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| Maintenance Welding Creates Failures |
Stop one major cause of Human Induced Failures to your assets, "Maintenance and Contractor Welding on equipment". (I learned this concept at Exxon in the 1970s from a maintenance welder with over 35 years’ experience. I have used it all my life).
Example of the problem: While visiting a plant recently I ask: “what is biggest problem being experienced and they stated they did not know, they have so many problems in this area”. So we began our tour on the 4th floor in a production building. I noticed the welding lead (electrode holder) connections mounted on the wall at different locations. I ask what the use of the welding lead connections was. They told the welding machine was located on the first floor because it is not possible to bring a welding machine to this floor. I looked around and ask the maintenance supervisor a few questions.
- Where is the ground for the welding machine? Answer - on the ground floor attached to the column. (Big Problem - electric current will travel through the pass of least resistance, ie. electrical panels, hydraulic cylinders, bearings, etc.)
- Do you have equipment problems on this floor (4th floor)? Answer: “We have failures all the time and assigned one person full time to handle these problems”
- Are the problems electrical or mechanical? He stated, “it depends on the day”.
This Maintenance Tip was developed based on a visit to this site however I have seen this problem at many plants, facilities, etc. In at least 5 sites the welding ground were connected to building columns far away from the welded area. All sites followed my suggestions, changed practices and noticed reliability site wide increased as a result.
Maintenance Tip - Welding on Equipment
Maintenance Supervisors should use this Maintenance Tip to train their maintenance techs, welders, and contractors - 10-20 minutes - Post this document in the Maintenance Shop and review with anyone who is about to weld on equipment. "Electric Arc caused by welding on equipment is one of the Failure Modes for Rolling Element and Non Rolling Bearings. Electric Arcing can also cause electrical component failure in MCCs and Electric Motors and Drives"
So why do we accept this failure mode when it can be eliminated? “People don't know what they don't know” General Rules which must be followed by maintenance personnel and contractors: (Caution: follow these recommendations only if you want to stop self-induced failures caused by welding)
- Ground leads and welding leads (cables) must be the same length on all welding machines by maintenance and contractors. No option by anyone. (Correct immediately)
- Grounding of welded surface must be within 6” of welded surface or a Reliability Engineer must approve variation to the process. (Post a notice on all welding machines)
- All contractors and maintenance personnel must follow this policy. (Management must enforce compliance to this policy, no options unless you enjoy failures)
Failure Modes experienced from Maintenance Welding
Electric Arcing caused by Welding on equipment - Flaking caused by Electric Arcing (secondary failure mode) WARNING: Ensure your contractors follow the same process to eliminate electric arcing. Warning: Failure to accomplish this one task properly will cause bearing failure by “electric arcing” which is a failure mode of bearings. In addition it will cause failure of many different electrical components.
Remember: Electric current from welding will always follow the path of least Resistance.
My recommendation, write a procedure for welding anywhere at your site and educate everyone in maintenance, reliability engineering and contractors. If a situation warrants a modification to this procedure make sure it is approved by Maintenance or Reliability Managers or Engineers. Welders and Contractors are not reliability experts but professionals whose job is to weld without knowledge of the damage they create, knowledge is key, be humble and respectful with anyone who is currently welding without the ground within 6 inches of the welded area.
I was a certified welder for many early years and later became a reliability specialist and conducted Root Cause Analysis on many failures around the world and have seen this problem in almost every plant and site I have visited. Stop this at your site today. For a Maintenance Tip on this subject go to: http://tinyurl.com/MaintWelding
The Author: Ricky Smith CMRP, CMRT, CRL
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