Sustainable, Long-Term Solution For MIC/SRB Corrosion In Hydrocarbon, Other Pipeline Systems

U-TECH
By Kent Weisenberg | July 2010 Vol. 65 No. 7
The MIC/SRB corrosion was a severe problem.

In the spring of 2008, a reliability engineer at a major oil refinery contacted Inspar Robotic Technologies Inc., regarding concerns about the continual microbial corrosion problems they were encountering. The facility was experiencing multiple perforations in a progressive sequence from the effluent source in their hydrocarbon pipelines.

As a matter of internal protocol, the plant’s operations was continually installing exterior clamps to arrest leakage from perforations, some as large as 3/4 inch, due to microbial activity. Because governing authorities consider exterior clamps a temporary solution, the client had attempted a permanent solution by replacing sections of the system with stainless steel pipe. The client almost immediately discovered that this changeover did not solve the corrosion problem and in effect, it actually increased the veracity and propagation of the microbial agent.

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An Inspar crew conducting their rehabilitation work on the industrial pipeline.

The pipeline system consisted of six-inch carbon steel pipe with multiple convolutions, ells and earthen penetrations through tank farm containment berms. The effluent composition contained hydrocarbons, acids and miscellaneous organic compounds. The pipeline’s design pressure was 180 psi, with an operating pressure of 120 psi linear to production requirements. Effluent design temperature was approximately 350 degrees F, and the soil load was approximately 12 feet to invert at all berm penetrations.

The problem
Inspection of the sump line revealed significant microbiological induced corrosion (MIC) and/or sulfate reducing bacteria (SRB), resulting in profound cavities, craters and large perforations in the pipeline. Determining specific full circumferential wall thickness measurements along the axis of the subject pipeline required long range ultrasonic testing (LRUT). Inspar performed this testing and subsequently advocated a ‘worst case’ approach due to the sporadic nature of the corrosion. This protocol determined the diameter, depth and quantity of detailed deteriorations in a specific segment of the pipeline.