AWS RWMA BULLETIN 14-1996 Maintenance Manual for Resistance Welding Machines《电阻焊接机械维护手册》.pdf

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1、RUMA BULLbL4 bt 7698558 0000816 380 A Publication of the RESISTANCE WELDER MANUFACTURERS ASSOCIATION Bulletin #I4 Maintenance Manual for Resistance Welding Machines RWMA BULLxLY t* W 7698558 00008L7 217 = RWMA BULLETIN 14 Maintenance Manual for Resistance Welding Mac hines BULLETIN 14 IPAGEi 1 RESIS

2、TANCE WELDER MANUFACTURERS ASSOCIATION PREFACE This publication is not intended to be a safety manual. Although attempts have been made to incorporate common safety cautions, specific machine safety guidelines as well as applicable Federal, State and local codes should be followed. When in doubt ple

3、ase contact the machine manufacturer before attempting to install, repair, or replace machinery components. Additional safety considerations for resistance welders are: - Possible exposure to high voltage (e. energy storage devices) or improperly installed equipment presents a shock hazard. - The pr

4、ocess in several forms may generate potentially hazardous molten metal ejections. This presents a direct operator hazard as well as a fire hazard in some applications. Appropriate operator protection must be used at all times. - Both organic and inorganic chemicals can be released as a result of the

5、 heat from welding. Depending on pari condition, supplemental ventilation or fume removal may be necessary to ensure compliance with OSHA exposure limits and local code conditions. - Since the process integrates water and power, proper grounding and operator protection are especially important. - Si

6、gnificant force is generated between the welding electrodes at pinch point. Observe ANSI 249.1 (Safety in Welding and Cutting), other applicable local codes, or contact the equipment manufacturer, before modifying or replacing safety devices. - Your LOCKOUT program must include provision for dissipa

7、ting stored voltage (e. capacitive devices). - Copyright pending. - No pari of this bulletin may be reproduced without the express prior written approval of the Resistance Welder Manufacturers Association. RWMA BULLrL4 * 7698558 00008L9 09T BULLETIN 14 r-l PAGE li RESISTANCE WELDER MANUFACTURERS ASS

8、OCIATION TABLE OF CONTENTS PREFACE i TABLE OF CONTENTS ii INTRODUCTION . i I N STA LLAT I O N i Unpacking/Assembly . 1 Setup 1 Utility Connection 2 Startup . 4 MAINTENANCE RECOMMENDATIONS 5 Cooling System . 5 Electrodes 6 PneumaticSystem . 8 HydraulicSystem 10 ElectricalSystem 1 0 QUALITY CONTROL .

9、13 WeldTesting 13 DimencionalVerification 14 SURFACE CONDITIONS OF SPOT. SEAM AND PROJECTION WELDS . 15 PREVENTATIVE MAINTENANCE 16 Weekly Activities 18 Quarterly Activities . 19 Annual Activities . 19 Removing Equipment From Service . 20 Daily Activities 17 TROUBLESHOOTING 20 CONVERSION TABLE . 24

10、RWMA BULLdL4 dt 7698558 0000820 801 BULLETIN 14 (PI.E1 1 RESISTANCE WELDER MANUFACTURERS ASSOCIATION INTRODUCTION This publication provides general guidelines for the installation, operation and maintenance of resistance welding machinery. The resistance welding process exploits the physical reactio

11、n of metals as a high current and concentrated force is applied to metals to be joined. The high current and resulting heat and strain produced will cause machinery to deteriorate over time if proper and timely maintenance procedures are not applied. The following sections will provide detailed sugg

12、estions that will help you get the most from your resistance welding equipment. For machine specific assistance please follow the guidelines and recommendations outlined in the original machine manual. Further assistance may be obtained from the original machine manufacturer or through other RWMA pu

13、blications. It is the responsibility of the equipment ownerloperator to ensure the equipment conforms to current safety standards. (This includes used or rebuilt equipment.) Care should be taken to ensure that all documents have been updated. INSTALLATION UNPACKING/ASSEMBLY DANGER: Before moving the

14、 welder to the operating site, ensure that the vehicle or crane is capable of carrying the load. Also ensure that sufficient clearance is available along the entire route for safe transit. Bumping, dropping or sliding can cause severe damage to the welders alignment and components Some equipment may

15、 be top-heavy making it essential that extra care be taken in moving it. Observe all warning signs on the equipment. Lift the machine only by the machine frame and at designated lifting points. The rigger should pay careful attention to the location of pipes, conduit and wires to prevent damage. The

