GhubrahIncidentInves.. - authority for electricity regulation, oman

R 8991 15 May 2006
REPORT ON INVESTIGATION OF
INCIDENT AT AL-GHUBRAH POWER
AND DESALINATION PLANT - 10TH
MAY 2006
Restricted to, Authority for Electricity
Regulation (AER), Oman & Advantica
PREPARED FOR:
John Cunneen
Authority for Electricity
Regulation (AER), Oman
PREPARED BY:
John Martin
Advantica
Navigation House
Furness Quay, Salford Quays, Manchester
M50 3XZ
United Kingdom
Tel: +44 (0)161 868 4488
Fax: +44 (0)161 868 4451
E-mail: john.martin@cogsys.com
Website: www.advantica.biz
Customer Reference:
This Report is protected by copyright and may not be reproduced in whole or in part by any means without the approval in writing of
Advantica Ltd. No Person, other than the Customer for whom it has been prepared may place reliance on its contents and no duty
of care is assumed by Advantica toward any Person other than the Customer.
This Report must be read in its entirety and is subject to any assumptions and qualifications expressed therein. Elements of this
Report contain detailed technical data which is intended for analysis only by persons possessing requisite expertise in its subject
matter.
Registered in England and Wales No. 3294136.
REGISTERED OFFICE: 1-3 STRAND, LONDON, WC2N 5EH

Report Number: R 8991
Issue: 1.1
Executive Summary
A serious incident occurred at Al Ghubrah Power and Desalination Plant, Muscat, on
9 th May 2006, which resulted in fatal injuries to two Sogex employees whilst
performing maintenance activities on the Phase 3 ‘D’ Hypochlorite storage cylinder.
Following the incident the AER requested Advantica to visit the site of the incident to
carry out a site inspection and to conduct an evaluation of the probable cause of the
incident.
The Advantica visit took place on 10 th May 2006. A verbal debriefing was conducted
at the AER offices with the Executive Director, and a document was prepared for
issue to all sites following the initial site survey and inspections, which stated that no
further work should be carried out on the Hypochlorite cylinders. The timetable for
the issue of this report was also discussed during the debriefing.
The principle cause of the incident at Al Ghubrah was a systemic failure of the
Permit to Work (PTW) system. ‘Hot’ work involving the use of electrical tools to
repair a section of the cylinder structure was allowed to take place under a
work order which referenced a ‘cold’ PTW. The ‘cold’ permit had been raised
previously to cover painting activities, and stated that no isolations, draining or
venting were required. The subsequent cylinder repair work should have been the
subject of a proper Risk Assessment which would have identified the need for the
work to be carried out under a ‘hot’ PTW with suitable gas detection and other safety
precautions, including necessary isolations and proper venting. The source of
ignition was in all probability the use of an electric drill (not fit for purpose - drill
brushes causing sparks in hazardous area, electrical connections badly made etc.)
in proximity to ‘D’ cylinder vent (not isolated and in service at the time).
There were no job-specific fire precautions (i.e. Portable fire extinguishers) in
place.
A new rigorous PTW system is required urgently for the Al Ghubrah site. Risk
Assessments should be carried out prior to all activities. The safety
department should be involved at all stages of an activity.
Scaffolding construction and inspection standards should be reviewed as soon as
possible. Although not a direct contributory factor to the incident, the poor standards
observed could be a danger to health and safety in their own right.
Page i

Report Number: R 8991
Issue: 1.1
Project Code: AER May 2006
Distribution
Name
Company
John Cunneen Authority for Electricity
Regulation (AER), Oman
Document Authorisation
Name Signature Date
Author (s)
Reviewers
QA
John Martin
Sikobe Litaba
Rebecca Gavin
Ian Mather
Authorisation
Sikobe Litaba
Page ii

Report Number: R 8991
Issue: 1.1
Contents
1 INTRODUCTION................................................................................................. 4
2 FINDINGS........................................................................................................... 5
3 PROCESS .......................................................................................................... 6
4 PROBABLE CAUSE .......................................................................................... 6
4.1 Inadequate Permit to Work considerations.......................................... 6
4.2 Probable source of ignition ................................................................... 6
4.3 Related Observations............................................................................. 6
5 CONCLUSIONS.................................................................................................. 7
6 RECOMMENDATIONS....................................................................................... 8
APPENDIX A LOA NO. 10795/L.......................................................................... 9
APPENDIX B LO 42/04/06................................................................................. 10
APPENDIX C PTW/LOA AUTHORISATION .................................................... 11
Page iii

