Comprehensive Course on Electrical and Instrumentation Detail Engineering

A: That's the most common mistake — assuming a PSV on the vessel nozzle covers everything hydraulically connected. Thermal expansion of a trapped liquid pocket downstream of a closed valve never sees the PSV because there's no relieving path back to the vessel. The pressure rise is local, fast, and well above MAWP before anything else reacts. The other cases all involve the vessel pressure rising, which is exactly what the PSV is there to limit.

A: That's the most common mistake — copying liquid-service practice into wet gas service. Sloping impulse lines toward the transmitter guarantees condensate pooling at the sensor, creating false DP and slow response. For wet gas, you want any liquid to drain back to the process taps so both legs see the same condition. The other suggestions sound tidy but don't fix the actual failure mode.

A: That's the most common mistake — treating intrinsic safety as just an insulation class problem. The separation exists to prevent fault energy from coupling into IS circuits via induction or contact, which breaks the energy limitation concept entirely. It's not about nuisance trips or cabinet zoning; it's about preserving the safety argument under credible faults.

A: That's the most common mistake — jumping straight to valve sizing or retuning. Opening the choke raises gas velocity, strips liquid, and shortens residence time, so the level signal becomes physically noisier even if average level is fine. The controller reacts to that noise and hunts. Density effects and flooding would show different symptoms.