LD type electric single girder overhead crane

FAQ 六 29, 2012 No Comments

1Purpose and structure

LD electric single girder overhead crane (the following says crane) is a kind of light lifting equipment, used with CD1、MD1 and other electric hoists, lifting capacity 1-20t, span 7.5-22.5m, working environment -25℃~+40℃, humidity ≤84%. It works under the environment without fire, explosion and corrosive matters and it is prohibited to lift liquid metal, and toxic, flammable and explosive objects. Work duty: intermediate work system(JC25%)

The product is a crane with general purpose, suitable for machinery fabrication, assembly, warehouse and other places. Features of its structures are as follows:

(1) Metal structure

Box type main girder is welded by U type trough plate rolled by steel plate and joist steel group. Cross girder is installed and welded by joist steel rolled by steel plate. For convenient storage and transportation, high tension bolts are used to connect main girder and cross girder.

(2) Lifting system

Be equipped with electric hoist which moves longitudinally along main girder, details of structure features are shown in the electric hoist specification.

3Moving system

Adopting independent driving form, the product uses driving device of LD model electric single girder overhead crane, use tapered rotor motor to match with “one open and one closed” gear reducer to finish moving

(4)     electrical parts

20t overhead crane

ZZHZ products take tapered brake asynchronous motor as matched motor. Electric hoist and crane moving system are equipped with safety device, such as lift limit switch, crane terminal point limit switch and others. LD model electric single girder overhead crane is controlled on the ground or in the cabin according to different control modes; has two types according to control circuit and voltage: low voltage (36v) and high voltage (380v); CD1 model (single speed) and MD1 model (dual speed) according to electric hoist lifting speed.

The specification provides electrical control principles diagram and installation wiring diagram under low voltage single speed and low voltage dual speed conditions.

1. Control principle for ground control

Moving speed for ground control has two kinds: 20m/min and 30m/min, CD1 model electric hoist moving speed: 20m/min and 30m/min, lifting speed 8m/min

Electrical devices for CD1 model electric hoist include electric control box, control button and fire cutoff stopper. As operating the machine on the ground, the operator must firstly start total startup button, make general contactor closed, then all systems can begin running. Start running buttons of all systems, contactor closes, then motor immediately moves forward or backward. To start crane moving system smoothly, connect a resistance in the motor stator, then immediately make a short circuit by time relay delay closed contact after finishing starting the crane (setting time 4-6s). When crane moves to the limit position, a pair of contacts of travel switch are opened, the system power is interrupted, so the system can only be controlled to move backward.

2. Control principle for cabin

Crane moving system controlled by cabin has three kinds of speed: 45m/min, 60m/min and 75m/min.

When the crane moves at a speed of 75m/min, moving system is driven by ZDR tapered wound rotor induction motor whose rotor connects the resistance to ensure smooth start, cam control operation, only the cam controller handle is in zero position, it can be started (zero position protection), connect bells before operation to send work guard signal to ground workers, press down start button to make general contactor work, then all systems begin running; when cam controller handle changes from zero position to forward moving or backward moving direction, motor immediately connects the rotor according to corresponding order and makes resistance change in different levels, thus the crane gradually reaches rated moving speed to ensure smooth moving.

When crane moves to the limit position, a pair of contacts of travel switch is opened, the system power is interrupted, then the crane can be re-started and moves backward only when cam controller handle is in zero position. As same with that in ground control, the system travel switch should not be regarded as a power off switch in the normal operation.Safe voltage 36v is usually used, if 380v voltage needs to be used, the users should tell us before placing an order. Protective device should be set to avoid damping if the crane will be used in the open air


2) Installation

1、            Install the driving device of crane moving system on the cross girder in the site

electric hoist

2、            Connect main girder and cross girder with high tension bolts referring to figure 2-a and figure 2-b. it should be guaranteed that shear shoulder on main girder connection plate should keep flat with horizontal plane of cross girder connection plate. To be on the safe side, it is allowed for users to make a slight but not too full welding on a, b and c by referring to the drawing to avoid deformation. Main girder and cross girder check after installation can be done in accordance with standard JB1306-94, corrosion and burr on the joint place of main girder and cross girder should be cleaned before installation.

