Piping leak inspection - Petrofac International Limited

Challenge

The client was experiencing Firemain line leaks at a major gas plant in Algeria during commissioning of the asset. Welding issues, such as, high chlorine and Sulphur content in the water and high temperatures during the summer period created an environment for microbial influenced corrosion (MIC) to form. This created flaws in the super duplex stainless steel Firemain welds and leaks appeared at several welds during hydrostatic testing.

The leaks were all less than 1mm in diameter and located at or directly adjacent the weld material. For positional accuracy a mechanized scanner was used. The Firemain piping was flushed, followed by chemical dosing to eliminate bacterial contaminants, all leaking pipes were wrapped and sealed. Stork was tasked with detecting the MIC and mapping the flaws in the welded segments of piping.

Solution

Stork ensured piping integrity by deploying its phased array ultrasonic inspection (PAUT) technique to both the heat affected zones and parent material adjacent to the weld area of selective piping where the MIC had formed. The selective region of the piping had thickness varying between 2.77mm and 4.76mm which posed a great challenge for the advanced ultrasonic inspection. Stork discovered several other leaking pipes not initially detected during the inspection program.

Stork’s specialized Phased Array Ultrasonic wedges ensured inspection coverage from weld edge using corrosion mapping PAUT probes. Specific test/validation blocks were fabricated to ensure the MIC was detected. The mapping of flaws was performed using weld overlays which ensured weld flaws were not reported. Due to Stork's Advanced Inspection solution for MIC, Petrofac issued a general internal notification to projects that they now have a solution for MIC.

Benefits

Reducing risk
Stork’s Phased Array Inspection solution quickly and effectively identified previously undetected leaks in the piping system. The Firemain line piping system is an integral part of any oil & gas installation. Stork ensured that this system was operating to the highest integrity level by ensuring all leaks were identified for further remedial works to be performed.

Efficient approach
Stork’s concentrated inspection strategy meant only specific welds suffering from MIC had to be replaced by the client.

Safe service delivery
The project was delivered with no incidents, injury or harm to the environment.

Project	Piping leak inspection
Client	Petrofac International Limited
Location	El Merk, Algeria
Services	Advanced Inspection Services - PAUT
Date	2015