Threaded SS316 swing check valve, 1/4" to 2"

A swing check valve in 1/4" to 2" (DN8 to DN50), with BSPT or NPT threaded ends and a body in SS316 with A351 CF8M cast stainless. The gasket is PTFE. Rated 200 PSI for service at −29 °C to 180 °C.

It is a disc on a hinge. Forward flow pushes it open and holds it clear of the bore; when flow stops or reverses, the disc swings shut under its own weight and the backpressure behind it. Nothing operates it — no handle, no stem, no actuator — which makes it the cheapest way to stop a stopped pump being spun backwards, and the least visible when it stops working. How it works, in full.

• The only option in this range below 1/2". 1/4" and 3/8" are available here and nowhere else in the swing check range — the flanged variants start at 1/2" and the brass one at 1/2".
• 16 part numbers: eight sizes in each thread form. VL‑S‑SC‑R‑200‑nn for BSPT and VL‑S‑SC‑N‑200‑nn for NPT, with identical dimensions and weights in both — only the thread differs. The R and N in the code are the thread form.
• ⚠ The pin, washer and bolt are SS304, not 316. Items 5, 6 and 7. The pin is in the flow path, so on chloride‑bearing service it will pit before the body does. The flanged SS316 variants use SS316 pins throughout — worth knowing if you chose stainless specifically for the fluid.
• Rated −29 to 180 °C, as the catalogue states — the only threaded variant in this range with a published working temperature.
• The range is 1/4" to 2", DN8 to DN50, with full dimensions and part numbers for every size.
• The materials are SS316 and CF8M for the body, disc and cap, with SS304 fasteners — the full bill of materials is below. A separate brass variant is stocked for water and air duty.
• 1/4" and 3/8" share one body. Both publish L 60, H 36.5, bore 10 mm — identical — and differ only in weight (0.24 against 0.26 kg). The same casting, tapped to two thread sizes.
• Weights for every size, 0.24 kg to 1.78 kg at 2". BSPT and NPT weigh the same.
• ⚠ Fit a Y‑strainer upstream. A flake of scale between disc and seat holds the disc fractionally open, and the valve then passes reverse flow while looking perfectly normal from outside. There is no stem position or indicator to check. A strainer is the single most effective thing you can do for a check valve.
• Orientation is not optional. Flow follows the arrow cast into the body; on a horizontal run the bonnet points up; on a vertical run flow must be upward. Never on downward flow — use a spring check for that. The three rules.

Four angles on the same valve. Photographs of the stocked item, not renders.

The manufacturer’s sectional drawing. The callout numbers correspond to the item numbers in the parts list.

• The disc and the seat face are what wear. Everything else is a casting or a fastener. On a valve that closes every time the pump stops, those two surfaces take the whole duty cycle.
• The hinge pin is the other one to ask about. A disc that chatters — which happens when the valve is oversized for the flow — wears the pin, and a worn pin lets the disc sit crooked on the seat.
• The item numbers are the manufacturer’s, matching the callouts on the drawing above, so a spares order matches the section.
• Everything here is published, not on request. If you need to know what touches your fluid, the whole list is above.

• ⚠ Do not design to these figures. The shell test is roughly twice the nominal rating and exists to prove the casting. The valve is not intended to operate there.
• ⚠ What actually breaks a check valve is not pressure. It is slam on flow reversal and chatter at low flow — both of which happen far below the shell rating. Why a swing disc slams, and when to use something else.
• The published figures across the five variants do not line up. Three of them publish no working temperature at all, one publishes no test table at all, and the two flanged stainless variants give the air test as a range where everything else gives a single figure. All five side by side, with every one flagged.