Manufacturing, installation, commissioning and maintenance practice
Manufacturing, installation and commissioning questions test whether you can move a design into a safe, functioning plant. The examiner looks for sequence, verification and records: fabrication quality, pressure testing, alignment, flushing, balancing and the handover package.
Core rules and concepts
- Fabrication control: welding needs a qualified WPS/PQR, qualified welders and NDT where specified. Keep material traceability and dimensional checks.
- Pressure testing: hydrostatic test typically at 1.5 times design pressure, with calibrated gauges, vents at high points and drains at low points. Test before concealment or insulation.
- Installation: check pipe strain, soft foot, alignment, support spacing, slope, access and isolation. Do not use the pump casing to pull pipework into line.
- Commissioning: pre-commissioning (checks, flushing, electrical isolation), static tests, dynamic running, then integrated systems test with controls and fire modes. Record flow, head, current, vibration, noise and control response.
- Maintenance: planned preventive maintenance, condition monitoring (vibration, thermography, oil analysis) and root-cause failure review. Use permit-to-work and lock-out/tag-out.
Worked example
A chilled-water pump runs at 70% of design flow after installation. Outline the diagnosis. Reasoning: first verify the actual system curve and instrument calibration. Check that the strainer is clean, valves are open, air is vented and the impeller rotates the correct way. Measure suction and discharge pressures across the pump to separate pump head from system losses. If the pump head is normal but system resistance is high, look for closed valves, debris or a wrongly sized strainer. If both head and flow are low, check speed, impeller diameter and cavitation. Do not trim the impeller or open a bypass until the cause is proven, because that may hide a debris or air problem.
Traps that cost marks
- Pressure-testing after insulation or concealment.
- Using an uncalibrated gauge or the wrong test pressure.
- Running a pump before flushing and damaging seals.
- Commissioning controls without testing fail-safe and fire modes.
- Handing over without as-builts, O&M manuals and training records.