新版輪機(jī)英語24 cargo handling equipment

1、新版輪機(jī)英語24 cargo handling equipmentCargo handlingThe duty of a deck winch(甲板絞車） is to lift and lower a load by means of a fixed rope on a barrel（卷筒）, or by means of whipping（纏繞） the load on the warp ends（帶纜端）; to top or luff the derricks（吊桿）, and to warp the ship.Hydraulic winch（液壓絞盤） systems are now

2、quite common but electric drives for cargo winches and cranes are most widely used. For the conventional union purchase（絞盤，起重裝置） cargo handling arrangement or for slewing (旋轉(zhuǎn)式） derrick systems handling loads up to 20 tons, standard cargo winches are normally used for hoist（起升）, topping（頂索） and slewi

3、ng（回轉(zhuǎn)） motions ,the full load duties varying from 310 tons at 0.65 to 0.3 m/sec.For the handling of heavy loads ,although this may be accomplished with conventional derrick systems using multipart tackle（多組滑輪）, specially designed heavy lift equipment is available.The winches used with these heavy li

4、ft systems may have to be specially designed to fit in with mast（桅桿） arrangements and the winch duty pull may be as high as 30 tons.Cargo winches are used with the various derrick systems arranged for cargo handling .The unit is rated according to the safe working load to be lifted and usually has a

5、 double speed provision when working half load. In the cargo winch, spur reduction gearing（正齒輪減速器） transfers the motor drive to the barrel shaft（卷筒軸）.A warp end（卷筒） may be fitted for operating the derrick topping lift 吊桿頂索 (the wire which adjusts the derrick height).Manually operated band brakes（制動(dòng)器

6、） may be fitted and the drive motor will have a brake arranged to fail-safe, i.e. it will hold the load if power fails or the machine is stopped .Most older ships and some recent ones use winches（絞車） in conjunction with derricks（吊桿） for working cargo.Derricks （吊桿）The derricks may be arranged for fix

7、ed outreach（向外伸） working or slewing derricks may be fitted.A fixed outreach system uses two derricks, one “topped” to a position over the ships side and the other to a position over the hold（貨倉） . Figure 24-1 shop shows the commonest arrangement adopted, known as Union Purchase rig （滑輪吊索）The disadva

8、ntages of the fixed outreach systems are that firstly if the outreach requires adjustment cargo work must be interrupted,And secondly the load that can be lifted is less than the safe working load of the derricks since an indirect lift is used. Moreover considerable time and man power is required to

9、 prepare for cargo working.The main advantages of the system are that only two winches are required for each pair of derricks and it has a faster cycle time than the slewing derrick system.The slewing derrick system has the advantages that there is no interruption in cargo for adjustments and that c

10、argo can be more accurately placed in the hold;however in such a three winches are required for each derrick to hoist, luff(變幅） and slew .A derrick rig, known as “union purchase”（組合滑輪裝置）, is shown in Fig.24-2. One derrick is positioned over the quayside（碼頭） and the other almost vertically over the h

11、old. Topping wires（吊索） fix the height of the derricks and stays（穩(wěn)索） to the deck may be used to prevent fore and aft movement .Cargo handling wires（吊索） run from two winches and join at the hook（貨鉤）.A combination of movements from the two winches enables lifting, transfer（轉(zhuǎn)移） and lowering of the cargo

12、. This is only one of several possible derrick arrangements or rigs（索具） .Although being very popular for many years, it requires considerable crew time to set up and considerable man power for operation.Deck cranesA large number of ships are fitted with deck cranes .These require less time to prepar

13、e for working cargo than derricks and have the advantage of being able to accurately place (or spot) cargo in the hold.On container ships using ports without special container handling facilities, cranes with special container handling gear are essential.Deck cranes require to hoist, luff (變幅） and s

14、lew and separate electric or hydraulic motors will be required for each motion. Most makes of crane incorporates a rope system(繩索系統(tǒng)） to effect luffing and this is commonly rove to give a level luff（桿式變幅）-in other words the cable geometry（形狀） is such thatthe load is not lifted or lowered by the actio

15、n of luffing the jib（吊臂） and the luffing motor need therefore only be rated to lift the jib and not the load as well.Some cranes are mounted in pairs on a common platform which can be rotated through 360.The cranes can be operated independently or locked together and operated as a twin-jib crane of

16、double capacity; usually to give capacities of up to 50 tons.Most cranes can, if required, be fitted with a two-gear selection to give a choice of a faster maximum hoisting speed on less than half load.On half loads hoisting speeds increase two to three times.Cranes have replaced derricks on many mo

17、dern ships. Positioned between the holds, often on a platform（平臺(tái)） which can be rotated through 360, the deck crane provides an immediately operational unit requiring only one man to operate it .Double gearing is a feature of most designs, providing a higher speed at lighter loads. Various types of c

18、rane exist for particular duties ,for example , a general duties crane using a hook（吊鉤） and a grabbing（抓斗） crane for use with bulk cargoes.A general cargo crane is shown in Fig.24-3. Three separate drives provide the principal movements: a hoisting（提升） motor for lifting the load, a luffing motor for

19、 raising or lowering the jib, and a slewing（回轉(zhuǎn)） motor for rotating the crane. The operator cab（操作室） is designed to provide clear views of all the cargo working area so that the crane operator can function alone .The crane is usually mounted on a pedestal（基座） to offer adequate visibility to the opera

20、tor.For occasional（偶然的） heavy loads arrangements for two cranes to work together, i.e. twinning can be made with a single operator using a master and slave control system in the two cranes. A common（共用的） revolving （旋轉(zhuǎn)） platform will be necessary for this arrangement. The operating medium（工作媒介） for d

21、eck crane motors may be hydraulic or electric, utilizing circuits referred to earlier.Hatch coversHatch Covers are used to close off the hatch opening and make it watertight. Wooden hatch covers, consisting of beams（桁條） and boards over the opening and covered with tarpaulins（防水油布）, were once used bu

22、t are no longer fitted.Steel hatch covers, comprising a number of linked（相連的） steel covers ,are now fitted universally（普遍的，廣泛的）. Various designs exist for particular applications, but most offer simple and quick opening and closing ,which speeds up the cargo handling operation.A MacGregor（麥格喬治） sing

23、le pull（單拉式） weather deck hatch cover is arranged to move on rollers（滾輪） along a track（軌道） on top of the hatch coaming. The individual covers are linked together by chains and ride up and tip（翻倒） onto a stowage rack at the hatch end.A hydraulic power unit, operated from a control box at the hatch en

24、d, is used to open and close the hatch cover. It is also possible to open and closed covers with a single wire pull (拉） from a crane or winch.Water-tightness of the closed covers is achieved by pulling them down on to a compressible jointing strip（對(duì)接帶）.This is done by the use of cleats（夾條，夾板） which may be hand-operated or