Major potential hazards in Urea Plants V6 090917 · problem of a valve in an ammonia line ... to operating the melt pump with ... packing ring of stuffing box HP reciprocating pump

Revision Hazard & Initiating Event Consequences Safety Study Reference Link C L R Sponsor 1 Sponsor 2 Sponsor 3 Sponsor 4 Sponsor 5 Sponsor 6 C L R

1V4, 1

August 2017

Human error to solve a vibration problem of a valve in an ammonia line

NH3 release to atmosphere Commissioning Feed HP NH3 valve Incident Database Incident 93-001 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=962

Major Unlikely (8) High 8 Prepare Standard Operating Procedures for operators and for start up and shut down phase. Perform vibration analysis on critical pipelines.

Major Rare (5) Moderate 5

2V4, 1

August 2017

NH3 leak due to a sight glass failure during start up

16 people injured Commissioning Feed NH3 pumps Incident Database Incident 15-002 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1189

Major Moderate (11) High 11 Several recommendations are included in: http://www.ureaknowhow.com/ukh2/library/1190-2017-ureaknowhow-com-top-10-revamp-tools.html

Several recommendations are included in: http://www.ureaknowhow.com/ukh2/library/1190-2017-ureaknowhow-com-top-10-revamp-tools.html

Moderate Rare (3) Moderate 3

3V4, 1

August 2017

High pressure in suction line due to operating the melt pump with hot condensate and no / low flow conditions leading to steam formation

Sight glass damages Commissioning Finishing Melt pump HAZOP Catastrophic Unlikely (10) High 10 Perform commissioning of melt pump with cold condensate, find alternative methods to test instrumentation. Apply a BUNGARTZ melt pump.

Catastrophic Rare (7) High 7

4V4, 1

August 2017

Tank damages due to vacuum created in tank

Major damage Commissioning Recirculation Atmospheric storage tanks

Incident Database Incident 15-003 & 03-001

http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1273

Major Unlikely (8) High 8Be aware that condensing steam / gases by a cold stream can easily create vacuum, install a water seal on a tank as a 3" vent stack of 100 m height could not compensate the vacuum pressure in this incident


5V4, 1

August 2017

Boiler explodes due to explosive mixture in boiler

3 casualties and 5 people injured Commissioning Utilities Steam boiler Incident Database Incident 16-003 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1392

Catastrophic Unlikely (10) High 10

Boilers, furnaces and reformer to be charged with fuel gas only when furnace draft fans are put into operation. Standard operating procedure to be modified accordingly. Fuel gas line leak test to be strictly done with nitrogen. Proper interdepartmental communication to be ensured between maintenance supervisor and control room and work area to be cleared of contract workman before initiating start up activities.


6V4, 1

August 2017

During construction of prill tower, accident occurred from high elevation

12 casualties, plant construction on hold

Construction Finishing Prill tower Incident Database Incident 09-001 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=272

Catastrophic Unlikely (10) High 10 When working at high heights take care of extra security to avoid falling down. Inspect condition of carrier equipment


7V4, 1

August 2017

Rupture of HP stripper due to fabrication defect

12 casualties, 71 mln US$ financial loss

Construction Synthesis Stripper Incident Database Incident 90-001 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=278

Catastrophic Moderate (12) Intolerable 12 Assure a proper design and experienced and qualified fabricator for HP urea vessels. Perform quality control during fabrication.

In case of a leak stop the plant. Catastrophic Rare (7) High 7

8V4, 1

August 2017

Crystallisation of carbamate and clogging upstream or downstream safety valve

High pressures than design leading to potential damage and carbamate / NH3 release

Engineering Carbamate Safety valves HAZOP

2008 Meessen Stamicarbon Urea

Plant Safety - A Review

Catastrophic Moderate (12) Intolerable 12 Trace pipeline upstream safety valve, trace body of safety valve and flush body and downstream pipeline of safety valve (best solution is LESER Flush safety valve)


9V4, 1

August 2017

Clogging of safety valve or other blow off devices upon activation due to solid formation of CO2 in blow off lines

Pressures increase above design pressure, damage

Engineering Feed CO2 compressor HAZOP



Major Moderate (11) High 11Avoid stagnant lines at inlet (L/D<3) or provide tracing and insulation. Check that upstream temperature is above mentioned treshhold value (discharge 3rd and 4th stage downstream cooler are critical areas). Threshhold value at 80 bars is abt 45 degC and at 140 bars is abt 80 degC.


10V4, 1

August 2017

Damage of carbon steel pressure bearing wall due to leakage of protecting sleeve in nozzle

Not clear but possibly bad design and thermal stresses

Engineering Synthesis HP Equipment Incident Database Incident 03-002 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1454

Catastrophic Unlikely (10) High 10Pay attention in the detailed design and fabrication and inspection of nozzles of HP urea equipment. Install a proper leak detection system for loose liners. Perform corrosion inspections at regular intervals and pay attention to leaks in the urea plant.


