ANSI FCI 70-2 [PDF] CONTROL VALVE SEAT LEAKAGE

ANSI/FCI 70.2, also known as “Control Valve Seat Leakage,” is a standard published by the American National Standards Institute (ANSI) in collaboration with the Flow Control Institute (FCI). This standard establishes a classification system for evaluating the seat leakage of control valves.

Control Valve Seat Leakage as per ANSI FCI 70-2

Control valves play a crucial role in various industries, including oil and gas, power generation, chemical processing, and more. They are used to regulate the flow of fluids within a system to achieve desired process conditions. Control valve seat leakage refers to the amount of fluid that escapes through the closed valve seat when it’s subjected to a specific pressure differential.

The ANSI/FCI 70.2 standard provides a framework for classifying control valve seat leakage into different levels, ranging from Class I to Class VI. Each class defines the allowable amount of leakage based on specific test conditions. The classification system helps in specifying and selecting control valves based on their ability to contain fluid when in the closed position.

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The different classes of seat leakage are as follows:

1. Class I: This class allows minimal leakage and is suitable for applications where a small amount of leakage is acceptable.
2. Class II: With slightly higher allowable leakage than Class I, Class II is applicable in cases where a bit more leakage is permissible, but still within controlled limits.
3. Class III: This class indicates moderate leakage and is suitable for applications where a moderate level of leakage can be tolerated.
4. Class IV: With higher allowable leakage compared to the previous classes, Class IV is used in applications where a relatively larger leakage is still manageable.
5. Class V: This class is often referred to as “metal-to-metal” seating and allows a significant amount of leakage. It’s used in applications where tighter shutoff is not a primary concern.
6. Class VI: This is the most stringent class, indicating very tight shutoff with minimal allowable leakage. Class VI valves are used in applications where no visible leakage is permissible.

Manufacturers use the standard to test and rate their control valves based on seat leakage performance. This information helps end-users and engineers select valves that match the specific requirements of their applications.

In summary, ANSI/FCI 70.2 provides a standardized way to classify and communicate control valve seat leakage characteristics. By adhering to this standard, industries can ensure that the control valves they select meet their performance and safety needs, ultimately contributing to efficient and reliable processes.