Sealed Enclosures » Testing

Testing

Materials
Testing starts with the material itself.  Although mechanical data is readily available for metals this is not always the case with plastics so we use our own method for obtaining the Young’s modulus or stiffness of the plastics we use.  In particular this allows us to take account of changes when the material is wet and when it is warm.

Leak Detection
The usual way to test for leaks is with a vacuum test. If glands are fitted they would need to be blanked off;  if cables are installed within the glands, a vacuum test is not possible as air will flow into the enclosure via the cable interstices. Where sub-sea bulkhead connectors or penetrators which contain water-blocks have been installed, a vacuum test can easily be performed and cable plugs are not required.

Pressure Resistance
To prove that a housing can withstand a given pressure we perform a hydrostatic test.  This involves applying water pressure to the external surfaces of the housing in a pressure vessel. The pressure is normally measured in bar with one bar applied for every ten metres of water depth plus a safety factor. Our pressure vessel (see picture below) has an internal diameter of 820mm, an internal height of 1500mm and can provide a pressure of 10 bar equivalent to 100 meters water depth.

Test 007

Test to Destruction
Occasionally it is important to prove the margin of safety, or how much pressure can be applied in excess of the working pressure before the housing collapses.  This can only be done with a test to destruction causing the housing to implode. In the case of the Sea Chest our FEA modelling results were confirmed by an implosion at fifty eight bar or seven times working pressure. At this pressure the housing would have been significantly distorted with the equivalent of over one hundred tons force applied over the largest face.
d - 58 bar later