Power and Geothermal Plants: Feed Pumps, Cooling Water and Condition Monitoring That Pays

Thermal, geothermal and hydro plants are good at monitoring the turbine and poor at monitoring everything that feeds it. Boiler feed pumps, condensate extraction pumps, circulating cooling-water pumps, binary-cycle working-fluid pumps and the lube-oil systems around them are the balance-of-plant assets that trip units. In an Organic Rankine Cycle geothermal plant, 24 pentane feed pumps on variable-speed drives were controlled at equal speed with conservative margins; the ReliaPump upgrade — sensorless operating-point control and flow balancing across the group — delivered energy savings 30 % above the target set for the project, with no shutdown and no original documentation to work from. The lesson transfers to any multi-pump group in a power plant.

Where power-plant pumps fail

System	Failure	Cause	Fix
Boiler feed pumps (high pressure, high temperature)	Seal failure, thrust-bearing wear, recirculation damage	Minimum-flow operation at low load; seal plan not matched to temperature; thermal transients	Triple-ply metal bellows seals rated above 100,000 kPa with no dynamic elastomers; Plan 23 cooling; operating-point monitoring on the drive or turbine governor
Condensate and cooling-water pumps (parallel groups)	Uneven wear, one pump near dead-head while others carry the load	Equal-speed control; curve differences between old and new pumps	Flow balancing (ReliaPumpSync); vibration trends per pump
ORC working-fluid pumps (pentane, isobutane)	Cavitation at low subcooling, seal leakage of flammable fluid	NPSH margin changes with ambient and condenser conditions	Run-out protection, speed limits from condenser conditions; dual seals with Plan 53 barrier; i-ALERT trend for cavitation
Turbine and generator lube-oil systems, gearboxes (hydro, wind, gas turbine)	Bearing and gear damage found late; oil degradation	Quarterly oil sampling misses the window; water ingress from coolers	Online oil-quality and wear-debris sensors (Poseidon Trident); 5,000+ systems on wind turbines, 400+ Duke Energy turbines
Cooling-tower and auxiliary pumps	Motor failures, voltage unbalance damage	Long cable runs, supply quality, no monitoring	Electrical signature analysis at the switchgear with NEMA derating calculation

The feed-pump seal problem

High-pressure feed pumps in coal, biomass and geothermal plants chew through seals when they run at low load for long periods — the minimum-flow recirculation keeps the pump alive hydraulically but the seal chamber sees heat, pressure pulsation and flashing. Reading the failed seal tells the story: heat-checked faces mean flashing or dry running; off-centre wear means shaft deflection from off-BEP operation. Flexaseal's triple-ply metal bellows seals exist for exactly this duty — no elastomers to harden at 200 °C, high axial and radial stiffness, pressure capability above 100,000 kPa — combined with an API 682 Plan 23 closed-loop cooler that keeps the seal chamber below the flash point. But the seal is only half the fix; the other half is keeping the pump in its preferred operating region, which is a control problem.

Oil systems: the earliest warning in the plant

For turbines, gearboxes and large pump bearings on circulating oil, wear-debris monitoring sees damage first on the P-F curve — ferrous particles appear when a tooth or raceway starts to pit, before vibration moves and long before temperature. A Poseidon Trident wear-debris monitor on the return line before the filter, plus a QW3100 oil-quality sensor for water, oxidation and additive depletion, converts a quarterly lab sample into a daily reading. The wind industry proved it at scale; in a documented case a Trident sensor detected a gear-tooth defect that both borescope inspection and vibration analysis had missed. For a hydro unit or a gas-turbine gearbox the installation is on an isolatable branch, done at a planned stop.

Why the geothermal result was possible without documentation

The 24-pump project had no usable original control documentation. ReliaPump's approach does not need it: each pump's curve is characterised from the drive data in operation, the operating-point model is built from that, and the coordination logic sits alongside the existing control system rather than replacing it. The plant kept running throughout. For older power plants where the EPC's documentation is a memory, this matters more than the technology itself.

Recommended sequence for a power plant

• Rank balance-of-plant pumps and oil systems by trip history and cost (PlusSmart Analytics from the historian and CMMS).
• Fix control on the worst multi-pump group — feed, condensate or cooling water — with operating-point protection and flow balancing.
• Install online oil monitoring on the three most critical oil systems and wireless vibration on the pumps that do not have permanent monitoring.
• Match seals to duty on the feed pumps at the next outage, with the correct API plan.
• Report energy and availability quarterly against the baseline; most plants recover the programme cost in avoided trips within a year.

Quick answers

Can ReliaPump be applied to pumps on turbine-driven or fixed-speed service?

The operating-point protection needs a drive or at least power measurement to work from; fixed-speed pumps can be monitored with electrical signature analysis and vibration, and protected with conventional minimum-flow systems. Variable-speed groups gain the most.

Is online oil monitoring worth it for a single hydro unit?

Usually yes for the turbine guide bearings and any gearbox: a sensor set costs far less than one bearing failure outage, and it removes the quarterly sampling gap. PlusSmart installs a trial sensor alongside your sampling schedule so you can compare.

Do metal bellows seals need a different seal chamber?

Generally no — Flexaseal supplies cartridge bellows seals to the existing pump dimensions, confirmed from the pump model, shaft size, pressure and temperature before quoting. The seal support plan (cooler, reservoir) may need to be added or upgraded.