Module No E18 PowerTools and Wkshop Equipment

8/10/2019 Module No E18 PowerTools and Wkshop Equipment

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Capabili ty & Improvement Dept.2004For Internal Use Only

PETRO NA S

G A S

TRAINING MODULE

ELECTRICAL

TITLE : ELECTRICAL DRIVEN HAND TOOLS AND

WORKSHOP EQUIPMENT

MODULE NO : E18


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Power Tools and Workshop Equipment Page 2 of 60

ELECTRIC DRIVEN HAND TOOLS AND WORKSHOP EQUIPMENT,

ENGINE-DRIVEN WELDING MACHINE,

ELECTRICAL OVERHEAD CRANE

OBJECTIVES

Upon completion of this module, the electrical multitask technician will be able to :

1. Demonstrate understanding on the hazards of hand and power tools.

2. Know the basic requirements before operating hand and power tools.

3. Understand and explain the safety rules to follow to prevent hazards.

4. Recognize obvious defects during the conduct of physical inspection on electric driven hand

tools, workshop equipment, engine-driven welding machine and electrical overhead crane.

5. Identify and understand the major items to be observed during the conduct of periodic

maintenance.

6. Understand and recognize the importance of routine electrical testing.

7. Understand and explain welding process and its application in the maintenance work.

6. Understand and explain the principle of operation of engine driven welding machine.

7. Demonstrate understanding and identify the major component parts of engine-driven weldingmachine and electrical overhead crane.

8. Explain the function and operation of the major component parts.

9. Explain the periodic maintenance to be conducted and the troubleshooting and repair to be

performed on the equipment.

10. Demonstrate knowledge and understanding on the safety precautions to be observed when

working on welding machines and electrical overhead crane.


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TABLE OF CONTENTS

Description Page No.

PART 1 -Electric Driven Hand Tools and Workshop Equipment................................................. 6

1.0.0 Introduction............................................................................................................................ 6

2.0.0 Typical Electric Power Tools and Workshop Equipment...................................................... 7

3.0.0 Hazards of Hand and Power tools.......................................................................................... 8

3.1.0 Serious Hazards and Dangers in using Electric Tools........................................................ 8

3.1.1 Injuries brought about by electrical shocks ................................................................... 8

4.0.0 Requirements before Operating Hand and Power tools......................................................... 9

4.1.0 Basic safety rules:............................................................................................................... 9

4.2.0 General precautions to be observed:................................................................................... 95.0.0 Physical inspection on Electric driven tools and Equipment............................................... 11

6.0.0 Care and Periodic maintenance of Electric Power Tools..................................................... 12

6.1.0 Maintenance: Main point of attention for Power tools..................................................... 12

7.0.0 Routine Electrical Testing.................................................................................................... 15

8.0.0 Troubleshooting and Repair................................................................................................. 16

PART 2:- Welding Machine Engine Driven.............................................................................. 19

1.0.0 Fundamentals of Welding .................................................................................................... 192.0.0 Applications of Welding in the Maintenance Work ............................................................ 20

3.0.0 Most Common Types of Welding Processes....................................................................... 21

3.1.0 Gas Welding ..................................................................................................................... 21

3.2.0 Arc Welding ..................................................................................................................... 21

4.0.0 Arc-Welding Equipment ...................................................................................................... 22

4.1.0 Power Source for Arc Welding ........................................................................................ 22

4.2.0 Motor-generator welding machines.................................................................................. 22

4.2.1 Principle Of Operation Of Engine Driven Welding Generator.................................... 23

4.3.0 Alternating Current Transformer Welding Machines ...................................................... 24

4.4.0 Rectifier Welding Machines............................................................................................. 25

5.0.0 Procedures of Manual Arc Welding. ................................................................................... 26

6.0.0 Typical Engine Driven Welding Machine Nameplate Rating ............................................. 27

7.0.0 Major Component Parts ....................................................................................................... 28

7.1.0 Description of Component Parts....................................................................................... 28

8.0.0 Preparation for Startup and Hookup at Site ......................................................................... 29


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PART 1 -Electric Driven Hand Tools and Workshop Equipment

1.0.0 Introduction

As the need for mechanization and use of power tools increases, dependable performance

and long service life of power tools are very important. A plants entire inventory of portable

tools can be kept in top operating condition for maximum production quality and cost efficiency

with a planned routine and periodic inspection.

There are many and varied causes of power tool failure. Variations will exist and will

depend upon the type of tool and the particular conditions of use. It is therefore of strong

importance that the recommended use and maintenance given in the manufacturers operation

and maintenance manual, supplied with each tool, be carefully followed.