11V6, 3

September 2017

Drain line ruptures due to corrosion/erosion

Large loss of containment Engineering Synthesis Drain system Incident Database Incident 09-003 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1474

Catastrophic Unlikely (10) High 10 Better design of drain system with double block and bleed possibilities. Be aware that drain valves easily pass. Apply high quality vendor and higher alloy materials (duplex).


12V6, 3

September 2017

Isolation valve fails during maintenance

11 casualties, 10 injured Maintenance Feed HP pump Incident Database Incident 92-002, N&S 2017 Fatima


Catastrophic Unlikely (10) High 10Install double block and bleed for isolation valves of HP NH3 and carbamate pumps or install blind plates, do proper maintenance on these block valves, limit number of people at these locations during maintenance, wear personal protection. Apply high quality vendor and higher alloy materials.


13V4, 1

August 2017

Explosion due to atmospheric corrosion of ammonia pipeline, erosion from process side

Six fatalities and 25 people injured Maintenance Feed Ammonia pipelines Incident Database Incident 13-001 and XX-009

http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=818 and http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=903

Catastrophic Moderate (12) Intolerable 12Do regular corrosion inspections. Colour ammonia lines for easy recognition. Assure proper quality of welds. Assure proper condition of insulation.What can be cause for erosion from process side, catalyst particles ? Any experience from others ?


14V4, 1

August 2017

NH3 leak due to loosening packing ring of stuffing box HP reciprocating pump

3 people injured Maintenance Feed HP Pumps Incident Database Incident 98-001 and 07-001


Catastrophic Moderate (12) Intolerable 12Perform proper (also preventive) maintenance on HP pumps, stuffing boxes have a limited lifetime Also check wear and tear of other related parts also like the condition of for example threads. Involve high quality and experienced companies.


15V4, 1

August 2017

NH3 pipeline weld joint fails Heavy ammonia leak Maintenance Feed NH3 piping Incident Database Incident 08-001 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1404


Corrosion-fatigue resulting from combined action of an alternating stresses and corrosive environment. On line sealing of leakages either from pipes or weld joints should be avoided. Contrary to pure mechanical fatigue, there is no fatigue limit load in corrosion-assisted fatigue. Much lower failure stresses and much shorter failure times can occur in a corrosive environment. OMIFCO has decided not to do online sealing for any developed leakages on ammonia pipe lines. Consider Boreal NH3 detectors.

Assure sufficient isolation possibilities (remotely controlled block valve) to limit ammonia emissions. In case of a leak stop the plant.


16V4, 1

August 2017

Leaking flange of CO2 line One person passes out Maintenance Feed CO2 compressor Incident Database Incident XX-014 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1455

Major Moderate (11) High 11CO2 is heavier than normal air and can collect at lower elevations reducing oxygen content to dangerous low levels. A proper CO2 detector should be present. Flange leakages are to be checked after a start up. Personal should be aware of the risks of CO2.


17V4, 1

August 2017

Acetic acid used for cleaning enters lube oil system of CO2 compressor via nitrogen network

Severe damage to bearings/seals Maintenance Feed CO2 compressor Incident Database Incident 09-005 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1476

Major Unlikely (8) High 8 Perform risk analysis also for maintenance activiities, do not trust check valves to stop flow completely. Consult expert companies.


18V6, 3

September 2017

During cleaning or maintenance activities heavy lumps can fall down causing casualities

several casualties during several incidents

Maintenance Finishing Prill tower / Granulation

Incident Database Incident 02-001 and 10-004


Major Likely (13) Intolerable 13 Working in a prill tower or granulator with urea lumps is dangerous: clean first maximum amount from outside. Make use of wet cleaning (refer to Nagarjuna paper)

Take care of proper protection Moderate Rare (3) Moderate 3

19V4, 1

August 2017

While trying to open clogged melt line, melt splasht out of 3-way valve or flange

one person injured (40 days in hospital) while wearing good personal protection

Maintenance Finishing Urea melt line Incident DatabaseIncident 87-001 and XX-015 and

XX-016

http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=329 and http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1457 and http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1460

Moderate Moderate (9) High 9

Do not compromise on safety: Flush drain lines of urea melt lines twice per shift to ensure drain line is clear, perform job safety analysis to identify unsafe situations (e.g. no escape path close to 3-way valve, work with safety watches at risky situations. Be careful when heating up urea melt lines as gasses occur and pressures increase. Avoid overheating of urea melt lines, pay attention to no flow conditions. Apply a reliable melt pump.

Do not compromise on safety: Wear always the right and full cover personal protection.

