6 - Kuwait Oil Company

stagnant areas with the intrusion of foreign materials.
KOC came across many situations where hydrocarbon
release incidents occurred due to accelerated excessive
internal corrosion on the walls of the dead legs. The
root cause of such acceleration is the accumulation of
trapped corroding materials referred to as ‘stagnant
oily water’ on the internal walls of the dead legs.
But how are these dead legs responsible for that
hazard Export Operations teams discovered that there
were two immediate causes to this. The first immediate
cause is the perforation of the girth welds at the 6
o’clock position. The perforation (corrosion) was caused
by water separation from crude at the dead legs. The
perforation was then accelerated by the imperfections in
welds (deep incomplete penetration effect). The second
immediate cause was wherever there was excessive
material loss due to pitting corrosion (in some cases
45-65% reduction in original pipe/elbow thickness),
which rendered the drain pipe segment completely
unreliable. Even if it were not leaking at the time of
the inspection, a leak may occur should the location of
the heavy corrosion coincide with external corrosion,
excessive loads or when there is a pipe surge due to bad
operations. Both immediate causes of deposit corrosion
will eventually lead to the failure of the drain segment.
An “L” shaped drain segment with deposited
sludge at the elbow segment of dead legs
Sludge formation
A second hazardous situation arises from the
accumulation of sludge in these dead legs, especially
at the elbow portion. Sludge is usually formed from
the settlement of the suspended waxes in the crude
into any ‘low point’, either at a natural rate or
accelerated due to pigging operations. This traps large
quantities of crude oil (maybe even under pressure)
upstream of the settle point, which in turn provides
false indication to the operations or maintenance
onsite personnel that the line has been completely
drained and is empty. The immediate cause of an
oil spill and discharge into the environment
would be one of the following two reasons:
• The sudden collapse of the sludge blockade
withholding the crude oil when verifying
the line emptiness by the onsite personnel.
• False indication that the line is empty when attempting
to carry out any modifications like cold cutting.
This dead leg with the solidified sludge was connected to a live line
Root causes
1. Standing operational instructions that
were not updated to incorporate the lack
of use of these drain segments.
Current KOC operations and external market obligations
require the heavy, nonstop use of the main carrier
pipelines to which the dead legs are attached to.
In other words, the drain segments would only be
‘flushed’ during the highly infrequent and uncommon
complete draining of these lines, like an emergency
situation where it would be crucial to completely drain
the main pipeline through these drain segments.
Furthermore, it would have been highly unfeasible
to enforce a routine flushing schedule for these dead
legs. In KOC export operations’ area alone, there
is an estimated quantity of 150 ‘U’ and ‘L’ shaped
drain segments so the routine flushing would require
a dedicated large workforce with a considerable
quantity of vacuum tankers and a fully dedicated
30
April - June 2013