Commissioning Experience of World's Largest Single-Train ...
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2011 [47] AMMONIA TECHNICAL MANUAL
Commissioning Experience of World’s Largest
Single-Train Urea Complex
At the end of 2010, Engro Fertilizers commissioned world’s largest single-train Urea complex capable
of producing 3835 tpd prilled urea. This paper presents an overview of the project and its journey of
commissioning thru various stages. It also shares the problems encountered & key lessons during the
project phase.
Muhammad Idrees, Muhammad Azhar & Muddassar Y. Rathore
Engro Fertilizers Limited, Daharki, Pakistan
Synopsis
his paper shares Engro’s successful Com-
missioning Experience of world’s largest
single-train Urea complex of 2200 tons per
day ammonia and 3835 tons per day prilled urea. It
explains the roadmap of the project followed by
the commissioning team; starting from operator’s
team build-up, training phases including training at
Operator Training Simulator (OTS) and then the
field execution of pre-commissioning & commis-
sioning activities in 2010. It also shares the prob-
lems encountered & key lessons learned during the
project phase for future projects of this sort.
Introduction
Engro Fertilizers Limited is the second largest
manufacturer of Urea in Pakistan. Previously, En-
gro was a 75% owned affiliate of Exxon Corpora-
tion. In 1991, Exxon decided to sell its 75% equity
holding in Engro as part of a global strategy to di-
vest from the fertilizer business. Nearly 500 em-
ployees of Engro, in partnership with a group of
leading local and foreign financial institutions, ac-
quired Exxon's equity holding in Engro. The Man-
ufacturing site is located in a small town of Pakis-
tan known as Daharki, which is 600 km north of
the famous Port City of Karachi.
The original ammonia-urea plant, with self sustain-
ing utilities, was commissioned in December 1968.
The capacity was 173,000 t (metric tonne) of
prilled urea per year. This was 80% of urea market
share in the country at that time. Over the next 22
years, the plant was debottlenecked in several low
cost steps to a production capacity of 270,000 t of
urea per year.
Urea production increased from an annual capacity
of 270,000 tons in 1991 to 600,000 tons after the
startup of relocated ammonia and urea plants from
Pascagoula (USA) & Bellingham (UK) respective-
ly in 1993 and then to almost 1 million tons in
2006 after a series of revamps and energy conser-
vation projects.
T
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After the commissioning of new plants in 2010,
annual capacity of the site has increased further to
2.3 million tons of urea. Engro has accomplished
significant progress not only in its base urea ferti-
lizer business but also in other diversified projects.
Other businesses include foods, power generation,
automation, polymer and a jetty for bulk chemical
and gas storage/shipping.
Project Overview
Pakistan is an agricultural country where the de-
mand for fertilizers has always been higher than
the in-house productions. To meet the increasing
demands of fertilizer and to use the natural gas re-
sources in an economically rational way Engro
took an initiative by developing the feasibility
analysis of ammonia-urea complex of 1.3 million t
urea production annual capacity. The feasibility
analysis was completed in 2006 and eventually gas
allocation was approved by the Government of Pa-
kistan in 1st quarter of 2007.
Plant Configuration & Process
Layout
The Ammonia plant is of Haldor Topsoe design
having a nominal capacity of 2200 t per day. In-
cluded are both front end flare, backend flare and a
CO2 removal section using BASF aMDEA solvent.
SAIPEM is the process licensor for urea technolo-
gy with capacity of 3835 t per day, including the
world’s tallest prill tower of 124 meters. The urea
plant is also equipped with continuous and discon-
tinuous flares.
Ammonia plant design is based on following Natu-
ral gas Composition.
Components Volume Percent
Methane 84.24
Ethane 1.06
Carbon dioxide 1.97
Nitrogen 12.11
Table 1. Design Composition of Natural Gas Feed
The Feed Gas contains less than 2% of Carbon
dioxide resulting in imbalance of Ammonia to
Carbon dioxide ratio for Urea Plant. In order to
compensate the above factor, the ammonia refor-
mer fluegas includes an amine based Carbon Dio-
xide Recovery unit (CDR) having the capacity of
349 t per day, based on Mitsubishi (MHI), Japan
technology.
Project Execution
Contract for license, engineering, procurement was
given to SAIPEM. Construction Contract was giv-
en to Descon Engineering Ltd (DEL), Pakistan.
Commissioning was Engro’s responsibility. This
was a unique project in comparison to other LSTK
projects, where normally a project management
consultant (PMC) is contracted by the company to
deal with EPCC contractor. Substantial utility inte-
gration was involved with the base plant, which
wouldn’t have been possible for EPC contractor to
manage. Hence, engineering and procurement of
integrated utilities and CDR unit was done by En-
gro under owner scope which makes the project
unique. The owner scope included;
• 26 MW GE frame 5 gas turbine with Heat Re-
covery Steam Generator (HRSG) cum Boiler
of 150 tons per hour, 41 Kg/cm2(g) Steam.
Unique HRSG design with Flying Takeover
system.
• 5000 tons Ammonia double-walled storage
tank
• CO2 recovery unit (CDR) from primary refor-
mer flue gas. A unit Based on MHI, Japan
technology using KS1 Solvent
• Offsite water production facility, containing 38
wells of 250 m3/hr each & a 2000 m
3/hr canal
water treatment plant.
• Onsite water treatment; containing reverse os-
mosis membranes of capacity 180 cubic meter
demineralized water (< 10 micro siemens) per
hour along-with two bed demineralization
trains of the same capacity
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• Instrument air system (3300 Nm3 per hour)
• Cryogenic nitrogen plant (750 Nm3 per hour)
• Natural gas receiving facility
• Plant effluent handling system and evaporation
ponds
Project Schedule
Fig. 1. Various stages of Project from Apr’07 to
Oct’10
Date Milestones / Activities
4-Apr-07 Effective Date of the Contract
Aug-08 Start of Mechanical Erection
26-Jun-09 Effluent System Commissioned
12-Nov-09 Natural Gas Receiving
Nov-09 Power available from Gas turbine
Dec-09 Steam available from HRSG
19-Dec-09 Start of Steam Blowing
25-Jan-10 Start of Air Blowing
20-Feb-10 Offsite facility Commissioned
12-Jun-10 Air Compressor Commissioned
20-Aug-10 Ammonia Storage Commissioned
12-Jul-10 Firing of Reformer for refractory
Dry-out
10-Nov-10 Firing of Reformer for startup
11-Nov-10 Feed-in to Primary Reformer
16-Nov-10 Gas to CO2 Removal & on-spec
CO2 availability
16-Nov-10 Synthesis Gas Ready
29-Nov-10 Fire at Synthesis Compressor due to
thermo-well failure
20-Dec-10 Synthesis Compressor Restart
23-Dec-10 Start of Catalyst Reduction of S-
300 Converter
26-Dec-10 Ammonia Production
29-Dec-10 Urea Production
Apr 2007
Apr 2008
Mar 2009
Oct 2008
Oct 2010
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Safety Reviews
Safety reviews were conducted at SAIPEM office
in Milan, Italy during various stages of engineer-
ing. Experienced Engro personnel from various
disciplines (i.e. Safety, Technical, Operations,
Maintenance & Instrument) participated in these
reviews.
