Problem
A manufacturing facility needed a boiler feed pump replacement after the existing pump developed cavitation symptoms and repeated mechanical seal failures. Root cause analysis pointed to insufficient suction head for the feed water temperature — the deaerator tank was mounted too low relative to the pump suction.
Engineering review
FlowCore reviews boiler drum pressure, required feed pump discharge pressure including static head and friction, feed water temperature, suction head available from the deaerator tank, NPSH required of candidate pumps, minimum flow bypass requirement, and mechanical seal selection for the temperature.
- Boiler drum pressure plus static and friction losses = required discharge pressure
- Deaerator tank elevation above pump centreline = available suction head
- NPSH required of the pump must be less than NPSH available at hot water conditions
- Minimum flow bypass — required on most high-head pumps to prevent overheating at low demand
- Mechanical seal — standard or high-temperature face material depends on feed temperature
Solution approach
A high-pressure multistage pump with NPSH margin adequate for the feed water temperature, minimum flow bypass valve, correct seal face material for hot duty, and a trial run with pressure and current record before the boiler is returned to service.
What this project confirms
Boiler feed duty should never be selected on motor horsepower alone. Temperature, suction head, pressure margin, and minimum flow requirement are the design variables that decide whether the pump survives continuous duty.