Authors: Jo Eijkenboom and Mark Brouwer UREAKNOWHOW.COM
Incidents happen in the chemical Industry. Many of these incidents do not surface but one should be aware of the fact that every incident has a learning factor and may avoid another incident in the future. UreaKnowHow.com has a Urea Incident Database in which the incidents are described and welcomes everybody to share an incident, anonymous or not in order to avoid a new incident. Sharing incidents will increase the safety of the industry. Avoiding incidents is of key interest for all stakeholders in the industry.
History shows that organizations do not have a memory. Incidents often repeat themselves and often are not shared. UreaKnowHow.com is an internet platform facilitating communication between all urea plants worldwide with the target to improve safety and performance in the urea industry. UreaK.nowHow.com has established an Incident Database to facilitate the sharing of incidents.
UreaKnowHow.com’s Urea Incident Database currently contains more than 45 incidents, ranging from severe explosions with casualties to near misses. We are also aware of the fact that because most incidents are not reported, the database cannot be considered a complete collection of all incidents. This Urea Incident database describes incidents and near misses as far as known and reported. It also gives a possibility to anonymously report incidents. We hope and trust this database will avoid future incidents in our industry. This Urea Incident Database can be found on the UreaK.nowHow.com Round Tables.
We urge all urea producers worldwide to share more frequently their incidents and near misses to fellow urea plants for the benefit of all. This Incident Database is the right place to file an irregularity. This paper will finally provide an example of such a success story. Find below the list of the incidents described in the UreanowHow.com Urea Incident Database to date March 2015:
- Incident 14-001: Fatality during bot bolting
- Incident 13-001: Fatal liquid NH3 pipeline leak
- Incident 12-001: Failure of bends in HP car- bamate gas lines
- Incident 11-003: Rupture HP gas hoe
- Incident 11-002: Fire
- Incident 11-001: Dismantling pressure gauge of HP flush pump
- Incident 10-004: Lump falling dlown from prill tower
- Incident 10-003: Corrosion HP NH3 line due to back:flow
- Incident 10-002: Twisted Butterfly Valve
- Incident 10-001: Fire in compressor section urea plant
- Incident 09-002: HP gas pipeline ruptured
- Incident 05-002: Rupture HP flange connections
- Incident 09-001: Accident during Prill tower construction
- Incident 05-001: Urea Reactor explosion
- Incident 04-001: Failure Reactor 200 mtpd
- Incident 02-002: Two people suffocate due to welding gas
- Incident 02-001: Casualties during prill tower cleaning
- Incident 01-002: Casualty valve maintenance
- Incident 00-001: Catastrophic failure of a weld-o-let
- Incident 98-002: NH3 leak in urea plant
- Incident 98-001: HP Pump NH3 leak
- Incident 97-001: Fire in Cooling Water Tower
- Incident 95-001: Urea Reactor explosion
- Incident 93-001: NH3 leak in urea plant during shutting down
- Incident 92-003: HP NH3 pump NH3 leak
- Incident 92-002: NH3 gas explosion N113 pump
- Incident 92-001: Urea Reactor explosion
- Incident 91-001: HP stripper explosion
- Incident 90-001: Reactor explosion
- lncident 87-001: Urea Melt splashes on per- son
- Incident 79-00 I : Reactor leak
- Incident 78-001: Urea Reactor Leak
- Incident 77-001: Urea Reactor explosion
- Incident 74-001: HP scrubber explosion
- Incident XX-012: Anhydrous NH3 Sampling procedure benchmarking
- Incident XX-011: Leak in liquid NH3 pipeline
- Incident XX-010: CO2 can ignite a flammable mixture
- Incident XX-009: Leak in liquid NH3 pijpeline
- Incident XX-008: Fall of scaffold from height
- Incident XX-007: Explosion CO2 vent pipe ex CO2 compressor
- Incident XX-006: Leak HPCC tube causes corrosion tubesheet
- Incident X:X-005: Collapsed wooden Cooling Towers
- Incident XX-004: Rupture Urea Reactor due to Nitrate SCC
- Incident XX-003: Severe nitrate SCC Urea reactor
- Incident XX-002: Severe corrosion HP NH3 pipeline
- Incident :XX-001: Rupture HP CO2 line
Overlooking all incidents, one can conclude that the safety risks in a urea plant are related to:
- High pressures
- Corrosive properties of ammoniumcarbamate
- Ammonia release
- Atmospheric corrosion, Corrosion under insulation
Analyzing more in detail the incidents of the UreaKnowHow.com database shows that some 35% of the incidents are related to the high pressure equipment, some 40% to high pressure piping, valves and accessories, and some 25% to others such as cooling towers, prill towers and compressors.