Report Number: R 8991
Issue: 1.1
1 INTRODUCTION
Following a serious incident at Al Ghubrah Power and Desalination Plant, Muscat,
which resulted in fatal injuries to two Sogex employees (Sogex are the principal
Operation and Maintenance contractor) whilst performing maintenance activities on
the ‘D’ Hypochlorite cylinder, the AER requested Advantica to visit the site of the
incident to carry out an evaluation of the circumstances and the probable cause of
the incident.
On 9 th May 2006 at 0825 hours, two Sogex employees were involved in the
replacement of cladding on the ‘D’ Hypochlorite cylinder when an explosion occurred
that resulted in the two employees receiving serious external burns, and also serious
respiratory problems due to inhalation of the gases during the explosion. Both
employees subsequently died from their injuries.
On 10 th May 2006 Advantica principal engineer Mr. John Martin (the author of this
report) visited the scene of the incident and met with Sogex senior management
personnel. The investigations carried out and detailed in this report should not be
deemed to be in lieu of any police and/or insurance investigative processes. The
following details a brief report on the findings of the interviews of the Sogex
personnel and a survey of the scene of the accident.
Page 4 / 11

Report Number: R 8991
Issue: 1.1
2 FINDINGS
On arrival at site, Senior Sogex personnel (including the site General Manager) were
interviewed to determine the circumstances and the probable root cause of the
incident. Work permits, work orders, procedures, evidence of competencies and
health and safety documents were requested and received. The author received full
and open co-operation from Sogex personnel throughout the investigation.
On the 25/03/06, a Limitation-of-Access (LOA) Permit-To-Work (PTW), LOA
No.10795/L was issued to carry out routine maintenance on the external surfaces of
the Phase 3 Hypochlorite Storage Tanks, C and D (See Appendix A). The permit
was issued for (1) cleaning, (2) surface preparation and (3) painting. The cylinders
were to be left in service and the permit clearly states that no isolations were to be
carried out and that the civil department (conducting the painting operation) were to
take all safety precautions. In this respect this specific PTW/LOA covered activity of
a ‘cold’ work nature, although it is observed that the relevant section of the permit
designed to indicate ‘hot’ or ‘cold’ status was left unspecified.
On inspection of the job site on cylinder ‘D’, the civil department reported that the
cylinder jacket was badly corroded and hence a work order (Reference No. LO
42/04/06) was raised on 05/04/06 to the Mechanical Department, to replace the
cladding (hood) on cylinders A, B, and D (See Appendix B). The work order No. LO
42/04/06 references PTW/LOA No. 10795/L.
Evidence was requested regarding the competency and authorisation of the permit
issuer and work order issuer. Sogex personnel produced relevant CVs and
authorisation memos stating that the persons concerned had been assessed and
found competent to sign permits (see Appendix C).
The work to replace the cladding involved the removal of the corroded cladding and
the fabrication and installation of replacement cladding. To replace the cladding it is
necessary to use drills for the riveting process.
It appears that the mechanical fitters were left to complete the work with no periodic
site inspections by the management and no safety departmental presence.
Work on the ‘C’ Hypochlorite cylinder had been performed under a separate internal
work order (LO 37/03/06, not included in this report), without incident. However,
during the process of installing the newly fabricated hooding of the ‘D’ cylinder, an
explosion occurred resulting in a ‘fire ball’ that fatally injured the two Sogex
maintenance fitters involved. They reportedly were able to climb down from the top
of the cylinder, a difficult feat, to seek assistance.
Once the incident had been discovered, the Hypochlorite plant was shut down and
the two employees were immediately transferred to hospital where they were placed
in intensive care, but subsequently passed away.
Page 5 / 11

Report Number: R 8991
Issue: 1.1
3 PROCESS
Hypochlorite is used during the desalination process to control bacterial growth
within the system. Hydrogen is a by-product of the process. The Hypochlorite
treatment process separates the majority of the hydrogen in separators prior to being
pumped into the hypochlorite storage cylinder. Each cylinder is allowed to vent to
atmosphere, and to assist the ventilation process, three fans, two running and one in
standby are used, common to the four cylinders. Although the majority of the
hydrogen is separated, prior to storage, there still remains a ‘trace’ level. The ‘D’
hypochlorite cylinder was reportedly 80% full (liquid) allowing the remaining head
space to fill with hydrogen separated from the hypochlorite before venting to
atmosphere. Note, the cylinders vent to atmosphere and are therefore not classed as
pressurised vessels.
4 PROBABLE CAUSE
4.1 Inadequate Permit to Work considerations
Permit PTW / LOA No. 10795/L does not state whether it is a hot or cold permit to
work, neither box is ticked. However, the wording on the permit indicates that it was
considered to be a ‘cold’ PTW covering the cylinder painting activity only. Under a
‘cold’ permit to work the painters contacted mechanical maintenance to assess and /
or replace the hooding on the four hypochlorite cylinders. Work order No. LO
42/04/06 was issued and progressed for Tanks A, B and D with reference to LOA
No. 10795/L with no Risk Assessment evident. Repair maintenance to Cylinder ‘C’
was completed without incident under a separate Work Order LO 37/03/06 (not
included). During the maintenance activities on the ‘D’ cylinder the two maintenance
fitters were using an electric drill in proximity to the cylinder vent, where the
probability of hydrogen gas being present should have been considered to be the
norm, and therefore a significant risk to health and safety given the work involving a
potential source of ignition.
4.2 Probable source of ignition
The electric drill being used at the time of the incident was of a standard ‘DIY’ type
with the original plug removed and ‘taped’ to extension cord with a 13 amp, standard
3-pin domestic plug. The plug was inserted into an extension lead drum (still coiled
(not good practice)) with an industrial plug fitted. An electric drill will always issue
sparks from the brushes and in all probability a spark from the drill brushes (or at
least, some similar form of ignition) ignited the hydrogen gas venting from the
hypochlorite tank which caused the hydrogen within the cylinder to explode (gas was
under the constraints of the cylinder) and hence a ‘fire ball’ issued from the vent
causing the fatal injuries to the two maintenance fitters.
4.3 Related Observations
The explosion was of sufficient force to lift the entire cylinder c. 100mm from its
anchoring bolts and snap a 200mm drainage pipe with pipe wall thickness of c.
12mm.
Page 6 / 11