Minor Rare (2) Low 2

20V4, 1

August 2017

Julla falls down from 10 m height due to shearing of pinion of electrical winch

3 persons were badly injured and 2 fatalities was reported

Maintenance Finishing Prill tower Incident Database Incident XX-008 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=896

Catastrophic Unlikely (10) High 10 Second holding of the julla to be made foolproof Catastrophic Rare (7) High 7

No:Hazard Scenarios Hazard Reference Information Mitigated Risk RankingSupport from our Sponsors

Ref No. Prevention measures reducing Likelihood Mitigation measures reducing Consequences

Risk Register of Major Potential Hazards in Urea Plants V6: September 3, 2017

Project phase Plant section Equipment itemUnmitigated Risk Ranking

Ref No.

21V4, 1

August 2017

Granulator door jammed close unexpectedly

One person injured Maintenance Finishing Granulation Incident Database Incident XX-017 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1461

Moderate Moderate (9) High 9 Mechanically secure the granulator doors in open position even when inspecting the granulator through open doors.

Moderate Rare (3) Moderate 3

22V4, 1

August 2017

Miscommunication during maintenance job

One injured Maintenance Finishing Reclaimer Incident Database Incident XX-018 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1504

Moderate Moderate (9) High 9 Apply the safest possible procedure even if it takes more time Moderate Rare (3) Moderate 3

23V4, 1

August 2017

People enter a pipeline (confined space) while welding was performed and welding gas was applied (inerts) leading to asphyxiation

Two casualties Maintenance Plant Confined spaces Incident Database Incident 02-002 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=925

Catastrophic Unlikely (10) High 10 Apply proper precautions when entering confined spaces, measure oxygen, use a safeguard Catastrophic Rare (7) High 7

24V4, 1

August 2017

Crane collapses during maintenance job

One casualty Maintenance Plant plant incident Database Incident 15-001 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1140

Moderate Unlikely (6) Moderate 6 Apply proper preparation procedures when using a crane, do a risk analysis Moderate Rare (3) Moderate 3

25V4, 1

August 2017

Sight glass ruptures One casualty and 2 people injured, all in one case

Maintenance Plant Sight glass Incident Database Incident XX-013 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1303

Catastrophic Likely (14) Intolerable 14Several recommendations. Refer to Round Table discussion (refer to: http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1303). Apply non-cavitating BUNGARTZ pump.

Several recommendations. Refer to Round Table discussion (refer to: http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1303). Apply non-cavitating BUNGARTZ pump.

Insignificant Unlikely (2) Low 2

26V4, 1

August 2017

Backflow from synthesis (discharge HP carbamate pumps) to recirculation (suction side) as during flushing mode the XPV (LPV) in the discharge is opened while people are in the area

Potential toxic ammonia release and/or high temperature/pressure carbamate release (SIL 2)

Maintenance Recirculation HP carbamate pumps

HAZOP



Major Moderate (11) High 11 Add position indicators on main blockvalves in order that XPV can only be opened in case pump is running or in case both pumps are stopped and blockvalves are closed

In case of a leak stop the plant. Major Rare (5) Moderate 5

27V4, 1

August 2017

Asphyxilation / unconsious while working on tank

one casualty, one person injured Maintenance Recirculation Atmospheric storage tanks

Incident Database Incident 16-002 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1336

Catastrophic Unlikely (10) High 10 Pay attention that vapours can escape from vents from the tank while working on top of the tank. Perform a job safety analysis.


28V4, 1

August 2017

Vent line of ammonia water tank explodes during grinding

One casualty and one injured Maintenance Recirculation Tanks Incident Database Incident XX-020 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1513

Catastrophic Moderate (12) Intolerable 12Assure proper blinding (spectacle blinds, double block and bleed) when doing maintenance or inspections on a equipment item. Perform a risk analysis before starting the job. Apply proper winterising measures


29V4, 1

August 2017

HP butterfly valve twists leading to leakage

Unsafe situation plus in ammonia plants risk for fire

Maintenance Synthesis HP piping Incident Database Incident 10-002 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=333

Moderate Moderate (9) High 9 Pay proper attention to the installation of high pressure butterfly valves between flanges with lens gaskets, consider the new BHDT design for these valves

In case of a leak stop the plant. Moderate Rare (3) Moderate 3

30V4, 1

August 2017

Pressure gauge ruptures after HP flush pump is put in operation due to malfunctioning pressure control valve

Unsafe situation Maintenance Synthesis HP flush pump Incident Database Incident 11-001 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=388

Moderate Unlikely (6) Moderate 6 Assure proper functioning of pressure control valve and relief valve In case of a leak stop the plant. Moderate Rare (3) Moderate 3

31V4, 1

August 2017

Reactor ruptures due to bad maintenance practice of closing the manway cover

One person injured due to toxic ammonia (double long transplantation)

Maintenance Synthesis Urea Reactor Incident Database Incident 01-001 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=515

Catastrophic Unlikely (10) High 10 Apply proper maintenance procedures and experienced and qualified services companies. Apply the right gaskets. Treat high pressure urea vessels as critical equipment


32V4, 1

August 2017

Rupture of valve due to high pressure pocket during maintenance

In one incident one casualty, in another case one person injured


Moderate Likely (11) High 11 Be aware that high pressure lines / valves can contain high pressure pockets and apply proper maintenance procedures taking this into account.