An important part of preventive maintenance is technician training in the proper care and

use of portable power tools, basic safety procedures and safeguards associated with hand and

portable power tools.


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2.0.0 Typical Electric Power Tools and Workshop Equipment

There are many and varied types of electrical driven hand tools and workshop equipment.

Good examples are:

Compact threading machine,

Drilling machine,

Hydraulic press,

Lapping machine,

Grinders,

Milling machine,

Hacksaw machine,

Lathe machine,

Sanders,

Shears,

Tapers ,

Electric drills,

Power and impact wrenches,

Jigsaws,

Power screwdrivers,

Air compressors and many others.


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3.0.0 Hazards of Hand and Power tools

Tools are such a common part of our lives that it is difficult to remember that they may

pose hazards. Tragically, a serious incident can occur before steps are taken to identify and avoid

or eliminate tool-related hazards.

Technicians and workers who use hand and power tools are exposed to the following

hazards :

1. Falling, flying, abrasive, and splashing objects

2. Harmful dusts, fumes, mists, vapors, or gases

3. Electric shock

3.1.0 Serious Hazards and Dangers in using Electric Tools

1. Electrical burns

2. Electrical shocks

3.1.1 Injuries brought about by electrical shocks

1. Injury due to a fall

2. Fibrillation of the heart

3. Death


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4.3.0 Protection against Electric Shock and Burns

A few of the basic protection that can be utilized to protect user against electric shock and

burns are as follows:

1. The electric tools must have a three-wire cord with a ground and be plugged into a grounded

receptacle

2. Electric tools should be double insulated. On double-insulated tools, an internal layer of

protective insulation completely isolates the external housing of the tool.

3. Electric tools should be powered by a low-voltage transformer


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5.0.0 Physical inspection on Electric driven tools and Equipment

1. Perform visual inspection and be able to recognize obvious defects such as:

Cut, frayed, spliced or broken cords, conduits and boxes

Cracked or broken attachment plugs and

Missing or deformed grounding prongs.

2. Examine tools causing shocks and repair it before further use.

3. Check circuit breaker, fuses, local control switches for sign of overheating

4. Ensure power distribution board is free from dust, moisture, dirt or spider web.

5. Inspect wire termination for loose connection and overheating


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6.0.0 Care and Periodic maintenance of Electric Power Tools

Whenever maintenance is taking place on a machine the greatest care must be taken to

ensure that the machine is completely isolated electrically against any possibility of inadvertent

startup or electric shock. Before any work on the machine is undertaken, the fuses must be

removed and a lockout and tag out device is attached to the supply.

1. Operation and functions of the equipment should be clearly understood. Refer to the tool or

equipment operation manual.

2. Power tools must be given an initial safety inspection by a competent electrician.

3. Service the power tools regularly, can be at six-monthly intervals.

4. Conduct visual inspection on plugs, leads and associated equipment.

5. Defective tools must be withdrawn promptly for repair or replacement.

6. Machines must be used only within their design capacity and no accessories larger than those

recommended by the manufacturer may be used.

7. Keep record of inspection and testing of electric power tools.

6.1.0 Maintenance: Main point o f attention for Power tools

Maintenance main point of attention should be given to the following:

1. Periodic inspection of crucial wear points

2. Excessive dirt accumulation.

3. Insufficient or improper lubrication.

4. Care of cord and attachment plug.

5. Integrity of the grounding circuit.


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1. Periodic inspection of Crucial Wear Points

Parts like, brushes and commutators should be inspected periodically. This is done by

removal of brush holder plugs or inspection plates. Brushes worn down to 50% of their original

size should be replaced.

2. Excessive dirt accumulation.

Power tools are commonly fitted with universal motors. Universal motors are fan

ventilated to prevent excessive heat. Even if many tools have filters and deflectors to prevent

destructive material from damaging the motor, a small amount of dust and dirt will pass through.

dirt affects the brush operation and reduces the volume necessary to cool the motor. When

required, the tool should be blown out with low pressure, dry compressed air.

3. Insufficient or Improper Lubrication.

Lubricant inspection is needed at frequent intervals to insure sufficient lubricant to

prevent wear to mechanical parts. Dirty lubricant should be removed and replaced. Since

lubricant varies from tool to tool, it is proper to follow the recommended lubricant by the

manufacturer. The wrong amount of lubricant can cause serious problems. Too little, of course,

means that surfaces are not adequately covered and excess wear will result. Too much lubricant

can cause excess pressure in the gear case and eventually ruin seals.

4. Care of cord and attachment plug.

The cord of an electric power tool is the life line. It should be kept free of oil, grease and

other material that may ruin the rubber cover.