16、 welding equipment should be very carefully uncrated and unpacked. An extensive visual examination should be conducted to verify that all items and accessories have been received, and that no damage has occurred during transit. SETUP With the equipment in place it should be levelled, and if required

17、, anchored. Anchoring will prevent shifting, minimize distortion and isolate or dampen vibrations. DANGER: If the operation of fhe equipment is not clearly understood, consult the operator manual or the manufacturer prior to beginning the setup procedure. After the equipment is set in place, remove

18、all shipping tie-downs and blocks. Care should be used to ensure that clamps or other moving members do not descend upon personnel while removing the shipping blocks. Separately mounted units should be located and interconnected in accordance with the manufacturers instructions. RWMA BULL*iLY * 7b98

19、558 0000821 748 Duty Cycle(%) Factor PAGE 2 RESISTANCE WELDER MANUFACTURERS ASSOCIATION 50 40 30 25 20 15 10 7.5 T 5 .71 .63 55 .5 .45 .39 .32 .27 .22 UTILITY CONNECTION Generally, three services will be required: electrical power, compressed air and cooling water. The connections must follow all ap

20、plicable federal, state and local codes. DANGE: A LOCKOUTflAGOUT procedure must be instituted and strictly followed. i. Electrical Power DANGER: Check equipment nameplate and control drawings to ensure that the electrical power supplied is of the same voltage and frequency as noted on the machine na

21、meplate. The supply cables should be suitably sized (contact the welder manufacturer if in doubt) and installed in accordance with appropriate codes to a safety disconnect or isolation switch with lockout provisions and overcurrent protection. One main disconnect (isolation) switch with overcurrent

22、protection must be provided for each machine. This switch may be built into the equipment. If other disconnects are required, they must be supplied from the main disconnect. Provide a ground connection from the machine frame to a suitable ground. The ground connection should comply with all applicab

23、le electrical codes. Duty cycle is the percentage of total current on time in a one minute period. (eg. Fifteen twelve-cycle welds per minute would represent a 5% duty cycle at 60 Hz) 2. Overcurrent protection Because of the high instantaneous demand, overcurrent devices are sometimes over-rated to

24、prevent nuisance tripping. According to the above two references, the overcurrent protection shall not be rated or set at above 300% of the rated primary current of the welder unless the upstream overcurrent RWMA BULLmL4 * m 7b8558 0000822 b84 m BULLETIN 14 IPIGEO I RESISTANCE WELDER MANUFACTURERS A

25、SSOCIATION device gives equivalent protection. i. Air Prior to connection of the air supply plumbing, the lines should be purged to prevent excessive contamination from entering the equipment. The lines must provide air to meet the equipment and safety code requirements. General air requirements are

26、: Pressure: 60 to 120 psi Volume: machine specific Allowable pressure drop: 10 psi Quality: Machine specific (must not overload primary air filter) An air isolation valve must be incorporated in the system to provide for LOCKOUT of the air supply. Traps and filters are recommended to reduce the harm

27、ful effects of moisture present in the air lines. If the machine has been designed for non-lube service, or if the area is known to have air problems, a coalescing filter (or system) must be included. If airline lubrication is incorporated into the machine, the lubricator should be filled with the r

28、ecommended fluid. CAUTION: Using fluids other than recommended by the manufacturer may cause considerable damage to the system components. iii. Water To ensure adequate cooling, the main water supply system must be large enough to support the flow requirements of all the welders connected. Prior to

29、connection of the water supply and drain lines they should be purged to prevent excessive contamination from entering the equipment. These lines should be of suitable size to at least match the inlet and drain connection points on the machine. The cooling water supply system must meet the equipment

30、requirements regarding volume, pressure, purity and temperature. Due to water conservation efforts and cost, city water should be reserved for small or intermittent water use. In all other cases, a recirculating system or a commercial water chiller should be used. This also provides the ability to c

31、ontrol the water parameters for more effective system cooling. If a water saver valve is used to reduce the water consumption it must not affect the water flow through SCR contactors. If voltage is present at the hose terminations on the SCR contactor, serious control damage may result from stopping

32、 water flow. The stagnant water in the hose may begin to heat from the constant leakage current, causing steam. The steam pressure in addition to arcing across the steam bubbles will destroy the hose. The general water requirements are: Pressure: 75 psi maximum with minimum 30 psi differential Flow:

33、 Machine specific Temperature: 65-85 F (consideration should be given to ensure condensation does not occur) -Qualitv The cooling water should have the following qualities: 1. 2. 3. 4. 5. 6. 7. pH between 7.0 and 9.0 Maximum Chloride content of 20 PPM Maximum Nitrate content of 10 PPM Maximum Sulpha

