Class on CRANES
By Gurunadham MSS Technical Services
Material Handling • Material handling system is used to move materials from one place to another. • Key questions in material handling: – why move – where to move – when to move • Important ideas: – point of usage storage: move the parts to work center – unit load: move a unit load instead of an item
• A typical material handling system
Central storage
Conveyor
Workstation Worker
• Basic equipment
• Basic equipment (continue) – – – – –
cranes and hoists automated storage / retrieval system (AS/RS) industrial trucks: fork lifts, hand cars, … containers: pallets, tote pans, … robots
• Some of the basic principles of material handling – – – – –
orientation principle: setup the goal planning principle: meet requirement with flexibility systems principle: coordinate all the needs unit load principle: use large but practical unit load space principle: effectively use all cubic space
• Crane is a material handling equipment & plays a vital role in boosting the production of any heavy industry. Its contribution is even more significant in iron and steel industries. • Crane is a machine used for lifting or lowering a load and transporting it from one place to another in which hoisting mechanism is an integral part. It may be driven manually or by Power and may be fixed or mobile. • The very nature of the material handling requirements in an iron and steel industry necessitates the use of various types of cranes and many of them are special purpose heavy cranes, specially designed to meet the specific requirements of the industry.
•
Crane serves the steel industry with two major functions. firstly, it helps in increasing production by cutting down the handling time. secondly, it helps in increasing production by putting down the repair and maintenance.
• Mobile Cranes – Diesel Powered Cranes (Tyre/Chain mounted) • Hydra • Husky • Demag
– Locomotive cranes
• Electrically Operated Cranes – – – – – –
Gantry / Portal Crane Semi gantry/ Semi portal crane Cantilever Crane Jib Crane Tower Cranes E.O.T Cranes
These cranes are Lorry chassis mounted and Caterpillar tracked(Chain capable of moving on rough surfaces) These are self powered and very slow moving. The Power unit is a Diesel Engine operating a generator set. Which provides the drive to the various components. Brakes are either electrically or hydraulically controlled. II) Electrically Operated Cranes: These are totally electrically controlled. Occasionally Pedal operated Hydraulic brakes are provided. Different types of cranes under this category are mentioned below: a) GANTRY/PORTAL CRANE: This is moving on the rails fixed at ground level. used in open areas and storages.
MOBILE CRANE (Tyre mounted)
MOBILE CRANE (Chain mounted)
These are totally electrically controlled. a) GANTRY/PORTAL CRANE: This is moving on the rails fixed at ground level. used in open areas and storages. b) CANTILEVER CRANE: Single supported Cranes with Counter weight arrangement
c) JIB CRANE: Jib Cranes are easily rotating cranes available with floor or column mounting & full floating on roller ball bearing upto 1800 or 3600. They are designed to compensate for radial thrust load & swing under rated load with exceptional ease. d) PORTAL CRANE: This is fixed or revolving type Jib crane mounted on a portal frame fixed in one place or traveling along a fixed path.
e) TOWER CRANE: It is a fixed or traveling type, supported on a Tower capable of hoisting, luffing and slewing its loads over high obstructions. f) EOT CRANES: This is a crane 'running on a pair of elevated runways, adopted to lift and lower a load and carry it horizontally or parlllel to or at right angles to the runways or both. These cranes are electrically operated.
What is an EOT Crane ? A crane running on a pair of elevated run ways, adopted to lift and lower a load and carry it horizontally or parallel to or right angle to the run ways. The capacities of the cranes varies from unit to unit depending upon shop requirement. Normally a crane is specified as 30t x16m, this indicates the crane capacity is 30 ton and span is16meters. Depending upon the utility a crane will have more than one hoist.
FEATURES OF EOT CRANES: •
These are used mostly in covered areas and outside, required mostly in Steel Plants and Engineering Industries. • These cranes are of primary importance in a Steel Plant. •
These cranes essentially consists of - Single Girder, - Double Girders ,or Four Girders attached at each end to End Carriages, travelling at elevated tracks - fixed in location and a Trolley equipped with Hoisting mechanism, traveling along such Girder or Girders. These Cranes are classified based upon their duty cycle.
Classification of EOT Cranes Working hrs / annum Up to 1,000 hrs Up to 2,000 hrs Up to 3,000 hrs Above 3,000 hrs
Class
Type
I II III IV
Light duty Medium duty Heavy duty Extra heavy duty
• The Crane is designed as Box or Torsion structure, consisting of I sections or rolled plates welded together to form a Box structure which gives a sustained trouble free life.
