PRACTICAL REPORT WRITING ON PROCESS CONSTRUCTION AND MINING EQUIPMENT ON OVERHEAD BRIDGE CRANE

Bridge crane with students on visit

Component part of the bridge crane

1 .Bridge, 2.End carriage, 3.Wheel of the bridge, 4.Crab (without auxiliary hoist), 5.Hoisting machinery set, 6.Wheels of crab, 7.Bottom Block (without auxiliary hoist), 8.Lifting hook, 9.Rail on the gantry girder for crane movement, 10.Rail on the bridge for crab movement, 11.Operators cabin

Hoist attached with hook via chains

Drive arrangement

SCHEMATIC Diagram arrangement

      

DESCRIPTION OF BRIDGE CRANE

Bridge crane is a type of crane found in mainly in the industrial environment, which consist of parallel runways with a traveling bridge spanning the gap. The hoist, the lifting component of a crane, travels along the bride. Which are mounted on the opposite wall, unlike mobile or construction crane that are supported on two or more legs running on a fixed rail at the ground level, which are known as Gantry crane or Jib crane.

The bridge or overhead cranes are commonly used in the refinement of steel and other metal such as copper and aluminum. At every step of the manufacturing process, until it leaves a factory as a finished product, metal is handle by an overhead crane. Raw materials are powered into a furnace by crane; hot metal is then rolled to a specific thickness and tempered or annealed, and then stored by an overhead crane and the fabricator. The automobile in industry also uses overhead crane to handle raw materials.

FEATURES

       I.            Bridge girder

    II.            Trolley frame

 III.            Hoist

IV.            Panel

   V.            Hook block

VI.            Run way rail

VII.            End truck

VIII.            End truck bumper

IX.            Wire rope

   X.            Bridge idler wheel

XI.            Handle chain

XII.            Driving gear

PRINCIPLE OF OPERATION

Overhead crane, also called bridge crane, is a kind of crane traveling on the elevated track to lift goods. Overhead crane move in longitudinal direction along the erected track and its trolley move in transverse along the elevated track, which work in a rectangle scope. Crane operators can lift and transport cargo with the space under the overhead crane without being hindered by ground equipment.

Overhead crane is widely used for warehouse indoor and outdoor, workshop, wharf, open-air yard and etc. Overhead crane can be divided into simple overhead crane, general overhead crane and metallurgy special overhead crane.

General overhead crane is composed of crane moving system, lifting trolley and metal structure. Lifting trolley can be divided into lifting mechanism, trolley moving system and trolley bogie.

Lifting mechanism includes brake, motor, reducer, coiling block and pulley block. Motor and reducer bring coiling block to rotate, finally realize to lift up and down goods. Trolley bogie support lifting mechanism and trolley moving system, it is always welded.

Driving method of moving mechanism of overhead crane can be divided into two types: one is centralized driving, that is, one motor drive long transmission shaft to drive active wheels on both sides; the other is separately driving, that is, active wheels on both sides are driven by one motor. Middle and small overhead cranes always adopt brake, reducer and motor to combine into “three-in-one” driving method. In order to install and adjust, most of overhead crane in heavy-duty always adopt universal coupling as its driving device.

As for moving mechanism of overhead crane, to increase wheels can be used to decrease wheel pressure if the lifting capacity is too large. If the amount of wheels exceed four, it had better adopt device to balance bogie to keep the loads of overhead crane can be distributed to every wheels.

Metal structure of overhead crane is composed of main beam and end beam, which can be divided into two categories: LD single girder overhead crane and QD double girder overhead crane. LD single girder overhead crane is composed of one main girder and both end beams, QD overhead crane is composed of two main girders and two end beams.

Main girder and end girder are in rigid connection, both ends of end girders are designed with wheels to support the overhead crane moving in the elevated track. There are traveling track welded to support the moving of lifting trolley.

a.     Bridge crane are mounted on tracks that are located on opposite walls of the facility.

b.     It enables three dimensional handling

c.      To riding (heavier loads) or under hung (more versatile)

d.     Bridge crane can transfer load and interface with other materials handling system.

e.      It move load over variable (horizontal and vertical) path within a restricted area.

f.       Use when there is insufficient or flow volume such that the use of a conveyor cannot be justified.

g.     Provide more flexibility in movement than conveyors.

h.     The loads handled are more varied with respect to the shape and weight than those handled by conveyor.

i.       Bridge crane utilize hoist for vertical movement, although manipulations can be used if precise positioning of the load is required.

MAINTENANCE PROFILE

WHAT IS A DAILY INSPECTION?

While only designated personnel may perform required maintenance and repairs on overhead crane systems, the crane operator should conduct inspections on a daily basis before and after use. A daily inspection checklist should be used and signed off on to ensure an effective and thorough assessment. OSHA 1910.179 refers to this daily inspection as a safety check. According to OSHA, the safety check must include all hoists and cranes prior to use at the beginning of each shift. Furthermore, visual assessments must be limited to areas that can be inspected from the floor, a catwalk, or other safe observation point.

