Laminated offset valve seals

Laminated, precision‑machined seals for offset butterfly valve applications

Precision sealing for offset butterfly valves

James Walker’s laminar seal is designed for critical service applications in double and triple offset butterfly valves. Manufactured from bespoke metal and filler laminates these seals are machined to customer specification providing a precision seal against rigid valve seats, delivering long life even at high cycle frequencies.

Butterfly valve sealing issues

Modern butterfly valves are frequently used as cut-off and regulating fittings in many high-temperature / high-pressure applications. One of the serious challenges in this type of applications is the internal sealing of the disc. On the one hand the seal should remain flexible, but on the other, should also be resistant to erosion and wear resulting from the conditions of its use. Often the basic soft sealing materials (elastomers, PTFE) do not fulfil these requirements due to their rapid ageing in higher temperatures; their wear reducing the life of the seal and the periods between maintenance.

Butterfly valve sealing solution

The solution to these issues lies in the development of precision-machined laminated offset seals which offer resistance to erosion and withstand higher working temperatures, pressure and cycle rates, guaranteeing a longer life for the entire valve. The most popular form of these seals is a graphite-metal laminated structure constructed of alternate layers of expanded graphite foil (specified for each application for quality, thickness and density) and inter-layers of flat metal elements. The final geometry and material characteristics of each laminar seal are determined by the valve manufacturer and bespoke to each valve.

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Laminated offset valve seal datasheet

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Product features Typical applications Construction Product variants How supplied Available sizes Performance

Improved sealing compared with soft material seals such as elastomer or PTFE. The laminated design combines the strength of metal with the compressibility of softer materials for an optimal seal.
Inherent flexibility allows the laminate structure of the seal to flex and adjust to slight imperfections or irregularities in the hard valve seat.
Enhanced wear resistance due to layered material design, offers superior longevity and durability compared to single-material seals.

These are bespoke precision seals manufactured to match the designs of individual double offset and triple offset butterfly valves most commonly for high pressure / high temperature applications;

Oil and Gas: harsh environments and aggressive media.
Power Generation: steam and gas turbine installations.
Chemical Processing: Ideal for highly corrosive and hazardous materials.
Marine Industry: Common in critical systems like water intake valves.

Seal geometry and material characteristics are matched to customer specifications.
The number of metal layers is typically between 2 and 12 with a thickness per layer of between 0.5 and 3.00 mm.
The number of intermediate graphite / PTFE / Mica layers may be between 1 and 10, with thickness varying from 0.5 to 1.5 mm. In the case of graphite, density is between 0.7 and 1.3 g/ccm).

Disc mounting for installation on the disc of the butterfly valve
Body mounting for installation on the valve body
Double eccentric where the main seat and shaft axes are offset
Triple eccentric where the centrelines of the seat and seal are inclined in respect to the pipe /valve centreline in addition to the main seat and shaft axis being offset.

Laminar seals are precision machined to customer designs in a choice of material combinations.
Metallic layers - 304L, 316L, 321, 347, Inconel® 625, Monel® 400, Duplex®.
Intermediate layers - Flexible graphite, PTFE, Mica
(Inconel and Monel are registered trademarks of Special Metals Corporation)

3” to 42” as standard.
Sizes above 42” can be considered on request, subject to design and machining feasibility

Graphite laminate
Maximum Temperature:
+450°C (+842°F)
Minimum Temperature:
Cryogenic

PTFE laminate
Maximum Temperature:
+260°C (+500°F)
Minimum Temperature:
Cryogenic

Mica laminate (Consult James Walker )
Maximum Temperature:
+1000°C (+1832°F)
Minimum Temperature:
Ambient

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