Wear proper personal protection. Moderate Rare (3) Moderate 3

33V4, 1

August 2017

Rupture high pressure flange connection

Large ammonia emission, complaints from neighbours



Carbon steel is not corrosion resistant and corrosion rate is very high. The installation of all equipment in the HP loop must be performed only by specialists with the right material. An independent check must be performed on all flanges in the HP section to check all dimensions. Grooves have been made in the carbon steel flange to allow the carbamate to escape


34V6, 3

September 2017

Rupture of weldolet after trial to stop leak by installing a clamp

Four casualties and 4 people injured


Catastrophic Moderate (12) Intolerable 12

Assure the quality of the applied materials fulfils the minimum requirements; Apply higher alloy materials (25-22-2 or duplex). Assure the quality of the installation and welding services. Apply better designs for weldolets with no dead volume. Pay attention to the right location of the weldolet (avoid gas phase). Perform proper inspections and testing during installation and after repair procedures (hydrotest, X-ray test of weld-o-let). Perform regular corrosion inspections of critical areas especially in plants older than 20 years. Never apply a clamp on a carbamate containing pipeline.


35V4, 1

August 2017

During hot bolting gasket fails One casualty Maintenance Synthesis HP piping Incident Database Incident 14-001 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1016

Catastrophic Unlikely (10) High 10 Never apply hot bolting at high pressures In case of a leak stop the plant. Catastrophic Rare (7) High 7

36V4, 1

August 2017

Failure of flanged head connection of a urea reactor

Major damage Maintenance Synthesis Urea Reactor Incident Database Incident 10-005 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1276

Catastrophic Moderate (12) Intolerable 12Avoid a design with a cooling jacket, apply a proper vacuum based leak detection system with an accurate and reliable ammonia detector. Never flush leak detection circuits with steam or condensate or water.


37V4, 1

August 2017

Leaking flange connection in high pressure pipeline

Risk of corrosion of carbon steel flanges, bolts and nuts, loss of integrity

Maintenance Synthesis HP piping HAZOP Catastrophic Likely (14) Intolerable 14 Apply right torques and high quality materials. Use clean bolts and nuts which are both in good condition. Do not reuse lens rings.


38V6, 3

September 2017

Failure of wooden structure of cooling water unit in some 15 Indian plants

Significant damage and production loss

Maintenance Utilities Cooling water unit Incident Database Incident XX-005 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=516

Minor Moderate (6) Moderate 6 Check design of wooden structure and avoid large weights at higher elevations, do proper quality control, perform proper corrosion inspections


39V4, 1

August 2017

Fire due to leakage CO2 compressor lube oil

Production loss, fire could be snuffed out before further damage

Operational Feed CO2 compressor Incident Database Incident 10-001http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=309&p=7446#p7446

Major Unlikely (8) High 8 Install fire detectors, cameras. Install oil system besides compressors / turbines. Minor Unlikely (4) Moderate 4

40V4, 1

August 2017

Large uncontrolled NH3 emission in case suction line of HP NH3 pump fails due to unwanted backflow scenario

As NH3 booster pump from NH3 plant keeps running, NH3 emission can be very large (SIL 3)

Operational Feed NH3 pumps HAZOP



Catastrophic Moderate (12) Intolerable 12 Install fast closing XEV to stop supply of NH3 from boosterpump or stop booster pump automatically. Wear personal protection when working on NH3 equipment

Minor Moderate (6) Moderate 6

41V6, 3

September 2017

A rupture disc on NH3 system opened without proper noticing

Large ammonia emission, complaints from neighbours

Operational Feed NH3 heat exchangers


Moderate Unlikely (6) Moderate 6 Apply NH3 detection system for leaks of rupture discs as these do not close again after damage

Minor Unlikely (4) Moderate 4

42V4, 1

August 2017

Fire / explosion during blow off due to icing and hydrogen ignition

Damage plus possible casualties Operational Feed CO2 compressor Incident Database Incident XX-007 and XX-010


Major Unlikely (8) High 8 Lower explosion limit of hydrogen is 4 vol%, are these levels possible. Is fire possible ? Anybody has experience ?

43V4, 1

August 2017

Anhydrous ammonia splashes during sampling

One person injured Operational Feed NH3 piping Incident Database Incident XX-012 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1131

Moderate Moderate (9) High 9 Apply proper sampling procedure. Perform job safety analysis. Wear sufficent personal protection Minor Rare (2) Low 2

44V5, 17 August 2017

Backflow from corrosive carbamate from synthesis to carbon steel NH3 and CO2 feed lines

Failure HP piping, large ammonia leak

Operational Feed HP piping Incident Database Incident 16-004 and 10-003



Two checkvalves in series with different design and high quality. Do not apply a design with vanes. Check valves to be installed in vertical line. Install a flushing connection upstream check valve to flush away solids. Install a fast closing MOV from DCS (some plants apply buffer vessel in CO2 supply line). Apply the specbreak upstream this MOV. Pay attention also to bypass / start up lines.


