by Steven Noel
Reliability Engineer / Group Leader
Batesville Casket Co.
The Batesville Casket Assembly Plant located in Batesville, Indiana has two Seam Welders in their fabrication department. These Seam Welders are resistance welders that are designed to weld a continuous weld that holds the casket bottoms in place while making an air tight seal. Each Seam Welder runs proximity 27 units each hour and is in use for up to 10 hours each day throughout the week.
When a seam welder starts failing due to insulation failure you start seeing poor welds which in some cases don’t show up until the unit is built and vacuum tested prior to ship out. At this point to make repairs to the casket is costly due to disassembly and removal of the interior to gain access to the bottom.
Furthermore if one of the Seam Welders were to fail during production it would reduce production by 50%. The lead time for making this type of repair is two to three hours causing production losses estimated at eight to ten thousand dollars.
These Seam Welders are 16 volt DC / 20,000 amp resistance welders so being very low voltage and high amperage any insulation breakdown will cause the foot and lower wheel to overheat and eventually fail.
To increase the reliability of the Seam Welders we developed a PM procedure to help prevent poor welds and losses due machinery failure. The PM schedule calls for the lower foot section to be disassembled every six months to clean connections and replace the 14 insulators that isolate the bottom welding wheel assembly from ground. Each welder PM had to be scheduled for the weekend due to the equipment availability during the week. The lower foot had to be disassembled and cleaned, then reassembled without cracking any of the small insulators that fit in-between the wheel assembly and the bolts that held them in place. In some cases the new insulators would get cracked or not be seated correctly causing the welder to develop problems shortly after returning to service.
The cost of the PM was $3,221.64 annually.
| 1 | Bolt Insulators | 6 @ $7.00 Each | $42.00 |
| 2 | Insulator Washers | 6 @ $4.00 Each | $24.00 |
| 3 | Flat Mounting Insulator | 2 @ $21.00 Each | $42.00 |
| 4 | Cool Amp Coating | 1 Pint | $192.45 |
| 5 | Labor @ $31.56 | 16 Hours | $504.96 |
| Total for Each Welder | $805.41 | ||
| Two Welders X Semi Annually | Total Cost Annually | $3,221.64 |
By using the P60 Infrared Camera we can now see any heat due to high resistance from poor connections or shorting to ground. The IR image will show any overheating and pinpoint where the problems are without any disassembly or disruptions in work. Each Seam Welder can now be checked more often and completed once a month for just pennies.
This example shows a failed insulator on the lower wheel for the #1 Seam Welder. The area or spot is at 242.2 degrees. This is hot due to the lower wheel support passing current to ground due to a cracked insulator. Although the welder is sending current to ground it is not enough to keep the welder from working but at this point the weld may not hold. Finding problems like this early is vital to stopping bottom leaks before they get to shipping where repair is costly.
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By replacing the old PM procedure we save $3,200.60 annually without even shutting down the welder.
Steven earns 7 ITC Certification Renewal Credits for his article. – Editor