ACTIIVITY TIMEFRAME
What If 17th to 24th July, 2007
Failure Mode & Effects
Analysis (FMEA) 17th Oct to 16th Nov, 2007
P&ID Review 28th Jan to 1st Feb, 2008
HAZOP 4th Feb to 29th Feb, 2008
Table 2. Safety Reviews Timeframe
A total of 1206 recommendations were generated
during these reviews and all of them were closed
before the startup of the plant. 3D model reviews
were also conducted at different project stages
(60% & 90% - excluding small bore piping) for
checking operability, accessibility, maintenance
spaces, safety distances, emergency escape routes
etc.
Operations Team Roadmap
A roadmap was developed by operations team lea-
dership in the mid 2008, the main stages are as fol-
lows;
1. Operations Team Build-up
2. P&ID Systemization
3. Procedures Development
4. Training
5. Pre-commissioning and Commissioning
Operations Team Build-up
An organogram was developed for startup organi-
zation for defining the total operations manpower
required for pre-commissioning, commissioning &
start-up activities of the complex. The final matrix
required a total of 18 engineers and 85 operators.
Position Ammonia Urea Utilities
Unit Manager 1 1
Day Engineer 1
Shift Coordinator 5
Shift Engineer 5 5
DCS Operator 10 5 5
Field Operator 35 25 10
Table 3.Operations Team Manpower
Recruiting and gathering such a big team was a
humongous task. Some trained resources were
transferred from the already running base plant,
while most of the population was hired from other
fertilizer and oil & gas industries. The hiring
process took almost eight months from Aug 2008
till March 2009, to get the required number of re-
sources.
Formation of operations team was completed al-
most 18 months prior to the actual commissioning
& startup of world’s largest plant.
Area Champions
From the very start, distribution of responsibilities
was made using area champion concept. For ex-
ample, the ammonia plant reforming section had an
area champion, an operations engineer, leading a
team of 10 operators. Area Champions were sup-
posed to bring themselves on-board and raise their
knowledge of reforming section through study of
technical material like PFD, P&IDs, vendor ma-
nuals, HAZOP and FMEA of the respective area.
From these, they developed the pre-commissioning
& commissioning procedures, and then prepared
training material and conducted training sessions in
classroom trainings to bring the knowledge of rest
of the population at par. In this way, the ammonia
plant, which also included ammonia storage area,
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was distributed to five area champions, similarly
the urea plant was divided into four sections, and
each section was looked after by a separate area
champion. Utilities were distributed to two area
champions. By following this methodology, the
management of activities became very effective
and efficient as each area champion was responsi-
ble for achieving the time-line and schedule of his
own area.
P&ID Systemization
The P&ID Systemization is the separation of the
plant into smaller and manageable packages called
systems & subsystems to support the mechanical
construction as per commissioning requirements.
In this way, pre-commissioning of certain systems
was started even before 100% construction was
complete. Similarly commissioning of certain early
needed systems (mostly utilities) was completed
even before the completion of pre-commissioning
activities at site. As a result of following a syste-
mized approach, there was the benefit of time sav-
ing. This prioritization was applied once 70% con-
struction scope was completed. The process of
systemization followed, consisted of the following
steps;
1. Defining systems & subsystems
2. Assigning specific color to each sub system
3. Marking on the P&IDs (using software)
4. Tracing each sub-system on P&ID and not-
ing down all the pipeline numbers, instru-
ments, vessel, control valves, safety valves,
ESD interlocking etc in a tabular form.
5. Interlinking for total system (Ammonia,
Urea & Utilities) and developing the com-
missioning requirements for each system
6. Assigning priority number to each sub-
system and handover of the final document
to construction shop to put focus on high
priority items accordingly.
7. Development of comprehensive barcharts
& Start-up Control Diagrams based on the
priorities defined in P&ID Systemization.
Procedure Development
After a lot of thought process, discussion and deli-
beration a procedure template was developed, it in-
cluded the following contents;
1. Circuit Information & acceptance criteria
2. Arrangements/Preparations to be made by
Instrument & mechanical teams
3. Personal protective equipment required
4. Hazards & consequences
5. Pre-checks
6. Field Execution checklists
7. Circuit/ Loop clearance certificate
8. Checklist for Reinstatement
9. Marked up P&IDs
More than 530 procedures for carrying out various
pre-commissioning and commissioning activities
were developed based on the above template. Ex-
amples include air blowing, steam blowing, chemi-
cal cleaning, lube oil circuits flushing, commis-
sioning and startup of machinery equipment,
refractory dry-outs, alkali boil-out, alkali washing,
over-speed trip (OST) testing of turbines etc. The
lists of preparatory items for each activity were
handed over to the mechanical pre-commissioning
group at an early stage. Each procedure was pre-
sented in class-room trainings, where it was re-
viewed by the trainee population and corrections
were incorporated. Furthermore, document ap-
proval protocol was developed for proper review
and approval of each procedure from the relevant
and knowledgeable authorities.
Training
Training is the key element, especially when it
comes to the startup of the Ammonia-Urea com-
plex, an intricate mixture of hazard and vulnerabil-
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ity. An elaborate training syllabus was prepared
covering all facets of operations: PFD, P&ID,
HAZOP, FMEA, pre-commissioning, commission-
ing, startup, shutdown, normal operation and
emergency handling etc. More than 40,000 man-
hours were spent on training with an average of
around 400 man-hours per person. The whole
training program had a complete methodology be-
hind it and that was a series of layers concept,
which clearly illustrated the connection between
one layer and the other.
