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…

Butterfly Valves 101

A basic introduction to Butterfly Valves Butterfly Valves get their name from the Butterfly appearance of the disc and stem. The design consists of a round disc that is attached to a shaft rotating 90°. When the disc rotates to be parallel with the flow, the valve is fully open. To close the valve, the …

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What is a Guided Shear Gate Valve and why is it a Severe Service Knife Gate Valve?

All valves perform a duty. Their ability to perform varies by valve type and internal design features and materials. In addition, knowledge and experience play a significant part in any successful installation. Accurate descriptions and consistent communication regarding the specifications of the valve required, and the attributes of the application it needs to perform within, …

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Six factors to consider when buying a Severe Service Valve

The term Severe Service Valve (SSV) is commonplace to the industrial valve industry. The problem is no one really knows exactly what it means. CGIS is in the process of establishing the exact definition. Once in place and approved by the Manufacturers Standardization Society of the Valve and Fittings Industry (MSS for short), there will …

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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 …

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The Building Blocks of Severe Service Valves (SSVs)

Most of us know when an application is severe. But what is it that makes it severe for a valve? Defining Severe Service Valves (SSVs) objectively is an important tool in attaining improved process control, safety, profitability, and environmental stewardship. SSVs can be defined as industrial valves specifically designed to perform in the most extreme …

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Defining Severe Service Valves

There is no clear or universal industry definition or mechanism to describe and accurately define severe service valves (SSVs) and separate them from general purpose valves. Yet, such a definition would allow the industry to benefit from improved process performance, increased profitability, safety, and environmental protection. Most experts agree that SSVs are identified by applications, …

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