Seat tightness

API Standard 527—Coimnercial Seat Tightness of Safety Relief Valves with Metal-to-Metal Seats, 1978, American Petroleum Institute, 1220 L Street, NW., Washington, D.C., 20005. 

Commercial Seat Tightness of Safety Relief Valves with Metal-to-Metal Seats... 

API Standard 527, Seat Tightness of Pressure Relief Valves This standard describes tests with air, steam and water to determine the seat tightness of metal- and soft-seated PRVs. Valves of conventional, bellows- and pilot-operated designs are covered. Acceptable leakage rates are defined for gas, steam and liquid. 

Resilient valve seats are frequendy used when a greater degree of seat tightness is required than is likely with metal-to-metal seats. 

Good and repeatable seat tightness, before and after cycle Limited on dirty or fouling service, unless with special configuration... 

If due consideration is not given to this point, considerable internal damage or misalignment can result and seat tightness might be adversdy affected. 

The main requirement for thermal relief valves in cryogenic conditions is to reduce their freezing risks at any cost (Figure 11.2). Therefore, we must select valves with low simmer, a rapid pop/snap opening and high seat tightness. We need to reduce unnecessary product loss, so again low simmer and preferably a short blowdown is required. 

American Petroleum Institute Washington www.api.org API Recommended Practice 520 Part 1 - Sizing and Selection API Recommended Practice 520 Part 2 - Installation API Recommended Practice 521 - Guide for Pressure Relief and Depressurizing Systems API Standard 526 - Flanged Steel Pressure Relief Valves API Standard 527 - Seat Tightness of Pressure Relief Valves API Recommended Practice 576- Inspection of Pressure Relieving Devices... 

API RP 521 API STD 526 API STD 527 Guide for pressure-relieving and depressurizing systems Flanged steel pressure relief valves Seat tightness of pressure relief valves... 

H a component is seated tight against the PWB, it may block the flow of solder into the FTH. A gas pocket may form at the primary side of the hole. Gas pressure may force Uquid solder out of the hole, preventing adequate PTH hole fill. This can be remedied by applying a small spacer under the component as shown in Fig. 47.29. 

API (American Petroleum Institute), 1991. Seat Tightness of Pressure Relief Valves. 

Minimizing pipe size would allow use of existing valve technology, lowered valve design costs, and improved valve seat tightness performance. 

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