by RUTH SMITH, Senior Design Manager
We’ve all been there. Spent weeks looking at process lines in tedious detail and discussed at length whether the situation is adequately mitigated. Being tripped up by HAZOPS and sent back to the drawing board (a few times!) is a design manager’s nightmare.
Surely it doesn’t need to be this way. No, in my experience, it doesn’t. But your design team needs to get in early.
I’ve seen how integrating safety, environmental and operability considerations as early in the design phase as possible, delivers a faster and easier HAZOP process. Fewer changes are required which results in what we all strive for – a cleaner and safer process.
In fact, HAZOPs should fit into the overall safety management and assessment program for any plant or project and this process should be a continuous thread through the design process – from concept to working plant.
First and foremost, all installations must adhere to local legislation and country requirements, as well as any company standards and specifications.
Thereafter, a systematic approach to hazard identification is the best route.
Here are some tips and checks I follow to integrate HAZOPS into the front end engineering processes on a new project:
1. Concept Design Phase
In this phase the design intent is documented and the raw materials, co-product streams, basic process equipment and operating parameters are outlined. Capacities and equipment sizes are proposed and any safety or environmental concerns, or novel processes are identified for possible further review.
New developments – such as different insulation materials, lower pressure steam, alternative refrigerants, and lower concentration cleaning materials, which could lead to a safer, cleaner operation should be evaluated now. Even at this early stage, the aim should be to remove and reduce safety, environmental and operational risks. Plan to take action earlier rather than later when it is more difficult and can be more costly! Trying to rework building design to accommodate emergency fans or route vents safely when the design is more advanced is definitely not optimal!
2. Detailed Design Phase
Approved conceptual designs are developed, and decision made regarding process options. It is here that the base design of the process and utility systems is completed, and operating temperatures, pressures, and flow rates are confirmed. Conceptual P+IDs (Piping and Instrumentation Diagrams) are produced. It is critical that these P+IDs include the safety and operability features required, such as pressure relief valves, vent panels, low-level switches, and emergency stops.
To prevent any surprises later on, I would recommend that the design team conduct a preliminary review at this stage to ensure compliance with all codes, standards and specifications. It is a good idea to use a checklist and to consult P+IDs from previous, similar projects as prompts. The design is still flexible and changes are still possible at this point, although they become more challenging.
3. Tender & Procurement Phase
Once the detailed design is approved, the conceptual P+IDs will be issued for tender. It is extremely important that the area classifications, design codes, standards and specifications are issued with the tender documents. It should be clear to any potential vendor what the requirements are, and to what standards they will be expected to produce plant and equipment. Any third-party inspection or validations required by the vendor should be highlighted. The technical and procurement teams need to ensure that all bidding vendors comply with the requirements and make sure the hard work done by the design teams is not negated.
4. Pre-Construction Phase
The tender and procurement phase is concluded by appointing a successful vendor. The contract should include a time within which the vendor must produce the final P+IDs, preliminary process descriptions and make themselves available for a hazard review.
Before being approved for construction, these documents will be subject to final scrutiny to check for any hazards or operability issues which might have slipped through previous phases.
This is usually a HAZOP, but there are other techniques which may be more appropriate, depending on the potential hazards and the novelty of the process design.
If a HAZOP is chosen, it should be well-structured, rigorous, focused on the selected process area, and include relevant technical and operational staff. The proceedings need to be documented and any findings or changes required issued in a report for action. The loop needs to be closed and changes required confirmed before the updated P+IDS can be issued for construction.
This is not an opportunity to redesign the process or include additional scope. Changes required at this advanced stage may result in additional costs– it may be expensive, but better than going ahead with a flawed plan which will cost more later. It has been proven that the business benefits from adopting this level of governance in reduced failures and improved operability outweigh the costs.
What hazard assessment process do you follow and what have you found works for you?