45V5, 19 August 2017

Backflow from carbamate from synthesis causing reverse flow of HP centrifugal carbamate pump

Damage HP carbamate pump (SIL 2)

Operational Recirculation HP carbamate pumps

HAZOP Moderate Moderate (9) High 9

Two checkvalves in series with different design and high quality. Do not apply a design with vanes. Check valves to be installed in vertical line. Install a flushing connection upstream check valve to flush away solids. Install a fast closing XV which acts on TSHH in the line to the synthesis (some plants apply two XV in series).


46V6, 3

September 2017

Failure of separator of CO2 compressor causing wet corrosive CO2

Pipe failed during clamping Operational Feed CO2 compressor Incident Database Incident 16-006 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1438

Major Unlikely (8) High 8The pipe was replaced by stainless steel. The efficiency of the liquid separator was improved. Do not apply clamps when the condition of the pipe is not clear. Apply experienced CO2 compressor vendors.


47V4, 1

August 2017

CO2 breakthrough with ammonia recycle.

Internal corrosion, possible damage

Operational Feed NH3 buffer vessel HAZOP http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=7&t=1519

Catastrophic Unlikely (10) High 10 Stainless steel liner with ammonia leak detection system or stainless steel vessel. In case of a leak stop the plant. Catastrophic Rare (7) High 7

48V4, 1

August 2017

Gas pipeline ruptures Fire and plant shut down Operational Plant Piping Incident Database Incident 11-002 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=451

Moderate Moderate (9) High 9 Apply high quality materials. Perform corrosion inspections of pipelines based on risk based inspection


49V4, 1

August 2017

Several scenarios lead to high pressure in the recirculation

Potential toxic ammonia release and /or high temperature /pressure carbamate release

Operational Recirculation Recirculation HAZOP



Major Moderate (11) High 11 Safety valve plus high pressure switch to realise the required Probability of Failure on Demand. The high pressure switch activates synthesis blocking situation. Apply a reliable pressure measurement.


50V4, 1

August 2017

Rupture of column due to hydrogen explosion

Major damage Operational Recirculation

MP scrubber, LP absorber and atmospheric

absorber

HAZOP Incident 00-002 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1446

Major Moderate (11) High 11Install a hydrogen converter in CO2 feed, use ammonia feed from atmospheric pressure (no dissolved H2 and CH4), be aware of flushing with condensate which can increase H2/NH3 ratio (larger explosive area). Apply an explosion dome or 7 times higher design pressure.

Insignificant Rare (1) Low 1

51V6, 3

September 2017

Hot fluid splashes (this risk is high with process fluids which easily crystallise)

Injuries Operational

Recirculation, evaporation and

waste water treatment

sample valves HAZOP Moderate Moderate (9) High 9 Make use of Tyco (Yarway) sample valves with no dead volume at inlet side Moderate Rare (3) Moderate 3

52V4, 1

August 2017

Rupture of reactor due to active corrosion due to weld defect in weld clip to liner

Rupture of reactor leading to severe damage to the plant, 10 people injured inside and 90 people outside the battery limits

Operational Synthesis Urea Reactor Incident Database Incident 92-001http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=267&p=1188#p1188


Proper active vacuum based leak detection system for loose liners with a reliable and accurate ammonia detector in operation, procedure to shut down the plant in case a leak is identified, apply a full penetration weld, proper quality control of critical welds, proper design of clip so that proper welding is possible, use high alloy welding material, include clip welds in corrosion inspection program


53V4, 1

August 2017

Rupture of HP CO2 line due to corrosion under insulation

Unplanned shut down of the plant Operational Synthesis HP piping Incident Database Incident XX-001 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=268

Moderate Moderate (9) High 9Insulated carbon steel at concerning temperatures has to be protected by a coating system or personal protection can be applied. Insulation should be in good condition. Regular inspections for atmospheric corrosion at critical areas is recommended. Be careful with flushing water.


54V4, 1

August 2017

Significant wall thickness reduction of HP NH3 line due to atmospheric corrosion

Repair during turnaround Operational Synthesis HP piping Incident Database Incident XX-002 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=269

Major Moderate (11) High 11Apply a protective coating system on the pipeline also in the area of the clamp. Apply a glass fibre tape between the pipeline and the clamp. Avoid wetting of the pipeline during flushing the floor. Apply Good Practice when guiding a pipeline through concrete floors.


