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.
·
Ministry of works, Kaduna.
·
Internet Google search.
