Composite pipeline repair technology has been around for more than a decade, representing an affordable and timesaving option for pipe rehabilitation. The introduction of national and international ASME and ISO engineering standards has helped composite repairs gain wider acceptance in the industry as an effective solution for restoration of pipeline integrity and structural strength.
Because they gain the ability to make repairs with no disruption to operations, more and more pipeline operators are making these systems part of their pipeline integrity programs—for repairing corrosion, dents, and other defects in their steel-piping systems.
“With more than 15 years of practice in place, the industry now has a fairly high comfort level with composite repairs,” said Andrew Hammerschmidt, research and development manager at Gas Technology Institute (GTI), a research and development organization serving the natural gas industry. “Today, they view them as cost-effective, safe, and reliable repair options.”
Which Is The Best Option?
When considering options for a repair project, an operator must first make an informed decision about whether composite repair products are appropriate for a specific application and, if so, which product is the best option. With more composite repair products entering the market every year, operators need guidance in choosing the right product for the right application.
Operators also need help in providing the engineering tests and analyses required by the U.S. Department of Transportation (DOT) pipeline integrity management regulations (49 Part 192). These include minimum requirements for damaged natural gas steel transmission pipelines operating at stress levels at or about 40% SMYS, as well as options for pipelines operating at or above 20% SMYS and in high consequence areas (HCAs).
Once repairs are completed for any pipeline, the DOT regulations require engineering tests and analysis data demonstrating that the serviceability of the pipe has been permanently restored. Yet, until now, operators have had to rely on manufacturer tests and industry experience for the data needed to demonstrate the long-term performance of the repairs they make using composite repair products.
For many years, researchers at GTI have been working to fill that critical information gap. Recent research has been designed to help operators understand the benefits of composite pipeline repair products, sort out their options when it is time to choose a repair method, and provide the backup data they need to demonstrate the permanence of the repairs they make.
“We’ve been working to provide the reliable engineering tests that the federal code asks for,” Hammerschmidt said. “We now have the data operators need to select a composite pipeline repair system based on its predicted service life.”
GTI Research Adds To Industry Intelligence
Three major research projects conducted by GTI engineers in recent years, funded by a pool of gas distribution companies through Operations Technology Development (OTD) and the Department of Transportation Pipeline and Hazardous Materials Safety Administration (DOT PHMSA), are beginning to provide the industry with the reliable engineering data that is so important when a pipeline repair is needed.
From their work, two new Web-based applications soon will be available to help operators determine: 1) what repairs need to be made for a specific repair project in order to comply with DOT pipeline integrity management codes; 2) what repair options are available for the project; 3) whether a composite repair system can be used to perform the repair; 4) if a composite repair is an option, which product is the best option; and 5) expected performance degradation of the composite repair.
The Pipeline Damage App (Application), a Web-based application that provides guidelines for evaluating the severity of mechanical damage of low-stress pipelines (operating below 40% SMYS), will provide the data needed to make determinations for items 1-3. While the application has been around for five years, it has been updated. “We recently did additional work to increase the database set behind it,” Hammerschmidt said.
When using the app to generate data about a given repair project, the operator will be able to enter data about pipe characteristics, operating conditions, and the severity of the pipe damage. Once the data are entered, the application will detail the repairs that are needed and direct the user to the relevant industry codes for schedule and repair options.
The Pipeline Damage App is the result of a research project in which GTI researchers identified the repair requirements for mechanically damaged low-stress natural gas pipelines (based on 49 CFR Part 192 and ASME 31.8 standards) in order to provide operators with field protocols and guidelines for selecting their repair options.
Another Web-based application will provide operators with the tests and analyses they need to make determinations for items 4-5 on the list—to help them choose the right composite repair product and to demonstrate permanence of the repair.
The CPR Product Selection App includes a database of seven commercially available composite repair systems, with information about the required number of wraps for each repair system based on pipe and damage characteristics—comparing manufacturer requirements for number of wraps vs. requirements based on ASME PCC-2 standards.
“The ASME PCC-2 design procedure was implemented in the Web-based app to provide users with the design parameters of the composite repair methods,” said Khalid Farrag, GTI research and development manager. “It provides the properties of the repair materials, the number of layers, and the length of repair for a given damage on the pipe surface.”
When using the app, the user will be able to input the damage and operating parameters to see how a specific composite repair product would perform over a 20-year life cycle (depending on the number of layers that would be applied). If it is above the current ASME PCC-2 standard, it qualifies as a permanent repair.
How GTI Developed The Data
Data for the CPR app resulted from two GTI projects in which GTI researchers tested and assessed the performance of seven commercially available composite repair systems in compliance with DOT integrity management codes.
“To choose the products for testing, we surveyed the utilities sponsoring this project (13 of the largest utilities in North America) about which systems they’re using and which ones they were interested in testing,” Hammerschmidt said.
“Once an operator determines that a pipe section can be repaired using a composite repair system, there are two components he needs to look at in conjunction with each other to determine the permanence of that repair,” Hammerschmidt said. The long-term performance of any composite repair system depends on several factors, including the long-term strength of the reinforcing fabric and the long-term shear strength of the adhesive used in the composite.
“We looked at the fabric of each system—how it holds up over time against stresses and strains, as well as the adhesives that keep the system together,” Hammershmidt said. “Both of these mechanisms can degrade over time, making them potential failure mechanisms.”
To predict the life expectancy of the repair (and to meet the ASME PCC-2 standard), GTI researchers evaluated composite repair systems in full-scale pipe sections by subjecting them to short-term and long-term hydrostatic pressures (up to 1,000 hours). Manufacturers provided the repair material and performed the sample installations.
Composites that show satisfactory long-term performance can be used as permanent repairs, as long as the number of plys used in the repair and their installation procedures satisfy ASME PCC-2 design and installation requirements. All seven composite repair systems passed the 1,000-hour test.
An important project is adding to industry knowledge about the adhesives used in a number of currently available composite repair systems. This is critical information, since adhesives not only bond the repair to the pipe, they also bond individual layers of the repair to each other. If the bond between layers is not adequate, the load will not be transferred from the pipe to the repair.
GTI researchers evaluated the long-term shear strength of adhesives used in composite repairs and cathodic disbondment of several repair systems. “We tested seven of the common composite systems on the market,” Hammerschmidt said. “We took them through a series of 10,000-hour standardized tests, shear tests, and extrapolated them to estimate their expected performance over a 20-year life cycle.”
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