A wealth of industry standards exist to set specifications and thresholds for valves in various applications. For example, API Standard 527 sets the maximum acceptable leakage rates for pressure relief valves.

One area where no standards currently exist is for defining severe service valves. Severe service valves are commonly identified by the applications in which they are used — applications that may alter a valve’s ability to meet its acceptable levels of performance.

If you use a valve that isn’t strong enough to do the job in these applications, you will no doubt end up spending more time and money on repairs than you’d like to. You may also be putting your plant, equipment, and personnel at serious risk if the valve doesn’t function correctly.

Is severe service the same as critical service?

Though the two terms often go together, they aren’t exactly the same thing.

  • Severe service refers to the challenges levied on the valve itself, such as very high pressures and temperatures.
  • Critical service refers to the potential consequences of the valve not working properly. For example, nuclear service is a critical service application because a bad actor can lead to serious environmental damage or safety risks.

What are some severe service applications?

Whether or not valves are considered severe service depends on their application. Here are some examples of conditions that require severe service valves:

  • Very high pressure or high pressure drops
  • Very high or very low temperatures
  • Flashing gas, which can cause erosion damage
  • Outgassing, which can cause a sudden increase in flow volume
  • Corrosive environments
  • Contaminated media
  • High vibration

Here are a few examples of industries that make frequent use of severe service valves:

  • Power generation
  • Chemical, where corrosive media is common
  • Pulp and paper, where high pressure drops and corrosive environments are common

What type of valves are best for critical and severe service?

Critical and severe service valves need to be durable and require as little maintenance and repair as possible. They also need to perform to incredibly high standards, such as zero leakage and abrasion resistance.

Metal-seated ball valves are ideal for these conditions because they are less susceptible to damage than soft-seated ball valves. Greg Johnson, former Valve Repair Council chairman, wrote last fall in VALVE Magazine,

“The key to metal-seated ball valve success is two-fold: 1) precision lapping techniques for precisely mating the ball with its seats, and 2) the development of ultra-hard and abrasion-resistant ball and seat coatings. These two areas of design advancement enabled the ball valve to perform feats of closure not successfully attained before. The success allowed the metal-seated ball valve to become the severe service valve of choice for many applications.” [emphasis added]

Allied Valve is a proud supplier of PBV Severe Service Ball Valves, which are metal-seated ball valves engineered for zero-leakage critical isolation applications. Contact us so we can help you select the right valve for your application.

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