輪機(jī)英語 Lesson 19.ppt

1、Jimei university,Lesson 19,Cargo handling equipment (貨物裝卸設(shè)備),Jimei university,The various items of machinery and equipment can be found outside of the machinery space.,Jimei university,These include deck machinery such as mooring equipment(系纜設(shè)備), anchor handling equipment(拋錨設(shè)備), cargo handling equip

2、ment and hatch covers(艙口蓋).,Jimei university,Other items include lifeboats(救生艇) and liferafts(救生筏), emergency equipment, watertight doors, valve actuator, stabilizers(減搖裝置) and bow thrusters(船頭推進(jìn)器).,Jimei university,The cargo handling equipment will now be described.,Jimei university,Cargo winches a

3、re used with various derrick(吊桿) systems arranged for cargo handling.,Jimei university,The unit is rated according to the safe working load to be lifted and usually has a double speed provision(裝置) when working at half load.,Jimei university,In the cargo winch, spur reduction gearing transfers the m

4、otor drive to the barrel shaft.,Jimei university,A warp end(卷繞端) may be fitted for operating the derrick topping lift (頂牽索) (the wire which adjusts the derrick height).,Jimei university,Manually operated band brakes may be fitted and the drive motor will have a brake arranged to fail-safe(故障保護(hù)), i.e

5、. it will hold the load if power fails or the machine is stopped.,Jimei university,A derrick rig(裝置) is known as union purchase(雙桿聯(lián)吊裝置).,Jimei university,One derrick is positioned over the quayside and the other almost vertically over the hold(貨艙).,Jimei university,Topping wires fix the height of th

6、e derricks and stays(穩(wěn)索) to the deck may be used to prevent fore and aft movement.,Jimei university,Winches,Derricks,Topping wires,Cargo handling wires,Jimei university,Cargo handling wires run from two winches and join at the hook.,Jimei university,A combination of movements from two winches enable

7、s lifting, transferring and lowering of the cargo.,Jimei university,Cranes have replaced derricks on many modern ships.,Jimei university,Positioned between the holds, often on a plateform which can be rotated through 360, the deck crane provides an immediately operational unit requiring only one man

8、 to operate it.,Jimei university,Various types of crane exist for particular duties.,Jimei university,In a general cargo crane, three separate drives provide the principal movements:,Jimei university,a hoisting(起升) motor for lifting the load, a luffing(變幅) motor for raising or lowering the jib(boom)

9、, and a slewing(旋轉(zhuǎn)) motor for rotating the crane.,Jimei university,The crane is usually mounted on a pedestal(底座) to offer adequate visibility to the operator.,Jimei university,For occasional heavy loads, two cranes can be arranged to work together.,Jimei university,The operating medium for deck cra

10、ne motors may be hydraulic or electric.,Jimei university,The use of hydraulic drives in cranes, winches and similar equipment is now accepted as a conventional method of drive in many case.,Jimei university,Many reasons can be suggested for the use of hydraulic systems in marine engineering:,Jimei u

11、niversity,a) A convenient method of transferring power over relatively long distances from, say, a central pump room to remote operating sites.,Jimei university,b) Fully variable speed control of both linear and rotary motion, with good inching capability and smooth take up of load.,Jimei university

12、,c) High static forces or torques can be achieved and maintained indefinitely(無限期地).,Jimei university,d) Complete safety and reliability is assured under the most difficult environmental conditions;,Jimei university,overload conditions are safeguarded by using a relief valve to limit maximum output

13、torques or forces.,Jimei university,The wide range of high torque, low speed motors are available for driving winch drums directly so dispensingwith(免除) the need to fit reduction gearing.,Jimei university,Motors of this type are more common on larger cranes where reduction gearboxes would be expensi

14、ve.,Jimei university,All fixed capacity motors, whether high or low speed, require a high flow at low pressure to obtain high light hook speeds and consequent short cycle times.,Jimei university,With large cranes this can become an embarrassmentand one solution with low speed motors is to use the tw

15、o speed type to double the speed and half the output torque at light hook load.,Jimei university,High speed motors with reduction gearing have the advantage that the brake can be mounted on the high speed shaft and so be much smaller and cheaper.,Jimei university,Because of the availability of stand

16、ard low cost gearboxes this arrangement is popular on light cranes.,Jimei university,Variable capacity axial piston motors have the important advantage that light hook speeds can be increased up to four times from a given oil flow by reducing the motor capacity to 25 per cent of the maximum.,Jimei u