55V4, 1

August 2017

Rupture of or cracks in pressure bearing wall due to atmospheric corrosion (Nitrate stress corrosion cracking)

Repair during turnaround or new reactor required

Operational Synthesis Urea Reactor Incident Database Incident XX-003 and XX-004

http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=270, http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=275


Regular corrosion inspections also for atmospheric corrosion is recommended. Take care of a proper aluminum cover sheeting to avoid ingress of water contaminated with nitrate and/or urea (especially at critical locations like supports, insulation rings). In case of risk of nitrate (or urea) contamination carbon steel equipment and piping operating at temperatures in between -10 and +240 oC have to be coated. The angle iron insulation support ring should be fixed on the carbon steel shell in area with a lower stress level. Consider a shelter on top of HP vessels.


56V4, 1

August 2017

Rupture of reactor due to stress corrosion cracking of carbon steel pressure bearing wall due to flushing of leak detection system with water and bad design leak detection holes in multi layer vessel

4 casualties, 32 injured Operational Synthesis Urea Reactor Incident Database Incident 05-001 and 95-001



Flushing leak detection systems with steam or condensate can introduce substances leading to stress corrosion cracks in the pressure bearing carbon steel wall. A proper sealing (design) is required between the leak detection holes and the first carbon steel layer. The same is valid for the nozzles of a high pressure urea equipment item.


57V6, 3

September 2017

HP carbamate gas line ruptures due to strain induced intergranular cracking (SIIC)

Unsafe situation, large ammonia emission, plant shut down

Operational Synthesis HP piping Incident Database Incident 09-002 and 12-001


Major Moderate (11) High 11

Apply proper tracing and insulation so that condensation will be avoided (dew point typically higher than 160 degC), apply stainless steel with small grain size or apply higher alloy material (25-22-2 or duplex). Perform corrosion inspections for HP gas lines and weldolets. End of lifetime for 316L UG high pressure gas lines is some 30 years.


58V4, 1

August 2017

HP NH3 pipelines ruptures due to backflow of corrosive carbamate

Unsafe situation Operational Synthesis HP piping Incident Database Incident 10-003 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=467


Pay attention to high quality materials, proper design and installation of checkvalves, Install two checkvalves in series with different design, Pu spec break of pipe upstream fast closing Motor Operated Valve, Install flushing connection upstream checkvalves so that any solids can be flushed away from checkvalves.


59V4, 1

August 2017

Rupture of urea reactor due to cracks in carbon steel behind the liner

Significant part of plant was destroyed, plant never started up again, no casualties

Operational Synthesis Urea Reactor Incident Database Incident 04-001 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=550

Catastrophic Moderate (12) Intolerable 12 Avoid any contamination in space between loose liner and carbon steel. Do not flush a leak detection system with water


60V4, 1

August 2017

Rupture of urea reactor due to defect in titanium liner

Massive damage and long period forced shut down

Operational Synthesis Urea Reactor Incident Database Incident 90-001 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=618

Catastrophic Moderate (12) Intolerable 12Apply an active leak detection system with an accurate and reliable ammonia detector. Perform corrosion inspections at regular intervals. Choose higher alloy material of conctruction for protective layer


61V4, 1

August 2017

Several scenarios lead to high pressure in the synthesis

Potential toxic ammonia release and /or high temperature /pressure carbamate release (SIL 3)

Operational Synthesis Synthesis HAZOP



Catastrophic Moderate (12) Intolerable 12 Safety valve plus high pressure switch to realise the required. Probability of Failure on Demand. High pressure switch activates synthesis blocking situation. Apply a reliable pressure measurement.


62V4, 1

August 2017

Tube rupture leads to high pressure on steam or cooling water side

Pressure on steam or cooling water side will be higher than design, damage with realease of carbamate and toxic ammonia

Operational Synthesis HP Heat Exchangers

HAZOP




Sometimes steam side is protected by a rupture disc, but spurious activation has led to a large release. Steam side are also typically protected by a safety valve, which also blows off at tube rupture. Analysis has shown this safety valve is sufficient and blow off needs to be located to safe loaction (suitable for large ammonia release). In case of cooling water on shell side a rupture disc remains necessary (assure safey location of blow off).


63V4, 1

August 2017

Steam supply to the HP stripper during blocking in situation

Pressure higher than design, damage (SIL 3)

Operational Synthesis Synthesis HAZOPDieltjes SIL

Classification in Urea Plants

Catastrophic Unlikely (10) High 10Safety valve plus high pressure switch to realise the required Probability of Failure on Demand. Switch activates synthesis blocking situation (closing steam supply). Apply a reliable pressure measurement.

Minor rare (2) Low 2

64V4, 1

August 2017

Failure of the tube to tubesheet weld

Carbamate entering the steam / cooling water side, potential risk of corrosion of carbon steel tubesheet


Incident Database Incident XX-006 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=880

Catastrophic Moderate (12) Intolerable 12 Apply a conductivity measurement to detect leak. Do not expand tubes in the tubesheet during fabrication of the heat exchanger.

