resistance welding
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RESISTANCE WELDINGRESISTANCE WELDING
1910.255, SUBPART Q1910.255, SUBPART Q
Samuel D. YatesSamuel D. Yates
Corporate Safety and EnvironmentalCorporate Safety and Environmental
Meadowcraft, Inc.Meadowcraft, Inc.
[email protected]@meadowcraft.com
VARIOUS TYPES OF RESISTANCE VARIOUS TYPES OF RESISTANCE WELDERSWELDERS
Rocker Arm, Seam, and Spot WelderRocker Arm, Seam, and Spot Welder
MULTIHEAD RESISTANCE WELDERMULTIHEAD RESISTANCE WELDER
In GeneralIn General
INSTALLATION – All equipment is to beINSTALLATION – All equipment is to be installed by qualified electrician.installed by qualified electrician.
There must be a safety-type discon-There must be a safety-type discon- necting switch, a circuit breaker or a necting switch, a circuit breaker or a circuit interrupter to open each circuit interrupter to open each power circuit to the machine conven-power circuit to the machine conven- iently located at or near the machine. iently located at or near the machine.
Ignitron tubes used in resistance Ignitron tubes used in resistance welding equipment must be equippedwelding equipment must be equippedwith a thermal protection switch.with a thermal protection switch.
Employees assigned to operate resis-Employees assigned to operate resis-tence welding equipment must be tence welding equipment must be properly trained and judged competentproperly trained and judged competentto operate the equipment.to operate the equipment.
All controls of automatic or air and All controls of automatic or air and hydraulic must be arranged or guarded to hydraulic must be arranged or guarded to prevent accidental activation by the prevent accidental activation by the
operator.operator.
NONPORTABLE SPOT AND SEAMNONPORTABLE SPOT AND SEAM
WELDING MACHINESWELDING MACHINES
For operator safety, all external For operator safety, all external weldweld
initiating control circuits shall initiating control circuits shall operateoperate
on low voltage (not over 120 volts).on low voltage (not over 120 volts).
CAPACITOR WELDINGCAPACITOR WELDING
Stored energy or capacitor dischargeStored energy or capacitor discharge
resistance welding equipment and con-resistance welding equipment and con-
trol panels involving voltages of overtrol panels involving voltages of over
550 volts must be insulated and pro-550 volts must be insulated and pro-
tected by complete enclosures with tected by complete enclosures with
interlocked doors with contacts wiredinterlocked doors with contacts wired
into the control circuit. These interlocksinto the control circuit. These interlocks
must interrupt power and short circuitmust interrupt power and short circuit
all capacitors when the door or panel is all capacitors when the door or panel is open.open.
CONTROL CABINETCONTROL CABINET
Capacitor WeldingCapacitor Welding
A manual switch or other suitable A manual switch or other suitable pos-pos-
itive device, along with other itive device, along with other mechani-mechani-
cal interlocks or contacts, must be cal interlocks or contacts, must be in-in-
stalled as an additional safety stalled as an additional safety measure.measure.
INTERLOCKSINTERLOCKS
All doors and access panels of all All doors and access panels of all
resistance welding machines and resistance welding machines and con-con-
trol panels are to be kept locked andtrol panels are to be kept locked and
interlocked to prevent access to liveinterlocked to prevent access to live
portions of the equipment by un-portions of the equipment by un-
authorized persons.authorized persons.
GUARDINGGUARDING
All press welding machines must be All press welding machines must be guarded where there is a possibility ofguarded where there is a possibility ofthe operator’s fingers being under thethe operator’s fingers being under thepoint of operation by such devices as:point of operation by such devices as:
► Electronic eye safety circuits.Electronic eye safety circuits.► Two hand controls similar to punch Two hand controls similar to punch press operations.press operations.
GUARDINGGUARDING
► All chains, gears, operating bus All chains, gears, operating bus
linkage and belts must be linkage and belts must be protectedprotected
by adequate guards.by adequate guards.
