Dear Peter,
HST or Hot set test or High stress test, we have problems of HST failures with tubular samples due to breakage of sample from clip end.( we are using purpose built clips to hold the tubular samples). Is it happening due to trapped air inside the sample?
Please advise.

2. What is gel content test (for testing the cross linking of XLPE) and what is the procedure? Is it possible to conduct the test without any special equipment?
Regards.

It is certainly because of trapped air inside. Try by inserting wire piece inside tubular sample before clamping. This will allow air to escape from wire ends.

Thank you again kishor for your input. It is really great to have someone with your experience and training around.

student:

Now that I understand the test that you are performing thanks to kishor, please remember that the volume of the air captured inside the tube is a function of the square of the inside diameter of the tube and the length of the sample between the clamps. If the diameter reduces faster than the tube extends, then the air pressure will quickly increase.

Re the gel content test and as I recall there is no special laboratory equipment required other than that found in a reasonably well equipped standard wire and cable manufacturing chemical laboratory. Please obtain the detailed procedure for this test from your XLPE polymer supplier.

Kindest regards,

Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com