In case of a leak stop the plant. Minor Rare (2) Low 2

65V4, 1

August 2017

Failure of pressure bearing wall due to leak in overlay welding

Urea / carbamate leaked through insulation

Operational Synthesis HP Equipment Incident Database Incident 78-001 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=883

Minor Moderate (6) Moderate 6 Perform corrosion inspections during turnaround. Apply higher alloy materials for repair or replacement of protective layer in HP equipment


66V4, 1

August 2017

Failure of HP scrubber due to hydrogen explosion

Major damage Operational Synthesis HP scrubber Incident Database Incident 74-001 and 00-002



Install a hydrogen converter in CO2 feed, use ammonia feed from atmospheric pressure (no dissolved H2 and CH4), monitor H2 content downstream hydrogen converter, never close inert valve, be aware of flushing with condensate in HP scrubber which can increase H2/NH3 ratio (larger explosive area). Apply an explosion dome HP scrubber

Insignificant Rare (1) Low 1

67V4, 1

August 2017

Failure of urea reactor due to no proper leak detection system

Major damage Operational Synthesis HP Equipment Incident Database Incident 77-001 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=885

Catastrophic Likely (14) Intolerable 14 Install a vacuum based leak detection system with a reliable and accurate ammonia detector. In case of a leak stop the plant. Catastrophic Rare (7) High 7

68V4, 1

August 2017

Massive leak in urea reactor due to no proper leak detection system

Damage of carbon steel pressure bearing wall


Catastrophic Likely (14) Intolerable 14 Install a vacuum based leak detection system with a reliable and accurate ammonia detector. Pay attention to a proper design of the nozzles of HP equipment.


69V6, 3

September 2017

Failure (SIIC) of pipe in bends of 316L UG high pressure gas lines

Large release of ammonia Operational Synthesis HP carbamate gas lines

Incident Database Incident 12-001http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=927

Catastrophic Moderate (12) Intolerable 12Perform corrosion inspections during turnaround, secure sufficient tracing and insulation of gas lines to avoid condensation corrosion, apply small grain size material, apply higher alloy materials (25-22-2 or duplex).


70V4, 1

August 2017

Hot fluid splashes, balloon collapses during sampling at high pressure section

Injuries Operational Synthesis sample valves HAZOP Moderate Moderate (9) High 9 Make use of the BHDT Zero Dead Volume HP Sampling Valve Moderate Rare (3) Moderate 3

71V6, 3

September 2017

HP scrubber ruptures due to not commissioning all leak detection holes


Catastrophic Unlikely (10) High 10 Asssure the correct and complete installation of a leak detection system to all leak detection holes. In case of a leak stop the plant. Catastrophic Rare (7) High 7

72V4, 1

August 2017

Cracks from outside in carbon steel pressure bearing wall due to dripping of carbamate from a leaking flange


Major Unlikely (8) High 8 Avoid that leaking carbamate can drip on high pressure urea equipment. In case of a leak stop the plant. Major Rare (5) Moderate 5

73V6, 3

September 2017

Stripgas entered reactor during blocking in causing active corrosion

Damage of carbon steel pressure bearing wall Operational Synthesis HP Equipment Incident Database Incident 13-002

http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1348 Catastrophic Unlikely (10) High 10

During blocking in monitor the vessel temperatures for any heat increases. If the temperatures increase by more than 20F, the synthesis loop must immediately be drained. Assure positive isolation of CO2 when the loop is blocked in by monitoring loop pressure. Ensure operators close the isolation valve downstream of HIC-1201. Modify the Urea Plant startup procedure to include lab analysis of the stripper bottoms for metals found in the stainless steel liner, specifically Ni as it will be dissolved in the solution. The first sample must be taken within 12 hours of startup and the second 24 hours later. If the values are stable or decreasing, no action is required. If the values are increasing, the plant will be shut down and drained.


74V4, 1

August 2017

Failure of titanium level pipe due to corrosion (hydrogen enbrittlement below fouling)

Large emission of carbamate / ammonia


Catastrophic Unlikely (10) High 10Be aware of fouling as below fouling active corrosion can occur or with titanium as material hydrogen enbrittlement (hydrogen is formed with carbamate corrosion reaction without oxygen present)


75V4, 1

August 2017

Severe damage of liner Replacement of liner Operational Synthesis HP Equipment Incident Database Incident 12-002 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1439

Catastrophic Moderate (12) Intolerable 12 Assure a proper active vacuum based leak detection system with a reliable and accurate ammonia analyser


76V4, 1

August 2017

Rupture of reactor due to stress corrosion cracking of carbon steel pressure bearing wall due to cooling jacket

Stress corrosion cracking Operational Synthesis Urea Reactor Incident Database Incident 64-001 and 59-001


Catastrophic Unlikely (10) High 10Do not apply cooling jackets for HP urea equipment. Do not flush leak detection systems with water. Take care of proper insulation of HP equipment so that water / moisture cannot enter. Build a shelter on top of HP equipment.


