99 Questions to Ask during a Design Review Session (Part III of III)

The design review acts as a forum where questions can be answered, assumptions clarified, and advice sought. It is a useful mechanism whereby the project design can be optimised through a systematic review and feedback on design process outputs. The design review process shall not be confused with process safety studies, like HAZID, HAZOP and LOPA. Typically, a number of formal and informal reviews are conducted during the project. These reviews may last a few hours or a few days depending on the scope and the phase of the project.

The design review process can be based on a checklist review, where questions are asked to Technology Licensor or EPCM to ensure deliverable documents contain necessary information for the design to continue. As many ammonia plant designs are similar, this is a good check on making sure the project specific requirements are covered, and any unusual, new, or otherwise note-worthy information is passed along to the downstream disciplines.

Below is a third list of 33 questions recommended to asked during a design review session:

  1. Has the relief case, design conditions and the possibility of cross-contamination been fully considered for complex system that usually cross battery limits?
  2. Have the criteria for avoiding fatigue failures from acoustic and flow induced vibration in piping subject to high velocity and/or large pressure drops been checked? If flow or acoustic vibration is considered a possible problem, have the proper support guidelines been specified?
  3. If air or oxygen can enter the process, has the possibility of deflagration been reviewed and the system designed accordingly?
  4. For a runaway reaction is this adequately addressed in establishing the design? (e.g., materials of construction, relieving loads, trip and interlock, etc.)
  5. Has overfilling of equipment been considered?
  6. Have all potential problems (e.g., corrosion, erosion, reactivity, improper mixing, vibration, etc.) caused by injection points been addressed? How?
  7. Are all potential problems (e.g., corrosion, erosion, reactivity, improper mixing, vibration, etc.) included and discussed in the HAZOP studies?
  8. Has tracing been provided where required?
  9. Does the discharge system drain adequately? (i.e., slope, no pockets, etc.) Have these been verified against the final layout of the piping?
  10. Have any relief valve or other emergency discharges to the atmosphere, that are potentially flammable or toxic and heavier than air, been reviewed with the Chief Engineer, Process Engineering or equivalent?
  11. Have the criteria for avoiding fatigue failures from acoustic and flow induced vibration in pressure relief valve discharge systems been checked? If flow or acoustic induced vibration is considered a possible problem, have the proper support guidelines been specified?
  12. Do discharge lines connect to the top of the Flare/Vent header?
    1. For atmospheric relief valve discharge lines:
    2. Are weep holes provided in bottom of pipe?
  13. Has a note been added to the P&ID to ensure that weep holes are located so as not to discharge onto access ways/equipment when relief valve is in operation?
  14. For a vessel, has the loss of liquid level been considered when evaluating the relieving load for the downstream equipment? Has the actual CV of the valve purchased been used?
  15. For systems with exchangers, has a ruptured tube case been considered when evaluating the relieving load?
  16. Has thermal expansion of piping and equipment contents been considered?
  17. Is every item of equipment protected from overpressure?
  18. Have the purging requirements and the purge gas availability been investigated and incorporated in the design?
  19. Have the designs of cooling water and steam condensate collection systems considered the potential leakages from exchangers in hydrocarbon or toxic service?
  20. Have flame arresters been considered for equipment vents?
  21. Are the details of interlocks between various controls and their subsequent impact on equipment and plant safety discussed and agreed with Control Systems and Commissioning and Operations Group?
  22. If any plant interlock must be bypassed for startup or shutdown, has the impact of this been addressed?
  23. Have the locations of critical valves and/or controls been identified; e.g. snuffing steam to fired heaters, operation of specific equipment isolation valves, ESD valves?
  24. Has tie-in coordination meeting occurred and philosophy been agreed with EPC contractor and implemented?
  25. Have changes which occurred after the HAZOP and Risk Assessment studies been documented and approved and their impact on safety and health of plant operators (been) addressed?
  26. Has adequate instrumentation, e.g., high temperature, low flow indication and/or alarm, been considered for protection of reformer superheat coils?
  27. For insulation:
    1. Is insulation and tracing of equipment shown as indicated on the Equipment Insulation Summary?
    2. Are dead legs covered?
    3. Is personnel protection shown where required?
  28. Have high pressure drop control valves been identified on the flow sheets?
  29. Has the line list validation report been processed and all items cleared?
  30. Has the effect of autoignition temperatures on process maintenance temperatures for lines that are electrically traced been considered?
  31. Where severe conditions of erosion or abrasion may arise have adequate provision been made for the replacement of parts most effected?
  32. Where pressure equipment requires monitoring of temperature excursions and shutdown action have these facilities been provided and adequately documented?
  33. Where pressure equipment may be subject to overheating, have the following been provided to minimise the risks of a significant loss of containment?
    1. Appropriate means of protection to restrict operating parameters such as heat input, heat take-off, fluid level so as to avoid risk of local and general overheating
    2. Sample points where required to allow evaluation of the properties of the fluid to avoid risks related to deposits and/or corrosion
    3. Adequate provisions to eliminate risks of damage due to deposits
    4. Means of safe removal of residual heat after shutdown
    5. Means of avoiding dangerous accumulation of ignitable mixtures of combustible substances and air, or flame blow-back



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