Maintence of marine gear pump is important to keep auxiliary machinery working properly, so we need to learn to how maintence during sailing.
1. Make sure that electrical wires are connected to the right terminals, because most of gear pumps don’t allow reverse rotating of the gears. In addition, the prime motor and pump should always be properly aligned, otherwise, abnormal vibration and wear of components will occur.
2. Although a gear pump has self-priming ability, a liquid film is generally required to seal internal running clearance. If a gear pump is started without liquid, air and other gases within the casing can be re-circulated through these clearances, which can extend the priming time definitely. In addition, dry operation may damage the internal components. Therefore, before a gear pump is started, it should be filled with liquid and vented.
3. Discharge pressure should not be over the rated pressure, or the driver and bearing may be overloaded. It may also cause wear, deformation and stuck of the working elements.
4. Suction pressure of gear pumps should not be lower than the net positive inlet pressure required(NPIPR), otherwise the cavitations will occur, which will reduce the capacity of gear pumps. Entry of air into the pump should always be prevented. When gas entrained or dissolved in the liquid enters a gear pump, cavitations-like symptoms may appear resulting from the expansion of thr gas in the low pressure region. Consequently the NPIP required for the proper performance of a rotary pump can be decreased by the presence of gas in the fluid being pumped.
5. The delivered lubricant should have proper temperature and viscosity. On one hand, too high temperature or too low viscosity may cause serious leakage and cavitations. On the other hand, too lower temperature or too high viscosity will cause lower capacity coefficient.
6. Keep proper internal clearance. The amount of leakage is proportional to the cubic of the size of clearance between the gear and cover. Clearance between end surface of the gear and the inner wall of the cover has great impact on the self-priming ability and capacity coefficient. The clearance is usually measured by means of lead wire.
7. The pumped liquid may contain impurities that could clog or damage the pump. Therefore a strainer with a net flow area equal to five times the suction pipe area should be installed in the suction line and cleaned regularly.