17、niversity,Hydraulic Crane,The hoisting of the cargo is effected by a hoisting winch driven by a hydraulic motor that,Jimei university,that provides a constant torque in both directions of rotation and at all speeds within the regulation range of the motor.,Jimei university,The winch is equipped with

18、 a mechanical belt brake that acts on the outside of the rotating motor housing.,Jimei university,During operation, the brake is released by means of oil pressure which compresses a spring.,Jimei university,The crane jib is raised and lowered by means of a luffing winch which is constructed in a sim

19、ilar manner to the hoisting winch.,Jimei university,The pumps are axial piston pumps and are driven by a common 3-phased synchronous motor(三相同步電動(dòng)機(jī)) at a constant speed of rotation.,Jimei university,The capacity of the pump is changed by turning the swashplate.,Jimei university,The crane is turned by

20、 a hydraulic motor of the same type as that described above, in that the rotor turns a pinion which engages with a toothed ring on the crane housing.,Jimei university,An oil cooler is used to remove the heat generated in the oil during the operation of the crane.,Jimei university,The system is also

21、provided with a preheater for heating the oil in cold weather.,Jimei university,If the temperature of the oil reaches 85oC, a thermostat(溫度調(diào)節(jié)裝置) in one of the oil lines switches off the electric motor.,Jimei university,Pressure relief valves are built into the system to protect the system and the cr

22、ane against excessive loads.,Jimei university,All moving parts in the hydraulic system are lubricated by means of the oil in the system.,Jimei university,The crane housing, which is a welded construction on a rigid baseplate, contains all the mechanical machinery, the hydraulic system and the electr

23、ic equipment.,Jimei university,The tops of the crane housing and the jib carry blocks(滑輪組) for wires for the hoisting of the cargo and the raising of the jib.,Jimei university,All of the blocks have enclosed ball bearing.,Jimei university,Both the luffing winch and the winch for turning the crane ar

24、e operated from the same control handle.,Jimei university,A small movement of this control handle either forwards or backwards results in the build up of oil pressure in the control oil line and the piston in the brake cylinder releases the brake.,Jimei university,Movement of the control handle furt

25、her than the position for releasing the brake starts the luffing winch.,Jimei university,The crane jib is raised or lowered by moving the control handle backwards or forwards respectively.,Jimei university,The speed at which the jib is raised or lowered is proportional to the distance the handle is

26、moved.,Jimei university,Changes in speed are effected by changing the pressure of the oil that is supplied to the control cylinder and which regulates the pump by means of a servomotor(伺服電動(dòng)機(jī)馬達(dá)).,Jimei university,This changes the oil flow and thus the speed of the rotor in the hydraulic motor.,Jimei

27、university,The safety system consists of: a main safety valve; two pressure reducing valves.,Jimei university,The slewing winch, which is almost identical to luffing winch, is controlled by using the same handle as that used for the luffing winch.,Jimei university,A small movement of the control han

28、dle to the right or left gives rise to oil pressure in the brake cylinder and releases the brake on the slewing winch.,Jimei university,Movement of the control handle to the right or left in excess ofthe positions that release the brake starts the crane moving to the right or left respectively.,Jime

29、i university,The closed hydraulic system consists of an axial piston pump with variable output and a hydraulic motor mutually connected through oil pressure lines.,Jimei university,The amount of oil flowing through the system and the direction of flow are regulated by means of a servomotor.,Jimei un

30、iversity,When in operation, it is unavoidable that a small amount of oil escapes through leakage, and in order to compensate for these leaks the system is connected to a feed pump.,Jimei university,For pumping up, two check valves are used, and a bypass valve limits the pressure to 17-25 bar.,Jimei

31、university,The safety system is designed for a certain maximum pressure, and the working pressure must therefore be limited.,Jimei university,For this reason there is included a main relief valve that connects the pressure side of the system to its suction side if the permissible pressure is exceede

32、d.,Jimei university,A double check valve with a common spring ensures that the relief valve always operates, regardless of which of the oil lines is the pressure side.,Jimei university,Reading materials,Mooring equipment (系泊，系纜設(shè)備),Jimei university,Winches with various arrangements of barrels are the

33、 usual mooring equipment used on board ships.,Jimei university,It usually consists of a driving motor, a reduction gear, a winch barrel or drum and one or two warp ends.,Jimei university,The winch barrel or drum is used for hauling in(拖) or letting out(放) the wires or ropes which will fasten the shi

34、p to the shore.,Jimei university,The warp end is used when moving the ship using ropes or wires fastened to bollards(系船柱) ashore and wrapped around the warp end of the winch.,Jimei university,The motor drive is passed through a spur gear transmission, a clutch(離合器) and thus to the drum and warp end.

