Abriox

AT TEST POSTS

Monitoring at test posts is the definitive check of whether CP is being applied correctly to the pipeline. However, the frequency of monitoring test posts varies from company to company and may also depend on external factors. Not all test posts are checked in every case.

Remote monitoring at frequently-read test posts, as for the TRs, will generate a relatively quick payback when compared to manual costs

However, there are other situations where remote monitoring can be considered for asset management and/or safety reasons:

• Drain points at TRs

• CP low points (often mid-way between TRs)

• Pipe crossings or other sources of foreign pipe interference

• Bonds between pipes

• Isolation joints

• Downstream of compressor stations (elevated temperatures)

• Pipelines with known or suspected susceptibility to AC (eg sited below power lines)

• Test posts located at busy roadsides, rail or river crossings where there is a safety hazard

• Test posts where access is difficult or authorisation is required from a landowner.

Useful measurements at Test Posts are:

• Pipe-to-soil (ON) potential

• Instant OFF potential

• Coupon current

• Current density

Traditionally, these measurements have all been DC levels. However, it is now recognised that AC levels can be significant for pipeline corrosion and the operation of the CP system. Regulatory bodies therefore now require AC measurements to be taken in addition.

The MERLIN Test Post Monitor takes all these measurements automatically, including AC measurements on all channels.