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7.0.0 Routine Electrical Testing

Periodic electrical testing will uncover many operating defects and their immediate correction

will insure safe operation and prevent breakdown and more costly repairs. Testing and the

related maintenance should be systematic. A visual inspection before and after each use when

issued and when returned to the tool crib should be required.


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References:

Electrical Equipment Maintenance

Hand and Power Tools Booklet, OSHA


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PART 2:- Welding Machine Engine Driven

1.0.0 Fundamentals of Welding

Welding is a process of joining together two metal parts by heating them to melting

point. Welding arcs are produced by electric current from a welding machines which in turn

produces heat to cause melting of metal parts. The amount of current is adjusted depending on

the size of electrode being used and the position in which the welding work is being performed.

The welding circuits require higher amperage at low voltage


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2.0.0 Applications of Welding in the Maintenance Work

Welding machine is an essential tool available in maintenance workshop and at site for a

variety of repair, construction, fabrication, strengthening, modification, erection works including

the following:

Fabrication of structures

Plugging old holes and making new ones

Fabricating broken parts, replacing castings by welded machined parts

Supports, jigs, fixtures

Joining two plates, bars

Strengthening weak parts


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3.0.0 Most Common Types of Welding Processes

1. Oxyfuel gas welding (OFW)

2. Arc welding (AW)

3. Resistance welding (RW)

3.1.0 Gas Welding

One of the most popular welding methods uses a gas flame as a source of heat. In the

oxyfuel gas welding process, heat is produced by burning a combustible gas, such as MAPP

(methylacetylene-propadiene) or acetylene, mixed with oxygen. Gas welding is widely used in

maintenance and repair work because of the ease in transporting oxygen and fuel cylinders.

3.2.0 Arc Welding

Arc welding is a process that uses an electric arc to join the metals being welded. A

distinct advantage of arc welding over gas welding is the concentration of heat. In gas welding

the flame spreads over a large area, sometimes causing heat distortion. The concentration of heat,

characteristic of arc welding, is an advantage because less heat spread reduces buckling and

warping. This heat concentration also increases the depth of penetration and speeds up the

welding operations. Arc welding is often more practical and economical than gas welding.

Arc welding provides the user the ability to join two metals by melting them with an arc

generated between a coated-metal electrode and the base metal. The temperatures developed by

the arc can reach as high as 10,000 OF. The arc energy is provided by a power source that

generates either direct or alternating current. The electrodes that carry the current produce a gas

that shields the arc from the atmosphere and supplies filler metal to develop the weld shape.


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4.0.0 Arc-Welding Equipment

All types of arc-welding equipment are similar in their basic function of producing the

high-amperage, low-voltge electric power required for the welding arc.

The basic parts of a typical shielded metal-arc welding outfit include the following:

Welding machine

Cables

Electrode holder (stinger)

Electrodes

Accessories such as combination chipping hammer and wire brush, welding

table (for shop work), C-clamps and protective apparel

4.1.0 Power Source for Arc Welding

The power source used in arc welding is called a welding machine or welder. The basic

types of welding machines presently in use are:

Motor-generator welding machines

Alternating current transformer welding machines

Rectifier welding machine

4.2.0 Motor-generator welding machines

Motor-generator welding machines are types of welding machines powered by electrical,

gasoline, or diesel motors, the diesel and gasoline motors are ideal for use in areas whereelectricity is not available. These machines have the capability of generating alternating or direct


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current. Typical example of this type is as shown on the figure which consists of a heavy-duty,

ac/dc generator powered by a diesel engine.

For general purposes, standardized ratings of welding machines are as follows:

1. Machines rated 150 and 200 amperes - 30 volts. For light welding jobs or shop work.

2. Machines rated 200, 300, and 400 amperes - 40 volts. For general welding purposes.

3. Machines rated 600 amperes - 40 volts. For submerged-arc welding.

4.2.1 Principle Of Operation Of Engine Driven Welding Generator

The generator is required to run and turn at a required number of revolutions per minute

(rpm) in order to produce the required welding current. The engine of the welding unit is

provided with governor which control the speed of the engine. Welding speed switch is provided

and can be set to idle the engine when no welding job is taking place. The welding speed switch

can also be set to run the engine continuously.

After the engine come to speed and the electrode is made to touch the work piece, the

engine governor will automatically increase the engine speed to the required number of turns

(rpm) required for welding.

Welding current control is done by moving or setting the selector knobs or switches toamount of current required for welding.

Engine controls and welding current controls are provided on the welding generator set.