E O T CRANE
BASIC PARTS OF OVERHEAD CRANES: 1. ELECTRICAL:Motors, controllers, protection systems (panels, relays and switches) main trolley lines and cross power trolley lines, current collectors. 2. MECHANICAL:Gears, wheels, pulleys, hook blocks, ladle beams,brakes, steel wire ropes, power transmission system etc. 3. STRUCTURAL:Girder structure, end carrige structures, trolley structure, Cabin, end stoppers, buffers, etc.
DIFFERENT MECHANISMS IN EOT CRANES 1. LONG TRAVEL AND ITS MECHANISMS. 2. TROLLEY AND ITS MECHANISMS. 3. HOIST AND ITS MECHANISMS. 4. SLEW MECHANISM.
CRANE GENERAL LAYOUT LT1
LT2
LT3
LT4
COMPONENTS IN LT / CT DRIVE 1)Motor 2) Motor Geared Input coupling 3) Gear box 4) Brake assy. 5)Floating Shaft 6) Wheel assembly 7) Rail Track
DIFFERENT MECHANISMS IN EOT CRANES i)
LONG TRAVEL AND ITS MECHANISMS:-
•
The two ends of the girders are connected with two end carriages. Wheels \ bogies are connected to the end carriages. Cranes have normally 4 wheels. but depending upon the capacity and type of design, the cranes may have 8 or more wheels. A crane moves along the bay is called long travel. The speed of the long travel is controlled by the operation of master controllers.
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•
• The drive transmission shaft runs across the bridge and consists of different sections. It is coupled to the reduction gear at one end and driving wheel shaft at the other. • The electro magnetic brake is mounted on the motor shaft. the transmission shafts are mounted on ball bearings. • The different sections are connected to another by means of gear couplings. • The cranes are fitted with spring loaded bumpers at the end girders. • For the power supply of the trolley electric equipments cross power lines (bus bars) are arranged on the trolley side bridge .The main switch is located generally in the top gallery of the bridge.
ii) TROLLEYAND ITS MECHANISMS:• The crane trolley comprises of the following main parts. 1. trolley frame. 2.hoisting gears (one or two) 3. travel gears. 4. auxiliary units such as buffers, railings, casings, current supply devices. etc. • The trolley frame is of welded construction and runs on 4 more wheels. all the trolley gears are mounted on the crane. the trolley is driven by motor. the speed of the motor is reduced through proper reduction gears and transmitted to the wheel through the trolley transmission shaft. buffers are provided at the ends of the trolley track to limit the trolley travel.
iii) HOIST AND ITS MECHANISMS:• The hoisting mechanism is mounted on the trolley. • This consists of an electric motor, gear coupling, brake assembly, reduction gearbox, pedestal, and the rope drum. the hoisting gear is equipped with a brake assembly. • There are two pulley blocks (top \ equalizer pulley & bottom pulley\Idle beam) through which the • Hoist rope is passed to enable the lifting of load or lower the load. • The arrangement for auxiliary hoists are similar to the main hoist.
b) SINGLE GIRDER EOT CRANES:• These are smaller in capacities, light in duty and used mainly for maintenance of EOT cranes and operation • Areas which do not have any provision of DG EOT and the area of operation is very much restricted. • Their capacities are restricted to 8 Tons. In rare cases up to 15 on also, SG EOTCranes are provided. There are about 200 nos. of SG EOT Cranes in VSP. All of them are indigenous make. Types of SG EOTCRANES:– S.G. Under slung EOT Cranes. – S.G. Rail Mounted EOT Cranes.
• DOUBLE GIRDER & FOUR GIRDER EOT CRANES:• The main chunk of cranes in the steel plant falls in this • category. These are of our categories class III & IV • There are 255 cranes installed. • in VSP (including 4 nos. in Mines) About 12nos. of Ladle Cranes in SMS, 2 nos in B.F, which are of Four girder Type - all others are D.G. EOT Cranes.
IMPORTANT CRANES IN VISAKHAPATNAM STEEL PLANT. A)HOT METAL CRANES\LADLE CRANESS • Blast furnace. – LRS HE C. 120\50t X20M – HMDP HE C. 180+63t X24M • • • • • •
2nos. 2nos.
Steel MeltShop. Charging bay. JESSOP 220+63\20tX22M 2nos. Mixer bay. JESSOP 180+63\20tX22M 2nos. L-P bay. HE C. 100+20t X19M 3nos. D-F bay. HE C. 200+63\20tX21.5M 3nos. Slag yard. Braith 100+20t X36M 2nos.
IMPORTANT CRANES IN VISAKHAPATNAM STEEL PLANT. B)ROTATING TROLLEY CRANES:-
• Steel Melt Shop. • B.S.Y. Mukand 16t X34M • H-Kbay. Mukand 16t X34M
11Nos.. 2Nos.
