Flat-seat composite rupture disc for low pressures

In short: the flat-seat composite disc is a multi-layer relief device that is clamped between flanges without a dome or prior bulging. It is intended for equipment that needs to open at low burst pressures and handles corrosive fluids, where a solid metal disc would be too thick or poorly compatible.

How it works

In a composite disc each layer performs a different task. The metal top section provides mechanical strength and, in general terms, defines the opening point. Underneath is a seal, which can be metallic or non-metallic, whose function is leak-tightness and chemical isolation from the fluid. Separating «what holds» from «what seals» makes it possible to use very thin membranes or corrosion-resistant plastic materials without their having to carry the load alone.

The fact that the seat is flat has a practical consequence: there are no cavities or curvatures where product can get trapped, so less material builds up and cleaning is faster. Since the disc has no dome, the mounting orientation and the shape of the disc holder are less critical than with a domed disc, although it is still essential to respect the face marked toward the process.

If the equipment may end up under vacuum, an optional vacuum support is added to prevent negative pressure from pulling the disc toward the vessel and deforming it. Protective rings, gaskets or a liner on the outlet side are also available, which according to the manufacturer help extend the life of the assembly and simplify maintenance.

When it makes sense (and when it does not)

• Suitable for tanks, reactors or lines with a low design pressure, where a precise burst within a narrow range is needed.
• Suitable for aggressive fluids: the seal can be chosen based on chemical compatibility without changing the structure that carries the load.
• Suitable when operation is static, cyclic or pulsating, conditions the manufacturer declares compatible with this line.
• Check carefully if the process runs very close to the burst pressure: the allowable operating ratio of a flat disc must be confirmed with the supplier, because it is usually more limited than in reverse-acting designs.
• Not the first choice in high-pressure services; one-piece domed discs are usually preferred there.

Data to specify it

• Required burst pressure and coincident temperature.
• Normal operating pressure and possible vacuum conditions (to decide whether it needs a support).
• Fluid and its composition, to choose a metallic or non-metallic seal.
• Nominal size and type of flanges or disc holder.
• Type of service: static, cyclic or pulsating.
• Desired accessories: protective rings, gaskets or outlet lining.

To learn more: Types of rupture discs and Rupture disc materials.

Descriptive sheet for educational purposes. For availability and a quote for this model, consult P&V Control Devices.