swing check valveSWING CHECK VALVES

In swing check valves, the disc swings on a hinge onto the seat to block reverse flow, or off the seat to allow forward flow.

The seat opening cross-section is perpendicular to the centerline between the two ports.


Forged of cast carbon, alloy and stainless steel, bolted joint between cap and body, renewable or welded seats.


Swing check valves are available assembled with bolted bonnet or with pressure seal bonnet,  that allows high pressure service. The main feature about the pressure seal bonnet is that the body-bonnet joints seals improves as the internal pressure in the valve increases, compared to other constructions where the increase in internal pressure tends to create leaks in the body-bonnet joint.

Internal pressure forces the bonnet upwards against the gasket, creating forces in the contact areas between the gasket and the bonnet. As pressure increases, leaks probability decreases, because of the tightening of the contact surface between the gasket and the body. The area where the body is in contact with the joint is covered by stainless steel, improving surface’s quality and avoiding corrosion issues.


1 Body

Available both in cast and forged steel, it has been designed to meet all the requirements of ASME, API and British Standards.

The body-bonnet connection is made by a pressure seal gasket. Its pre-stress condition is achieved by mean-sof bolts screwed to the bonnet flange. Ends are normally butt-welding although they can be also flanged on request.

All bodies are provided with integrally cast bosses, located and sized in accordance with ASME B16.34, which allow the provision of drain.

3 Cover

Usually constructed in the same materials as the body.

6 Seat ring

Supplied in forged stainless steel, hardfaced with Stellite-6 (2mm of min. thickness). Seat ring is renewable, normally welded to the body.

Sealing contact surface is lapped for a perfect tight seal.

8 Disc

The disc is normally constructed in forged stainless steel for diamters upto 8”, and in cast steel of the same material as the body for larger sizes. Contact face is overlayed with 2 mm minimum thickness of Stellite-6.

It is designed so that the valve can operate both in horizontal and vertical positions.

17 Pressure gasket

The pressure seal gasket is usually supplied of compressed graphite, bordered on the upper and lower edges with braided filaments of carbon fiber.

Gasket can also be made in stainless steel.

dismantling of a non return valve25 Hinge (arm)

The arm is constructed of the same material as the valve body. Designed to swing smoothly, is provided with an integral mechanical stop, suitably machined, which contacts the valve body when the valve is in fully open condition, and avoids the disc to create the first contact.

27-Hinge pin (shaft)

Constructed from a stainless steel forged bar, is normally designed for being assembled externally through the side/s of the valve body, although internal shaft designs are also available on request.

In the normal external shaft construction, one or two cover/s (19A), fitted to the body with 4 studs (28A) assure a perfect tightness. Seal between cover/s and body is achieved by using spiral wound gaskets (17A).

For some special applications, to avoid slamming effect, shock absorbers (dashpots) are installed in the valve, connected to the hinge pin through stuffing box/es.

132-Spacer ring

Made of a single piece covering the upperpartofthepressuresealgasket. It is normally manufactured in the same material as the body.

133-Gasket retainer

It is made normally of the same material as the body, and constructed in four pieces, called segments. The segments are sized to minimize the gap between them.

The segmental ring supports all the forcers transmitted from the bonnet through the pressure seal gasket and the spacer ring. It is calculated to withstand all the force withoutcrac- king.

134-Cover retainer

Designed sufficiently resistant to withstand the forces transmitted by the cover stud (28). The cover retainer is normally made of the same material as the body, but it can be constructed in any other material on request. It is machined to match exactly with the body, what guarantees a perfect alignment of the unit.


Our check valves are typically constructed from cast iron, ductile iron, cast carbon steel, gun metal, stainless steel, alloy steels and forged steels, under our customer requirements.

standard materials


Other materials are available on request. The trim (•) materials are:

  • Seat ring seating surfaces
  • Discs seating surfaces
  • Hinge pin