Plant, Manufacturing and Process Equipment
Core toolkit
Expect questions spanning rotating equipment, static equipment and process safety. Pumps: system curve versus pump curve, operating point, NPSH available versus required, cavitation, affinity laws; throttling and bypass control waste energy where a VSD does not. Fans and compressors follow the same curve logic; for compressed air, pressure drop, leakage (often 20-30% of output) and dew point are standard exam material. Static equipment: design pressure versus MAWP, corrosion allowance, relief valve sizing for the governing scenario (blocked outlet, external fire, thermal expansion), rupture discs and pressure testing. Heat exchangers: LMTD, fouling factor, approach temperature.
Process safety: HAZOP for deviations, LOPA and SIL for instrumented protection, management of change, layers of protection, flammable and dust atmospheres, and isolation/LOTO before maintenance. Manufacturing performance: OEE = availability x performance x quality (multiplied, never averaged), takt time, bottleneck theory, SPC control charts and the distinction between common and special cause variation. Condition monitoring by vibration, thermography and oil analysis also sits here.
Traps
- Reading NPSH available at the wrong point, or forgetting hot liquid reduces NPSHa.
- Assuming a relief valve sized for blocked outlet also covers the external fire case.
- Applying affinity laws to a valve-throttled system (they apply to speed change).
- Averaging the three OEE factors instead of multiplying them.
Worked example
A fan drawing 45 kW at full speed run at 85% speed gives (0.85) cubed = 0.614, so about 27.6 kW - a 39% saving, valid only where the system curve is friction-dominated rather than static-head dominated.