Rubber and reinforced diaphragms

Rubber diaphragms are flexible and airtight components which are employed to divide two chambers with variable volume and pressure.

Diaphragms advantages

Compared to pistons or radial seal (Fig. 1), the application of diaphragms offers the following advantages:

Perfect airtight seal;
Simple assembly;
Modest production tolerances and surface finishing;
No sliding and static friction;
Minimal hysteresis and high degree of sensitivity;
No need of lubrication.

Reinforced diaphragms with fabric inserts, in particular, are a great replacement for rubber diaphragms thanks to their:

Higher resistance to pressure and mechanical stress;
Perfect watertight seal, especially in case of toxic or dangerous fluids
Reduced elastic elongation

EXSTO manufactures three different types of diaphragms:

diaphragms in 100% rubber;
diaphragms in rubber-coated fabric;
reinforced diaphragms in rubber + fabric insert which guarantee higher resistance to pressure and to corrosive fluids than all-rubber diaphragms. Their elastic stretching is restrained.

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REINFORCED DIAPHRAGMS – RUBBER COATED FABRIC

While the diaphragms with rubber-coated fabric are made by shaping the fabric, the reinforced diaphragms are made by moulding and attaching a fabric insert to the rubber. EXSTO can produce diaphragms with rubber and fabric insert which best suit to the
customers’ needs. Thickness and shape can vary according to the client’s drawing, so that no additional cardboard gaskets are required.
The illustrations from Pic 10 to Pic 13 show some characteristic shapes of reinforced diaphragms.
The concave diaphragm (Pic 10) must be assembled to take on a configuration similar to the convoluted diaphragm (Pic 11).
The convoluted diaphragm, however, is moulded into the same shape that it will take during the assembly phase.

Advantages of the reinforced diaphragms, compared to the diaphragms with rubber-coated fabric:

Better height-to-diameter ratio, therefore longer travel
More efficient seal
Greater resistance to pressure
Possibility of using all types of rubber and fabric inserts
Lower sensitivity and greater hysteresis
The ply is not positioned at centre, as with the rubber-coated fabric, but on the outside surface. As a result, the differential pressure will always be applied to the side of the rubber.

Disadvantages: Lower sensitivity and greater hysteresis; The ply is not positioned at centre, as with the rubber-coated fabric, but on the outside surface. As a result, the differential pressure will always be applied to the side of the rubber.

Diaphragms, in different materials and with different designs, are employed in the following machineries:

Pressure regulators
Flow regulators
Linear actuators
Pneumatic servo-mechanisms
Positioning valves
Safety valves
Acceleration pumps in carburetors
Pressure stabilizers
Pressure transducers
Brakes
Pneumatic switches
Household hot water regulators
Dosing pumps
Waste-gate valves in turbo-compressors

OUR PRODUCTION

EXSTO Italia produces rubber diaphragms with thickness from 0.35 mm and in rubber-coated fabric with thickness from 0.18mm, with diameters from few mm to 800 mm.
We can produce both big series and small quantities, like 50-100 pieces.
We supply also rolls of rubber coated fabrics designed for LPG and methane gas,
EXSTO Italia has 2 automatic die-cutters to cut rubber sheets and rubber coated textile.