3、            Install crane electrical equipment such as over-travel limit switch and switch box on the cross girder, connect related electrical parts, debug two crane moving motors to keep them move to the same direction

4、            Electric hoist can be installed on the main girder in advance, then mount on the rail, respective installation is also allowed

5、            Cabin can be connected before crane mounting on the rail or after. Concrete details should refer to site conditions

6、            Power sliding contact line device can be set up in accordance with figure 3 and

figure 4

7、            Connect all the electrical lines according to electrical diagram, after installation, crane must move to the direction that is set by control button

8、            Referring to figure 9 and table 5, users can set up resistance device and safety controller.

9、            Control cabin installation refers to figure 1, firstly install connection support 2 and cross girder with bolts, then connect connection 2 and 3 after connecting link frame 4 with control cabin 5


3) Use and rules

1General rule

1、Switch on under condition with no load, start and check all moving systems and safety device of control system, all of them should be flexible, accurate, safe and reliable.

2、Crane must have a safe and reliable grounding system, main loop ground insulation resistance after installation should not be less than work voltage 1000 ohms/v

3、It is prohibited to use the crane if the lifting capacity is more than stipulated lifting capacity.

2Operation safety rules

1、Driver must receive necessary training and has good eyesight and sense of hearing

2、Nobody is allowed to stand on the crane span structure when the crane works

3、To prevent starting a crane with trouble, “fault” warning board should be set near to press button switch or in the cabin.

4、Power supply must be cut off as the crane is being checked and maintained, check, lubricating and repairing are forbidden as the crane is working.

5、Unqualified steel wire rope is prohibited

6、Surface inspection for steel wire rope should be done at each crew changing time and a full check every 7-10 days.

7、As crane is working with load, the hook should be lifted at least one person’s height

8、As crane is working with load, the goods should be at least 0.5m higher than goods on the lifting line

9、Lifting objects are strictly forbidden to move over worker’s head

10、Moving with trouble for crane is forbidden, if it goes wrong as working, please immediately stop and maintain the crane.

3Driver’s responsibility

1、Drivers should be familiar with crane’s purpose, systems, control method, performance, maintenance and safety rules

2、Before operating the crane, check whether tools are left on the crane to avoid hurt people once falling down, then run all systems with no load, begin work after confirming everything goes well

3、Send a warning signal before staring the crane

4、Lifting objects with weight more than rated lifting capacity is strictly forbidden

5、It is not allowed to lift objects slantedly along the main girder

6、Moving and lifting objects should be done according to signal from ground commander, but drivers should stop the crane no matter who give the signal “stop”.

7、Crane controller should be started step by step, before the mechanism stops running totally, it is forbidden to brake by changing controller from positive position to reverse position.

8、It is not allowed to drag objects by using crane and trolley.

9、It is prohibited for people to leave crane with suspended objects or falling down hook

10、When the crane stops working, lift the hook and cut off the power supply.

4) Maintenance and overhaul

electric hoist

1、Make the following check for the crane every half a year, whether connection bolts of main end beam is loosen, whether shear shoulder on the connection plate of main end beam has flaw, whether bottom flange of joist steel has permanent down-warping deformation, once the trouble is found, stop and maintain the crane immediately.

2、Crane used outdoor should be painted on the appearance every year, crane indoor should be painted again every 3 years

3、Check whether wheels have flaw or overwearing, whether abrasion on the tread diameter of driving wheels at two sides is uniform, when abrasion on the wheel margin reaches 30% of original thickness or the flaw is found on the wheel, it should be changed; when two wheels tread diameter difference caused by uneven abrasion reaches 1/190 of its nominal diameter, please polish wheels again, but 10mm less than original nominal diameter is not allowed, change a new wheel in principle.

Wheels change method sees figure 11: loosen bolt 1, then take down 2, loosen bolt 4, then take down shaft slide plate and elastic ring washer, next pull out wheel axle 7, take down wheel 3, assembly order is contrary with that.

4、Crane moving system lubricating

(1)Take down oil plug 6, infuse calcium soap grease (GB491-65) to lubricate wheel bearings, the suggestion is to change grease once not more than 3 months, oil volume is 1/2-1/3 of bearing volume.

(2)Take down oil plug 8, infuse machine oil (GB443-64) with viscosity 5.11~5.89 ,E50, the suggestion is to change grease once not more than half a year.

(3)Daub often lubricating grease(GB491-65)on the exposed gear to ensure its lubricating.

5、steel wire rope

Sling rotating must be avoided as handling the objects.

