How to choose a grab crane for your business

DATE: Jun 4th, 2023

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1. Grab Crane General introduction

Grab crane (in other words: grabbing crane or bucket crane) is one of lifting equipment with grab spreader, widely used in port, yard, station freight, mines, power plant, refuse recycling, wood-fired co-generation power stations and steel production factory etc. Kingda grab crane mainly used for bulk material and recycling’s handling and shipment, for example：round log, mineral, coal, sand and gravel, clay, stone, grain, furnace slag, steel scrap, cement, renewable resource, gypsum, iron ore and so on.

Kingda grab crane is a automatic load handling device, its loading and unloading are controlled by driver or PLC intelligent system, no need personal assistance, avoiding heavy labor, handling efficiency is greatly improving finally. Grab crane generally is divided into overhead grab crane, gantry grab crane and folding-jib grab crane, in this article, we will talk about overhead grab crane and gantry grab crane only.

2. Grab Crane Characteristics

2.1 Improving production efficiency

For example: before the application of grab crane, loading and unloading mineral fines in yard, 12-16 worker will be needed in cabin, one worker-one spade, two workers as a team, one team fitted with a big net sling, one spade-one spade mineral fines is thrown into net sling, one net sling’s maximum capacity is 4t mineral. Under this condition, in one cabin, Maximum working capacity is 200t mineral fines in 8 hours. Now, under the assistance of big grab ship unloader, working capacity can up to more than 2000t, working efficiency is boosted greatly.

2.2 Improving production safety

For example: before the application of grab crane, loading and unloading round log in yard, 4-6 worker in cabin. First, small wire rope cross in round log’s gap again and again, forming a wanted dimension, hanging wire rope’s two ends on the hook, lifting 1m-2m, let one ends of round log up; then, the worker need to take a φ16-28mm wire rope, there is a hook tied in the end of this rope, the rope and hook will be throw out from log’s up end and log’s gap;

Third, on the other end, one worker should catch the rope and hook, otherwise, it will drop in the log hill, the same work need to repeat again. In the process, ground log will roll maybe, crushing worker’s foot and hands, or wore rope cut off in the air because of over loading log, dozen or many dozen logs drop from the air, worked will be died or hurt. While, after the ground log grab crane’s invention, personal injury accident is reduced greatly.

3. Grab Crane Classification

Grab crane can be divided by crane type, crab type and driving type.

3.1 By crane type

Kingda grab crane can be divided into overhead grab crane and gantry grab crane. It also can be divided into single girder grab crane and double girders crane.
This kind of grab crane transport for bulk materials such as coal minerals, grain, clay, iron ore, sand or gypsum to pointed position.

3.1.1 Overhead grab crane

Kingda overhead grab crane mainly dedicated on bulk material, graininess material, steel scrap and waste.

Overhead crab crane is equipped with cabin room to control the crane, and there are open and closed two types control room; while, for some special working environment, cabin room will be not suitable, replaced by remote operation station room or wireless radio controller, for example: refuse recycling and blast furnaces granulating pit. All traveling mechanism employ wound-rotor crane motor or inverter motor (will follow end user’s requirements), speed controlled by resistor or frequency inverter. Grab crane’s working class can be: A6, A7, A8, working ambient temperature 20℃~+40℃，this grab crane canot be used in explosion proof condition and insulation requirement workshop.

1. grab’s open-close direction: paralleled to main girder or vertical to main girder;
2. crane’s rated lifting capacity includes grab’s weight;
3. when there is rain cover, crane’s top extreme dimension should be H+h;
4. when crane be used in outdoor, crane total weight and max. Wheel pressure should increase 5%;
5. crane’s power supply type；JGHX, DMHX and cable festoon;
6. for trolley, there standard trolley and weighting device trolley;
7. depending on material’s nature, grab be customized for sugarcane, garbage, log, steel scrap.