Normally, engine controls include the following:

Starter

Voltmeter

Fuel gauge

Temperature gauge

Running hour meter


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4.3.0 Alternating Current Transformer Welding Machines

Practically all the alternating current arc-welding machines in use are the static-

transformer type as shown in figure.

These types of machines are the smallest, least expensive, and the lightest type of welders

made. Industrial applications for manual operation use machines having 200, 300, and 400

ampere ratings. Machines with a 150-ampere rating are used in light, garage and job/shop

welding.

The transformers are usually equipped with arc stabilizing capacitors. Current control is

provided in several ways. One such method is an adjustable reactor that is set by turning a crank

until the appropriate setting is found. Another method is by plugging the electrode cable into

different sockets located on the front of the machine.


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4.4.0 Recti fier Welding Machines

Rectifier welders are single-phase or three-phase transformers that have selenium or

silicon rectifiers added to rectify (change) the output current from alternating to direct current.

Most of these machines have the capability of producing either ac or dc straight or reverse

polarity. By flickering a switch, the welder can select the current that best suits the job.


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5.0.0 Procedures of Manual Arc Welding.

Electrodes with coating of shielding material are commercially available in standard

lengths (250 or 500 mm). Consumable electrode is fixed in electrode holder held in hand. The

two cables from AC welding transformer or DC welding generator are connected to electrode

holder and the work piece. (Normally positive is connected to the electrode holder and the

negative connected to the work piece)

Welding is begun by touching the electrode tip to the work piece near the location of the

joint and establishing electric circuit. Arc is initiated by withdrawing the electrode slightly

manually.

The electrode holder is lowered gradually as the welding continues, thereby maintaining

a steady arc length. Electrode is moved forward manually along the desired weld contour.


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6.0.0 Typical Engine Driven Welding Machine Nameplate Rating

Nameplate

Serial No.

Phase 1

Volt 120/240 Amp 26/13

Hz. 50/60 PF 1.0

Max. rpm 1,850

Rated weld output

Max. OCV 95 95

Volts 40 40

Ampere 400 250

Duty cycle 40% 100%

Max. rpm No load 1850 1850

Welding Range 40 to 400 A


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7.0.0 Major Component Parts

Engine

DC welding generator

Control circuitry

Metering system

Welding cable, welding cable lugs or connectors, quick disconnects, ground clamps,

electrode holders, cable terminals

7.1.0 Descript ion of Component Parts

Engine -The size and type of the engine varies and it depends on the capacity of the welding

generator.

Arc welding generator- Its size is determined by the ampere rating output at a given duty cycle.

Duty cycle refers to the amount of time in a 10-minute period the welding machine can

continuously produce its rated amperage without undue overheating. A welding machine can

have a 10%, 20%,30%,40%,60% up to 100% duty cycle, i.e. 400A at 40% duty cycle (250A at

100%)

Welding cable -Large diameter cable can carry more welding current. Welding cable sizes vary

from No. 8 AWG to No. 4/0 AWG. The size of the cable depends on the amperage load as well

as the distance the current will travel. In measuring the distance, add the lengths of the electrode

lead and the ground lead. Cable amperage requirement is determine by the rated capacity of the

welding machine.

Lugs They are used to connect the welding cable to the welding current terminals.

Quick disconnects They serve as cable extensions for connecting two lengths of welding

cable.

Ground clamps They are mechanically connected to the end of the welding cable (ground

cable) and provides connection to the work piece.Electrode holders They are mechanically connected to the end of the welding cable and

provides electrical contact between the electrode and the welding cable.


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9.0.0 Inspections for Component Parts (Prior To Start Up)

Engine driven welding machines require regular inspection prior to its use. In most cases

an operator will be required to fill up and turn in an inspection form before starting the engine.

After all the required information have been checked and completed, welding works can

commence. Common information required involved results of the following checks and

inspection:

Check before and after use the condition of the following: Engine oil and filter, fuel oil and

filter, cooling system, batteries, belts, exhaust system, air filter, injectors, meters, enclosure,

any visible leaks.

Verify that welding cable is long enough to reach the work area. Welding cable should be

inspected for cuts or breaks before use. Breaks in the welding cable insulation when comes in

contact with metallic surfaces could result an arc which will damage the surface and the

cable itself.

Check that cable lugs are tightly crimped onto welding cable to ensure good attachment.

Ensure quick disconnects are tightly connected to prevent arcing and overheating.

Ensure the size of the ground clamps is at least the same as the rated capacity of the welding

set to prevent overheating. Position the ground clamp so that welding current will not pass

through any contacting surface. Never connect the ground clamps to pipes carryingflammable or corrosive materials. Make sure there is a good electrical contact on the

connections to avoid overheating and sparks.

