Optimum running and usage of boiler feed water system would not only ensure high efficiency of the overall system, including the boiler but would also lead to less demand of maintenance by the system. There are many parameters that helps in efficient running of the feed system. The chief component among them is the feed water level controller. For this reason, it is imperative to check the feed water controller at regular intervals and carry out routine maintenance to ensure efficient running.
Condenser is the most important part of the feed system and thus proper care should be taken to prevent collapsing of any internal parts due to corrosion. The condenser is also subjected to high temperature and pressure conditions and therefore it requires additional attention.
The sacrificial mild steel plates that protects the sea water boxes of the condenser should be changed at regular interval of time. Moreover, even the tube plates should be checked on regular basis for any kind of erosion due to high velocity of the circulating water. The tubes should also be checked for leakages to prevent feed water contamination. In case a tube is found leaking, it should be either plugged or isolated from the system.
Improper working of pumps may disturb all the operating components of the system and therefore regular inspection of pumps is extremely important.
The sealing arrangements of the extraction pumps should be checked on regular basis to prevent any air from entering the system. Moreover the gland packing should be done in such a way that slight leakage of water is allowed to ensure lubrication of the shaft and the gland.
The feed pumps should also be provided with adequate attention. If the feed pump is a reciprocating pump, relief valves and air vessels should be checked on routine basis.
In case of turbo-feed pumps, the pumps should be started with a closed discharge valve in order to build up the pressure rapidly and bring the hydraulic balance into operation. The blades of the turbine should also be checked for damage due to cavitation and high speed of the fluid. Moreover, the turbine requires initial warming up, which is provided by keeping the drains open till the time the turbine reached an appropriate speed. Safety measures such as the overspeed trip should also be checked at regular intervals of time. The axial clearance should also be taken only with the help of proper gauges.
As in most other systems on board all types of ships, heat exchangers have an important role to play in the performance and functioning of the boiler feed water system also. The general principles of maintenance of heat exchangers apply equally to this scenario. The system’s heat exchanger should be regularly inspected for tube leakages and the heat surfaces should be kept clear of any type of scale deposits or corrosion.
Air ejectors should be checked for the ejector nozzles which if chocked, coated or eroded, will result in reduction in performance and inefficient operation. The vacuum retaining valve should also be inspected for air tightness. The ejector casing should be checked for leakages which otherwise would lead to loss of vacuum.
Malek, M. (2004) Power Boiler Design: Inspection & Repair. New York: McGraw-Hill Professional