* Double girder overhead grab crane technical data sheet

Technical Parameter
Lifting capacity				t	5	10	16	20
span				m	31.5	31.5	31.5	31.5
working class				A6
Lifting height				m	20	18	22	26
speed	lifting			m/min	40.1	40.7	41.8	48.6
	Cross travel				44.6	45.6	43.2	43.2
	long travel				86.4	89	87.3	87.3
weight	trolley			Kg	5200	8200	14800	19300
	total weight		indoor		41300	50400	67900	75600
	total weight		out door		42100	51200	69000	76800
Max wheel pressure			indoor	kn	144	196	263	312
Max wheel pressure			out door		148	201	268	316
Grab	Model	113	110	106	102	130	148	144
	Type	light	medium	heavy	super heavy	super heavy	heavy	super heavy
	Volume(M3)	2.5	1.5	1	0.75	2.5	4	3
	Density t/m3	1-1.7		1.7-2.5	2.5-3.3	2.5-3.3
	Dead weight(kg)	2632	2615	2568	2546	8305	10123	9927
Recommended rail					43kg/m		QU70
Power source	380-600V 50HZ 3 Phase

3.1.2 Gantry grab crane

Kingda gantry grab crane mainly used in outdoor yard, to transport iron ore, coal and wood etc.

Technical Parameter
Lifting capacity(T)		5	10
Span(m)		35	35
Lifting height(m)		10	10
Lifting speed(m/min)	Lifting	37.08	40.92
	Cross travel	49.4	49.6
	Long travel	34.5	30.5
Weight(T)	Trolley	13.8	17.7
Weight(T)	crane	126.3	137.5
Wheel pressure (Kn)		22.9	26.6
Grab	distance to cabin(mm)	1181	1104
	length after opening(mm)	3000	3700
	width(mm)	1852	2256
	volume(M3)	3	4
	density of material(t/m3)	0.8-1.0	0.8-1.0
Recommended rail		43kg/m	43kg/m

3.1.3 single girder grab crane and double girder grab crane

Mainly for overhead crane, depending on the different main girder number. One main girder, we call single girder overhead grab crane; Two main girders, we call it double girder overhead grab crane.

3.2 By grab’s type

3.2.1 Clam-shell grab crane

Kingda crane clam-shell grab crane mainly used in port, yard, station goods yard, for kinds of bulk material: mineral ,sand, stone, clay, slag, cement...., also can be used for earth-rock excavation, railways construction, railway lay-down etc.

3.2.2 Multi-jaw grab or orange Peel grab

Kingda multi-jaw grab or orange Peel grab suitable for steel scrap grab in steel plant and steel scrap sorting; refuse treatment; bulk waste’s sorting, loading and unloading and transportation in construction site; automobile’s disassembly, smelting and recycling. Grab’s cutting teeth can be replaced in rated time, its material is high strength wear resistance steel, service life is extended. Petal shell can be changed by different working environment: all closed petal shell, semi-closed petal shell, broadside petal shell and short side petal shell. Wood fetch grab crane is mainly used for fetching different size of log, timber, piping, round barrel and so on, can fetch in single piece, or in many pieces, used under the assistance of gantry crane or tower crane. Straw bunch and transport needs a special customized material handling equipment in wood-fired co-generation power stations, for unloading, stacking, storing, feeding work. Straw handling grab crane features heavy working duty, suitable for humid working environment, heavy-dirty, continuous operation.

3.3 By grab’s driving mode

By grab’s driving mode, there are hydraulic multi-jaw grab crane, mechanical grab crane and motor driven grab

3.3.1 hydraulic multi-jaw grab

hydraulic multi-jaw grab itself has open-close mechanism, usually it use hydraulic ram to drive, organized by multiple jaws, mainly used in refuse recycling, wood-fired co-generation power stations and steel production factory etc., for waste handling, slag handling, steel scrap handling, straw handling....