35、,Jimei university,A substantial frame supports the assembly and a band brake is used to hold the drum when required.,Jimei university,The control arrangements for the drive motor permit forward or reverse rotation together with a selection of speeds during operation.,Jimei university,Mooring Winch,M

36、ooring winches provide the facility for tensioning(拉緊, 使緊張) the wire up to the stalling capacity of the winch, usually 1.5 times full load,Jimei university,thereafter the load is held by the prime mover brake or barrel brake when the power is shut off.,Jimei university,The winch cannot pay out wire

37、unless the brake is overhauled or recover wire unless manually operated, thus wires may become slack.,Jimei university,Automatic mooring winches provide the manual control previously described but in addition incorporate control features such that,Jimei university,in the automatic setting, the winch

38、 may be overhauled and wire is paid off the barrel at a pre-determined maximum tension;,Jimei university,also wire is recovered at a lower tension should it tend to become slack(松弛).,Jimei university,Thus there is a certain range of tension, associated with each step of automatic control, when the w

39、ire is stationary.,Jimei university,It is not practical to reduce this range to the minimum possible as this result in hunting(振蕩，不穩(wěn)定) of the controls.,Jimei university,It should be noted that the principal reason for incorporating automatic controls with the features described is to limit the rende

40、r(絞上，拖) value of the winch and avoid broken wires;,Jimei university,also to prevent mooring wires from becoming slack.,Jimei university,Load sensing devices are used with automatic mooring winches, e.g. spring-load gearwheels and torsion bars are widely used with steam and electric winches;,Jimei un

41、iversity,fluid pressure sensing either steam or hydraulic oil pressure, is also used where appropriate.,Jimei university,The majority of automatic mooring winches are spur geared to improve the backward efficiency of the gear train(齒輪系) for rendering,Jimei university,the gearing and bearings being t

42、otally enclosed and lubricated from the oil sump.,Jimei university,On larger mooring winches where a barrel brake is fitted, it is now common practice to design the brake to withstand the breaking strength(斷裂強(qiáng)度或負(fù)荷) of the mooring wire.,Jimei university,Worm geared (蝸桿傳動(dòng)的) automatic mooring winches a

43、re uncommon as the multi-start(多頭) feature required to improved gear efficiency reduces the advantage of worm gear i.e. the high gear ratio.,Jimei university,B. Anchor handling equipment (拋錨設(shè)備),Jimei university,The windlass(錨機(jī)) is the usual anchor handling device where one machine may be used to han

44、dle both anchors.,Jimei university,A more recent development, particularly on larger vessels, is the split(分離的) windlass where one machine is used for each anchor.,Jimei university,Chain or cable locker,Spurling pipe,Cable lifter,Anchor,Jimei university,The rotating units of a split windlass consist

45、 of a cable lifter(錨鏈輪) with shaped snug(凸起) to grip the anchor cable,Jimei university,a mooring drum for paying out or letting go of mooring wires and a warp end for warping duties.,Jimei university,Each of these unites may be separately engaged or disengaged by means of a dog clutch(爪形離合器), althou

46、gh the warp end is often driven in association with the mooring drum.,Jimei university,A spur gear assembly transmits the motor drive to the shaft where the various dog clutches enable the power take-off.,Jimei university,Separate band brakes are fitted to hold the cable lifter and the mooring drum

47、when the power is switched off.,Jimei university,The cable lifter unit is mounted so as to raise and lower the cable from the spurling pipe(錨鏈管), which is at the top and center of the chain or cable locker(錨鏈艙).,Jimei university,Anchor capstans(起錨絞盤) are used in some installations where the cable li

48、fter rotates about a vertical axis.,Jimei university,Only the cable lifter unit is located on deck, the driving machinery being on the deck below.,Jimei university,C. Preliminaries(準(zhǔn)備工作) for operating the hydraulic deck machinery,Jimei university,Filling the deck machinery with oil,Oil specially mad

49、e for operation of hydraulic pump, hydraulic motor and hydraulic equipment should be used.,Jimei university,In case such oil is not available, turbine oil of a good quality may be used.,Jimei university,Use of water, light oil, heavy oil, animal or vegetable oil and also ordinary machine oil is strictly prohibited.,Jimei univ