On-line leak repair (or leak sealing) has saved operators countless millions of dollars in the 100 years since it was invented. What was at first a craft practice of stopping steam leaks with rubber-based compounds has matured into a highly engineered specialty service that serves all industries and leakage scenarios.
Given this, one would assume standards would be well-defined and the industry well-informed. Not necessarily.
"On-line leak repair is a niche activity where many operators don't have the in-house expertise to ensure work is performed in a safe and compliant manner," said Adam Thistlethwaite, TEAM Industrial Services' service line director for on-stream repair. "That is why we engage in policy development with most major operators."
Understanding the defect and expected repair life
The consequences of failure during a leak repair can be catastrophic. Understanding the defect and expected life of the repair is crucial. Corroded and/or leaking piping compromises the integrity of the entire system.
External corrosion damage mechanisms will not typically propagate once the repair is in place; therefore, the risk of future line separation is low. For active internal corrosion, even a successful leak repair will not prevent the defect from propagating. Continued internal degradation leading to pipe separation and complete loss of containment can occur. Such instances are rare but can be catastrophic in nature.
"In partnership with our most progressive customers, TEAM continues to develop robust procedures that ensure operators are guided down the correct path in terms of piping restraints or strong-backs," said Thistlethwaite. "These research and operating experience-based procedures are considered to be at the forefront of the industry."
Best practices driven by failure mechanism knowledge
Bolted joint leakage is becoming less common with the development of ASME PCC-1 compliant procedures and robust bolt-load software platforms like TEAM's IQ55. However, when a leak does occur on-stream, leak sealing is typically the operator's go-to technology to prevent downtime.
Sealing a leaking flange modifies one key design assumption of the flange bolt: It may become exposed to the line content. Exposing flange bolting to the line contents can in some cases increase the risk of stress corrosion cracking (SCC). This failure mechanism can be rapid and difficult to detect.
Until recently, SCC was not well-understood in a leak-sealing context due to numerous variables, particularly in a steam-raising plant.
"TEAM has invested greatly in understanding this failure mechanism and building our procedures on the back of this research," said Thistlethwaite. "We believe we have a duty of care to our employees, our customers and our competitors to raise the awareness level in industry."
TEAM subject matter experts chair and actively contribute to the ASME PCC-2 Subgroup on Mechanical Repair to move toward producing industry-wide standards related to on-line leak repairs. Thistlethwaite is serving as project manager for the in-progress leak repair article related to this subject, while working alongside many major operators and consultants to ensure it provides industry with solid guidance.
For more information, visit www. TeamInc.com or call (800) 662-8326.