No.	Volume m3	Mode	Material density t/m3	Pulley multiplying	wire rope Dia φmm	pulley Diam φmm	Dead weight t	crane lifting capacity t	Close height Amm	Open height Bmm	Close length Cmm	Open length Dmm	Witdth Emm
1	3	light	≤1	3	φ16	φ400	2.75	5	2922	3403	2200	3020	1820
2	2.5	light	≤1	3	φ16	φ400	2.73	5	2975	3514	2200	3120	1600
3	2	Mid	＞1~2	5	φ16	φ400	2.71	5	3084	3547	2150	2985	1520
4	2	Mid	＞1~2	5	φ16	φ400	2.73	5	3137	3658	2150	2985	1520
5	1.5	Mid	＞1~2	5	φ16	φ400	2.50	5	2984	3429	1950	2750	1360
6	1.5	Mid	＞1~2	5	φ16	φ400	2.57	5	3037	3540	1950	2860	1360
7	1	heavy	＞2~2.5	6	φ16	φ400	2.45	5	2855	3270	1850	2535	1150
8	1	heavy	＞2~2.5	6	φ16	φ400	2.5	5	2908	3381	1850	2635	1150
9	0.75	super heavy	＞2.5~3.3	6	φ16	φ400	2.3	5	2760	3144	1650	2340	1054
10	0.75	super heavy	＞2.5~3.3	6	φ16	φ400	2.32	5	2813	3255	1650	2460	1054
11	5	light	≤1	3	φ20	φ500	4.26	10	3795	4430	2820	3800	2050
12	4	light	≤1	3	φ20	φ500	4.24	10	3595	4153	2445	3431	2210
13	3	Mid	＞1~2	5	φ20	φ500	4.38	10	3595	4153	2445	3431	1810
14	3	Mid	＞1~2	5	φ20	φ500	4.42	10	3695	4332	2445	3431	1810
15	2	Mid	＞1~2	5	φ20	φ500	4.25	10	3640	4127	2200	3251	1550
16	2	Mid	＞1~2	5	φ20	φ500	4.29	10	3694	4268	2200	3251	1550
17	2	heavy	＞2~2.5	6	φ20	φ500	3.95	10	3640	4127	2200	3251	1550
18	2	heavy	＞2~2.5	6	φ20	φ500	4	10	3694	4268	2200	3251	1550
19	1.5	super heavy	＞2.5~3.3	6	φ20	φ500	3.78	10	3357	3814	2020	2969	1470
20	1.5	super heavy	＞2.5~3.3	6	φ20	φ500	3.82	10	3409	3955	2020	2969	1470
21	1	super heavy	＞2.5~3.3	6	φ20	φ500	3.46	10	3052	3445	1676	2280	1464
22	1	super heavy	＞2.5~3.3	6	φ20	φ500	3.5	10	3141	3578	1676	2280	1464
23	8	light	≤1	3	φ24	φ600	7.96	16	4545	5292	3205	4387	2370

3.3.2 Mechanical grab crane

Kingda mechanical grab itself has no open-close mechanism, usually driven by external force rope or interconnecting linkage, following operation features, grab can be divided into single rope grab and double rope grab, and double rope grab is the most popular mode in industrial application.

For double rope grab, there are supporting rope and open-close rope, they are wound on supporting drum and open-close drum separately. Double rope grab is a reliable, easy operation , high-efficiency and wide application lifting attachment. If the grab uses twice double ropes, it will be four ropes grab, with the same operation process as double rope.

Kingda single rope grab will use one rope for supporting and open-close together. Through a special lock catch, wire rope can carry out its supporting and open-close work in order. Single rope grab’s winding mechanism is simple one, but with low-productivity and seldom used in big hand heavy loading and unloading work.

3.3.3 Motor driven grab crane

Kingda motor driven grab mostly used for single rope and single girder grab crane, grab’s supporting rope is one piece wire rope, open-close mechanism is fulfilled by a motor. This structure is a simple mechanism, only can be used in small work amount, equipped with a electric hoist.