Ensure the size of the holder is big enough to carry the rated amperage to avoid overheating.

Ensure that termination points are free from dirt and corrosion and welding cables are tightly

terminated


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10.0.0 Preventive Maintenance Program

Good maintenance habits are especially important on more advanced welding systems

that use robotics and automation. Proper upkeep includes an appropriately administered

preventive maintenance program.

Appropriately administered preventive maintenance program can be started by performing the

following:

1. By compiling a complete equipment list

2. Prepare equipment inspection schedule

3. Catalogue all maintenance performed and chart based on inspection analysis

4. As maintenance is performed, create a thorough record and history of inspections,

analysis and repairs

Along with preventive maintenance, a maintenance schedule should include clearly

defined areas of inspection and procedures. Critical areas of inspection include:

1) Lubrication

2) Bearings

3) Fasteners, brackets and bolts

4) Commutators

5) Condensers6) Brushes and holders

7) Controls, programmable logic controllers and master panels

8) Motor stators

9) Generator frame

10) Armature

11) Relays

12) Exciter generator

13) Engine

14) Manipulators, feed rolls and positioners

15) Cords, cables, nozzles and guns


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10.1.0 A General Schedule for Routine Maintenance

The following is a general routine

maintenance schedule, but should

be modified according to a

companys specific

conditions: (Operating hours)

Description of tasks

8 hours Wipe oil and fuel spills immediately

Check fluid levels (oil & fuel)

Service the air filter (refer to engine manual for specifics)

50 hours Service air filter element (refer to engine manual for

specifics)

Clean and tighten weld terminals

100 hours Change oil

Change oil filter (refer to engine manual for specifics)

Clean and tighten battery connections

Clean cooling system (refer to engine manual for

specifics)

200 hours Replace unreadable labels

Replace fuel filter

Check valve clearance (refer to engine manual for

specifics)

250 hours Check and clean spark arrestor

500 hours Tape or replace cracked cables

Clean/Set injectors (refer to engine manual for specifics)


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11.0.0 Troubleshooting and Repair

TROUBLESHOOTING CHART FOR ARC WELDING

TROUBLE CAUSES REMEDIES

Power supply dead Check voltage

Power lead broken Repair or replace

Supply voltage wrong for welding set Check nameplate rating

Main switch or set switch open Close

Starter button has open circuit Repair

Welding does not start,

starter does not operate

Contactor stuck open Release, maintain or replace

Brushes worn-out/missing Replace

Brush connections loose Tighten

Welding start, but

welding current does not

pickup Open field Correct

Electrode connection loose Correct it

Ground connection loose Correct it

Poor ground Correct it

Brush fitting improper Correct it

Current falls during

welding

Connections loose Tighten

Check relay setting Set as per required current,

time

Defective relay ReplaceWelder set stops

Ventilation poor due to blocking Clear it

Arc makes sputtering

noise

Current high

Polarity wrong

Check setting

Correct the polarity

Touching the set gives a

shock feelingFrame not grounded Ground the frame solidly

Current controller of

generator failsCheck field circuit

Correct the defective

contactor


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12.0.0 Safety Precautions

1. Electric shock can kill

Always wear dry insulating gloves

Insulate yourself from work and ground

Do not touch live electrical parts

Stop engine before installing or servicing

Keep all panels and covers securely in place

2. Welding can cause fire or explosion

Do not weld near flammable material

Watch for fire, keep fire extinguisher nearby

Do not locate unit over combustible surfaces

Do not weld on closed containers

3. Arc rays can burn eyes and skin; noise can damage hearing

Wear welding helmet with correct filter

Wear correct eye, ear, and body protection

4. Fumes and gases can be hazardous

Keep head out of the fumes

Ventilate the area or use breathing device

5. Engine exhaust can kill

Use in open, well ventilated area or vent exhaust outside

6. Engine fuel can cause fire or explosion

Stop engine before fueling

Do not fuel while smoking

Do not overfill tank; clean up any spilled fuel

7. Moving parts

Keep away from moving parts

Keep doors, panels, covers, and guards closed and securely in place


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References :National Electrical Code

Testing, Commissioning, Operation & Maintenance of Electrical

Equipment by S. Rao

Miller Electric Mfg. Co. Technical Articles


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2.0.0 General Requirements

All overhead cranes must meet the specifications of American National Standard Safety

Code for Overhead and Gantry Cranes, ANSI B30.2

The rated load of the crane shall be plainly marked on each side of the crane.

Clearance must be maintained above and to the side of cranes. Walkways cannot be

placed in a crane operating zone that would compromise employee safety when the crane

is in operation.

