Page 78 - Pipeline Pigging Technology

Pre-inspection-survey activities

Restraints, if any, should be mentioned (e.g. intermittent operations, other
operational limitations, weather window, etc.)

PIPE-WALL SURFACE CONDITION

The surface condition of the pipe wall can usually be predicted from the
available pipeline data. The following guidelines indicate whether an inspec-
tion survey can be started or a pre-survey cleaning programme is required.
The inspection survey can be started if the pipeline is either:

(1) new (a 'baseline' survey), and:

the construction procedure has prevented debris entering the line;
the test water was removed using bi-di pigs, the pigs showing no sign
of excessive wear and not bringing in debris;
the product is clean (e.g. treated gas, white products, injection water,
etc.)

or (2) the pipeline is:

proved clean by regular pigging (a minimum of 4 times/year) with bi-di
pigs, and has perhaps even been surveyed before;
carrying a clean product (e.g. treated gas, white products, NGL, LPG,
injection water, etc.)

It is suggested that a pipeline pre-survey cleaning programme will be
required if the pipeline:

is more than 10 years old and is not pigged regularly;
carries products that form and/or settle-out hydrates, iron sulphates,
salts, sand, waxes or asphalts;
is more than 60km long.

These lines could be gas, crude-oil or water-transmission lines.

59