Mitigating inline inspection operational risk.

Author:Hartnell, Chris
Position::TECH NOTES: Product Development
 
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Each year, every pipeline operator must assess the integrity of their pipeline system. Assessment programs range from a few lines for some operators to hundreds for other larger operators. For most operators with piggable pipelines, inline inspection (ELI) tools are usually the preferred assessment method. However, the road to a successful inspection run has many pitfalls.

Pipeline operators must do as much as possible to reduce the likelihood of run failures due to operational problems or errors. The cost to run an inspection tool is high enough, but coupled with a failure where the pipeline operator was at fault only multiplies the cost.

A consistent planning procedure developed by the operator can be a key component to obtaining first-run success. There are a number of pipeline operational factors that should be part of the preparation assessment.

First, obtain measurements and photos of both the launch and receive facilities. Measurements should include all of the key components of the launcher and receiver. Length of oversize pipe, length of nominal pipe, location of bypass tees, and wall thickness of those pieces should be known in advance of an inspection. Additionally, knowing the amount of workspace in front of the launcher and receiver can help mitigate problems in loading and removing the inspection tools.

These measurements may be a factor in choosing the inspection tool. ILI tool vendors have different dimensions for their inspection tools. Proper fit of the tool in the launcher or receiver may be a differentiating factor for choosing to use one vendor over another. If launcher or receiver modifications need to be done to accommodate a certain ILI tool, knowing as far in advance as possible is beneficial.

Other factors to be assessed during the preparation stage are the pipeline pressure and flow rates during normal operation. A review of the ILI tool specification sheet will indicate the minimum and maximum tool speed and line pressure for inspection. The pipeline should operate within those parameters. If the required speed is outside of the normal operating parameters of the pipeline, then a plan must be devised to modify the flow rate such that the specified speed can be obtained.

Pipeline cleanliness can be a large factor in obtaining a successful inspection. Some ILI technologies will negotiate more debris than others. The ILI tool vendor will be able to consult on the cleanliness requirements for the given tool. Cleaning pigs should...

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