Only designated personnel will be permitted to operate a crane


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3.0.0 Major component parts of Hoists System

Overhead crane is a crane with a movable bridge carrying a movable or fixed hoisting

mechanism and traveling on an overhead fixed runway structure. Major component parts are as

follows:

Hoist motor

Brake motor

Gearbox

Hoist

Rope drum

Runway

Bridge

Trolley

Load detectors

Geared limit switches

Power supply disconnecting means

Multi-button pendant control switch

Electrical controls

Cables,

Wiring , contacting devices


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3.1.0 Typical Bridge Crane Installation and Specification


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4.0.0 Typical sectional drawing of Crane Hoist Mechanism

Parts description is as shown:


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5.0.0 Description of Major Parts

1. Hoist motor:

Commonly, motor is a combination of electric motor and brake which operates on the

sliding rotor principle. The motors are equipped with Positive Temperature Coefficient (PTC)

thermistors to protect against overheating. The PTC thermistor triggering devices are

electronically interlocked in order to prevent the motors being switched back on. It is possible to

continue operation after the motors have cooled down by briefly switching off the mains switch

or crane isolator.


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2. Brake motor:

Brake motors are asynchronous motors with cylindrical squirrel-cage rotor and integrated

brake. The brake mainly consists of

Brake disc with bonded brake linings

Armature disc

Housing with coil

Brake springs

Opposing brake surfaces

Operation :

The brake disc with toothed plastic hub can move axially on the shaft. The armature disc

can slide axially guided by two pins.

When no current flows, the brake springs press the armature disc against the brake disc

and consequently press this against the opposing brake surface. The frictional force applied on

both sides of the brake disc causes the braking torque to build up and this is held by the fixing

pins on the housing.

If there is a loss of voltage at the solenoid, the brake is applied.

When a voltage is applied to the solenoid, the magnetic field builds up, pulls the armature

disc away from the brake disc in opposition to the spring forces, and the brake is released.


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3. Gearbox

The torque of the motor is transmitted to the planetary gearbox by a roller coupling which

is flexible in both radial and axial directions. The 2 or 3-stage planetary gearbox inside the drum

houses all gear stages.

4. Hoist

A hoist is an apparatus which is a part of a crane, exerting a

force for lifting or lowering. Main hoist is the hoist mechanism

provided for lifting the maximum rated load. Auxiliary hoist is a

supplemental hoisting unit of lighter capacity and usually higher

speed than provided for the main hoist.

The size of the hoist is determined by the load spectrum (light,

medium, heavy, very heavy), average operating time per working

day, safe working load and reeving.

5. Rope drum

The drum is the cylindrical member around which the ropes are wound for raising or

lowering the load.

6. Load block

The load block is the assembly of hook or shackle, swivel, bearing sheaves, pins, and

frame suspended by the hoisting rope.


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7. Geared limit switches:

Limitation of motion at the upper and lower end positions is effected by the geared limit

switch. Geared limit switches are mounted in the electrical equipment casing. It switches off the

hoist motor when the top or bottom hook position is reached. The direction of movement can be

reversed. Operating limit switches are required where the end positions are approached regularly

during normal operation.

Normally, there are four switching element contacts, each with different functions:

S1 - Emergency limit switch for top hook position

S2 - Main lifting limit switch. Operating limit switch for top hook position

S3 - Emergency limit switch for bottom hook position

S4 - Operating limit switch for bottom hook position

The emergency limit switch must not be actuated during normal operation.

8. Control Pendant

Normally a multi-button pendant control switches are used to

control the hoist unit. The control pendants are available in different

sizes with openings for switching elements, so that they can be adapted

according to the given drive combination requirements.

Pendant switches house the operating and emergency limit

switch switches.

The strainer wire for the control cable should be secured by the

clamps which are fixed to the sides of the electrical equipment enclosure. The multi-button

pendants should be suspended so that the bottom edge is approximately 1 meter above the floor


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level. The arrow symbols on the buttons must indicate the correct direction of the respective

movement.

Every hoist unit is fitted with an emergency-stop equipment which can stop the entire

hoist unit in the event of a hazard. The emergency-stop button is arranged on the control

pendant.

To actuate the emergency-stop button, press the button until it reaches the end stop. It

then locks automatically. To unlock the actuated emergency-stop button, turn the push button in

the direction of the arrows and release.

9. Electrical Control

It is a master switch which dominates the operation of contactors, relays, or other

remotely operated device. For standard controls, electrical switch gear is installed in the

electrical enclosure of the hoist unit. The enclosure casing is protected to IP 55, that is protected

against harmful dust deposits and is hose-proof in all directions.