It is our firm belief that fairly simple measures and adhering to some critical points of attention can avoid a significant part of these incidents. In this paper we will summarize these critical points for high pressure equipment and high pressure piping and valves for each phase of the lifetime of a urea plant.
Note the significant difference between equipment and piping when one considers corrosion inspection:
- High pressure equipment is designed in such a way that all parts in contact with the process can be inspected during a turnaround and all urea producers do these inspections. Conversely most of the high pressure piping cannot be inspected from the process side as it is simply not accessible. Inspection techniques of pipe line systems also have its limitations.
- When manufacturing High Pressure equipment, welds are executed in a workshop under ideal conditions, while many welds in high pressure piping are executed in the field. Often these welds are done in difficult positions and under difficult circumstances that impede the required and necessary quality.
- It is not yet common practice to perform corrosion inspections to high pressure piping, valves and accessories on a regular basis. Also the execution of the inspection of a piping system is time consuming, and the interpretation of the inspection results is not that simple.
General measures and attention points to avoid / minimize high pressure equipment and piping incidents in urea plants
During the design and engineering phase one should pay attention to:
- Correct choice of materials of construction according to licensor’s specification; or better, choose a more corrosion resistant material of construction in certain cases
- Design avoiding crevices and dead legs. Install a state of the art leak detection system (active system with a continuous analysis) in equipment with a loose liner or at other areas where it is needed.
- Specify application of adequate coating systems in case of risk of atmospheric corrosion (chlorides, nitrates and sulphides)
- Specify adequate insulation/tracing system to avoid ingress of moisture and condensation of gas phases
- Lay-out of grass root plant with location of cooling towers opposite prevailing wind direction
During the fabrication, construction, storage and shipping phase one should pay attention to:
- Quality control of materials of construction according to licensor’s specification. The use of Positive Material Identification (PMI) techniques in this stage is unavoidable
- Guidance and control during manufacturing of equipment and erection of plant
- Choose qualified and experienced fabricators.
- Maximize prefab welding of high pressure piping and make use of qualified and experienced welders
- Guidance and control during application of coating and insulation systems
- Guidance and control during pressure testing and flushing of equipment
- During storage and transport/shipment in a chloride-containing atmosphere the equipment should be inerted with nitrogen
During operation and maintenance phase one should pay attention to:
- Proper operation within the windows of licenser’s manual
- Perform regular inspections based on Risk Based Inspection philosophy to be able to set up predictive maintenance programs for example for HP piping one can consider to inspect high pressure carbamate gas lines for condensation corrosion and weld-o-lets for higher corrosion rates.
- Perform maintenance/repair according to specifications
- Continuous monitoring to be performed on addition of oxygen in CO2 supply
- A continuous check on proper functioning of Leak Detection System
- The blow down steam/condensate of HP heat exchangers to be monitored on conductivity, pH and chloride content
- In case of any doubt analyze end product for Nickel content
- Proper inspection/maintenance of insulation/tracing systems to avoid ingress of moisture and condensation of gas phases
- In case of a leak, stop the plant and repair the leak