Testing & Inspection
On completion of the trenchless installation or rehabilitation works using PE100 the works must be inspected and tested. This inspection and testing follows the normal procedures of the customer. No special procedures are necessary because a trenchless technique has been used for the installation, rehabilitation or replacement.
Pressure testing of plastic pipes, especially PE, is complicated because the pipe material creeps under pressure therefore the pressure reduces without any leakage so results can be misleading. A water loss method is therefore not practical. This is true for all PE pipes irrespective of the method used to install them.
A method such as the UK IGN 4-01-03 Type 2 test is advisable. Flow and pressure are logged continuously throughout the test and a time correction made for creep. Pass or fail is calculated from the different creep decay rats as the test progresses. The presence of air in the pipe can affect the results so some experience is required in interpretation of the results to identify the influence of air volume.
A useful site test has been developed for trenchless replacement works, especially those using coiled pipes, to test joint integrity. This is known as the 10 Minute Test. All joints are left exposed and checked visually during the test. Test pressure is 1.5 times the pressure rating of the lowest rated component in the system. Flow and pressure are logged throughout the test. Pass/fail criterion is based on the flow of water required to maintain the test pressure in the pipe. The Figures below show results for both passed and failed tests.
Image Courtesy : Exova Utilities
PASSED TEST. Flow (red line) to maintain pressure (blue line) remains low
Image Courtesy: Exova Utilities
FAILED TEST. Flow (red line) to maintain pressure (blue line) remains high