10. Load detectors:

Load detectors are used to protect hoist units and supporting structures against excessive

stresses. Load detectors can either be electronic type or mechanical type.


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11. Bridge

Bridge is that part of a crane consisting of girders, trucks, end ties, foot walk, and drive

mechanism which carries the trolleys.

12. Runway

Runway is an assembly of rails, beams, girders, brackets, and framework on which the

crane or trolley travels. Hoist travel on track beams must in no way be obstructed by protruding

suspension bolts, screw heads, butt straps, clamping plates, etc. End stops must be fitted at both

ends of the runway.

The running surfaces of rails or track beams must not be painted as this would impair

hoist travel. Rails and track beams should be kept clean; oil, grease, and dirt on the running

surfaces will cause travel wheel to skid.

13. Trolley

The trolley is the unit which travels on the bridge rails and carries the hoisting

mechanism

14. Power supply disconnecting switch (Isolation and De-isolation switch)

It is the main switch controlling the entire power supply to the crane.

Disconnecting means for cranes and monorail hoists should have a continuous ampere

rating not less than the motor nameplate rating and to be provided between the runway contact

conductors and the power supply.

Such disconnecting means shall consist of a

1) motor-circuit switch,

2) circuit breaker, or

3) molded case switch.


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The disconnecting switch should be installed to meet the following requirements:

(1) Readily accessible and operable from the ground or floor level

(2) Capable of being locked in the open position

(3) Open all ungrounded conductors simultaneously

(4) Placed within view of the runway contact conductors

The runway supply conductors and main contact conductors of a crane or monorail shall be

protected by an over current device that shall not be greater than the largest rating or setting of

any branch circuit protective device plus the sum of the nameplate ratings of all the other loads.

Crane, hoist, and monorail hoist motor branch circuits shall be protected by fuses or inverse-time

circuit breakers.

Runwa Conductor


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6.0.0 Typical Technical Specification for a Bridge Crane

Item Description

1 Manufacturer:

2 Installation: Outdoor, Indoor, Under Roof

3 Service:Erection, Maintenance, Storehouse

4 Type: Single girder bridge, single girder gantry

Double girder bridge, double girder gantry

5 Class of bridge crane

6 Control system:Manual, Electrical by cab

Electrical with push button station sliding along the bridge

Electrical with fixed push button station on the trolley

Electrical with fixed push button on the bridge side

7 Control Station: with push button , with spring recovery levers

8 Electrical equipment protection:IP 55, 56, 65,...

9 Electrical power supply:415 V, 50 Hz., 3 phase10 Ambient conditions:minimum temperature, maximum temperature

11 Hook capacity: ______ton

12 Vertical traverse: ______meter

13 Normal lifting speed: ______m/min

14 Slow lifting speed: _______m/min

15 Lifting motor power (main/creep hoist): ______kW

16 Normal traverse speed: _______m/min

17 Slow traverse speed: _______m/min

18 Traverse motor power (travel motor): _______kW

19 Bridge sliding speed _______

20 Bridge sliding motor power (travel motor): _______kW

21 Electric motor manufacturer

22 Bridge sliding:drive on both sides with 2 motors, in short circuit, slip-ring

23 Runway substructure: in masonry, in steel

24 Winch trolley (cm): gauge, wheel diameter, wheel pitch

25 Transmission pulley pitch diameter: lifting

26 Brake type:

27 Mechanical stop device

28 Auto electric limit stop

29 Hook capacity: kg

30 Anti release device (safety latch)

31 Gears

32 Electric feeding line trolley/winch

33 Electric feeding line along the runway.Festoon type normal, festoon type

explosion proof, armor-plate type, junction boxes, isolators

34 Mechanical limit stop

35 Lubricants


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7.0.0 Operation of the Hoist units

The manufacturers instruction must be followed when operating the crane system. Basic

procedures are as follows:

1. Attach the load to the block hook by means of slings or other approved devices,

making sure the sling is clear of obstacles.

2. Once the load is properly secured and balanced in the untwisted sling, slowly raise the

load.

3. Horizontal movement must also begin slowly to prevent the load from swinging or

coming into contact with other obstacles.

4. The crane warning signal or horn must be sounded when the load or hook comes near

or over personnel. Carrying loads over personnel is not recommended.

5. A load should not be left suspended.

6. Audible and discernible voice communication should be kept with the operator at all

times. If this cannot be accomplished, a signal system should be used.

7.1.0 Guidelines and safety instruct ion in operating hoist system

Hoist units are systems used for lifting and moving loads, such as cranes, crabs, traveling

hoist units, rail systems.