• LMMM. • D-E bay. JESSOP. 20t X34M • D-E bay. JESSOP 16t X34M • E-F bay. JESSOP 16t X34M
4 nos. 3 nos. 3 nos.
• • • • • • • •
WRM. MMSM. G-H bay. K-L bay. L-M bay. W M I 5+5tX 33.5M 5nos. 20t X33.75M 4nos. 12.5+12.StX34M Ino.
C) CIRCULAR CRANES:– B.F I & II – CASTHOUSE
USSR.
4nos. 20\S+St
D) GANTRY CRANES\GOLIATH CRANES:– Stores complex. – Open bays – Steel Yard
Conveyors • Belt conveyors – Carrying raw materials • Chain conveyors - Carrying semi-finished products • Bucket conveyors– Carrying loose materials • Tray conveyors – Carrying cast pigs iron and finished products
Types of cranes -Tower
cranes : mostly used in construction of huge structures -Mobile crane : mostly used in outdoor works a) Tire mounted cranes b) Chain mounted cranes -Locomotive cranes : mostly used by railways for risk and retrieve operation -EOT Cranes (Electrical Over head Traveling Cranes) : mostly used in the process industries for carrying material and products
TOWER CRANE
EOT Cranes are further divided in to
Hoists (Telfers) Single girder cranes Double girder cranes Four girder cranes Gantry cranes Semi gantry cranes Cantilever cranes Jib cranes
ELECTRICAL HOIST
DOUBLE GIRDER CRANE
FOUR GIRDER CRANE MAIN TROLLEY GIRIDERS
AUXILIARY TROLLEY GIRIDERS
CANTILEVER CRANE
SEMI PORTAL / SEMI GANTRY CRANE
Types of EOT Cranes in VSP There are 255 nos. of EOT Cranes like - Hot metal / Steel ladle cranes - Rotating trolley cranes - Circular cranes - Gantry / Semi gantry cranes - Bucket / Grab cranes - Service / Maintenance cranes
HOT METAL CRANE
CIRCULAR CRANE
ROTATING TROLLEY CRANE
Safety system employed In EOT cranes the no. of inbuilt safety devices are fitted to avoid any untoward happenings causing loss of men/ material / machine. The types of safety devices are: 1. 2. 3. 4. 5. 6. 7.
Gravity limit switches Rotary limits switches Lever type limit switches Buffers Anti-collision limit switches End rail stoppers Interlocking systems ( Cabin door , crane entry switches )
Gravity limit switch These are fitted in the hoists. It guards against collision of the hook block with the trolley structure / beam. A dead weight hangs from the lever which gets activated when the bottom block touches the weight. Power trips and stops further operation of the drive.
Rotary limit switch The function of the limit switch is to prevent the over hoisting / over lowering of the hook. In absence of the switch the bottom block may hit the cane girder or trolley. The switch is flange mounted on the rope drum pedestal and its shaft is coupled with stub shaft of the rope drum. The gear train of the switch is adjusted in such a manner that after specified number of rotations of the gear, the power of the hoist motor and brake will be cut off. As a result total hoist motion is stopped.
Lever type limit switch These are meant to guard against over traveling of long travel / cross travel. The switches fitted by the side of the track rail and trolley structure.
Anti-collision limit switch These are similar to the lever type switches, but the purpose of the switch is to avoid collision of cranes among themselves. One switch is fitted on the one corner of one crane while the sticker arm is fitted on the other crane. When one crane comes near ( 1 meter distance ) the sticker strikes the limit arm, resulting in power tripping.
Buffers These are designed to absorb the shock resulting in the collision of the cranes. These are fitted on the four corners of the end carriage. Buffers are also provided to the CT trolleys.
End rail stoppers If all the other devices, like Lever type switch, buffers and anti-collision switches fails to stop the drives, the rail end stoppers will prevent the crane going out of the bay.
In addition to above safety devices the following safety guards are provided - Emergency switch in operator cabin - Alarm / bell for warning - Rubber mats in front of electrical panels - Fire extinguishers for fire fighting - DSL Power supply signal lamps - Visual lights and cabin lights - Hooter alarm signal when main power goes off and battery in line - Operator should have good eye sight and good hearing.
Handing over of crane After stopping crane, the operator ensures all the levers are kept in neutral position and to make main power switch off. The operator while handing over the crane informs the incoming operators any defects and working condition of the crane.