In-house Classroom Training (Apr-Jun
2009)
The first layer was the in-house classroom training
which started in April 2009 when the hiring
process had been completed. Respective Area
champions were nominated for In-house Trainings
with an objective to develop area-wise trainings &
then share these with whole group. Extensive In-
house training sessions were conducted to develop
knowledge & base of individuals for upcoming
practical trainings. Contents of each area training
were;
• Process description
• PFD / P&IDs
• Control Systems / ESD logic
• Standard Operating Conditions (SOC)
• Safety Reviews (FMEA / HAZOP)
• Pre Commissioning & Commissioning
procedures
• Startup / Shutdown / Emergency Handling
Procedures
Dedicated sessions on site safety systems (work
permit protocol, process safety management etc)
were also delivered to individuals hired from other
industries. Written tests were also conducted at the
end of each session to evaluate knowledge retained
by individuals and it was made a pre-requisite for
each individual to pass the written evaluation be-
fore getting skill certified at that area.
Training at Similar Technology (Jul-Oct
2009)
Second layer illustrated the importance of practical
exposure where, special groups of people were sent
to similar technology plants i.e. Fauji Fertilizer
(FFC) for seven weeks & then to Oman India Ferti-
lizer Company (OMIFCO) for two weeks to get
hands-on to Topsoe & SAIPEM technologies. Tai-
lor-made training programs were developed which
covered the following training aspects;
• Startup / Shutdown Discussions
• Emergency Handling Procedures
• DCS orientation
• Field Orientation
• Experience Sharing of Pre-commissioning
/ commissioning
• Problems Encountered during commission-
ing
Training by Technology Licensors (Oct -
Nov 2009)
The representatives of SAIPEM / Haldor Topsoe
delivered lectures on design and operating philoso-
phies of urea / ammonia plants, however, till that
time, operations team had been so well-prepared
after going through series of trainings that repre-
sentatives appreciated the team by calling it ‘a very
well prepared team, ready for start-up’. Extensive
discussions were carried out in these sessions on
Pre-commissioning, Commissioning, Startup,
Shutdown, Emergency Handling and Trouble
Shooting.
Operator Training Simulator (OTS)
The final and most important layer was the imple-
mentation of the Operator Training Simulator, the
phases are explained as follows.
Development
Justification of OTS implementation for the am-
monia plant had been approved on the basis of cost
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saving during the commissioning. Engro’s team
remained involved right from the start of the
project. To harmonize the architecture and ergo-
nomics, the same vendor (Honeywell) was selected
for both DCS & OTS. In addition, the training hall
structure & layout were developed in a manner that
the operator had the feeling of sitting inside the ac-
tual control room (Fig. 2 & 3).
In Jan 2009, a team comprising of Engro opera-
tions and process engineers was sent to Honeywell
Singapore for kick off meeting. In that meeting,
scope of work was finalized and P& ID markup
was done to build a Unisim model for the ammonia
plant OTS. Later in May 2009, in the presence of
Engro engineers, Model Acceptance Test (MAT)
was conducted in Singapore. The completed model
was tested for initial conditions and startup as per
SOP. It took around ten days to do the start-up as
at that time no DCS schematic was linked to the
model. This start-up test was done on the model in-
terface which made for quite a chaotic activity.
Subsequently plant shutdown was also tested and a
detailed punch list was made for the corrections. In
August 2009, all the logics & schematics database
of Integrated Control System (ICS) including DCS
and Emergency Shut Down (ESD) were sent to the
vendor to do complete linking of ICS with the
ammonia plant model.
The Factory Acceptance Test (FAT) was carried
out in Dec 2009.
Fig 2. Operators training in OTS hall
Following sequence was followed;
• MAT punch list killing and Steady state
verifications as per PFD
• Initial conditions verification
• Plant Startup
• Plant Steady state conditions verification as
per PFD
• Plant Shutdown
• Malfunctions Testing
During these activities, the following observations
were recorded;
1. During startup, shutdown and malfunctions
execution, a number of needed changes
were identified to make model operation
more close to actual plant operation.
2. Several points on schematics for which in-
dications were not appearing because of
having no link between model and sche-
matics were identified.
3. DCS related logics and complex control
loops testing was carried to see model be-
havior. A few logics were found incorrectly
built-in in the database and were sent back
technology licensor for corrections.
4. All ESD logics were tested. Anomalies
were identified in some of the logics which
needed correction by technology licensor.
Fig 3. Operators sitting at DCS inside control room
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On completion of the FAT activity, two days of in-
structor training was conducted in Singapore to
train the Engro team instructors about different
features of OTS and trainee evaluations by induc-
ing the malfunctions.
Training on OTS
Effective utilization of OTS played a vital role in
safe and trouble-free commissioning of the plant
and resulted in cost saving during commissioning
phase of the plant through upfront identification of
problems, controllers tuning, troubleshooting,
smooth start-up, emergency handling and above all
due to ZERO tripping on operator error.
The OTS arrived at site four months prior to actual
commissioning. A well structured training program
had developed for round the clock training of oper-
ators and shift engineers in day and night shifts.
Skill certification of DCS operators was done on
the basis of their scores in various exercises at
OTS. A sense of competition among different op-
erators was developed while completing the scena-
rios with quick and correct actions.
Benefits
A number of potential shutdowns were saved by
the OTS trained operators during actual startup of
the plant. Frontend was normalized in record time
of five days from Feed-in till methanator outlet.
Following are the benefits that Engro team ex-
tracted out of OTS training.
1. Testing & validation of Operating Proce-
dures.
2. Based on experience from OTS, controller
tuning parameter adjustments were made
on DCS prior to startup. Process & steam
vents were tuned to act very fast while lev-
el controller were tuned to act relatively
slower. Tuning parameters of all the con-
trollers in OTS were simply replicated in
DCS and they worked well.
3. Cascade controllers / split range controller
mistakes were identified in the OTS and
corrected in DCS. For example, the 3-
element controller algorithm for steam
drum level had problems, so this was cor-
rected and then incorporated in DCS pro-
gramming.
4. Mistakes in interlocks were identified and
then these were corrected in the ESD e.g.
protection steam to air coil is established
when air to secondary reformer is cut but in
the interlock, it was mandatory to keep 60
tph of protection steam flow through air
coil to prevent the reformer trip.
5. Delay time and set points of the protection
securities were adjusted on the basis of ex-
perience e.g. 110 Kg/cm2(g) steam (KS)
coil outlet temperatures rose sharply when-
ever there was a tripping of any major con-
sumer of KS i.e. synthesis or CO2 com-
pressor. After discussion with technology
licensor; high temperature trip set point
was slightly increased and a delay time was
added.