Report Number: R 8991
Issue: 1.1
There were no job-specific fire precautions (i.e. Portable fire extinguishers) in place.
Also of note, although not a direct contributory factor to the incident, was the poor
conditions of the scaffolding erected to allow work on the cylinder to take place. The
scaffolding had no inspection tags, the scaffold boards were not fixed, the safety rail
(if that is what is was supposed to be) was at knee height, no kick boards were in
place, no secondary means of escape was installed and access to the work area
was by using the cylinders built-on ladder making it difficult to get on and off the work
area.
5 CONCLUSIONS
The principle cause of the incident was a systemic failure of the permit to work
procedure.
Under the directive of a ‘cold’ permit, issued to carry out painting, which clearly
stipulates that isolations were NOT to be carried out, a work order was issued to the
mechanical department to carry out what should have been considered ‘hot’ work
and a new permit considering the new risks should have been required.
There was no evidence of periodic management site inspections being carried out
and there were no representatives of the Safety department.
Risk Assessments were not carried out and the general statement in the procedures
that ‘maintained, where applicable, by the Discipline Engineer who issued the
Internal Work Order. Safety of the employees working on the Internal Work Order is
taken care of’ is clearly insufficient.
The ‘cold’ permit states that ‘civil to take all safety precautions’ in an attempt to place
the safety onus on the employees, rather than the management assessing the risks
involved before signing.
There should clearly have been a separate permit to work issued following a
thorough Risk Assessment, that insisted upon mechanical and electrical isolations,
draining and venting the cylinder, and gas testing prior to any work commencing.
The work procedures are on the whole generic, and little work has been carried out
to codify tasks and note inherent risks in the differing operation and maintenance
protocols.
The tools in use during the maintenance activities on the hypochlorite cylinders were
not fit for purpose (drill brushes causing sparks in hazardous area, electrical
connections badly made, extension lead coiled etc.).
Additionally, the poor condition of the scaffolding erected to allow work on the
cylinder is of concern.
Page 7 / 11

Report Number: R 8991
Issue: 1.1
6 RECOMMENDATIONS
No further work is to be undertaken on the hypochlorite cylinders until a thorough
Risk Assessment has been carried out and a new Permit To Work system has been
instigated that has a check list and calls for electrical and mechanical isolations and
gas detections. It should also state that hydrogen gas should always to be assumed
to be present and not expected to be in ‘trace’ amounts only.
No work orders should be allowed to fall under a ‘general’ cold PTW. Each process
should be considered to require a new PTW along with rigorous Risk Assessments.
A Safety representative should be present as the Risk Assessment is being
undertaken and should be a signatory to the permit to work.
If possible, pneumatic tools should be used and where this is not possible, a rigorous
risk analysis and gas detection regime should be in place if electrical tools are to be
used. All tools should be fit for purpose and inspected regularly. All portable
electrical devices should fall under a Portable Appliances test regime. If contractors
are used, any tools used should conform to the above standards and should be
verified as part of the permit to work system.
On issuing of a PTW a ‘tool box talk’ should be carried out by the permit issuer to
inform personnel assigned to carry out the activity of the risks involved and ensure
that the risks are fully understood and that all possible safety precautions have been
carried out. During activity, management should periodically inspect the job along
with the safety representative.
The PTW system should be re-assessed regularly by management in liaison with the
safety representatives, operators, and maintenance personnel.
Job site-specific fire risks should be carried out and the correct equipment put in
place prior to work commencing.
Note: A recent independent ISO audit of Al-Ghubrah also pointed out inadequacies
in the PTW system. The Sogex management were, at the time of the incident,
reviewing the PTW system they had received from another operator.
From the author’s brief inspection of this third party PTW system, it appeared to be
on the lines of Al-Ghubrah’s requirement. The new PTW system should be agreed
upon by Sogex management, checked by a third party and instigated with all speed.
Scaffolding construction and inspection regimes should be reviewed and practices
improved as soon as possible.
Page 8 / 11

Report Number: R 8991
Issue: 1.1
APPENDIX A LOA NO. 10795/L
Page 9 / 11

Report Number: R 8991
Issue: 1.1
APPENDIX B LO 42/04/06
Page 10 / 11

Report Number: R 8991
Issue: 1.1
APPENDIX C
PTW/LOA AUTHORISATION
Page 11 / 11