The Shear Test, also known as Alyeska Shear Test, simulates the shearing action a buried pipeline’s external coating receives due to pipe and soil movement. These stresses may lead to wrinkling and disbondment of tape or sleeve coatings, thereby, providing a route for ingress of moisture under the coating. The purpose of this test is to assess the shear resistance if the tape or sleeve in a situation that might result from friction between the tape and the ground during pipe movement. The normal shear loads used in this test simulate the forces experienced in actual operation.
During the test procedure, sample is attached on the test fixture and the normal load of 18.6 kg is applied for about 1 hour before the test is started. Sandpaper is attached to the weight in a manner that exposes the rough side to the coating, preventing the weight from slipping. Subsequently, the shear load of 6.8 kg is applied to the upper weight and the movement of the coating is measured for approximately 50 hours or until 1 inch of travel is achieved. Finally the mode of failure of the coating is assessed.