6. Because of repeated exercises on OTS, op-
erator familiarization of the screens made
the transition to the DCS easier.
7. On the basis of training exercises, Emer-
gency handling groups were developed.
Thus controllers to be operated in a par-
ticularly emergency were kept in the same
group.
8. Identification of problematic areas prior to
the actual startup was another operator
benefit. As an example, BFW coil tempera-
tures remained close to the upper limit at
lower load especially before air introduc-
tion due to low steam generation during
start-up exercises. The same phenomenon
was also experienced during actual start-
up, however, operators were prepared for
that and drain at the coil outlet was opened
to control the temperatures.
9. Emergency handling skills developed
through various OTS exercises later
averted plant shutdowns.
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Skill Qualification Protocol
The operations team goal was safe and flawless
pre-commissioning, commissioning and start up of
Ammonia, Urea and Utilities. Through a well ma-
naged skill qualification program, better trained
and skilled operating personnel can be developed
and contribute towards safe and timely start-up of
the complex. This protocol provided for the skill
qualification of operations personnel for the pre-
commissioning, commissioning and startup activi-
ties of respective areas. Skill Qualification was
made mandatory for everyone before taking the in-
dependent duty. Skill qualification process in-
cluded the initiation, preliminary evaluation, final
evaluation and certification process. Skill qualifi-
cation process was applied to:
• Field Operators
• DCS Operators (Boardmen)
• Shift Engineer
• Shift Coordinators
For each individual, two bodies were involved in
the process;
• Mentoring body (Level-II); responsible for
the initial training & evaluation. This was
comprised of Shift Supervisor and Shift
Coordinator.
• Reviewing Body (Level-I); responsible for
the final evaluation of the skill forwarded
by mentoring body. It was comprised of a
board who reviewed the skill and know-
ledge of the individual. For DCS Opera-
tors, the board was comprised of one shift
coordinator, 02 unit managers, Operations
and Startup manager and SAIPEM com-
missioning manager.
The skill qualification process started with the is-
suance of training plan to the individuals and then
the self training on technical literature was carried
out by the individual. Help and guidance was pro-
vided by respective mentoring bodies, which also
conducted routine reviews to monitor the progress
of the individual. Then the individuals went
through the in-house training for the assigned area.
It was mandatory for the individual to clear the
Process Safety Management tests and the in-house
evaluation before skill certification is initiated and
forwarded to the reviewing body. An oral and prac-
tical review was conducted by the review board
and results were recorded on the review sheet. If
knowledge and skill of the candidate was found sa-
tisfactory, the candidate was skill certified for in-
dependent duty at his respective area. If the candi-
date failed to satisfy the board, his skill
qualification process was halted and his mentoring
body was informed regarding the areas of im-
provement. The candidate would be called for re-
evaluation after an interval set by the reviewing
body. Anyone, who failed to get skill certification,
was not allowed to work in the field.
Pre-commissioning
Pre-commissioning of the project, a gigantic task
was initially the contractor's responsibility, but
looking at the tight deadlines, this task was taken
over by the operations team, which started with
development of pre-commissioning procedures in
line with DuPont Process Safety Risk Management
(PSRM) guidelines. It was well understood right
from the beginning that success of project would
lie with a ‘once through’ approach for pre-
commissioning and saving of two hours by skip-
ping any step can cost you days during commis-
sioning. Pre-commissioning execution was done
with high quality and there was no problem of sys-
tem cleaning. During commissioning phase, none
of the control valves had problems getting sticky.
The thoroughness of steam blowing and lines
flushing resulted into smooth startups of all steam
driven turbo-trains. Maximum steam consumption
of 100 to 120 tph was recorded from HRSG for
blowing for large bore pipes like steam line to syn-
thesis compressor turbine.
Respective area champions carried out regular list-
ing of deficiencies in the form of punch & butt lists
as the construction progressed. This provided con-
tinuous feedback to the construction group for cor-
recting deficiencies as soon as they happened. This
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also resulted in a significant time savings and mi-
nimized rework.
Proper cleaning of aMDEA system is very impor-
tant as it is sensitive to any foreign material. Con-
sidering that fact, extra focus was put for cleaning
of packing and the circulation established with sa-
crificial strainers of fine meshes for almost double
the duration than recommended. Antifoam dosing
was continued right from the start as per licensors
recommendation. After LTS line-up, gas was
vented for six hours at 80% equivalent load before
gas introduction to aMDEA section which also
helped in avoiding catalyst dust carry-over the
clean system. As a result, the commissioning of
CO2 removal system was very smooth.
High pressure test of synthesis loop was carried out
at 200 Kg/cm2(g) by an outsourced company. More
than 25 leakage points were identified and at-
tended.
Audits before Feed-in The following audits were carried out in the field
prior to feed-in, to ensure that area is free of ha-
zard.
1. System-wise requirements audit before
feed-in.
2. Pre-startup PHA recommendations closure
3. Pre-startup Safety Reviews (PSSR) rec-
ommendations closure
4. Temporary gaskets audit
5. Piping conformity audit by SAIPEM for
frontend
6. Instrument air leakages audit
7. Flow meters audit
8. Sample coolers audit
9. Audit for completion of permissive for
feed-in
10. Housekeeping & unnecessary material
(scaffolding, cabling etc) audits
Commissioning and Startup
Unlike the conventional EPCC (Turn Key) projects
where contractor provides a complete team for
commissioning & startup, Engro decided
to keep this responsibility with the operations
team, showing confidence on the in-house opera-
tional expertise and training systems. The team
measured up to the mark and saved millions of dol-
lars which are normally paid to the contractor for
commissioning services.
The team endured all external pressures & chal-
lenges (like gas limitations, abstruse steam bal-
ances, steam drum level fluctuations, BFW leakag-
es, synthesis gas fire, unreliable flow indications).
Barring the time lost due to gas limitations and
synthesis compressor outage Engro started the
world’s largest fertilizer complex in 12 days. Front
end was normalized in a record time of five days
from feed-in to reformer. On-spec production of
urea was also registered within 48 hours of the
urea plant startup.
Fig 4. Energy & Gas Consumptions during Project
Because of the advance training and preparation,
many start-up emergencies were well handled by
operations team making swift and correct deci-
sions. The team proved its competence to counter-
act those emergencies, which could have delayed
the production for an indefinite period of time. As
shown in figure 4, the total energy consumed dur-
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ing pre-commissioning and commissioning phase
was 1,200,000 Giga Calories.
