right selection depends on the needs and preferences of each facility. Colder has created a robust product portfolio to help address the need for intuitive, simple, and cost effective sterile connections. For more information about Colder’s Aseptiquik product family, contact a Holland Sales Engineer today.

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