Page 75 - Pipeline Pigging Technology

Pipeline Pigging Technology

PRE-CONTRACT ACTIVITIES

The activities prior to an inspection can be summarized as follows:

gather all relevant information;
determine if inspection can start, or if further cleaning is required;
design a pre-survey cleaning programme;
establish if debris is present;
remove debris by pigging until the inspection pig can be run.

These, and related, activities are discussed below:

Relevant information

Relevant information shall be gathered and should be recorded in a
pipeline-inspection reference file. The information should include:

design parameters;
mechanical properties;
operating data (normal and during survey);
anticipated pipe wall condition;
design (as-built) drawings;
welding records;
any remarks about the history of the pipeline construction or opera-
tions that may be relevant to the corrosion rate (e.g. hydrostatic test
water remained in the pipeline for two years before start-up, the line
was flooded with untreated water, flow conditions were very
different in the past, deviation in cathodic protection readings, etc.)

The corrosion survey equipment will produce a snapshot of the pipe-wall
metal loss. This is useful information, of course, and is suitable for identifying
defects for immediate repair. However for future planning of a cost-effective
maintenance programme, the information from the corrosion-reference file
and the results of the survey should be merged for further study.

Inquiry preparation

Although this paper deals mainly with technical matters, the major
commercial aspects are highlighted:

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