Important Numbers During the Project
Energy for Pre-commissioning 550,000 G cal
Energy for Commissioning & star-
tup
650,000 G cal
Total Energy Consumption 1,200,000 G cal
Frontend Startup & Normalization
from Feed-in
05 Days
Backend Startup & Production 07 Days
Effective Ammonia Plant startup
time barring the gas outages & syn
comp incident
12 Days
Total waste water generated 26,000 K Gal
Construction Completion Time
from Effective date of Contract
43 months 22 days
Table 4. Important numbers during the project
Problems Encountered
The cooperative efforts by the construction, in-
strument and electrical teams resolved each prob-
lem diligently and patiently. Even though some
disturbances did occur during the construction
phase (like man-power unrest and extended rainy
season) and then during the initial startup, first
product was obtained in 45 months from the effec-
tive date of the contract.
The following summaries provide the details of
some major problems encountered during commis-
sioning and startup.
1. Syn Gas Fire
On Nov 29th, 2010, fire occurred due to dislodging
of a thermo-well from recycle suction line of syn-
thesis gas compressor. The machine was imme-
diately shutdown by using field manual switch and
vents were accordingly opened to depressurize the
system. The fire was extinguished immediately by
operating deluge system (water sprinkler).
Incident background
Synthesis compressor was started around 2330 hrs
for surge mapping and ramped to minimum gover-
nor (7227 rpm). In order to draw the surge curve
the anti-surge valve was closed very slowly till it
was 35% closed and the final discharge pressure
was 157 kg/cm2(g). At that moment, when the re-
cycle stage suction pressure was 139 kg/cm2g, a
thermo-well (11-TW-5053), installed at recycle
suction dislodged resulting in synthesis gas leakage
and explosion. Flames from the fire hit the instru-
ment cable tray beneath the air compressor turbine
resulting in air compressor tripping as its ESD
cables got damaged. The synthesis compressor was
tripped using manual trip switch, and the compres-
sor inter stage was depressurized immediately. The
deluge system was operated resulting in the forma-
tion of water curtain around the machine and fire
was extinguished in five minutes of occurrence.
Key Findings
The root cause of the incident was the faulty instal-
lation of threadolet on synthesis gas recycle stage
suction. This did not allow the thermo-well to be
fully tightened.
Fig 5. Inadequate height of thread (courtesy SAFR)
At various instances the construction team encoun-
tered a problem during installation of thermo-wells
not properly screwing inside threadolet. This was
primarily due to issues with fabrication and weld-
ing of the threadolet installed on piping at con-
struction contractor’s fabrication shop. These holes
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had been made with gas cutting set which is not a
standard practice especially where instrumentation
is involved. In some cases, excessive root penetra-
tion was also found hindering thermo-well inser-
tion (Fig 6).
Fig. 6. Excessive root penetration hindering insertion
Recommendations
1. Carry out mechanical and quality assurance
checks of all thermo-wells, instrument hook-
ups and small bore piping on all critical / ha-
zardous systems.
2. Install all thermo-wells as per standard practice
given in ANSI Standard on NPT threads.
2. Leakage at Ammonia Export Line
On Sep 30, 2010, an ammonia leakage occurred
during the commissioning of ammonia export line
from ammonia storage facility to existing base
ammonia plant. One of the transfer line drain
bleeders failed at the pipe rack.
Background:
Prior to the introduction of ammonia, a survey of
the entire transfer line was carried out and all the
bleeders were found closed and capped. Further to
ensure the tightness of the flanges, a soap test of all
the flanges on the line was carried out and the ni-
trogen pressure of 7 kg/cm2g was held in the line
for three hours which hardly dropped to 6.85
Kg/cm2(g). Ammonia vapors were then introduced
from the existing base ammonia plant in the trans-
fer line to carry out gassing up and controlled cool-
ing of the line. After ensuring the displacement of
the nitrogen with ammonia vapors, the jump-over
valve towards the tank was opened to avoid over
pressurization of the line.
After two hours, leakage at one drain bleeder on
the line at pipe rack top was reported. The line was
isolated immediately and depressurized through
the jump-over line going back to the tank. Water
curtains were developed immediately to avoid the
impact of ammonia to the surroundings.
Key Findings
1. An audit of the bleeders and drains found that
the bleeder at which leakage occurred might
have been choked by some rust/dust in slightly
open position and on exposure to the low tem-
perature liquid ammonia might get released.
2. The high cooling rate of the line might have
caused a sudden contraction of the line. The
earlier survey showed that all the bleeders were
capped; however, the leaking point cap might
not be completely tightened and the sudden
contraction might have caused the bleeder cap
to displace.
Recommendations
1. A lock-out & tag-out strategy was developed
for bleeders and drain points provided on the
ammonia service lines.
2. To ensure all the bleeders are being mentioned
and isolated, the procedure and checklist was
updated by carrying out the field audit using
isometric drawings.
3. BFW leakage at Valve Gland
Pusher
On Dec 02, 2010, the isolation valve of a BFW
control valve at the back-end BFW preheater began
to leak excessively. Plant shutdown seemed immi-
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nent but the plant parameters were adjusted in a
way that BFW consumption reduced to minimum
decreasing the BFW header pressure and helped in
leakage rectification.
Background
Just after the introduction of air to secondary re-
former, at about 2330 hrs, a heavy BFW leakage
started from the isolating valve of BFW control
valve to Back-end BFW heater (see fig 7). The
valve was in closed position and its gland pusher
was found cracked from middle. Attempt was
made to open the valve for back-seating but the
moment valve was opened, the extent of leakage
further increased. Decision was made to go for
normal shutdown of the plant and if leakage further
increased, total trip (I-1) to be activated to avoid
WHB dry-out condition.
In parallel, the following strategy was developed to
avoid complete shutdown,
• Process air to the secondary reformer was
stopped which reduced the BFW consump-
tion.
• Furnace firing was reduced by lowering the
fuel pressure and extinguishing some burn-
ers in the top row.
• Front end load and steam drum pressure
was reduced and BFW header pressure was
also reduced by reducing the speed of tur-
bine driven BFW pump.
• BFW main isolation valve (Butterfly type)
towards steam drum through LTS and con-
verter preheater was closed and all BFW
flow to Steam drum was directed through
BFW convection coil.
• The level of Steam drum was put on ma-
nual and board man was advised to actuate
I-1 if in any case level drops. The area op-
erator was also deputed at local glass level
guage of the steam drum to observe any
unusual level variation.
