Introduction to Process Design Engineering

A: Driving the pump harder under cavitation eats impellers and fails seals fast. Reducing flow demand restores NPSH margin that was lost due to higher vapor pressure, stopping vapor collapse at the eye. That protects rotating parts while you assess upstream heat input.

A: Ignoring thermal expansion in a blocked-in liquid line can split tubes or shells as pressure climbs quietly. Providing thermal relief addresses a real overpressure mechanism even without process heat, aligning with why the standard treats trapped liquid as a credible hazard.

A: Letting a valve choke the line without checking extremes can cause high ΔP, noise, and control instability that show up during SAT. Revalidating all cases ensures the selected size handles start-up and upset flows, not just normal operation.

A: Pushing more vapor into an already flooding column can collapse separation and damage internals. Reducing feed eases hydraulic load, allowing trays or packing to drain and restoring mass transfer before fine-tuning heat duties.

A: Blurring measurement and control roles can lead to wrong assumptions during FAT, leaving loops untested or misconfigured. Clear symbol separation prevents logic gaps and ensures everyone reads the same control intent.

A: Building with the wrong material risks early corrosion or contamination and a failed pressure test. Reconciling documents against the corrosion study locks material choice to service conditions, avoiding silent spec drift.

A: Forcing more flow or heat through a fouled exchanger can breach tubes or trip upstream equipment. Planning cleaning addresses the root cause, while temporary duty adjustment keeps operation within mechanical limits.

A: Designing only to normal pressure leaves piping vulnerable during start-up, shutdown, or control failure, leading to leaks or rupture. The margin covers credible excursions so integrity holds when operations stray from steady state.

A: Running past the mass transfer zone breakthrough contaminates product and can poison downstream catalysts. Resetting cycle time respects adsorption kinetics, then allows a proper review of capacity limits without degrading quality.