Pin Me

Engine Room Watch-keeping Duties: Temperatures & the Sense of Touch

written by: Willie Scott • edited by: KennethSleight • updated: 11/7/2011

Engineroom watch keeping duties include the estimate of component temperatures using the sense of touch. Engineers can rely on this as well as instruments and gauges in checking equipment such as relief valves, and air start valves for leakage or incorrect operation.

  • slide 1 of 3

    In the previous article we discussed the duties of a watch-keeping engineer taking over a watch on a marine diesel engine, where he has to satisfy himself that the main engine and auxiliaries are running normally.

    In the following section we shall examine how we not only depend on instruments to tell us the engines condition, but also how we rely on the human sense of touch.

  • slide 2 of 3

    Watch keeping and the Sense of Touch

    The following components can be checked for undue heat using the sense of touch. Starting from the top of the engine room;

    As we walk along the top plates we check for the relief valves and air start valves that they are not leaking back by resting a hand on the connecting pipework. The reason for this action is that if a relief valve is leaking back the pipework will be hot, due to hot combustion gases, sometimes this is caused by the relief valve having lifted and not re-seating properly. A sharp tap on the top of the valve with a hammer can reseat it. However if leaking for some other reason, this will affect the efficiency of the combustion process and the valve should be replaced.

    Similarly if an air-start valve is leaking back, the pipework will be hot due to the combustion gases. Here however the similarity ends! A leaking air-start valve can allow the gases to flow back down the air supply pipework and into the air-start vessel, where it can combine with the compressed air/oil vapor and cause the vessel to explode.

    To avoid the possibility of such an explosion involving compressed air, the individual air-start isolating valves and compressed air vessel outlet valves should be shut at all times except when maneuvering. Any suspect air-start valves should be replaced. Compressed air vessels should be drained of the mixture of water and oil, the oil having been carried forward by the air compressor lubrication.

    A hot crankcase door can be indicative of a bearing or other engine component running hot. An oil mist forms on the inside of the crankcase and the crankcase gets progressively hotter due to lube-oil overheating in an attempt to cool the bearing/s.

    One sure-fire way of confirming this is by walking along the bottom plates of the engine room and running a hand along the crankcase doors; any overheating problems will soon manifest themselves through the skin on the back of a hand, much faster than relying on the oily-mist detector or in the extreme situation of the crankcase explosion doors lifting.

    Lastly we will look at the propeller drive shaft bearings and stern gland. The propeller shaft will have been aligned to the main engine at the shipyard where the ship was built, and alignment subsequently checked in drydock during yearly survey. However, the larger ships of today such as VLCC, LNG or Container ships have a lot of for and aft movement, especially if sailing light-ship or in ballast, so there is a lot of stress on the prop shaft which is transmitted as torque to the shaft bearings.

    I remember on one occasion we lost the tip of our prop in Toronto Ontario, we were allowed to proceed to UK at half speed; such was the vibration that we had a junior engineer on constant prop shaft bearing watch. So it is always worthwhile and, indeed part of a good watch-keepers duties to walk along the tunnel regularly, checking the bearing oil levels on the level glass (these bearings are white metal and lubricated by ring splash feed) again resting a hand on top of the bearing checking for any undue heat or vibration will ensure that the bearing and shaft are running correctly.

    Moving on down the tunnel the rest of the bearings are checked in the same manner, until we reach the stern gland. The stern gland should always have a trickle of seawater running out of it {except when in port}. This ensures not only a cool running gland but also that the gland packing and shaft are being lubricated. Again laying a hand on the gland will tell if it is running hot – carefully slackening off the gland adjusting nuts in sequence will increase the flow of seawater through the packing and cool the whole stern gland down.

    All this touching of pipes and components by hand to check for excessive heat soon becomes second nature to the experienced watch-keeper.

    The following sketch shows a typical air-start system with a leaking air start valve; note the location of the pipe that will become hot very quickly, and the devices in place to prevent and explosion.

  • slide 3 of 3

References

  • Author's Experience