3.4 By control mode

1.cable pendant
2. radio remote control grab crane
3. semi-automated control grab crane
4. Fully automated control grab crane
5. cabin control grab crane
6. remote operation station (ROS) grab crane

3.4 By grab’s manufacturing material

There are stainless grab crane, alloy steel grab crane.
Stainless grab crane specially use in food industries, for example: wine factory.

4. Grab Crane Operation Instructions

4.1 Driver Responsibilities

1.The basic requirements for operation: stability, accuracy, speed, safety, and rationality.
2. Familiar with crane’s main parameters, purpose, components, operating methods, and maintenance requirements.
3. Strictly comply with the basic operation, safety technology, and maintenance requirements of the "Crane Driver's Manual"
4. The crane must issue a driving warning signal before start.
5. The driver must closely cooperate with the hooker and keep pace. Moving and lifting heavy objects should only follow the signal sent by the hook operator, but whoever sends the "stop" signal, crane should stop immediately.
6. The controller should be started step by step. Before the mechanism completely stops running, it is prohibited to directly turn the controller from forward to reverse for reverse braking. In case of emergency, the controller can be
set to the reverse gear for braking.
7. Proficient in using fire extinguishers.

4.2 Crane operation instructions

1. Crane operators should operate the crane;
2. When the crane is working, no one is allowed to stay on the crane;
3. When the crane is running with a heavy object, it should be at least 0.5 meters above the highest obstacle on the heavy object running line;
4. It is prohibited to throw objects directly from the crane;
5. It is strictly prohibited to place flammable items on the crane. Tools and spare parts must be placed in specialized boxes, and it is prohibited to casually place them on large or small vehicles, to prevent them from falling off;
6. It is strictly prohibited to lift heavy objects over people's heads;
7. During operation, if any abnormalities are found in the crane, it must be immediately stopped for inspection, and the fault must be eliminated before operation;
8. When the lifting brake of the crane suddenly fails, the driver should remain calm and take appropriate measures based on the specific situation. If the surrounding environment does not allow the lifted object to be directly dropped, it can be lifted repeatedly and the crane or trolley can be started to select a suitable location to drop the lifted object, without allowing it to fall freely;
9. When lifting the grab, the speed of the lifting rope and the open-close rope should be equal, to ensure that the force on the steel wire rope is uniform;
10. It is not allowed to use a grab to grab a whole piece of object;
11. Before each shift, check the fastening of the rope at the suspension of the grab and the condition of the guide wheel of the grab opening and closing rope.

4.3 End of driver's job responsibilities

1. After the grab crane’s work is completed, place the grab on the ground and do not hang it in the air;
2. Cut off the main power switch in the protection box;
3. Inspect each mechanism and lubrication according to regulations;
4. All problems and solutions found during the operation and inspection, should be recorded in the handover manual. Only after handing over all the question to next driver, can the crane be left;

4.4 Operation notes

1) Before power transmission, check that all controllers are stopped at zero and that the switch positions are correct. The circuit breakers of each mechanism on the control cabinet are closed, and the railing door is closed;
2) Press the power button to power on, observe if there are any abnormalities in the electrical components, and confirm that there are no errors before operating each mechanism;
3) The lifting and long travel-cross travel mechanism use controller to control the motion, same as general crane;
4) The brakes of the lifting mechanism should be inspected every shift, and the brakes of the operating mechanism should be inspected every 2-3 days. If problems are found, they should be adjusted and repaired in a timely manner;

4.5 Grab operation

1) Grab opening operation: Lower the lifting and open-close mechanism simultaneously to the appropriate position, stop lifting mechanism to lower, open-close lower continuously, the grab open gradually. Finish grab operation;
2) Grab closing operation: open-close drum starts to lifting motion, grab’s top pulley with no move, the bottom pulley start moving up, the open-close motion been finished when grab tooth cross together. During open-close process, lifting drum make some lifting motion, ensure that the lifting steel wire rope does not sag;
3) Grab’s up and down operation: no matter the grab under open or close, the lifting movement can be operated at any time. The lifting drum and open-close drum should operate at the same time.

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