1、Dalian Ocean University,LESSON 14 MARINE MEDIUM SPEED DIESEL ENGINE III,Dalian Ocean University,Operation When an engine is to be run for the first time in the ship or after an extensive overhaul, it is first of all essential to make sure that,Dalian Ocean University,that the various services provid
2、ing sea water, fresh water, fuel, compressed air and lubricating oil have been checked for cleanliness, satisfactory operation and freedom from leaks.,Dalian Ocean University,The first run should be limited to a low speed and low load, preferably no load.,Dalian Ocean University,The run should conti
3、nue for only three to five minutes after which the engine should be shut down and all external surfaces(should be) checked for over heating.,Dalian Ocean University,If there is no sign of over heating externally, the crankcase inspection doors should be removed and a check(should be) made on interna
4、l bearings and running gear to ensure that all temperatures are normal.,Dalian Ocean University,If the engine is found to be in order after inspection it may be restarted and run for a little longer.,Dalian Ocean University,During this run it is prudent(谨慎的) to check the action of all safety devices
5、 such as low lubricating trip(润滑油低压跳闸) and the over speed shutdown(超速停机).,Dalian Ocean University,During the first running balancing the load between the cylinders must be done. On each cylinder head will be found a special valve to which a pressure indicator can be fitted.,Dalian Ocean University,M
6、aximum pressure readings should be taken when the engine is running on full load as steadily as possible.,Dalian Ocean University,Before fitting the indicator the valve should be opened to blow out carbon and then closed before the indicator is screwed into position.,Dalian Ocean University,Once the
7、 indicator is securely in place the valve is opened fully. After use, the valve should be closed and the indicator removed.,Dalian Ocean University,If the maximum cylinder pressures are out of balance they should be adjusted by retiming the fuel pumps.,Dalian Ocean University,To increase the maximum
8、 cylinder pressure the fuel pump timing should be advanced by means of the screw adjustment on the tappet.,Dalian Ocean University,The adjustment should be made in small steps with frequent checks on the maximum pressure.,Dalian Ocean University,The tappet adjustment will advance the injection in bo
9、th ahead and astern senses(方向).,Dalian Ocean University,If it is necessary to advance the one direction but not the other then this adjustment must be made by altering the position of the follower with reference to the cam, by adjusting the eccentric pivot(偏心支点) for the rocker lever or by using what
10、ever other mechanism provided.,Dalian Ocean University,The peak pressure indicator may be used to measure compression pressure. This is done by the engine on no load and cutting off the fuel to the cylinder which is being indicated.,Dalian Ocean University,The reading with the peak pressure indicato
11、r is then the compression pressure.,Dalian Ocean University,If the compression pressure is found to be low it is an indication that piston rings are stuck or that exhaust valves are leaking.,Dalian Ocean University,In this condition the maximum pressure will not respond to adjustments of the fuel pu
12、mp.,Dalian Ocean University,The fuel pump racks are marked in graduations(刻度) and, within reasonable manufacturing tolerance(公差).,Dalian Ocean University,When the original setting has been lost, as in the case when pumps have been replaced during overhaul, the racks should be set to the same reading
13、 at the full fuel position as a first step in balancing the load between the cylinders.,Dalian Ocean University,Pyrometers(高温计) are provided for registering the temperature of the exhaust gas at the outlet from each cylinder.,Dalian Ocean University,This temperature is an indication of the amount of
14、 fuel burnt in the cylinder concerned and, in general, temperatures of all the cylinders should be in close agreement with each other, say within 17oC.,Dalian Ocean University,In balancing the fuel from each pump by adjusting the racks, care must be taken not to turn the adjusting nuts in the same d
15、irection every time (when) an adjustment is required.,Dalian Ocean University,If the adjustment is always made in the direction which reduces the fuel, it could lead to the engine eventually not carrying the full load.,Dalian Ocean University,If adjustment is always to increase fuel, it might not be
16、 possible to stop the engine.,Dalian Ocean University,It will be noticed that for the first three millimetres of rack movement from zero the pump does not deliver fuel at all.,Dalian Ocean University,This is termed dead rack travel(齿条行程死区) and is to allow the engine control stop position to be adjus
17、ted.,Dalian Ocean University,During the normal running in service a constant check should be made to see that every thing is operating satisfactorily.,Dalian Ocean University,The only adequate way of doing this is by keeping an Operating Log in which instrument readings of engine performance are ent
