Check Valves

Frequently Asked Questions

Swing, lift, dual-plate, or tilting-disc — which check valve should I specify?

Swing: most general service, horizontal or vertical-upflow piping, moderate flow velocity, cost-effective — the default where slam isn't a concern. Lift: small-bore (½"–2"), horizontal lines, similar body to globe valve — convenient for inline combinations. Dual-plate (wafer check): low pressure drop, short face-to-face, ideal for larger sizes (6"+), LNG and cryogenic service, any application where space or pressure drop matters. Tilting-disc: pump discharge where water-hammer could occur — closes faster than swing, prevents slam. Axial-flow: silent, non-slam, the premium option for critical pump-discharge and cycling service.

How do I size a check valve correctly to avoid flutter?

Check valves must be sized for the minimum normal flow, not the pipe bore. A check valve in a partly open position (disc not fully lifted or swung clear) will flutter under flow pulsation, causing rapid wear of the seat and pivot. Rule of thumb: design flow velocity should be above the valve's minimum lift velocity (manufacturer-specified, typically 1.5–3 m/s depending on design). If your design flow sits below the full-open threshold, size down by one or two sizes and accept slightly higher pressure drop — a flutter-free undersized check is far better than an oversized one wearing out in 6 months.

Is water-hammer a real concern on pump discharge?

Yes — in systems with long discharge piping (100m+) or high suction head (high-rise pumping, water-supply networks), a swing-check closure under reverse flow can produce a pressure spike several times the normal operating pressure. Equipment damage (pipe fractures, pump seal failures, concrete anchor displacement) has been documented. For such systems, non-slam check valves (tilting-disc, axial-flow, or dual-plate with spring assist) are standard specification. Himalay can arrange transient-analysis review with the manufacturer to confirm valve selection.

What's the typical MOQ for check valves?

Swing and lift check valves in standard carbon or stainless, ½"–6": MOQ 20–100 pieces. Dual-plate check valves, 3"–12": MOQ 10–30 pieces. Large-bore check valves (16"+): typically per-piece (MOQ 1–5) for project-specific specs. Axial-flow non-slam check valves: per-piece for most sizes; they are engineered items with longer lead times.

Can check valves be specified as double-block-and-bleed?

A single check valve is not DBB — it blocks reverse flow only, with no positive isolation in the forward direction. For true DBB isolation, pair the check with a dedicated isolation valve (trunnion-mounted ball valve, gate valve, or triple-offset butterfly) and a bleed connection. Some manufacturers supply integrated DBB units with an isolation valve, check valve, and bleed in a compact block — Himalay can source these for hydrocarbon service where DBB is mandatory (Shell DEP, ADNOC specifications).

What standards apply to pipeline-service check valves?

API 6D is the primary standard for pipeline check valves in oil & gas transmission — it specifies design, testing, and marking requirements. API 6D check valves are available as swing, dual-plate, or axial-flow configurations. For general refinery and petrochemical service, API 594 (swing and wafer check valves) and BS 1868 are the common references. For power and water, BS EN 1171 and AWWA C508 apply. Himalay matches the applicable standard to the service and confirms in quote documentation.