VARIOUS TYPES OF GUARDINGVARIOUS TYPES OF GUARDING
SHIELDSSHIELDS
Where practical, shields guards of safetyWhere practical, shields guards of safetyglass or suitable fire-resistant plastic,glass or suitable fire-resistant plastic,shall be installed to guard against flyingshall be installed to guard against flyingsparks.sparks.
Additional shields or curtains shall beAdditional shields or curtains shall beinstalled as necessary to protect passinginstalled as necessary to protect passingpersons from flying sparks.persons from flying sparks.
SHIELDSSHIELDS
All operators and attendants shall All operators and attendants shall useuse
transparent face shields or goggles transparent face shields or goggles toto
protect their eyes while operating protect their eyes while operating resis-resis-
tance welders or resistance brazingtance welders or resistance brazing
equipment.equipment.
FOOT SWITCHESFOOT SWITCHES
All foot switches shall be All foot switches shall be guarded toguarded to
prevent accidental operation of prevent accidental operation of the the
machine.machine.
STOP BUTTONSSTOP BUTTONS
Two or moreTwo or more emergency stop emergency stop
buttons shall be provided on allbuttons shall be provided on all
special multispot welding special multispot welding machines,machines,
including 2-post and 4-post including 2-post and 4-post weldweld
presses. presses.
SAFETY PINSSAFETY PINS
On large machines, four safety pinsOn large machines, four safety pins
with plugs and receptacles (one inwith plugs and receptacles (one in
each corner) shall be provided soeach corner) shall be provided so
that when the safety pins are re-that when the safety pins are re-
moved and inserted into the ram ormoved and inserted into the ram or
platen, the press becomes inopera-platen, the press becomes inopera-
tive.tive.
GROUNDINGGROUNDING
WHEN?: When technically practical.WHEN?: When technically practical.WHAT?: The secondary of all WHAT?: The secondary of all welding transformers welding transformers
usedused in multispot, projection,in multispot, projection, and seam welding.and seam welding.HOW?: By permanently groundingHOW?: By permanently grounding one side of the weldingone side of the welding secondary current circuit.secondary current circuit.
GROUNDINGGROUNDINGWhen not technically practical:When not technically practical: Use a center tapped groundingUse a center tapped groundingreactor connected across the sec-reactor connected across the sec-ondary or use a safety disconnectondary or use a safety disconnectswitch in conjunction with theswitch in conjunction with thewelding controls. The safety discon-welding controls. The safety discon-nect shall be arranged to open bothnect shall be arranged to open bothsides of the line when welding sides of the line when welding
currentcurrentis not present.is not present.
PORTABLE WELDING MACHINESPORTABLE WELDING MACHINES
Counterbalance: All portable weldingCounterbalance: All portable welding
guns shall have suitable counter-guns shall have suitable counter-
balanced devices for supporting thebalanced devices for supporting the
guns, including cables, unless the guns, including cables, unless the
design of the gun makes counter-design of the gun makes counter-
balancing impractical or balancing impractical or unnecessary.unnecessary.
PORTABLE WELDING MACHINESPORTABLE WELDING MACHINES
Safety Chains: All portable welding guns,Safety Chains: All portable welding guns, transformers and related equipment transformers and related equipment that is suspended from overhead that is suspended from overhead structures, eye beams, trolleys, etc.structures, eye beams, trolleys, etc. shall be equipped with safety chains orshall be equipped with safety chains or cables capable of supporting the totalcables capable of supporting the total shock load in the event of failure of anyshock load in the event of failure of any component of the supporting system.component of the supporting system.
PORTABLE WELDING MACHINESPORTABLE WELDING MACHINES
Clevis: Each clevis shall be capable Clevis: Each clevis shall be capable of of
supporting the total shock load of supporting the total shock load of thethe
suspended equipment in the event suspended equipment in the event ofof
trolley failure.trolley failure.