18、ered regularly.,Dalian Ocean University,It covers engine speed, some indication of the load and the important temperatures and pressures of engine and its ancillary equipment.,Dalian Ocean University,A record should be entered every watch, more frequently if conditions are changing or during a trial
19、 period such as the first full load run after overhaul.,Dalian Ocean University,A careful watch should be kept on exhaust temperature. A sudden rise in the temperature of the exhaust gas from one cylinder is a certain indication that some part in that cylinder needs attention.,Dalian Ocean Universit
20、y,The component which requires the most frequent servicing is the injector.,Dalian Ocean University,In the normal way the first symptom(表现) of the fuel nozzles not functioning properly will be high exhaust temperatures, perhaps accompanied by dirty exhaust or a knocking noise.,Dalian Ocean Universit
21、y,If the load on the engine can be reduced a little it is possible to check on the dirty exhaust and the knocking noise by cutting out the fuel to each of the cylinders in turn to find out if cutting out of one of them will cure the symptom.,Dalian Ocean University,This procedure should not be follo
22、wed when the engine is running on full load as there would be a danger of overloading the remaining cylinders.,Dalian Ocean University,READING MATERIALA. INSPECTION AND RECONDITIONING OF INJECTORS AND INJECTION PUMPS,Dalian Ocean University,The fuel injectors will need replacing by reconditioned uni
23、ts at intervals of 500 to 1,500 hours according to the duty of the engine and the type of fuel used.,Dalian Ocean University,Smoke in the exhaust gas or a rise in exhaust temperature at full load is an indication that perhaps an injector requires attention.,Dalian Ocean University,The fuel control m
24、echanism between the governor and the fuel pumps should be examined at intervals of every 500 running hours.,Dalian Ocean University,The fuel pump, including the delivery valve, should be inspected at annual overhauls.,Dalian Ocean University,Any imbalance in exhaust temperatures or unsatisfactory c
25、ombustion which cannot be cured by changing fuel injectors should be the occasion for close examination of the fuel pump control mechanism and,Dalian Ocean University,and perhaps for the replacement of a fuel pump by a reconditioned or a new one.,Dalian Ocean University,Before dismantling an injecto
26、r it should be cleaned thoroughly and carbon deposits(should be) removed from the nozzle taking care not to damage the tip(喷嘴,雾化头).,Dalian Ocean University,If the nozzle is held in the nozzle nut by a formation of carbon it may be necessary to push it out using a tubular drift(管、筒状拆卸套) made of coppe
27、r(紫铜) or brass(黄铜).,Dalian Ocean University,It should certainly not be driven out by striking(敲击,打击) the nozzle end. As the parts of the injector are dismantled they should be placed in a bowl in clean paraffin(煤油,石蜡油) and left to soak(浸泡).,Dalian Ocean University,It is necessary to have a separate
28、bowl for each injector being dismantled as the parts from different injectors are not interchangeable(可互换的).,Dalian Ocean University,Carbon and lacquer(漆,用漆涂) should be cleaned from the parts using a nozzle fuel chamber scraper(刮刀), a nozzle hole pricker(探针), a seat cleaning tool and a brass wire br
29、ush as supplied by the injector manufacturer.,Dalian Ocean University,Care must be taken not to scratch(擦伤) a needle valve, its seat in the nozzle or any mating surfaces(配合表面) which are intended to seal fuel oil pressure.,Dalian Ocean University,If any of these mating surfaces show signs of damage s
30、uch as pitting, scores(刻痕) or grooves when examined under a magnifying glass(放大镜), they are not acceptable and should be replaced with new parts or parts that have been reconditioned by the makers.,Dalian Ocean University,Before assembling the parts of an injector they should be thoroughly washed in
31、 light fuel oil and assembled whilst wet.,Dalian Ocean University,Before replacing a fuel injector in the engine, whether it is a new or reconditioned unit, it should be checked by connecting it to a test pump fitted with a pressure gauge and the injection pressure(should be) measured and set, whils
32、t the spray is inspected for quality, pattern(型式) and absence of dribble(滴漏).,Dalian Ocean University,Spraying should be set to commence at the pressure recommended by the engine builder, and there should be no sign of leakage or dribble at any lower pressure.,Dalian Ocean University,The spray shoul
33、d be in the form of fine mist free from streaks(条纹痕) of unatomized fuel and be symmetrical about the centre line of the nozzle hole.,Dalian Ocean University,A reconditioned injector which is not required for immediate use should be carefully stored, having been covered with preservative(防腐的) grease,
