Valve Sizing: What Are Security Factors?

When sizing a valve for an application, you may have heard engineers discuss safety aspects. What is a security factor, and why is it essential to have it factored into the valve’s size?

A security aspect is basically a procedure of security against a modification in process conditions. It guarantees that the valve will still operate as needed, even if the procedure conditions alter and are outside the parameters originally created for the valve. The safety aspect frequently oversizes the valve. A valve that is oversized is even more manageable and much safer than a valve that has been undersized.

Safety aspects are applied as an engineer reviews the following requirements:

Streaming Conditions

Normally valves are sized anywhere from 60-80% of valve open. Should stream surpass this, additional capability will be available in the upper circulation variety. Not having a safety factor here will limit flow through the valve, causing a greater pressure drop, possibly starving the downstream equipment of the flow and pressure needed.

dsi-forged-steel-globe-valve.jpg Pressure and Temperature Scores Pay cautious attention that the pressure– temperature rankings of a specific valve are well within the requirements of the service. This also uses to the packing and gasket materials as this may restrict the score of the valves.

Valves are ranked for pressures, i.e. class # 150, # 300, # 600 and so on. When sizing a valve for pressures you also need to take the temperature level of the process as a factor. Water on a class # 150 carbon steel valve at 100 ° F service temperature level is rated for up to 285 PSIG operating pressure. A class # 150 carbon steel valve at 1000 ° F is only rated to 20 PSIG. This is the ranking on the body just not the rest of the valve products like the packing and seats. Those likewise need to be taken a look at.

Different products of building provide different pressure and temperature level limitations. Though we only spoke here of high temperature levels, it’s simply as crucial to think about lower temperatures. Basic carbon steel is only ranked to -20 ° F and would require different materials listed below -20 ° F.

Process Media

Water is quite direct. Unique procedure media like a syltherm or Dow therm require unique attention to not only the body product, however also the kind of end connections for procedure sealing of the piping. Some users prefer using # 300 flanged connections on a class # 150 pipeline line because they can make tighter connections. PTFE would be problem for syltherm at -50 ⁰ F as it can break the PTFE and trigger leaking. This would be true for both seats and seals.

Need assistance sizing or selecting a valve? Ask us about it! We happily provide technical support to services and municipalitites throughout the continental United States.

Source

https://blog.craneengineering.net/valve-sizing-what-are-safety-factors