• Partial gas vent was started at HTS inlet to
reduce heat load in the LTS upstream BFW
heater.
By taking the above actions, leakage at the valve
reduced to almost 50%. So the valve was opened
for back-seating using necessary personal protec-
tive equpiment (PPE), and the leakage initially in-
creased a bit but after 60% valve opening the lea-
kage trend started to reduce. On 100% opening of
the valve (back-seating), the leakage from gland
reduced to minimum - sufficient for repacking of
the valve and a new gland pusher, fabricated in two
pieces, was welded & tightened.
It was found, that the original gland pusher was of
low strength due to hollow configuration. That re-
sulted in a crack in the middle of gland pusher
leading to the BFW valve leakage.
Fig.7. BFW leakage at Valve Gland Pusher
4. Unreliable Flow Transmitters
Flow meters are very important for the uniform
and normal operation of the plant as they are the
direct indication of the system behavior. Flow
transmitters remained problematic especially for
the case of steam flows to compressor turbines
which caused tremendous problems in steam calcu-
lations and understanding the behavior of turbine
drivers. On tripping of synthesis or CO2 compres-
sors, problematic flow transmitters resulted in dis-
turbance of entire steam system. Steam consump-
tion signals continuously go to KS-HS letdown
station (PRDS) and on tripping of any of the com-
pressor PRDS opens to let down the additional
steam. Since the flow meters were not showing the
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correct indications of steam consumption so a ma-
nual value of steam consumption, based on steam
balance was input to PRDS.
Due to unreliable behavior of the flow transmitters
during steam introduction, feed-in and process air
line-up, flows were controlled by manipulating the
opening of control valves through valve Cv calcu-
lations.
The operation remained smooth even with unrelia-
ble flow indications of plant’s most critical para-
meters. This was due to the Abnormal Situation
Management Skills that the team had developed
over the period.
5. Delay in Air Introduction to Sec Refor-
mer
On Nov-26, 2010, at about 20:15 hrs air introduc-
tion to Secondary reformer failed twice due to
stuck check valve but was successfully lined up in
the third attempt. The activity delayed the startup
activities for about six hours.
Background:
Air introduction to the secondary reformer failed in
the first attempt and it was concluded that the air
pressure (35 Kg/cm2g) might be slightly lower than
the required driving force as reformer pressure was
around 25 kg/cm2g. During the second attempt the
air compressor discharge pressure was increased
till 38 kg/cm2g and valve was opened till 35 % to
allow significant flow but still no indication of
temperature rise in secondary reformer was ob-
served.
The startup activity was delayed for about six
hours for inspecting all the flanges for any blind
left in place, however no such blind was observed.
It was decided to increase the air compressor dis-
charge pressure to 40 kg/cm2 and the opening of
valve to 50 % to allow maximum flow. An abnor-
mal sound was observed from the 2nd air coil inlet
check valve resulting in the establishment of air to
secondary reformer.
Fig 8. Process air to secondary reformer
6. Syn Machine faulty RPM Indications
During startup of synthesis compressor, it was ob-
served that the governor speed indicator was show-
ing more RPM than the actual - the prime reason
for unpredictable behavior of the compressor. Dis-
charge pressure and steam consumption was not up
to the marked value. After getting RPM confirmed
by the portable tachometer the indication got cor-
rected. The activity delayed startup for about six
hours.
Background:
On Nov 26 at about 0900 hrs, synthesis gas com-
pressor was started and ramped to minimum gov-
ernor but the behavior of the turbine was quite un-
predictable as the machine reached at min governor
(7227 RPM). It was consuming only 30 tph of the
steam and the discharge pressure was about 56
kg/cm2 instead of 90 kg/cm
2 at min governor.
When the speed of the machine was checked by us-
ing portable tachometer it showed that the actual
RPM were 2/3rd of the RPM indication at gover-
nor. After that the governor speed indication was
checked and rectified.
Key Findings
On checking the speed indication calculation chart
following observations were made.
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1. Total no of teeth at the turbine are 30 per
revolution.
2. The value of no. of teeth placed in speed
calculation formula was 20 teeth per revo-
lution.
This was a clear indication of the unpredictable
behavior of the turbine as in actual the RPM of the
machine was quite lower than the governor speed
indicator. The speed calculation formula was cor-
rected and activity was resumed.
7. Surging of CO2 Compressor Low Pres-
sure Case
Surging was observed in low pressure stage of the
compressor during the surge mapping of CO2
compressor.
Background:
The inter stage schematic of Compressor is shown
below,
Fig 9. CO2 Compressor interstage schematic.
On 20th December 2010, surge mapping activity of
CO2 compressor was started at 6476 rpm. Dis-
charge pressure was being increased slowly to ob-
serve any signs of "incipient surge" but nothing
appeared. Suddenly at pressure of 168 kg/cm2(g),
the machine went into active surge. Abnormal
sounds were heard in field and machine was
tripped manually. It was found that the machine
2nd stage was surging first and as flow measure-
ment was at 3rd stage, incipient surge couldn’t be
detected. Also machine discharge pressure safety
valve (PSV) and high pressure trip was configured
at170 kg/cm2(g) so surge map could not be drawn
for speeds higher than 6476 rpm. Therefore, it was
decided to obtain two points lower than 6476 but
above 5693 rpm (min governor speed).
The exercise again started on the night of 21st De-
cember 2010. Machine speed was increased to
6084 rpm, and valve HV-1803 was being closed
slowly to increase the pressure of the machine so
that the test could be started. On closing HV-1803
to 40 %, surge was observed in the field, but valve
also HV-1803 also opened suddenly and it was as-
sumed that there was some loose connection from
Woodward governor system. But on investigation,
it was found that HV-1803 is interlocked to open
with min governor speed and tripping of machine.
Since in the entire test, the variation in speed was
observed and speed reduced to min speed resulting
in opening of HV-1803.
Key Findings:
It was clear from the above tests that the inter stage
valve cannot be closed at speed of 6048 rpm
(which was above min governor ie 5693 but lower
than 6476 rpm, this was not the case at 6476 rpm).
Doing so caused the 2nd stage of the compressor to
go into active surge causing whole train to surge.
So after discussion with the vendor it was con-
cluded that the minimum governor speed (5693)
given by vendor is wrong, as the machine goes into
surge if an attempt is made to close the inter stage
valve so the minimum governor speed of the ma-
chine was changed to 6476 rpm.
