ANSI 150 cast steel swing check valve, 1½" to 6"

A swing check valve in 1½" to 6" (DN40 to DN150), with ANSI 150# flange ends and a body in ASTM A216 WCB cast steel. The gasket is SS304 + graphite. Rated 150# for service at −29 °C to 425 °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 variant in this range above 4", and the only one rated above 180 °C. 1½" to 6" and −29 to 425 °C. If your duty is hot or large, this is the one — and the reason is the graphite gasket, not the carbon steel body.
• It is the only one with a separate hardfaced seat. Item 2 is A105 + F6, a 13% chrome facing, with the same facing on the disc. That resists the wear of repeated closure far better than the 316‑on‑316 seating of the stainless variants.
• Face‑to‑face is quoted as the catalogue prints it for this variant — 162.5 mm at 1½" up to 356 mm at 6". The ANSI 150 SS316 table carries its own figures, which differ by a few millimetres at some sizes — quote from the table of the variant you are buying. Measure the gap in your run, and on a replacement measure the valve coming out.
• The flange OD column reads 127 to 281 mm — ASME B16.5 Class 150 outside diameters — and the table heads it flange OD D.
• The bonnet fastening is a B7 bolt with a 2H nut — listed in the catalogue as “bonnet bolt, ASTM A193 B7” and “bonnet bolt nut, Gr.2H”, the standard high‑strength combination.
• Nothing here is stainless except the hinge pin. Body, disc, hinge and bonnet are all A216 WCB carbon steel; the pin is A276 410. On corrosive duty use the SS316 version.
• ⚠ 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.