Plain or fabric-reinforced: choosing a rubber diaphragm

A diaphragm is a flexible rubber wall that moves with pressure: it pumps, it regulates or it separates two fluids. Whether it should be plain rubber or reinforced with fabric depends mostly on pressure and stroke.

Plain rubber diaphragms

Plain diaphragms are moulded from rubber alone. They suit:

• low pressure,
• short strokes,
• applications where the diaphragm needs to be very sensitive to small pressure changes, such as some regulators and valves.

Fabric-reinforced diaphragms

A layer of fabric moulded inside the rubber stops the diaphragm stretching under load. Reinforcement helps when:

• the pressure is higher,
• the stroke is longer,
• the diaphragm must hold its shape through many cycles, as in diaphragm and dosing pumps.

The rubber still does the sealing; the fabric carries the load.

Choosing the rubber

The compound follows the fluid and the temperature, as with any rubber part: nitrile for oil and fuel, EPDM for water and outdoor service, and higher-grade compounds for hot chemicals. See the compound guide.

Ordering a replacement

Send the old diaphragm, or photos beside a ruler, with:

• the outside diameter and the bead (the rim that is clamped),
• any centre hole or bolt holes,
• the stroke,
• the fluid, its pressure and temperature,
• the quantity.

We measure it and remake it to match. See our diaphragms or send the details.