Page 68 - Pipeline Pigging Technology

Pipeline design for pigging

Shutdown or - product removal
repair

Types of product

Gas - with H 2O, H 2S, chlorine, etc.
Crude oil - - do -
Injection water - -do-
White products

Types of pipeline

Onshore
- well lines: short, small-diameter, multi-line grids, etc.
- transmission lines: long, mainly larger-diameter

Offshore
- well lines: subsea to platform
platform to platform
subsea to subsea manifold and
flowline tie-in
- transmission lines: platform to platform
platform to shore

Comments

(1) The difference between well lines and transmission lines may be simply
their life cycle. Transmission lines are designed for at least 30 years' service,
while well lines may only be required for 10 years' operation.
(2) Transmission lines usually carry treated product.
(3) Well lines may form a localized grid of short pipelines which may be
considered as suitable for portable pig traps and launchers.
(4) Offshore lines may qualify for multi-pig or sphere traps for remote
launching and reduced supply-boat visits.
(5) Current designs for inspection pigs are shorter than before, and the
difference in length between inspection and cleaning pigs is therefore
becoming less important.
(6) Subsea launchers and receivers require a relatively-low capital invest-
ment, but need a high operational expenditure. That is why there is a special
interest in the development of multi-pig traps and pig diverters (Y-pieces).

49