Full Scale Burst Validation Tests for Crack Arrestor Designs for NPS 48 Grade 550 Rich Gas Pipeline

Two full scale burst tests for the assessment of different crack arrestor designs were carried out on the pipes that will be used in the Coastal GasLink (CGL) Pipeline project. The tests supported by LNG Canada and TransCanada Technology Management Program were conducted at the Spadeadam test site of DNV GL, United Kingdom (UK), on 1219 mm (48 inch) outside diameter CSA Z245.1 Category II Grade 550 pipe at a nominal pressure of 13.38 MPa (1,940 psig) with 80% SMYS and temperature of −5°C, and with a gas representative of the richest gas envisaged for transport in the CGL pipeline project. The reservoirs are spaced with a gap between the reservoir ends of approximately 130 m, where the test section, comprising eleven pipe lengths and a tie-in pup, was installed. The centre of the test section consisted of an 18.5 mm thick low toughness initiation pipe. The remaining pipes were referenced as 1E to 5E in the easterly direction and similarly 1W to 5W in the westerly direction. The propagation pipes (1E and 1W) with 18.5 mm wall thickness, used to establish steady-state propagation, were located immediately either side of the central initiation pipe. For the first test, two crack arrestor pipes with 29.6 mm wall thickness were installed adjacent to the propagation pipes in the west and east directions, with a lead-in transition of 18.5 mm wall thickness for a distance of 130 mm then a 4:1 taper running back to the full pipe wall thickness. To the east, the first crack arrestor pipe had an average Charpy Vee-notch (CVN) energy of 246 J and to the west it had an average CVN energy of 341 J at the inboard end. In both directions, the fracture propagated from the initiation pipe, through the propagation pipes (1E/1W) before arresting in the first 29.6 mm thick crack arrestor pipes (2E/2W). In both directions, the arrest resulted in the fracture turning at the toe of the tapered transition on the front end of crack arrestor pipes 2E and 2W. The pipe arrangement for the second test was similar to the first one. In the east direction, in order to optimize crack arrestor design, two 24.7 mm wall thickness pipes replaced the 29.6 mm pipes which were used in the first test. In the west direction, the test section contained four 18.5 mm wall thickness test pipes arranged with a progressively increasing Charpy energy, up to 452 J. A low toughness, 18.5 mm thick pipe (5W), with a 1.8 m long Clock Spring® crack arrestor completed the test section. To the east, the fracture propagated from the initiation pipe through pipe 1E before arresting near the inboard end of the crack arrestor pipe 2E. In the west direction, the fracture was observed to run through all four of the pipes arranged with increasing CVN energy, before being arrested by the Clock Spring® crack arrestor fitted to the fifth pipe.

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