77V6, 3

September 2017

Liner bulges and ruptures due to too high pressure behind the liner or due to draining the synthesis

Severe damage of liner and extensive repair


Minor Moderate (6) Moderate 6 Be aware that pressure difference over liner is very limited. Apply a vacuum based leak detection system. Be careful with draining, install a vacuum pressure measurement in synthesis


78V4, 1

August 2017

Chloride from atmosphere (cooling water effluent, marine atmosphere) entering the steam condensate system via atmospheric steam condensate tank

Chlordes causing chloride stress corrosion cracking in for example the falling film high pressure carbamate condenser or high pressure scrubber in gap between tubes and tubesheet


HAZOP Catastrophic Moderate (12) Intolerable 12 Assure always a higher pressure than atmospheric pressure in atmospheric steam condensate tank, check conductivity on steam side of HP heat exchangers leaks in tubes or tube-tubesheet welds


79V4, 1

August 2017

High vibrations of discharge line HP reciprocating carbamate pump

High pressure carbamate line rutpures, hot carbamate sprays around, luckily nobody got injured

Operational Synthesis HP Pumps Incident Database Incident XX-019 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1510

Catastrophic Unlikely (10) High 10Pay proper attention to the the welding and installation of discharge pipelines of high pressure pumps. In case of severe vibrations, stop the plant and improve the installation, consider dampeners in case of reciprocating pumps. Install vibration detectors on vibration sensitive pipelines


80V4, 1

August 2017

316L UG HP pipeline at inlet of reactor (conventional plant) ruptures due to erosion corrosion close to thermowell

Luckily no injuries, unplanned shut down and repair

Operational Synthesis HP pipeline Incident Database Incident 09-006 http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=1515

Catastrophic Moderate (12) Intolerable 12Also take into consideration erosion corrosion caused by turbulence of internals in piping and vesselsApply better grades of materials like 25-22-2 or duplex.


81V6, 3

September 2017

316L UG liquid outlet line HP NH3 stripper leaks due to relatively high temperature and as a consequence higher corrosion rates

Carbamate / ammonia can injure people

Operational Synthesis HP Piping HAZOP Catastrophic Moderate (12) Intolerable 12Replace pipe by better material like 25-22-2 or duplex. Perform regular corrosion inspections. Apply continuous corrosion measurement (EMERSON Permasense). Refer to: http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?t=1525


82V4, 1

August 2017

Explosion / damage of motor Major damage Operational Synthesis, Hydrolyser

HP pumps, hydrolyser pump


Major Unlikely (8) High 8 Pay attention to proper alignment, perform regular and preventive checks on condition (vibrations) of heavy duty centrifugal pumps


83V4, 1

August 2017

Fire in cooling water unit due to leak in heat exchanger

2 mln US$ financial loss and 55 days out of operation

Operational Utilities Cooling water unit Incident Database Incident 97-001http://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=298. Minor safety risk but catastrophic financal risk

Minor Unlikely (4) Moderate 4 H2 and NH3 analyser in each cooling water cell (FFBL) Minor Rare (2) Low 2

84V6, 3

September 2017

Explosion ammonia water tank due to combining NH3 and urea plant drain system

Damage the vessel, pipeline and instrumentation around it. No casualties.

Operational Waste water treatment

Ammonia water tank Incident Database Incident XX-022 https://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?t=1553

Minor Moderate (6) Moderate 6 Separate drain and vent system for ammonia and urea plant. Prepare proper Standard Operating Procedures for draining and venting for start-up and normal cases in both ammonia and urea plants.


85V6, 3

September 2017

316L UG High Pressure gas line ruptures due to condensation corrosion and dead end design

Large ammonia emission, plant shut down, no casualties

Operational Synthesis HP carbamate gas lines

Incident Database Incident 11-003

https://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?f=33&t=945&p=5045#p5045

Major unlikely (8) High 8

Avoid dead ends. Apply proper tracing and insulation so that condensation will be avoided (dew point typically higher than 160 degC), apply stainless steel with small grain size or apply higher alloy material (25-22-2 or duplex). Perform corrosion inspections for HP gas lines and weldolets. End of lifetime for 316L UG high pressure gas lines is some 30 years.


86V6, 3

September 2017

High Pressure reactor offgas line leaks from weld defect

Ammonia detectors alaram, plant shut down, no casualties

Operational Synthesis HP carbamate gas lines

Incident Database Incident 15-004 https://www.ureaknowhow.com/ukh2/round-table/viewtopic.php?t=1555


Apply proper tracing and insulation so that condensation will be avoided (dew point typically higher than 160 degC). Apply stainless steel with small grain size or apply higher alloy material (25-22-2 or duplex). Perform corrosion inspections for HP gas lines and weldolets. End of lifetime for 316L UG high pressure gas lines is some 30 years.


Documents

Major potential hazards in Urea Plants V6 090917 · problem of a valve in an ammonia line ... to operating the melt pump with ... packing ring of stuffing box HP reciprocating pump