Page 210 - Pipeline Pigging Technology

Ethyiene pipeline cleaning

was responsible for the decommissioning and recommissioning and the
handling of all community awareness, safety and environmental concerns.
The project plan was based on the recommended course of action taken from
an engineering report prepared in 1988 by Novacorp, which compared
various methods of establishing the mechanical integrity with associated
costs.

PREWORK

The prework phase included all the work necessary to ensure the work
scope was completed safely and successfully within the 28-day outage.
Procedures were written, manpower selected and trained, the field sites
prepared and the piping assemblies prefabricated. This was difficult, consid-
ering:

AGEC had little experience in decommissioning or recommissioning its
12-in pipeline;
no company had successfully internally-inspected an entire ethyiene
pipeline;

the polymer problem was not clearly understood. Decisions were
based on pressure-drop information and polymer samples retrieved
in filters. Consequently, AGEC relied heavily on the experience of
other ethyiene pipeline companies and pigging contractor exper-
tise to develop the cleaning programme.

PROJECT PLANS

Decommissioning

Based on successful decommissioning of other pipelines, and in order to
meet the tight schedule, it was decided that the decommissioning process
would be carried out by using nitrogen to displace the ethyiene at normal
operating conditions. The nitrogen/ethylene interface would travel at 1.1 m/s
(2.5mph) to maintain fully-turbulent ethyiene flow and to reduce the inter-

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