PORTABLE WELDING MACHINESPORTABLE WELDING MACHINES
Switch guards: All initiating switches,Switch guards: All initiating switches, including retraction and dual including retraction and dual
scheduleschedule switches, located on the portableswitches, located on the portable welding gun shall be equipped withwelding gun shall be equipped with suitable guards capable of preventingsuitable guards capable of preventing accidental initiation through contactaccidental initiation through contact with fixtures, operator’s clothes, etc.with fixtures, operator’s clothes, etc. The initiating switch voltage shall notThe initiating switch voltage shall not exceed 24 volts.exceed 24 volts.
PORTABLE WELDING MACHINESPORTABLE WELDING MACHINES
Moving Holder: The movable holder,Moving Holder: The movable holder,
where it enters the gun frame, where it enters the gun frame, shall have sufficient clearance to shall have sufficient clearance to prevent the shearing of fingers prevent the shearing of fingers carelessly placed on the operating carelessly placed on the operating movable holder.movable holder.
PORTABLE WELDING MACHINESPORTABLE WELDING MACHINES
Grounding: The secondary and case Grounding: The secondary and case ofof
all portable welding transformers all portable welding transformers shall be grounded by center shall be grounded by center tapped secondary or by a center tapped secondary or by a center tapped grounding reactor tapped grounding reactor connected across the secondary.connected across the secondary.
FLASH WELDING EQUIPMENTFLASH WELDING EQUIPMENT
Ventilation and Flash Guard: FlashVentilation and Flash Guard: Flash
welding machines shall be equipped welding machines shall be equipped with a hood to control flying flash. with a hood to control flying flash. In cases of high production, where In cases of high production, where materials may contain a film of oil materials may contain a film of oil and where toxic elements and and where toxic elements and metal fumes are given off, metal fumes are given off, ventilation shall be pro-vided in ventilation shall be pro-vided in accordance with 1910.252(c).accordance with 1910.252(c).
FLASH WELDING EQUIPMENTFLASH WELDING EQUIPMENT
Fire Curtains: For protection of the Fire Curtains: For protection of the operators of nearby equipment, operators of nearby equipment, fire-resistant curtains of suitable fire-resistant curtains of suitable shields shall be set up around the shields shall be set up around the machine and in such a manner machine and in such a manner that the operators movements are that the operators movements are not hampered.not hampered.
MAINTENANCEMAINTENANCE
PERIODIC INSPECTION SHALL BE MADEPERIODIC INSPECTION SHALL BE MADE
BY QUALIFIED MAINTENANCE PER-BY QUALIFIED MAINTENANCE PER-
SONNEL.SONNEL.
A CERTIFICATION RECORD MUST BEA CERTIFICATION RECORD MUST BE
MAINTAINED TO INCLUDE:MAINTAINED TO INCLUDE: DATE OF INSPECTIONDATE OF INSPECTION
THE SIGNATURE OF PERSON CONDUCTING THE INSPECTIONTHE SIGNATURE OF PERSON CONDUCTING THE INSPECTION
SERIAL NUMBER OR IDENTIFIER OF EQUIPMENT INSPECTEDSERIAL NUMBER OR IDENTIFIER OF EQUIPMENT INSPECTED
MAINTENANCEMAINTENANCE
OPERATORS SHALL BE INSTRUCTED OPERATORS SHALL BE INSTRUCTED TO TO
REPORT ANY EQUIPMENT DEFECTS REPORT ANY EQUIPMENT DEFECTS TOTO
HIS SUPERVISOR AND THE USE OF HIS SUPERVISOR AND THE USE OF THETHE
EQUIPMENT DISCONTINUED UNTILEQUIPMENT DISCONTINUED UNTIL
SAFETY REPAIRS HAVE BEEN COM-SAFETY REPAIRS HAVE BEEN COM-
PLETED.PLETED.