OVERHEAD CRANE DAILY INSPECTION CHECKLIST

According to OSHA 1910.179, the daily safety inspection must be conducted by the crane operator each day and/or prior to use at the beginning of each shift. To start, the operator should ensure that all required safety equipment is present and in use. He or she should also be trained and authorized to use the equipment in question.

Once the operator has ensured all safety equipment is present and in use, he or she should then check to see if the crane or hoist has been locked-out or tagged-out. OSHA 29 CFR 1910.147 mandates that the control of hazardous energy or lockout/tag out must be used to de-energize the crane.  Before the operator begins the safety inspection, he or she should assess the area around the crane for potential safety hazards.

AREA CHECKOUT:

ü Know where the crane disconnect switch is located.

ü Verify there are no warning signs on or around the push button pendant.

ü Make sure workers aren't performing their duties nearby.

ü Ensure that the load can travel freely or without impediments.

ü Ensure there are no obstructions in or around the area where the load will be moved, and that the area is large enough to move and place materials safely.

ü Check that all below-the-hook devices are designed for the crane in use and can safely lift loads.

ü Ensure that the load capacity is less than or equal to the rated capacity of the crane.

Once the crane operator has checked out the area around the crane, he or she can begin a preliminary equipment checkout. Preliminary checkouts should occur before the operator touches any crane controls.

PRELIMINARY EQUIPMENT CHECKOUT:

ü Ensure there are no loose, broken, or damaged parts on the hoist, trolley, bridge, runway, or electric systems.

ü Check that the wire rope is reeved and seated in the drum grooves properly.

ü Verify that the bottom block is not twisted (no two lengths of wire rope should touch).

ü Check that nothing is contacted or close to open power sources and that enclosures are secured.

ü Ensure there are no wires pulled from strain reliefs or bushings.

ü Verify that the pushbutton pendant controls are not damaged (check for cracks, torn parts, or missing labels).

After checking out the crane area and conducting a preliminary equipment checkout, the crane operator can inspect the overhead crane itself for any potential malfunctions or safety hazards.

DAILY EQUIPMENT SAFETY CHECKOUT (POWERED SYSTEMS):

ü With the pushbutton turned off—check that the buttons are not sticking and operating smoothly. When the button is released, it should always return to the off position automatically.

ü With the pushbutton turned on—check that the crane warning device operates properly.

ü Ensure that the hoist hook rises when the button is pushed to the “up” position.

ü Check that the upper limit switch is functioning properly.

Ensure that all other pushbutton controls are operating properly and moving in the right direction.

DAILY EQUIPMENT SAFETY CHECKOUT (HOOKS):

ü Check that there’s no more that 10 percent wear on any part of the hook.

ü Check for bending or twisting and cracks.

ü Check that safety latches are in place and functioning properly.

ü Ensure that the hook nut (if visible) is tight and locked to hook.

ü Make sure that the hook rotates freely without grinding.

DAILY EQUIPMENT SAFETY CHECKOUT (BOTTOM BLOCK ASSEMBLY):

Check bottom block assembly for:

ü Structural damage

ü Cracks on any component

ü Capacity markings are present

ü Sheaves rotate freely without grinding

ü Sheaves are smooth

ü Sheave guards are intact and unbroken

DAILY EQUIPMENT SAFETY CHECKOUT (WIRE ROPE AND LOAD CHAIN):

ü Check wire rope and load chain by walking 360 degrees around the hook block and examining wire rope/chain.

ü Check that there’s no reduction in diameter.

ü Check that there are no broken wires.

ü Make sure there’s no kinking, cutting, crushing, un-stranding, or thermal damage to the wire rope.

ü Check that there are no cracks, gouges, nicks, corrosion, or distortion on any link of the load chain.

ü Ensure that there’s no wear at contact points.

ü Verify chain sprockets are operating smoothly.

DAILY EQUIPMENT SAFETY CHECKOUT (MISCELLANEOUS ITEMS):

ü Ensure the bridge and trolley motor brakes operate properly.

ü Check that there is little or no hook drift when releasing controls in the up or down position.

ü Check that the trolley and bridge are on-track and functioning smoothly.

ü Ensure there are no loose items on the crane that could fall

ü Check for oil leaks.

ü Ensure a working fire extinguisher is available if needed.

ü Check that air or hydraulic lines are in working condition.

ü And, ensure all below-the-hook devices are in good condition.

Effective daily safety inspections are essential to the maintenance of any overhead crane system. It’s important to create a safety regimen following the inspection checklist listed above, and to stop using the crane immediately if any malfunction, unusual noises or movements are detected.

FIELD SITE

·        Ministry of works, Kaduna.

·        Internet Google search.