34、 the pipe connection(should be) plugged and the complete unit(should be) wrapped(包装) in greaseproof(不透油的) paper.,Dalian Ocean University,The fuel pump delivery valve should be removed from the pump, inspected and its seat (should be) checked for wear, score or pitting, none of which is acceptable.,D
35、alian Ocean University,The fuel pump performance can be checked by connecting a new or reconditioned fuel injector to the outlet and, with the fuel control rack in the full fuel position operating the pump and observing the spray and comparing it with that from an injector connected to a new pump.,D
36、alian Ocean University,Operating the pump by hand often gives an indication by feel of whether the clearances are maintained and the pump operating correctly.,Dalian Ocean University,Pumps should be dismantled, following the makers instructions, and the parts(should be) washed in paraffin and (shoul
37、d be) placed in bowls, each bowl containing the parts only from one pump.,Dalian Ocean University,The contact surfaces of the plunger and barrel and the sealing face of the barrel should be inspected with a magnifying glass for evidence(迹象) of possible leakage which will show as fine irregular radia
38、l tracks(痕迹) on the surface.,Dalian Ocean University,If any blemishes(瑕疵) are found they can seldom be rectified(修正) and it is safer to replace the element assembly.,Dalian Ocean University,Damaged or flattened(变平) sealing rings should be renewed. Any washers(垫圈) removed should be discarded(丢弃) and
39、new ones fitted.,Dalian Ocean University,Prior to assembly all parts must be thoroughly cleaned and oiled and assembled whilst still wet. Careful attention should be paid to the manufactures instructions.,Dalian Ocean University,When a pump is replaced on an engine it will require retiming and adjus
40、ting to carry its correct share of the load.,Dalian Ocean University,B. PREPARATION FOR STARTING A GENERATOR ENGINE,Dalian Ocean University,1. Checking for Bolts & Nuts and Cranking(转动曲柄)Check to see if there is any loose bolt or nut.,Dalian Ocean University,Next, open the indicator cock of each cyl
41、inder, and crank(转动) the flywheel a few turns in order to check if the suction & exhaust valves are sticking or not and that there is any abnormal noise at some place.,Dalian Ocean University,2. Supply of Fuel Oi1 Since fuel oil contains a certain amount of moisture and dirt, from time to time open
42、the cock provided at the lower part of fuel oil tank in order to carry out draining.,Dalian Ocean University,Also at the time of fuel supply, drain the tank prior to supplying. The bottom part of a drum can(油罐) is another source of drain; thus, avoid using fuel oil pumped out from this part of drum
43、can.,Dalian Ocean University,3. Supply of Lub. OilBe sure to use the designed lub. oil.,Dalian Ocean University,Also at the time of supplying lub. oil, do not use lub. oil of different brand name. The amount of lub. oil supplied to the oil sump should be within the range between the upper and lower
44、scales(刻度) of the oil level gauge.,Dalian Ocean University,However, at the time of lub. oil exchange or in the case the engine has not been used for a long time, supply lub. oil a little bit more although the oil level should stay within the said(上述的) range.,Dalian Ocean University,For measurement,
45、do not screw in the oil level gauge.,Dalian Ocean University,Since lub. oil is served to distribute to the lub. oil cooler, lub. oil filters, and pipe, carry out priming by means of a wing pump(手摇泵) prior to starting,Dalian Ocean University,and once more confirm of the oil volume with use of the oil
46、 level gauge.,Dalian Ocean University,4. Priming of Fuel OilWhen a brand new engine is installed or when fuel oil pipes are dismantled or when air is found in the fuel oil pipe system, carry out priming of fuel oil in proper manner.,Dalian Ocean University,During the engines running, carry out air v
47、enting of fuel oil filter once more.,Dalian Ocean University,If the engine has not been used for a long time, conduct priming of fuel injection pump and confirm that fuel is injected.,Dalian Ocean University,5. Priming of Lub. Oil Set the 3-way change-over cock(三通转换阀) located at the upper part of lu
48、b. oil wing pump in the PRIMING position, and operate the wing pump until lub. oil pressure becomes about 0.6kg/cm2.,Dalian Ocean University,Next, shift the maneuvering lever in the STOP position, and turn the flywheel for several turns. After priming, return the 3-way change-over cock to the RUN po
49、sition.,Dalian Ocean University,6. Oiling to Various Parts Feed lub. oil to the feeding port of starting air-distributing valve. Feed oil to the oil cup of governor (about once a week).,Dalian Ocean University,7. Checking of Starting Air Reservoir Check the pressure of compressed air in the starting air reservoir.,Dalian Ocean University,Since the allowable maximum pressure of air reservoir is 30 kg/cm2, maintain at least the pressure of above 20kg/cm2.,Dalian Ocean University,If the pressure of starting air reservoir is less than 20kg/cm2, charge up by means of an air compressor.,
