Table 5 - Flanged Body Inlet and Outlet Diameters Nominal Body Size 1 1.5 2 3 4 6 8
150 1.06" 1.63" 2.06" 3.00" 4.00" 6.00" 8.00"
ANSI Pressure Class 300 600 900 1500 1.06" 1.06" 1.00" 1.00" 1.63" 1.63" 1.63" 1.63" 2.00" 2.00" 2.00" 2.00" 3.00" 3.00" 3.00" 2.69" 4.00" 4.00" 4.00" 3.69" 6.00" 6.00" 5.75" 5.75" 8.00" 8.00" 7.62" 7.25"
2500 1.00" 1.50" 1.75" 2.69" 3.44" 5.50" 7.00"
SEAT LEAKAGE The Fluids Control Institute (FCI) Standard ANSI/FCI 70.2 establishes a Valve’s allowable seat Leakage Rate. The standard recognizes five degrees of seat tightness.
Table 6 - ALLOWABLE SEAT LEAKAGE CLASSES Maximum Seat Test Test Relative Seat Leakage Fluid Pressure Tightness Class II 0.5% of rated CV Water 45 to 60 PSI 1.0 Class IIA (Norriseal) 0.2% of rated CV Water 45 to 60 PSI 2.5 Class III 0.1% of rated CV Water 45 to 60 PSI 5.0 Class IV 0.01% of rated CV Water 45 to 60 PSI 50 0.0005 ml /min/inch Max Operating Class V Water 300,000 of trim size/ P(PSI) P Class VI Air 50 PSI 600,000 About 0.9 ml/min Leakage rate varies by valve size, Refer to the Standard ANSI/FCI 70.2. Norriseal offers Class IIA (Norriseal), Class IV, Class V & Class IV The Relative Seat Tightness is at a 50 P. For example, a Class IV leakage rate is 1/50 as much as Class II Class VI is for resilient seated valves; the other classes are for metallic seats. Leakage Class
ACTUATOR SIZING The actuator sizing process matches our actuator’s force output with our valve trim’s required stem forces. The result is the maximum obtainable pressure drop at the different seat leakage classes. The process considers the valve’s shut off
condition. The flowing conditions also require an adequate match between the actuator and trim forces but the shut off condition is dominant and determines the allowable.
UA UnbalancedArea BalancedTrim Cage ID Seat ID 2
2
4 = In
2
2 2 UA UnbalancedArea UnbalancedTrim Seat ID = In 4
CL Seat Contact Load Seat ID Load Factor = Lb./In. of circumference Load Factors vary with seat leakage class //data/public/pdf/valve-sizing-maual.doc 12 of 43 Norriseal – P.O. Box 40525 Houston TX 77240-052–- Ph: (713) 466-3552, Fax: (713) 896-7386
10/10/2008