On another occasion, passivation air had been
lined-up to CO2 compressor, while compressor re-
mained on circulation for more than six hours, that
resulted in accumulation of air in the circuit and
lowering down the molecular weight of resultant
gas from 44 to 36 and compressor started surging
due to handling of lighter gas.
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8. Damaged Auto Recirculation valve (ARV)
of BFW Pump.
On Jun 26, 2010 at about 1000 hrs, an abnormal
sound was observed from the BFW pump Auto
Recirculation valve (ARV). The minimum flow
ARV was found damaged after only one month of
operation. The ARV lets down BFW from a pres-
sure of 160 kg/cm2(g) to 1 kg/cm
2(g).
Background:
During reliability checks of the BFW pumps, the
pump was kept running for long duration on total
recirculation through ARV. The BFW header pres-
sure is 165 kg/cm2 when the pump is operated on
ARV. By closing the pump discharge valve, it will
let all the flow back to deaerater which is operated
at atmospheric pressure. On observing abnormal
sound from the ARV, the valve inspection of was
carried out and it was found badly damaged as
shown in fig 10.
Fig: 10 BFW Pump damaged ARV
Key findings
When the BFW is let down from 165 kg/cm2 to 1
kg/cm2 velocity of liquid reaches to its maximum,
the liquid temperature may reach its boiling point
and liquid flashes to form bubbles. These bubbles
collapse with explosive force (~10,000 psi) near
metal surface causing metal to be destroyed. To
avoid this, high alloy and low velocity designs are
used. The material of ARV was upgraded.
9. Medium Pressure Absorber, C-01 Trays
Damage:
After 11 hrs of urea plant startup, the ammonia
feed pump, P-01 tripped on suction filter high dif-
ferential pressure. The stand-by pump was started
but it also tripped on same cause after 20 minutes.
Both filters were found choked with carbamate in-
dicating CO2 slippage from the medium pressure
absorber, C-01. However, process data (tempera-
tures of C-01) did not show any indication of CO2
slippage. C-01 was opened for inspection; and all
five trays (each comprising of five segments) were
found disengaged, fig. 11. Investigation revealed a
design flaw in the mechanical joints of tray seg-
ments. To strengthen the trays & avoid recurrence,
the segments were tack welded to existing joint
scheme.
Fig. 11 Disengaged segment of bottom tray
found at C-01 bottom.
10. Carbamate Control Valve to Urea Reac-
tor, HV-1009, Damage
In the first start-up, when HV-1009 was operated
to establish carbamate flow to the reactor, an ab-
normal sound and high vibrations were observed in
valve vicinity. After 20 minutes, the valve glands
started leaking. Leakage increased rapidly & after
about 45 minutes, the carbamate feed had to be cut
due to excessive leakage in the area.
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Key findings
Initial investigation revealed an unsupported actua-
tor as main cause of valve failure. The actuator
support was installed but the same problem ap-
peared in subsequent start-up. Further investigation
suggested the provision of cage around the valve
stem. Due to being unsupported and at very high
differential pressure across the vale, the stem and
plug experienced very high vibrations against the
flow direction. That also explained the high noise
and vibrations observed during the start-up. Even-
tually that vibration resulted in the failure of teflon
gland packing of the valve. It was also proposed
that vendor should review the design.
11. Ammonia Feed Pump Rotor Failure:
On 29th December, 2010; ammonia feed pump, P-
01B tripped on high vibration security just after 20
minutes of startup. Pump was restarted but it
tripped again and its rotor seized. Issue was com-
municated to vendor to send the pump service ex-
pert.
Key findings
The ammonia feed pumps to urea reactor (P-
01A/B) have eight stages each with a discharge
pressure of 240Kg/cm2(g). The pump was disas-
sembled in presence of the vendor expert, its eight
stage impeller was found dislocated from its posi-
tion towards the DE (Drive End) by 8mm and had
rubbing marks (see fig. 12). Further study revealed
a design flaw in the balance of axial thrust along
the 8th stage impeller. As per design, axial thrust
should be on the NDE side (towards impeller suc-
tion eye) and a split ring had been provided to re-
strict impeller movement. But due to longer hub of
8th stage impeller, original thrust was towards DE
side (impeller discharge end), which resulted in the
dislocation of 8th stage impeller. To resolve this is-
sue impeller hub was shortened.
The same modification was proactively carried out
on P-01A.
Fig. 12 Modification of 8
th stage impeller hub
12. Polisher Mixed Bed Failure:
On 26th March 2011, during regeneration of mixed
bed 'A'; resin was observed in the neutralization
pit. Trains 'B' and 'C' were also checked and it was
observed that resin is also slipping from these
trains through the chemical effluent drain lines. It
was also observed that the resin level was low in
mixed bed ‘B’ (thru site glass).
Key Findings
On 27th March Mix Bed train B was handed over
for internal inspection. It was decided to unload the
resin and inspect mixed bed Train ‘C’. On inspec-
tion, following were observed.
1. Support channels of inlet distributor had
been bent and twisted.
2. Support channel angles welded to vessel
had also been twisted, two of them were
found dislodged.
3. Several distributor U clamps were found
loose/missing.
4. Distributor piping was found loose from
the threaded connections.
5. Main distributor pipe found bent in U
shape (as if great hydraulic force was ap-
plied from top).
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6. Most of the plastic strainers were deformed
and damaged.
Investigation revealed that distributor supports
were not adequately designed for 100% load on the
unit. In addition to that, when contaminated con-
densate with corrosion products (not per mixed bed
design) arrived at the polisher unit, it caused plug-
ging of plastic strainers and created high pressure
drop. Higher than design hydraulic pressure and
chocking resulted in damage of Mix Bed internals.
The origin of the contaminated water was a plant
was shut down for a 60 days gas outage. Some wa-
ter / condensate remained stagnant at low portions
of the piping and as a result corrosion occurred.
During the startup, the system was put online
without flushing the lines, so the dirty water went
into mixed beds resulting into the above mentioned
damages due to increased pressure drops.
Actions Taken
The chemical outlet distributor’s supports were
welded and the rubber liner inside the vessels was
reinstated where damaged. On completion, a holi-
day test was carried out to ensure the rubber liner
properly fixed. All nozzles were again tightened to
ensure that no resin will slip for the coming opera-
tion.
13. Miscellaneous Problems
A. Low pressure steam (LS) injection to air
compressor turbine cut resulting into surging of
Process Air Compressor.
