What to check on a Ballast Pump.
5 models from SHURflo in Ballast Pump. Below: the full model list.
What sets a ballast pump apart
A ballast pump is built for high flow at moderate head, since ballast operations move large volumes of seawater over a short time rather than a small flow against high pressure. Most are centrifugal pumps, self-priming or primed by an eductor, distinguishing them from the positive-displacement pumps used for viscous fuel and lubricating oil duties elsewhere in the engine room. On many ships the ballast pump doubles as a general service or fire pump, so its capacity is sized against more than one duty.
Read the full guide
Main components
Impeller and casing
A single or multi-stage centrifugal impeller in a bronze or duplex stainless casing handles the corrosive, sediment-laden seawater typical of ballast intakes, particularly near port and in silty anchorages.
Priming arrangement
Ballast pumps mounted above the waterline need a priming system, commonly a water-ring or eductor-based vacuum priming unit, to draw water up before the impeller can take suction.
Valves and piping
A ballast main runs to remote-operated valves at each tank, controlled from the ballast control console, with cross-connections allowing pumps to serve tanks beyond their normal line.
Ballast water treatment interface
Where a ballast water management system is fitted, the pump discharges through filters and a treatment unit (UV or electrolytic, typically), adding backpressure that the pump's duty point must be checked against.
Selection and sizing
Sizing is set by the largest ballast tank volume divided by the target de-ballasting or ballasting time in the ship's stability and loading manual, plus the additional head from the treatment system if fitted. Suction lift, seawater temperature range and sediment load in the trading area all affect impeller and seal material choice.
Regulations and class requirements
Ballast water exchange or treatment falls under the IMO Ballast Water Management (BWM) Convention, which sets discharge standards the pump and treatment system together must achieve, along with a Ballast Water Management Plan specific to the vessel. Class rules cover the pump itself under machinery survey requirements, and periodic performance and capacity tests confirm the pump still meets its rated duty point.
Typical faults
| Fault | Consequence |
|---|---|
| Impeller wear from sediment abrasion | Falling capacity and longer ballast operation times |
| Mechanical seal failure | Seawater ingress to the pump room bilge and possible loss of suction |
| Air leak on the suction side | Loss of prime, pump runs but delivers little or no flow |
| Fouled strainer ahead of the treatment unit | Backpressure rises, pump runs off its duty curve, treatment throughput drops |
| Corroded remote valve actuator | Tank cannot be isolated or filled from the control console, forcing manual local operation |
What to look for in a supplier
- Confirmed duty point including the added head of any fitted ballast water treatment system
- Impeller and casing materials proven against the sediment and salinity of the vessel's trading area
- Compatibility with the existing ballast control console and remote valve actuators
- Seal type suited to the maintenance interval the vessel's engine crew can realistically hold
- Spare impeller, seal and wear-ring availability at the vessel's usual repair ports
Check the pump's actual duty point against its curve after a ballast water treatment system is retrofitted; the added backpressure alone has pushed some pumps into cavitation at rates they handled fine before.