Bellows Seal Valve Brochure

Bellows Seal Valve

Conval Bellows Seal Valves meet all of the rigorous requirements of MSS SP-117, ensuring bellows longevity.

Standard Bellows Seal Sizes

Sizes through 4”

Pressure Rating

Through ASME Class through 2500 #

Standard Forging ASME Materials

SA 105, SA 182-F22, SA 182-F91, SA 182-F92, SA 182-F316
Other materials available upon request.


Actuators – Electric, Pneumatic or Hydraulic
Locking Devices – Open, Closed or Both
Limit Switches – Single or Dual
Stem Shroud
Position Indicator
Leak-Off Port

Bellows Seal Design Features

Conval Bellows Seal Valve vs. Packed Valves

Packed valves require two seal boundaries: a 360° seal on the stem surface and a 360° seal on the stuffing box wall. The Conval bellows seal valve removes these two leak paths. Conval bellows seal valves are used when packed valves may not reliably contain light gases or hazardous system fluids. In all applications, the 6-ply Inconel®, welded bellows stem seal is more reliable than sliding stem seals.

Zero Fugitive Emissions

Every Conval bellows assembly is tested for zero leakage using a helium gas mass spectrometer before undergoing further shell and seat leakage testing. Conval’s bellows seal emits no detectable leakage, well beyond Method 21 Fugitive Emissions Test Protocol.

No Torsion of the Bellows

A robust rising, non-rotating stem system prevents destructive torsion, providing extremely long service life from the advanced bellows design.

Three Body Styles

Conval bellows seal valves are available in Y-pattern, Angle-pattern, and T-pattern body styles.

Low Operating Torque

The manual bellows seal valve is provided with a rugged bearing system and grease fitting to minimize operating torque over the life of the valve.

Double Back-up Seating

In the full open position, Conval bellows seal valves are equipped with a superior backseat, isolating a secondary stem seal from the process fluid. The graphitic stem seal is precisely loaded by Conval’s balanced axial gland and Integral Gland Wrench (IGW), providing superb sealing to back up the bellows.

Extended Seat Life

Positive shut-off is achieved over a very long operational life due to the solid cobalt-chrome seats and discs, even in high cycle and high fluid velocity services. A cobalt-free option is available for nuclear and chemical applications.

Flexibility of Design

Conval offers a double height bellows which provides the highest bellows valve flow capacity (Cv) available per pipe size. Test ports (with lantern gland) may also be specified.

Axially-loaded Packing System

The Axial design ensures tight concentricity, which eliminates side loading of the packing and minimizes wear forces on the trim components. This feature is critical for superior valve performance.

Pressure Seal Bonnet

The simple and effective pressure seal bonnet provides ready access for servicing with no welds to cut or seal rings or gaskets to replace. The body-to-bonnet joint integrity is maintained through countless thermal cycles.

Single-piece Gland

In extreme environments, the simpler the design and the fewer the parts, the better. The durable single-piece stainless steel gland contributes to the longevity of the valve.

Pressure-Actuated Backseat

The Clampseal® pressure-actuated backseat provides maximum valve integrity by ensuring a positive internal stop for the valve stem and disc assembly. The pressure actuated backseat also extends packing life by securely isolating the packing from the pressure when the valve is fully open.

Rapid In-Line Renewability

The CLAMPSEAL® Valve is much easier to renew than anything else on the market. The CLAMPSEAL® Valve line provides a modular solution to rising maintenance expenses. Low acquisition cost is not as important as low cost over the serviceable life of a valve. Maintaining a Conval valve is far easier and much less costly than replacing a competitor’s valve.