ANSI FCI 70-3-2016 pdf free download.Regulator Seat Leakage
1. PURPOSE
1.1 This standard establishes a series of seat leakage classes for regulators and defines the production test procedures.
2. SCOPE & LIMITATIONS
2.1 This standard applies to pilot operated and direct acting pressure reducing, pressure relieving (back pressure), differential pressure and temperature regulators.
2.2 Selection of a leakage class is not restricted as to regulator design, but acceptable values for various commercially available designs are suggested for each class under Section 4.
2.3 The standard cannot be used as a basis for predicting leakage at conditions other than those specified.
2.4 This standard is similar to ANSI/FCI 70-2 Control Valve Seat Leakage.
3. DEFINITIONS
3.1 Regulator.A self-contained valve operated by the flowing fluid or by the process energy from a directly connected sensing device.
3.2 C v – An experimentally determined valve sizing coefficient. (Ref. ISA S75.01.01, ISA S75.02.01 and FCI Standard 84-1).
3.3 Lockup (Dead End Shutoff). The deviation of the controlled variable from set point obtained at a no flow position.
3.4 Maximum Capacity – The flow rate at maximum travel generally used for safety or relief valve sizing.
3.5 Maximum C v. – Maximum C v is C v at maximum capacity calculated per ISA S75.01 generally used for safety relief valve sizing. For pilot-operated regulators maximum C v includes the C v of the pilot.
3.6 Maximum Travel. The regulator travel in the fully open position at the maximum design travel corresponding to maximum capacity.
3.7 Seat Leakage. The quantity of test fluid passing through an assembled regulator in the closed or locked up (shutoff) position under the test conditions as defined.
3.8 Nominal Seat Diameter. Basic diameter used to determine maximum allowable seat leakage (Leakage Class VI). This is also referred to as port diameter or orifice diameter (of the seat ring). It should be noted that this is not the same as NPS.
4. LEAKAGE SPECIFICATIONS & CLASSES
4.1 The maximum allowable seat leakage as specified for each class shall not exceed the seat leakage in Table 1 using the test procedure as defined in Section 5. For Classes II through VIII each and every regulator shall be tested. The C v of the pilot must be included.
4.2 Leakage Classes 4.2.1 CLASS I. A modification of any Class II, III or IV regulator where the design intent is the same as the basic class, but by agreement between user and supplier, no test is required. 4.2.2 CLASS II. This class establishes the maximum permissible leakage generally associated with commercial double-seat regulators with metal- to-metal seats. 4.2.3 CLASS III. This class establishes the maximum permissible leakage generally associated with Class II (4.2.2), but with a higher degree of seat and seal tightness. 4.2.4 CLASS IV. This class establishes the maximum permissible leakage generally associated with commercial unbalanced single-seat regulators with metal-to-metal seats. 4.2.5 CLASS VI. This class establishes the maximum permissible seat leakage generally associated with resilient seating regulators either balanced or unbalanced with “O” rings or similar gapless seals.
4.2.6 CLASS VII. This class establishes the maximum permissible seat leakage generally associated with Class VI (4.2.5), but with test performed at the maximum operating differential pressure.
4.2.7 CLASS VIII This class establishes a no permissible leakage standard generally associated with resilient seating regulators either balanced or unbalanced with “O” rings or other gapless seals.
5.2.1 Reducing Regulator
5.2.1.1 Reducing Regulator Class II-VI The pressure of the test medium shall be 3-4 bar (45- 60 psig) or the maximum operating differential pressure, whichever is less. 5.2.1.2 Reducing Regulator Class VII For regulators with normal operating differentials less than 17 bar (250 psig), the pressure of the test medium shall be the maximum operating differential pressure or 3.5 bar (50 psig), whichever is greater. For regulators with normal operating differentials greater than 17 bar (250 psig), the pressure of the test medium shall be 17 bar (250 psig) unless otherwise agreed to with the customer.