Checking the effectiveness of cranes in VSP Deviation of crane span from : +/- 6 mm the nominal 2) Difference of diagonal : = / - 10 mm 3) Wear of wheel flanges : 50 % of original 4) Deflection of bridge on 25% overload: 1/700 of span 5) Deviation in rail span : =/- 6 mm 6) Difference in wheel diameter : 0.0005 of dia. 7) Brake shoe liner thickness : 40 % of original thickness 8) Rope thickness : 10% of original dia. 9) Difference in track level : +/- 10 mm 10) Brake drum rim thickness : 50% of original 11) Clearance of brake pins : 5 % of original 1)
Attachment parts of crane 1) Traverse 2) Magnets 3) Finger tilt beam 4) Buckets 5) Laminated hooks 6) Tongs
TRAVERSE
LAMINTED HOOK SPREADER BEAM
Finger tilting beam
Check list for inspection LT mechanism -
Checking the thickness of wheel flanges Checking the bogie bolts Checking the bogie pins and locking Checking the drive structure platform Checking the Coupling and oil in GB Checking the effectiveness of brakes
Long travel drive
Checklist cont‌ Cross travel mechanism: -
Checking the thickness of wheel flanges Checking the wheel fixing bolts Checking the trolley structure Checking the Coupling and oil in G/Box Checking the effectiveness of brakes
Cross Travel drive
Checklist cont‌ Main / Aux Hoist mechanism: -
Checking the thickness of wheel flanges Checking the rope , rope clamps and rope drum Checking the trolley structure Checking the Coupling and oil in G/Box Checking the effectiveness of brakes Checking of top/ bottom pulley condition Checking the vibration readings of G/box and motor - Checking of load members
Hoist mechanism
Load testing of crane Load test is done every year for heavy duty and extra heavy duty EOT cranes to assess the health of the equipment. To check the Girder deflection. 100% load lifted and check all the drives. Before and after Load test visual inspection is carried for all the components.
Proof loads for all lifting machinery / cranes / hoists Safe working load - Up to 20 tons - >20 T and up to 50 T - >50 tons
Proof working load - 25% in excess of SWL - 5 Tons in excess of SWL - 10 % in excess of SWL
The proof loads for all lifting tackles Safe working load Chain pulley blocks
• Proof working load - 50 % in excess of SWL
-Chain/ ring/ hook/ shackles/ Swivels -Single sheave pulley -Multiple sheave pulley (up to and including 20T -Multiple sheave pulley (up to 40 T -Multiple sheave pulley (Over 40 ton)
- Twice the SWL - 4 times the SWL - Twice the SWL - 20 tons in excess of SWL - 50% in excess of SWL
Statutory inspection at VSP S.No.
Description
Certified
1
Double/ Four girder cranes
263
2
Mobile cranes
34
3
Jib cranes/ Semi-portal cranes
32
4
SGEOT/ MH / EH/Hoisting skips
1384
5
Chain pulley blocks/ Max pulls
635
6
Wire rope slings/ Chain slings
2029
7
Fork Lifts
43
8
Traverse
19
9
D-Shackle
226
10
Air receivers / Pressure vessels
280
11
Elevators
32
12
Lifters of CCCD department
12
13
Safety relief valves
102
Safety in usage of cranes • EOT cranes are designed for safety of operating personnel first in mind your own safety and that of your fellow workers will be assured when the overhead material handling equipment is used as recommended. Disregarding such recommendations endanger to life and property. The following are the basic rules worthy of your consideration and attentions.
• Do not use any overhead material handling equipment for handling personnel • Do not load beyond rated capacity, this will cause immediate failure of load carrying parts. • Conduct periodic inspection for signs of damaged or wear. • Particular attention should be paid to the wire ropes and hooks. If there are signs of wear or damages, call to the attention of concerned safety engineers before loading. • Do not use hoisting ropes or chains as a substitute for slings. Use tested slings only. • Whenever travel a load over the heads of other personnel give ample warning of your intention before you move. • Do not leave the load suspended in the air. • Limit switches are for emergency use only and should not be trip during normal operation. If it is necessary to travel to the limit use extreme caution and approach the limit in slow speed.
• Wire ropes for load handling should not be place for portion of the load which may cause them to move or slip off. • Do not drag the load, dragging the load creates higher stress in the ropes and hoisting mechanism. • Know the hand signals for hoisting, cross travel and long travel if working with cabin operated cranes. Operator should accept the signals of only those persons authorised. Do not operate when signals are not clear. • Use padding on the edge of loads if it is sharp and angular to prevent damage to the rope.
Conclusion EOT Cranes having potential to cause serious accidents. As a prerequisite to their use, it is necessary that the cranes are safe by design and are well maintained. Their use can still be hazardous unless it is ensured that crane operators and other concerned are selected with due regard to the job requirements and are trained and further safe procedures are established and enforced for safety during their use.