A test specimen is held between two annular clamps under sufficient pressure to minimize slippage. The under clamping surface which is in contact with the test specimen has a continuous spiral groove and the lower clamping surface has a number of concentric grooves. A circular diaphragm of pure gum rubber is clamped between the lower clamping plate and the pressure cylinder so that before the diaphragm is stretched by pressure underneath it the center of its upper surface is below the plane of the clamping surface.
The equipment is fitted with a motor driven cam mechanism which increases fluid displacement on the lower side of the diaphragm at a specified rate. The equipment is also provided with an arrangement which automatically brings down the pressure and stops the motor on completion of the test cycle. A maximum reading type pressure guage gives the bursting pressure.
The tester is finished in off white stowing enamel paint and bright chrome / zinc plating to give it a corrosion resistant finish.
For conducting tests on material where one pressure guage does not cover the full range of loads encounted with the desired accuracy in measurement, a special model fitted with two pressure gauges with isolating values is also available.