Various problems of marine gear pump may be encountered during the voyage, especially the mostly used lubricating oil transfer pump, so the troubleshooting skill is necessary for engineer.
1. Reasons for no delivery or low capacity
1) Operation at too low speed or with the wrong direction of shaft rotation(when a gear pump is driven backwards, the flow path through the casing is in the recer direction)
2) External leakage through casing joints or piping connection
3) Excessive shaft-seal leakage, excessive internal clearance
4) The presence of foreign material or air in the pump or suction line
5) Insufficient submergence of the suction pipe
6) Insufficient NPIP available to the pump
7) A clogged suction strainer, machanical defects
8) Too high viscosity(which results in an increased resistance to flow) or too low(which results in increased leakage)
9) An excessively high back pressure and a leaking relief valve
2. Reasons for too much noise
1) Liquid noise which may be caused by entrained air in liquid and cavitations
2) Mechanical noise which may be caused by misalignment of prime motor
3) Loosing of bearings
4) Blow off of safety valves and bent pump shaft and so on
3. Reasons for too much wear for pump
1) Foreign particles in oil
2) Running for a long period without flowrate
3) Too high discharge pressure and deformation of the pump shaft
4) Misalignment
