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Swagelok Pittsburgh | Tri-State Area - Western & Central PA, OH, WV, and MD

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STAMPED Valve Selection Parameters with Swagelok® Sales Engineer Bob Sarber

Swagelok Pittsburgh | Tri-State Area - Western & Central PA, OH, WV, and MD About Us Blog STAMPED Valve Selection Parameters with Swagelok® Sales Engineer Bob Sarber
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Here's a modified excerpt from the recent Swagelok® Valve Selection Best Practices Webinar with Sales Engineer Bob Sarber. You can watch that webinar in its entirety on YouTube. 

Valve selection is a critical part of safely designing and maintaining any fluid system. When considering which valve will perform optimally at your facility or job site, Swagelok recommends using a STAMPED methodology:

  • S - Size

  • T - Temperature

  • A - Application

  • M - Media

  • P - Pressure

  • E - End Connections

  • D - Delivery

Understanding the STAMPED Methodology for Valve Selection

Here's how we define each parameter of STAMPED:

Size

Valve size is essential in the valve selection process because valve size directly correlates to maximum flow capacity, otherwise known as its flow coefficient or CV. The CV indicates the number of US gallons per minute that will flow through a valve with a one psi pressure drop at 60°F. In other words, the flow coefficient of a valve is a relative measure of its efficiency at allowing flow. 

As an example, a ball valve will generally have a larger flow capacity than a needle valve because the ball valve has a larger orifice for the media to pass through, as this graphic illustrates:


Both valves contain half-inch tube connections, but their flow coefficients are different because of their orifices. The ball valve on the left provides minimal resistance to flow, so it has a CV of 7.5. The needle valve on the right has a flow path that restricts flow, so it has a CV of only 2.1. 

For more information on valve sizes, download the Swagelok valve sizing bulletin. 

Temperature

Every valve has a maximum and minimum operating temperature, and these temperatures are directly influenced by both the media's operating temperature and the environmental ambient temperatures in which the valve is operating. 

These temperatures directly influence valve durability. When temperatures rise, the strength of the valve materials decreases, which then lowers the valve's pressure rating. If a valve experiences extreme temperature fluctuations, it may require early or frequent maintenance.

Application

Important questions to consider include:

  • Do I need to start and stop flow quickly? If so, you may want to start by looking at ball valves.

  • Do I need to control the direction of flow? If so, you may want to start by looking at check valves. 

  • Do I need to regulate flow levels? If so, you may want to start by looking at bellows-sealed valves.

  • Do I need to protect my fluid system from overpressure? If so, you may want to start by looking at relief valves. 

Media

System media is another important consideration for valve selection. Media can be anything from inert gases like nitrogen or argon to corrosive media such as hydrogen sulfide.

When selecting a valve, consider the opportunities for potential leakage. For instance, a metal-to-metal diaphragm seal may be more appropriate for corrosive gases than a soft-seated valve with a plastic or elastomeric stem pack.

Chemical compatibility is another important consideration. For example, embrittlement or stress corrosion cracking can occur depending on the raw materials chosen for your media. There are a number of chemical compatibility charts available on the internet that can help you select chemically compatible components. You can find excellent charts from DuPont and Cole-Parmer. 

Pressure

When considering pressure in valve selection, be mindful of two different types of pressure:

  • System maximum pressure - The maximum pressure the valve could encounter.

  • System operating pressure - The normal operating conditions the valve should encounter.  

The higher the pressures, the more durable your valve materials must be. 

We should also consider the pressure differential or ΔP. ΔP is the difference between the upstream and downstream pressures across the valve. The higher the pressure differential, the greater the wear on internal valve components. 

We should also consider the temperatures the valve will be exposed to (as discussed above) because changes in temperature often lead to changes in pressure.

End Connections

Pay close attention to your valve end connections as they determine whether the valve can properly connect to your fluid system while ensuring reliable, leak-tight performance. 

Delivery

"Delivery" refers to your valve manufacturer and supplier's ability to meet the needs of your company and job site or facility. Important considerations include:

  • Does my valve manufacturer/supplier consistently deliver the correct valves?

  • Does my valve manufacturer/supplier consistently deliver my valves on time? 

  • Does my valve manufacturer/supplier have the ability to work with me to assess my valve needs? 

  • Does my valve manufacturer/supplier have the ability to develop solutions for my operational goals?

To see how your peers have reviewed the past performance of Swagelok Pittsburgh | Tri-State Area's performance, see the results of our Global Survey. 

Additional Valve Selection Support

For more assistance in valve safety and selection, contact Sales Engineer Bob Sarber at Robert.Sarber@swagelok.com.