The stopping of LS injection to the air compressor
turbine resulted in the decrease of RPM which re-
sulted in opening of antisurge and process air flow
to the secondary reformer stopped momentarily. As
the high pressure steam valve (HP lift) of the air
compressor turbine responded, the RPM was res-
tored and flow again reestablished. The tuning of
HP lift was carried out to make its response faster
so speed would not drop under similar changes.
B. Level indication of common Surface Con-
denser of synthesis, air and ammonia compres-
sor turbines remained problematic.
The level indication at common vacuum condenser
of synthesis, ammonia and air compressor was a
differential pressure indication between the va-
cuum and the liquid head pressure in the condenser
hot-well. During start-up of the synthesis compres-
sor, even a slight variation in the vacuum resulted
in huge disturbances in the level indication but the
actual level in the condenser sight glass (mechani-
cal level glass) remained unchanged. Modification
was carried out and a displacer type level transmit-
ter was provided to show the actual level in con-
denser in place of differential type level indication
at DCS.
C. Purge and leak Test of reformer furnace was
not getting cleared, resulting in delay of startup
activities for hours.
The required pressure of 1 kg/cm2 was not being
maintained in the fuel headers as the individual
burner valves were heavily leaking-through and the
limiters allowed the valve to over travel. The re-
sulting pressure was reduced below 0.9 kg/cm2
within 12 min. It has been observed that the valve
stopper on some of the valves allows the valves to
travel beyond the fully closed position resulting in
depressurization of the header within the limits of
timer and lead to a failure of leak and purge test.
The limiters of the valves were replaced. Fig. 13
shows an example of over travelling of lever.
Fig: 13 Over-travel of lever beyond full close position
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D. Water Ingress in Syn Compressor Dry Gas
Seal
During the hydro testing of the nitrogen header to
dry gas seal system of synthesis and refrigeration
compressor, water ingressed into the synthesis
compressor seal system. A blind at nitrogen supply
line to secondary vent of dry gas seal was found
missing. The dry gas seal of compressor was sent
to the vendor and was reinstalled after inspection
and cleaning (removal of debris that the hydro test
water carried).
E. aMDEA towers high and low level switches
abnormal behavior.
The low & high level switches of aMDEA towers;
(stripper, absorber and flash vessel) were wrongly
actuated numerous times and resulted in the trip-
ping of circulation even though the level transmit-
ter and local glass gauge remained in normal range.
This abnormal behavior of switches is still un-
known. Security trips were then moved to level
transmitters.
F. Cryogenic nitrogen plant tripping because of
excessive CO2 venting.
The ammonia plant front end was started and nor-
malized - leading to significant CO2 production.
Due to some issues at the CO2 compressor, CO2
was vented for longer durations. The CO2 being
heavier than air and because of wind direction set-
tled towards the suction of raw air compressor be-
cause of wind direction.
The compressed air to nitrogen unit is passed
through molecular sieves to separate oxides. The
sieves were designed for very low limits of CO2
(atmospheric CO2 concentration). The high con-
centration of CO2 exhausted the molecular sieve
and CO2 / oxides slipped to the cold box resulting
into tripping of the nitrogen plant numerous times.
Restart of the nitrogen plant takes around six
hours, during that time, nitrogen to compressor dry
gas seals is through liquid nitrogen storage which
obviously had limited quantity of nitrogen availa-
ble. A number of liquid nitrogen bowsers (tankers
used for liquid transportation) were purchased to
meet the demand.
Plant Trippings
Complete plant trippings (I-1 actuations) were
faced a few times due to following reasons;
1. Cooling water low pressure was observed
during pump changeover resulting into I-1
actuation.
2. A wrong signal was generated by cooling
water pumps ESD which resulted in nuis-
ance actuation of I-1.
3. On Nov 9th, 2010, I-1 actuated on power
failure to reformer induced draft (ID) fan
speed probes due to tripping of power dis-
tribution cabinet.
4. On Nov 29th, 2010, I-1 was manually acti-
vated due to fire at synthesis machine.
5. On Mar 15th, 2011, I-1 actuated when air
compressor tripped and protection steam in
air convection coil was not established in
time due to slow response of protection
steam flow control valve.
Safety Performance
The primary emphasis and main focus during the
project was prevention of accidents that could re-
sult in injury or fatality to the workers or damage
to the property. All the contractor employees were
taken through Engro's well-established safety
orientation and training. Approximately, 50 million
man-hours were worked at the Daharki site to
complete the project. There were no disabling inju-
ries. However, there were two lost workday inju-
ries to contract workers during the construction
phase.
Housekeeping with special emphasis on proper
placement of fire extinguishers was ensured
throughout the project duration. The traffic regula-
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2011 [66] AMMONIA TECHNICAL MANUAL
tion compliance was ensured with due considera-
tion paid to crane operation and rigging.
Potential adverse effects on health and applicable
exposure control of the materials like feed and
product residue, catalyst dust, and chemicals were
identified and were satisfactorily handled.
Upon completion of the project, the total recorda-
ble incident rate (TRIR) was recorded at 0.27
which is a highly commendable achievement for a
construction site.
Conclusion
After adequately furnishing themselves with every
tool in their weaponry, Engro’s operations team
exhibited splendid display of their skills in the
field. The journey which started from P&ID Sys-
temization, manpower built-up, training, Procedure
development, pre-commissioning, commissioning
& startup came to a successful end. The result of
untiring efforts of the entire team and in-depth
planning by leadership that led to the successful
startup of world’s largest single train Urea com-
plex. Following main factors contributed to the
success of this project;
• Extensive training of manpower and well-
structured utilization of OTS helped a long
way towards smooth startup of plant.
• Thorough and ‘once through’ pre-
commissioning also resulted in saving of a
lot of time during commissioning.
• Good quality workmanship also played a
vital role in successful commissioning.
• Several layers of audits performed before
bringing in the natural gas to the site prior
to feed-in. Hundreds of points were picked
and closed before feed-in.
• All critical circuits were pressure tested
with nitrogen / air.
• Frontend was pressure tested with nitrogen
and leak test was carried out with soap so-
lution.
• Synthesis loop was tested at 200 Kg/cm2
pressure with nitrogen for duration of 04
hours.
Acknowledgements
Authors acknowledge all the colleagues of Engro
who helped in collection of data for this paper, es-
pecially Mr. Abul Fazal Rizvi, Mr. Mohsin Mukh-
tar, Mr. Wasim Yasin, Mr. Ahmad Shakoor, Mr.
Syed M. Ali, Mr. Majid Latif, Mr. Hafiz Samad &
Mr. Imran Haider.
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