Bidirectionality in Isolation Valves

There are many types of valves used to isolate process flow. Each valve type has its own ability when it is fully closed and in isolation mode. The degree of tightness varies with valve type, make, media, differential pressure, temperature, and time in service. Some valve types or special preparations have unequal isolating abilities depending on the flow direction while isolating.

Understanding how valves isolate, especially with challenging applications, can help one choose the appropriate valve technology. All isolation valves are bidirectional, that is, they can seal from either flow direction. However, bidirectionality can add some isolation wrinkles and thus needs further explanation.

Many valves cannot isolate equally from either direction. Think of a car; it can go backward and forwards, just not equally well. Isolation ability, the ‘tightness’ of the closure, is a misunderstood subject in the valve industry. It has been made more complicated due to the valve’s ability to handle bidirectional flow at…

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Allowable Leakage vs. Zero Leakage vs. Bubble Tight

Valve leakage is one of the main issues in industrial processes. Different valve leakage standards are specified by different organizations. Valves go through pressure tests which determine if they provide allowable leakage, zero leakage, or are bubble tight. Allowable leakage: Some valves have an allowable leakage rate. These rates differ depending on what organization sets them. Common organizations for allowable

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Class 150 Does Not Equal 150 psig

Pressure-Temperature Ratings for Valves When it comes to valves, there are guidelines in place to protect workers and the environment from valve failures and leakage. In this example, we are talking about how much operating pressure a valve can withstand at a specific temperature. This is known as a Pressure-Temperature Rating. Based on the material(s) of construction, the Pressure-Temperature ratings

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