Mk IV - C11

Compression Stress Relaxometer

Compression Stress Relaxometer Mk IV - C11


The Wallace Compression Stress Relaxometer has the following features:

  • Fast and slow approach and return speeds are adjustable to suit test conditions
  • The Force value to change from fast to slow approach can be selected to suit
  • The Force value limit protects the load cell and jig
  • The Force value limit has a visual and audible warning device


The Compression Stress Relaxometer is widely used in the aerospace, automotive and construction industries for the accurate testing of elastomeric seals. Through the measurement of a single force value, the instrument helps to predict the complex changes that occur in an elastomer (and therefore its service performance) when it is to be used in a new sealing application.

The Compression Stress Relaxometer measures the ability of an elastomer to seal efficiently when held in compression between two rigid faces, for example, rings in pipe joints.

A seal must perform efficiently for long periods of time without attention, sometimes at high and low temperatures, sometimes in liquids, gases, or aggressive chemicals.

Stress at the interface between the elastomer and the rigid faces is important to efficient sealing and is a function of the modulus of the elastomer and the strain applied.

Measurement of stress relaxation detects and measures change in modulus with time.
A single test piece is compressed a known amount in a jig. The stress at the interface between the test piece and jig is measured. The test piece in the jig can be subjected to specified environmental conditioning. The stress is again measured and any reduction in stress is noted.

Stress is measured in the Force Measuring Instrument. Only one Force Measuring Instrument is needed for any number of jigs.
The jig is made of stainless steel. The test piece is compressed between two flat circular faces. Only one face is adjustable to give the correct compression. The second face is mounted in a frictionless manner to permit measurement of stress.

The Wallace Jig is illustrated. The Force Measuring Instrument will receive other jigs including the Lucas and ASTM types.
The Force Measuring Instrument contains a friction less air cylinder to apply force to the jig. The force applied is measured by a load cell and indicated digitally. The test cycle consists of:

  • Press Start Button.
  • Fast approach of measuring head to jig.
  • Change to slow approach at pre-set force value.
  • When force applied is equal to test piece force, digital indicator is locked and instrument returns to start position at return speed.


Compression Stress Relaxometer Features

See the table below for a run-down of this product’s specifications.


Overall Dimensions:

380 wide x 365 deep x 665 mm high

Weight of Instrument:

55 kg net.

Electricity Supply:

110/240 volts AC. 60/50 Hz. 1 ph. 24 watts max.

Air Supply:

Standard Model 300 kPa. 4.5L Free air per minute. or 1.5L Free air per cycle.

Maximum Jig Height:

120 mm.

Minimum Jig Height:

30 mm.

Weight of Jig:

1830 g.

Load Ranges:


0 – 2.2 kN

0 – 225 kgf

0 – 500 lbf


0 – 220 N

0 – 22 kgf

0 – 50 lbf


0 – 1.1 kN

0 – 112kgf

0 – 250 lbf

Operating Speeds:

Fast approach:

2 mm/sec. maximum.

Minumum rate of load increase on Standard Model:

0.25 N/sec.


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