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Control Valve Leakage Class (ANSI FCI 70-2)

The term “Control Valve Seat Leakage Class” comes from ANSI / FCI 70-2. This is a control valve seat leakage specification Standard. ( 🔴 ) Link to FREE Udemy Course for I&C Professionals 1500+ Engineers have taken the Course (Engineers have said it is even BETTER than the PAID Courses available) Give it a Try 😊 Link 👉 https://asad-shaikh-instrumentation.c... Valve Leakage Classifications Class I – Valve Leakage Classifications Identical to Class II, III, and IV in construction and design intent, but no actual shoptest is made. Class I is also known as dust tight and can refer to metal or resilient seated valves. Class II – Valve Leakage Classifications Intended for double port or balanced singe port valves with a metal piston ring seal and metal to metal seats. • 0.5% leakage of full open valve capacity. • Service dP or 50 psid (3.4 bar differential), whichever is lower at 50 to 125oF. • Test medium air at 45 to 60 psig is the test fluid. Typical constructions: • Balanced, single port, single graphite piston ring, metal seat, low seat load• Balanced, double port, metal seats, high seat load Class III – Valve Leakage Classifications Intended for the same types of valves as in Class II. • 0.1% leakage of full open valve capacity.• Service dP or 50 psid (3.4 bar differential), whichever is lower at 50 to 125oF. • Test medium air at 45 to 60 psig is the test fluid. • Balanced, double port, soft seats, low seat load • Balanced, single port, single graphite piston ring, lapped metal seats, medium load Class IV – Valve Leakage Classifications Intended for single port and balanced single port valves with extra tight piston seals and metal to-metal seats. • 0.01% leakage of full open valve capacity. • Service dP or 50 psid (3.4 bar differential), whichever is lower at 50 to 125oF. • Test medium air at 45 to 60 psig is the test fluid. Typical constructions: • Balanced, single port, Teflon piston ring, lapped metal seats, medium seat load • Balanced, single port, multiple graphite piston rings, lapped metal seats • Unbalanced, single port, lapped metal seats, medium seat load • Class IV is also known as metal to metal Class V – Valve Leakage Classifications Intended for the same types of valves as Class IV. • The test fluid is water at 100 psig or operating pressure. • Leakage allowed is limited to 5 x 10 ml per minute per inch of orifice diameter per psi differential. • Service dP at 50 to 125 oF. Typical constructions: • Unbalanced, single port, lapped metal seats, high seat load • Balanced, single port, Teflon piston rings, soft seats, low seat load • Unbalanced, single port, soft metal seats, high seat load Class VI – Valve Leakage Classifications Class VI is known as a soft seat classification. Soft Seat Valves are those where the seat, shut-off disc or both are made from some kind of resilient material such as Teflon. Intended for resilient seating valves. • The test fluid is air or nitrogen. • Pressure is the lesser of 50 psig or operating pressure. • The leakage limit depends on valve size and ranges from 0.15 to 6.75 ml per minute for valve sizes 1 through 8 inches.