Assessing the Use of Composite Materials in Repairing Mechanical Damage in Transmission Pipelines

Abstract

Mechanical damage involving dents with gouges is one of the leading causes of transmission pipeline failures in terms of both static and cyclic pressure loading. Because of the severity of this defect type, pipeline companies are required to respond to these anomalies by either removing damaged sections or repair using welded sleeves. For more than 10 years, composite materials have been used to repair corroded pipelines and their use has gained wide acceptance across the pipeline industry. Numerous systems have been tested with results being presented in the open literature. Testing was recently performed to assess the use of a water-activated composite repair system, Aquawrap®, in terms of its ability to repair mechanical damage subjected to cyclic pressure service. The Aquawrap® repair system has been extensively tested on corrosion defects but testing on pipes with dents had not been done. The water activated pre-preg urethane resin system offers excellent long tern (creep-rupture) strength combined with easy low cost field installation. Pipes having diameter to wall thickness ratios ranging from 34 to 68 were fitted with dents and gouges. Repair involved removing the gouged material of the pipe after indentation and repairing using the composite sleeve. The result of this specific test program showed that on-average the fatigue life for mechanically-damaged pipes can be increased on the order of three orders of magnitude when repaired by grinding and installing composite sleeves. This paper provides details on the methodology of the test program, results, and most importantly, information that can be used by operators in repairing their pipeline systems.

Intentional Destructive Testing: A Means for Establishing Mechanical Integrity

“…Consider the table provided in Figure 2 a 4 th order relationship is assumed between stress and cycles as expressed in the following relation based on Miner's Rule. (1) In this equation N is the number of respective cycles and ΔP is the applied pressure range in units of psi. For each pressure range captured from the rainflow counting exercise (and shown in the histogram in Figure 2) a new equivalent cycle number is generated for the 1,104 psi (7.6 MPa) pressure range.…”

The Use of Composite Materials in Repairing and Reinforcing Pipelines, Piping, and Structures

“…To evaluate the effect of composite materials utilized in the repair of mechanically damaged pipe, Alexander and Worth performed fatigue testing on damaged pipe that had been repaired to varying degrees [29]. Pipes were intentionally gouged to simulate mechanical damage.…”

CFRP Reinforcement and Repair of Steel Pipe Elbows Subjected to Severe Cyclic Loading

“…Previous research on this subject has been directed towards the reinforcement of large diameter pipelines and pipe elbows, with the purpose of improving their structural integrity against pressure containment. Relevant studies have been reported on where the use of composite materials to repair and strengthen pressurized transmission pipelines against corrosion, dents, wrinkle bends and other pipe wall anomalies and in other hand to reinforce large diameter pipe elbow subjected to extreme bending loading [14], [15], [16], [17]. A more recent study focused on the repair of offshore pipe risers using composite materials [18], considering three conditions of corroded pipe riser.…”