Steel wire rope should be lubricated in a fixed period. Clean old grease with rag with kerosene (using steel brush to clean old grease and stain is absolutely forbidden). It will be declared useless if steel wire broken numbers in a lay length reaches that stipulated in table 3

Table 3

钢丝绳安全系数steel wire rope safety factor5.5

钢丝绳结构steel wire rope structure



交 互 捻Twisted numbers

同 向 捻Synclastic numbers

交 互 捻

Twisted numbers

同 向 捻

Synclastic numbers





6、When crane brake can not meet the demand of working, please adjust tightness degree of motor tripping spring, referring to figure 12, take down fan guard 9, loosen set screw 8, then turn to adjust and tighten  nut 7, then loose a circle and a half, fix screw 8, adjustment is finished.


7、Electric hoist installation, use and maintainance should refer to the corresponding electric hoist specification

8、Driving device (take figure 20; 21 and table 4 as a reference)



Table 4 Code name of technical parameters and bearing


Code name table of technical parameters and bearing

速度(米/分)speed (m/min)






速比i1 Speed ratio






22  (m=2)













 Speed ratio


24 (m=2.5)





Speed ratio






总速比i General speed ratio






所用轴承代号Bearing code name

轴承A Bearing A


Bearing B


Bearing C

















5)Wearing parts list (with wearing parts drawing, electric hoist not included)         

Table 6

序号No 图     号Drawing No. 名     称Item 材    料Material 备    注Remark
1 LD20.20.102A 齿轮轴gear shaft 20CrMnTi
2 LD20.20.15A 齿圈 gear ring 40Cr
3 LD20.20.12 主动车轮 driving wheels ZG45Ⅰ
4 LD20.20.21 被动车轮driven wheels ZG45Ⅱ
5 Zg3.70 锥形制动环tapered brake ring 氯丁橡胶石棉树脂(详见图纸)Neoprene asbestos resin (details see drawings) 用于1.5KW电机1.5KW motor
6 ZDY3.70 平面制动环 plane brake ring 用于0.8KW电机0.8KW motor


Note: ground control motor 0.8KW(ZDY121-4), cabin control motor 1.5KW (ZDR112-4)



6) Bearing detailed list (without electric hoist and driving device)

Table 7


名  称  规  格

 Items and specification



Installation parts

附    注Remark


单列向心球轴承412(60×150×35)Single-row radial ball bearing412(60×150×35)


主、被动车轮Driving, driven wheels


Snap ring groove in the outer ring


单列推力球轴承(35×52×12)Single-row thrust ball bearing(35×52×12)


ZDR112-4或ZDY21-电机ZDR112-4 or ZDY21- motor


单列向心短园柱子轴承(20×47×14)32204Single-row radial short column bearing




ZDR12-4 or ZDY21-motor


 7) Product specification representation method

The product specification representation method is as bellows:


1、Ground control

For example: lifting capacity 3t, span 10.5m, moving speed 30m/min

Representation method LD3-10.5-30

2、Cabin control

For example: lifting capacity 20t, span 16.5m, moving speed 75m/min

Representation method LD20-16.5-75


8) Order requirements

1. Electric hoist installation, use and maintenance should refer to the corresponding electric hoist specification

2. Users should explain the followings (according to actual demand)

(1)lifting capacity           t

(2)span           m

(3)lifting height           m

(4)moving speed             m/min

(5)Working system                 JC=        

(6)Power supply              v             HZ

(7)Control mode (ground or cabin)         

(8)Control cabin door (at end or side)           ; control cabin form (open or closed)          ;

(9)Power supply importing way (plane current collector or soft cable);

(10)Crane moving rail width            mm (referring to figure 10 and table 6)

3、If problems are found as using the product, please contact our company as soon as possible so that we can better and improve the products

9)  Electric drawing

20T electric single girder overhead crane

▲    Further warning

1、            It is strictly forbidden for crane (with electric hoist) to work with workers, people standing under heavy objects is strictly forbidden.

2、            Wedge joint for crane (electric hoist) steel wire rope must be in accordance with the regulation of GB5973-86 standard, steel wire rope head remaining length 200mm and install two rope clips to close and lock steel wire rope at wedge joint. Installation without license, maintenance and operation is strictly prohibited.

After crane (with electric hoist) finishes working, the height from hook to ground ≥ 2m.

Users can debug and start the crane after infusing oil into the reducer.









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