Backseat
A secondary sealing surface inside the valve body that seats against the stem when the valve is fully open. Prevents leakage through the stuffing box when fully open, allowing packing replacement under pressure. Required by API 600/602 for gate valves.
Related Terms
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Applicable Standards
Specification for Steel Gate Valves - Flanged and Butt-Welding Ends, Bolted and Pressure-Seal Bonnets
API 600 is the primary design and manufacturing standard for full-opening steel gate valves in sizes NPS 2 and larger with flanged or butt-weld ends and bolted or pressure-seal bonnets.
Gate, Globe, and Check Valves for Sizes DN 100 and Smaller for the Petroleum and Natural Gas Industries
API 602 covers compact forged steel gate, globe, and check valves in sizes NPS 1½ and smaller for petroleum and natural gas service.
Frequently Asked Questions
What is a Backseat in a valve?
A secondary sealing surface inside the valve body that seats against the stem when the valve is fully open. Prevents leakage through the stuffing box when fully open, allowing packing replacement under pressure. Required by API 600/602 for gate valves.
What materials are used for the Backseat?
Backseat material selection depends on the process fluid, operating temperature and pressure, and required corrosion resistance. Standard materials include carbon steel (A216 WCB/A105), austenitic stainless steel (SS316/316L), and corrosion-resistant alloys (Hastelloy C-276, Inconel 625, duplex stainless steel 2205/2507) for aggressive service. All materials must be certified with EN 10204 Type 3.1 MTCs traceable to the heat number.
What standards govern the design of the Backseat?
Valve component design is governed by ASME B16.34 for pressure-temperature ratings, API 600/602 for gate valves, API 609 for butterfly valves, and API 6D for pipeline valves, as applicable. Third-party inspection to these standards ensures compliance. Vajra Industrial Solutions supplies valves with full documentation packages including dimensional inspection records and material certificates.
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