Lessons from Krechba – In Salah Gas Project Algeria
Krechba is the Gas Gathering Centre for the Algeria Phase 1 In Salah Gas
Project. The facility comprises of two near identical gas processing trains that
treat gas from the production centres of REG and TEG. The facility provides
final gas treatment to sales gas spec before the gas is exported along the new
export pipeline line to Hassi R’ Mel. Treatment is simple comprising glycol
dehydration and CO2 removal. The JGC/ KBR consortia are the EPC
contractor, front end engineering design was undertaken by the KBR
At the time of the incident (May 19), the plant was in the final stages of
commissioning. Train 1 had been flowing gas for a couple of weeks, Train 2
was brought on stream on May 19. Within a matter of hours of start-up,
problems with the CO2 plant resulted in gas being diverted to flare. During the
start-up of Train 1, it had been note that the flare system seemed excessively
noisy and vibration in some of the pipe work resulted in bolts holding pipe
clamps becoming loose. As Train 2 started to send gas to flare the situation
became worse. Within hours the 6” line taking gas off the top of the glycol
contactor to the flare header failed catastrophically at the header. The plant
then went into automatic emergency shutdown resulting in a large proportion
of the gas inventory (calculated circa 80 tonnes) venting through the hole left
by the failed 6” pipe in the flare header. Luckily the wind was blowing away
from the plant and the gas did not ignite.
Fig 1 Showing the 6” Pipe bent back Fig 2 Hole left in the Train 2 Flare
Coming from VB - 0241O2
VB - 0241O2 Undersized
VB - 0241O1
Initial Investigation Findings
The 6” dia line connecting the glycol contactor to the flare header was
grossly under designed – should have been 12 “dia. The under-design
caused sonic velocities resulting in excessive vibration and very rapid
fatigue failure. This line has now been replaced.
A complete engineering check of the entire blowdown system including
the systems at REG and TEG revealed numerous instances where gas
velocities exceeded code levels. Over 20 minor modifications to the
system involving the insertion of orifice plates and reinforcing of some
tail pipes has been necessary.
The design case for the flare system at Krechba was assumed to be
simultaneous blowdown of the two trains together. In fact a significantly
worse case is the blowdown of a single train. Single train blowdown
should have been the design case, checks on this case revealed the
header to Train 2 to be grossly under sized. This header is being
replaced – a major modification to the plant.
Root Cause Findings of the Engineering Authority Investigation
The investigation showed multiple breakdowns of the Project system,
Incompetent designer and failure to appreciate the importance of the
blow down system to the safety of operations.
Failure to apply what should have been a good QA/QC system. The
original calculations for the 6” pipeline have not been found. The
Contractor QC system required independent checks of critical safety
systems. These checks were not carried out for this line.
Failure to follow through on PHESR/HAZOP findings. The HAZOP
commented on the unusual configuration of pipe work entering the
header. These comments were not followed upon.
Failure of the commissioning team to adequately respond to excessive
noise and vibration in the blow-down system. Bolts that fell out of pipe
clamps were replaced and re-torqued without reference back to the
Barriers that broke down at Krechba
In competent Good PHESR/HAZOP Commissioning Lack of an
designer QA/QC queried design Staff failed to ignition
failed to system not but failed to realise significance source
understand applied follow through of vibrations prevented
of design cases
Many barriers were broken in this incident. Had there been a source of
ignition in the vicinity of the pipe failure, a major fire could have ensued with
some danger to personnel and the potential loss of a $1bn facility.
Request to Engineering Authorities
Flare systems are one of the primary safety systems that protect staff and
plant. They need to be designed by competent engineers to a basis of design.
The design needs to be thoroughly checked.
The Projects & Engineering Function requests to ensure that:-
There is a basis of design for the system that explains the design
That piping calculations for the full system exist, show gas velocities
within code limits, and that the calculations have been checked by
That there has been a Project HAZOP that has included a detailed
review of the blowdown system, and that actions/ recommendations
from the HAZOP have been closed out.