Page 136 - Handbook Of Multiphase Flow Assurance

132 5. Flow restrictions and blockages in operations

and deal with either blockage causing a leak, a leak leading to blockage or a projectile move-
ment. In several cases projectile movement allowed to expand knowledge about hydrate ef-
fects on process safety.
There are multiple experiences of hydrate projectile movement, both in subsea lines, off-
shore topsides process facilities, onshore process facilities and onshore pipelines, some im-
pacting on pipe elbows, some on closed or partly opened valves. In some cases this resulted
in a significant pipe movement observed by ROV camera subsea or by personnel on topsides,
in some cases this resulted in a loss of primary containment and hydrocarbons leak, and in
some cases both onshore and offshore this resulted in a pipe rupture and a severe leak of
hydrocarbons. In one instance the formed flammable vapor cloud offshore did not result in a
FPSO catastrophe as wind direction was away from the source of ignition.
18 February 1957 Europe pipeline
Operator noticed inlet pressure increase in a gas condensate field 32 cm gathering network
pipeline while production rate reduced. Following management's command to maintain the
production rate overriding operator's objection, the operator increased inlet pressure which
led to line rupture and ignition as shown in Fig. 5.24. The rupture point was approximately
700 m upstream of the gathering network connection node point. The connection point was at
the crest of a hill. Next day the ruptured pipeline was repaired and the production resumed.
Nine days later another gathering network pipeline ruptured and ignited, downstream of
and close to the connection node point. The connection point valve was closed. A slug of con-
densate discharged from the ruptured segment downstream of the connection point. The slug
fell on a group of repair workers which caused multiple injuries and eight fatalities. Hydrate
blockages were later determined to be the causes of the pipeline ruptures.

FIG. 5.24 First encounter with real consequences of gas hydrates plug effect on process safety, 1957 (Makogon,
personal communication, 2018).