During the design phase a number of key review studies are conducted that require involvement of Commissioning Group.
Typical reviews studies include HAZID, HAZOP, LOPA, SIMOPS, layout reviews, P&IDs reviews, 3D model reviews, isometric drawing reviews, risk assessment and constructability reviews.
A commissioning team representative shall attend the reviews, especially if no operation representative is present. His role is to visualise the work of equipment when it is built and anticipate potential problems, for example:
- Insufficient drainage
- Isolation for maintenance
- Temporary connections
- Initial commissioning issues
Expressed in terms of cost the price of redrawing a P&ID or reconfiguring the 3D model during the design phase of a project is obviously significantly more cost-effective than redesigning of poorly installed section of pipe or piece of equipment in the field.
Towards the completion of Detail Design stage, the commissioning and process engineering groups should meet to discuss all alarms, interlocks and trips and to ensure that potential nuisance alarm and plant trips are removed. Raising action items and close them during a formalized process is a common method of managing this process.
Commissioning team in a HAZOP study
Before the hazard study, commissioning specific guide words are selected for discussion and the HAZOP study team expects the commissioning members to provide the input framed by those guide words.
The guide words associated with commissioning process would incorporate:
- Shut down
- Control sequence
- Spare parts
- Leak testing
- Vacuum testing
- Interlocking alarm testing
Commissioning team members involved in the hazard study process shall make a detailed check of the P&IDs in discussion prior to the actual study, using the guide words above to ensure their contribution is meaningful and constructive.
During the study, main considerations shall be given to:
- Can a unit be started up correctly; is everything in place for the start-up to be carried out safely?
- Can units be shut down correctly; is everything in place to allow the activity to be conducted safely?
- Do we have adequate drainage (typically used for maintenance)?
- Can the equipment be isolated correctly according to the pressure class?
- Is anything specifically required (equipment, spare parts, consumables) to allow initial commissioning of the unit?
- Is there sufficient instrumentation; is there pressure, temperature, level or flow indication necessary for the start up?
- Are the control loops adequate? Will they create any potential problems operating the plant?
- Are there sufficient vent and drains to allow the filling and draining of system?
- Has a siphon situation been created that requires a vacuum breaker (in particular, for tank filling)?
- Is provision adequately considered for system leak testing, chemical cleaning, steam blowing drying out and other specific tests?
- Is sample system practical and safe (e.g. transportation of hazardous chemicals from plant to a laboratory)?
- Mechanical interlock system
“What if” analysis is another process hazard tool for identifying risks to a process plant. Here, prior to the use of formal guide words, the hazard study team will review the process from a systematic perspective rather than a line by line approach like in a HAZOP study.
A general theme discussion will be facilitated by the hazard study leader where the team will brainstorm what if scenarios for the process (e.g. what if the pipe ruptures, what if the tank overflows). The team will then determine the consequence, rank the risk, determine the safeguards, make a reservation and allocate the action for remediation.
It is recommended for all commissioning personal not familiar with a HAZOP study to attend the formal training course to understand the methodology and become suitably prepared for the role they are to undertake.
akh.deocamdata.ro together with UreaKnowHow.com perform such training courses and HAZOP workshops for ammonia and urea plants.
akh.deocamdata.ro will develop a guidance for a HAZOP study methodology and procedure to be used by operators in the fertilizer industry.
A separate risk register to document extensive commissioning experience will be developed in FIORDA database.
Among many others experiences during the commissioning, some of the key lesson learnt are:
- Deploying Company Commissioning Resources early during Construction phase offers the best training opportunities and reduces construction mistakes.
- Shift from construction to commissioning site – the commissioning staff shall be involved into construction at about 70% overall construction progress. From that point the operation staff was engaged, and the Commissioning Work Permit Rules applied. This shift had positive safety implications as the incident rate significantly dropped.
- Aligning construction and commissioning priorities. It is important that Construction is flexible enough to respond to the Commissioning requirements throughout.
- Contracts to include commissioning reviews sessions during engineering to identify how the facilities will be commissioned and the modifications required for quicker and more systematic commissioning of the facility.
- Temporary Equipment – Proper planning of temporary commissioning equipment (like boilers, cooling towers) was critical during early commissioning phase.
- Commissioning Spares – insufficient commissioning spares can lead to delays.
- Preservations – Lack of proper preservation of some equipment resulted in leaking of many ball valves, control valves and blockage of caged valves.
- Lack of drain points in the steam system resulted in longer heating time for some machineries.
- Collect Trip and Interlock logics and diagrams in one area/document. – There was confusion as logic blocks are described in separate vendor documents and may not be reflected in the main plant shut down logics.
- OTS – Operator Training Simulator – OTS was not delivered at the right time for operator training during the commissioning phase. An OTS shall be delivered and set up early, preferably during construction phase.
- Killcross, M.: “Chemical and Process Plant Commissioning Handbook” (2012)
- Ali Abdi Jama “Commissioning and Start-up of QAFCO 5 and 6 (AICHE Ammonia Safety 2014)