Hoist units are only intended for lifting and moving loads and may be used both as stationary

or traveling units.

Hoist units may only be operated when in perfect working order by trained operating

personnel in accordance with the relevant safety and accident prevention regulations. This

also includes compliance with the operating and maintenance conditions specified in the

operating instructions.

Hoist units are industrial equipment designed to be used with a rated voltage between 50 and

690 V AC. Power feed is via power supply lines (mobile cables, open or enclosed powerconductor systems). These systems are live up to the terminals of the isolating switch. During

operation or when the main switch is not switched off, electrical components inside

enclosures, motors, switch gear cabinets, terminal boxes, etc., carry dangerous voltages.

Before starting the work using the hoist units, the operator must first check the function of

the hoist unit brakes and emergency limit stop devices. Only operate hoist units when all

protective devices and safety-related equipment, i.e. movable protective devices and

emergency-stop devices, are fitted and fully functioning. The operator must be satisfied that

the installation is safe and in correct operating condition.


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8.0.0 Taking Hoist Unit Out of Service

The hoist unit is considered out of service during the following conditions and

appropriate action should be taken at the said state:

At the end of the shift

During emergency or hazard

During maintenance work

8.1.0 At the end of the shift

When the work has been completed, raise the hook assembly or bottom block to the

upper limit position. Switch off the power supply at the mains connection or isolating switch.

8.2.0 During emergency or hazard

Emergency-stop equipment is fitted in the hoist to stop the entire hoist unit in the event of

a hazard. The emergency-stop button is arranged on the control pendant. To actuate the

emergency-stop button, turn the push button until it reaches the end stop. It then locks

automatically. To unlock the actuated emergency-stop button, turn the push button in the

direction of the arrows and release. The emergency-stop equipment must only be reset after the

hazard and its cause have been eliminated.

8.3.0 During maintenance work

Maintenance work on the hoist system must not commence before the load has been

removed and the main switch/isolator switched off.

Tests and inspections required in addition to those outlined in the maintenance schedule

should be carried out.


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9.3.0 Periodic inspections (Monthly to yearly intervals)

Items to be inspected are:

Deformed, cracked or corroded members

Loose bolts or rivets Cracked or worn sheaves and drums

Worn, cracked or distorted parts such as bearings, gears, rollers, etc.

Excessive wear on brake system parts

Inaccuracies in load, wind and other indicators

Electric motors

Excessive wear of chain drive sprockets and chain

Deteriorated electrical components such as circuit breakers, fuses, pushbuttons,

limit switches or contactors


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Item

no.Description of task Frequency

15

Check adhesive grease in bearings of return sheaves,

crossheads, compensating sheaves and pins of rope

anchorage and re-grease, as required

Every 4 years

16Change oil in following gearboxes: hoist reduction gear,

cross travel unit gearboxEvery 4 years

17Change grease in the protective caps of the last stage of the

gearbox on monorail hoist carriagesEvery 4 years

18 Check corrosion protection, improve or supplement Every 12 months

19

Check suspension of rope anchorage. Check play of the set

bolt/pin in the counter bore hole of the retaining plate.

Check retaining ring for correct fitting in the groove of the

set bolt/pin

Every 12 months

20 Check the coupling of the creep speed hoist motor Every 12 months21 Overhaul hoist unit completely

After 8-10 years

operation


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11.0.0 Troubleshooting and Repair

Simple repair work such as replacing of original parts like relays, terminals, can be

generally carried out in electrical workshops. Major repair works should be carried out by

suitably experienced technicians.

When troubleshooting and repair work is to be performed on the electrical equipment, a

circuit diagram showing all the details of the control system must be secured and referred to

prior to the commencement of the work. Follow the procedures as recommended in the

equipment manufacturers operation and maintenance manual.

Safety guidelines during the conduct of troubleshooting and repair are as follows:

1. Before work is started, the equipment must be disconnected from the supply.

2. Electrical equipment must be earthed or connected to protective earth conductor.

3. It must be secured against accidental or unauthorized switching on, install locks.

4. A warning sign must be placed at the disconnecting point prohibiting switching on of

the installation while maintenance work is being performed.

5. Faults in electrical installations can originate from the electrical equipment or from the

cables. Defective cables must be replaced.

6. Fuses must not be replaced by others of higher capacity, as otherwise short circuit

protection for the contactors and cables would not be ensured.


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References :

National Electrical Code

Operating Instructions for Demag hoist units


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Module No E18 PowerTools and Wkshop Equipment

Documents

Transcript of Module No E18 PowerTools and Wkshop Equipment