34、te content of 1 O0 PPM Maximum Solids content of 250 PPM Maximum Calcium Carbonate content of 250 PPM Resistivity greater than 2,000 ohm-cm at 77 OF (25 OC). RWMA BULLm14 xx = 7b98558 0000823 510 m PAGE 4 RESISTANCE WELDER MANUFACTURERS ASSOCIATION Deionized water should not be used in a closed wate

35、r system unless the water is constantly recirculated through the deionizer. Deionized water is ion-hungry and still contains many water soluble gases which will quickly reduce the resistivity of the water if not continually run through the deionizer. Sizina The Coolina Load The actual cooling demand

36、 is not possible to calculate because of the complexity of the system. While this can be measured once the equipment is in operation, the problem we are trying to address here is installation. For this purpose, two methods are referenced for your consideration. 1. For approximating the water chiller

37、 size, a general rule of thumb has been suggested to be: one ton (1 2,000 Btu/hr. or 200 Btu/min.) is required per 1 O0 KVA. 2. Sizing of water chillers by thermal recovery rates are done with the following formulas assuming one-half (1/2) input kilowatts is picked up for A.C. single-phase machines,

38、 and three-quarters (3/4) input kilowatts on D.C. machines. a. A.C. Welding Machines Btu/minute = 1/2 (KVA/C ) x (Duty Cycle) x (.57 BtulminJKw) b. D.C. Welding Machine Btu/minute = 3/4 (KVAIJ2) x (Duty Cycle) x (.57 Btu/min./Kw) iv. Hydraulic Connect hydraulic lines (if used) and fill the reservoir

39、 as recommended with the specified fluid. If water cooling is used to regulate the hydraulic fluid temperature, it should be kept separate from general controVelectrode cooling and not run in series. In cases where preheating is required to raise the cooling water above the dew point surplus heat fr

40、om the hydraulic system may be used. DANGER: The Material Safety Data Sheet (MSDS) must be consulted for safe fluid handling and spill clean-up procedures. STARTUP Consult the machine manual to find out the manufacturers recommended startup procedure. In the case of specialized equipment, initial st

41、artup is generally the responsibility of the manufacturer or their representative. If the startup procedure is not specified by the manufacturer, the supply services should be tested in the same sequence as the connections have been made. RWMA BULL*:/4 * PAGE 5 7698558 0000824 457 rn RESISTANCE WELD

42、ER MANUFACTURERS ASSOCIATION COOLING SYSTEM Very high secondary currents are developed in resistance welding equipment. This, coupled with compact design, high upset temperatures, and fast cycle times, makes the need for proper cooling apparent. The water supply must be sufficient and at the proper

43、temperature, pressure and required flow rate as recommended by the supplier of the welding equipment. Failure of the cooling system to function properly can cause serious damage to a resistance welder. Water circulation should be checked oten to ensure that all parts of the welder requiring cooling

44、receive the proper amounts of water. Water filters and strainers should be cleaned at regular intervals. When equipment is not to be used for a period of time, the water should be shut off to avoid damage from leaks and condensation. This can be accomplished by using a manual or electrically operate

45、d shutoff valve. The electrical “water saver“ valve provides for an automatic means of stopping water flow when the interval between machine cycles is long. Water should continue to flow for a period of time after the weld is made. It is advisable to have the water flow for one (1) to three (3) minu

46、tes after completing a weld. If the period of machine lay up will be long or if the machine may be exposed to freezing temperatures, the cooling water circuit must be drained and purged. Water leaks should be repaired promptly. Neglecting water leaks creates a safety hazard to personnel and can caus

47、e serious damage to the welder. When repairing the water circuit make sure the water circuit is not changed. DANGER: Do not touch ignitron tubes or SC packages until control is safely LOCKED-OUT. Proper cooling of ignitron tubes and SCR packages is very important. Water flow rates should be per the

48、recommendations of the ignitron tube or SCR package manufacturer. In the case of the ignitron tube, the water should enter the bottom of the metal jacket and be discharged at the top. For SCR packages, follow the “in-out“ markings on the device. Normally some type of thermal protective device is fur

49、nished and is employed to inhibit initiation of the weld control if the safe operating temperature of the ignitron tube or SCR package has been exceeded. CAUTION: Do not defeat thermal protective devices. As discussed in the connection section, the resistivity of the water should be greater than 2,000 ohm-cm. This is necessary to prevent electrical leakage currents from causing injury, or premature mechanical system failure. It should be noted that some pump lubricants and anti-freeze may be conductive. When recirculating water from an open system, dont just add ma