Check Valves for Power Generation

Check valves in power generation service must withstand extreme pressures and temperatures while providing reliable non-return protection for critical boiler feed pump discharge, HP/LP steam extraction, and feedwater heater connections. Vajra Industrial Solutions supplies tilting disc check valves, forged piston check valves, and dual plate designs in P91, WC9 and WC6 alloy steel - IBR certified for Indian power plants, with full EN 10204 3.1 documentation and ASME Section I compliance for export projects.

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What check valves does the Power Generation industry use?

Key Applications - Check Valves in Power Generation

Boiler Feed Pump Discharge Check Valves

Boiler feed pump (BFP) discharge check valves prevent reverse flow through the idle pump when the duty pump is running and during emergency pump trip. Tilting disc check valves are preferred because their fast, controlled closure minimises water hammer in the high-pressure boiler feed water circuit - reverse flow surge can cause catastrophic damage to the BFP.

HP Steam Extraction and Turbine Bypass Non-Return

Non-return valves on HP steam extraction lines to feedwater heaters prevent reverse flow of steam and water back into the turbine during transient conditions. A check valve failure here allows water induction into the turbine, causing catastrophic blade damage (water hammer in turbine). IBR certification is mandatory for Indian power plants.

Feedwater Heater Shell-Side Check Valves

Shell-side safety and drain check valves on feedwater heaters operate in high-pressure wet steam condensate service. The check valve must provide reliable non-return function even with very small differential pressure across it when the heater shell is nearly at system pressure.

Condenser Hotwell and Condensate Extraction

Check valves on condensate extraction pump discharge prevent reverse flow of condensate through idle CEP units. At the low pressures of the condensate system (1–10 bar), swing check or lightweight dual plate check valves with elastomer seat inserts are specified for low cracking pressure and tight shutoff.

Required Certifications

ASME Section I (boiler application)IBR (Indian Boiler Regulations - mandatory for Indian power plants)ASME B16.34 pressure-temperature ratingsAPI 594 (for non-IBR applications)EN 10204 3.1 MTRs + heat treatment recordsThird-party inspection (Lloyd's, TÜV, BV accepted)NACE MR0175 if wet H₂S in gas plant combined cycle

Recommended Materials

ASTM A217 WC9 (2.25Cr-1Mo) - Primary material for high-temperature HP steam check valves; excellent creep resistance to 600°C

ASTM A217 WC6 (1.25Cr-0.5Mo) - For intermediate temperature service (up to 540°C); lower alloy content, lower cost than WC9

ASTM A182 F91 (P91 forged, 9Cr-1Mo-V) - For supercritical and ultra-supercritical boiler circuits above 600°C; mandatory for USC power plants

ASTM A351 CF8 (SS 304) - Condensate and low-temperature steam service; austenitic stainless for corrosion resistance in wet steam

ASTM A216 WCB - Low-pressure utility steam and condensate return (below 425°C) where alloy steel is not required

Selection Factors

IBR compliance for India: All check valves on steam-generating boilers, steam piping and associated equipment in India must comply with Indian Boiler Regulations (IBR) - IBR certification includes material approval, design calculations, hydrostatic testing, and a stamped IBR certificate from a Boiler Inspector. Vajra supplies IBR-certified check valves for all sizes and pressure classes

Tilting disc vs swing check for BFP service: Tilting disc check valves close faster than swing checks because the disc geometry creates a self-closing torque before reverse flow develops; this minimises the reverse velocity before full closure, significantly reducing water hammer in the high-energy boiler feed water circuit. For BFP discharge - always specify tilting disc; swing check is not recommended

Creep resistance - P91 requirement: Supercritical and ultra-supercritical power plants operating above 600°C require P91 (F91 forged or C12A casting) valve bodies and trim; standard WC9 has inadequate creep strength above 600°C. P91 requires specific post-weld heat treatment (PWHT) at 760°C ±15°C - verify that the installation contractor performs proper PWHT if butt-weld ends are specified

Low cracking pressure for feedwater heater service: Shell-side check valves on feedwater heaters must open at very low differential pressures (as low as 0.01–0.05 bar) when the heater shell pressure is nearly equal to the inlet pressure. Specify maximum cracking pressure on the purchase order; tilting disc and piston check designs can achieve low cracking pressure; heavy-spring designs are not suitable

Integral bypass requirements: Some power plant check valves require an integral bypass valve (equalising valve) to allow pressure equalisation before opening the main valve - this is specified for large-bore check valves on high-pressure systems where operating against full differential would require excessive actuating force or where thermal shock from rapid opening is a concern

Technical FAQs

Are IBR-certified check valves available from Vajra in all sizes?

Yes. Vajra Industrial Solutions supplies IBR-certified check valves for boiler and steam service across the full size range from DN15 to DN600, in Class 150 through Class 2500. IBR certification involves material approval (the specific heat/charge of the casting or forging must be IBR approved), design calculations submitted to the state or central boiler inspector, hydrostatic pressure testing at 1.5× design pressure witnessed by an IBR inspector, and a stamp on the valve and an IBR certificate in the documentation package. For orders requiring IBR certification, provide the project state (Maharashtra, Gujarat, etc.) with your purchase order as each state's inspector has specific requirements. Standard lead time for IBR-certified valves is 8–14 weeks for alloy steel (WC6, WC9) and 12–18 weeks for P91.

What causes water hammer at the boiler feed pump check valve and how is it prevented?

Water hammer at the BFP check valve occurs when: the running pump trips suddenly; flow reverses in the BFP discharge line; a slow-closing swing check valve is still open when full reverse flow velocity (typically 2–4 m/s in BFP lines) has developed; the disc slams shut abruptly against the seat, generating a pressure transient (Joukowsky pressure rise = ρ × c × ΔV, which can reach 50–100 bar in high-velocity BFP systems). Prevention: (1) Tilting disc check valve with inherent closing torque - closes before full reverse velocity; (2) Non-return valve with dashpot (hydraulic damper on the disc arm) - controlled slow final closing eliminates slam; (3) Anti-slam check valve with spring-loaded disc - cracking open with forward flow, closing under spring force when differential drops, before reverse flow; (4) Variable speed drives on BFPs - controlled ramp-down reduces reverse flow rate. Vajra recommends tilting disc non-return valves for all BFP discharge service.

Can swing check valves be used in vertical upward flow in power plant service?

Standard swing check valves are not suitable for vertical upward flow installations because the disc hangs under gravity rather than being held open by flow; at low-flow conditions the disc will flutter partially closed, causing chattering damage to disc and seat. Solutions for vertical upward flow: (1) Tilting disc check valve - the disc geometry creates self-closing torque but the disc opens against gravity under forward flow; suitable for vertical-up installation; (2) Spring-loaded dual plate check valve - the spring holds the disc partially open, ensuring it stays open under low forward flow, and provides closing force in reverse flow; suitable for vertical and horizontal installation; (3) Piston (lift) check valve - spring-loaded piston works in any orientation including vertical upward; suitable for small bore (DN15–DN100) high-pressure service. For large-bore (DN150+) vertical upward installation in power plant service: specify tilting disc or spring-loaded dual plate check valve and confirm vertical installation on the purchase order.