Multimeter - Blows Up (8-27-99)
Digital Multimeter Explodes
Back in summer of 1997, one of our engine mechanics who looks after our generator sets in a US Army camp in a Saudi Arabian desert got the shock of his life. It was one o'clock in the morning when he started a generator to take over the running unit as part of our daily routine. Before he changed the position of the manual transfer switch, he opened the generator breaker enclosure to check that the required 480 volts is attained. Using a Fluke digital multimeter, he attempted to measure the voltage between two terminals. The moment his probes touched the terminals a loud bang and shout was heard by enlisted personnel nearby, who immediately rushed to the scene. Paramedics arrived and our technician's life was spared.
Our investigation showed that the mechanic had his multimeter set on ohmmeter when he tried to measure the voltage. The spark caused by this mistake startled him that he instinctively dropped the tool. His hand however got into contact with the live terminal of the generator breaker. He suffered burns in his hand and was in shock for a good number of hours.
Since that day, a qualified electrician has been assigned to go with the mechanic to do the electrician's part of the job.
Response No. 1
Thanks for the story. One thing that is note worthy. Most of the Flukes have a rotary selector on the front of the meter. I have seen incidences where an older model Fluke was connected to a live circuit in the "off" position and as the selector was rotated to the "volts" selection, it had to pass over the "Ohm" selection causing the meter to blow an internal fuse. Fortunately, this was on a 110V circuit and the meter withstood the surge. I think the Fluke company has since corrected this problem on the newer models. At Westinghouse Savannah River Company, we have a policy against using a general purpose multimeter for measuring voltages such as 440V. The meter that we are required to use is called a TEGAM Safety Volt meter. These are very safe, "idiot proof" meters. Due to the size of our company and our safety philosophy, these are the only meters that can be used to verify absence of voltage as part of our lockout program. Because there are no voltage range to select, the meter only measures voltage, the leads are hard wired to the meter, and there is only an on-off switch. Again thanks for the "lessons learned" and the opportunity to share my experiences. God Bless.
Response No. 2
I have used a Fluke meter for years and I have never had such an incident occur from similar a mistake.....and we all make such mistakes.
Gary Hedger (Master Electrician) email@example.com
Response No. 3
I was an electrician onboard a nuclear submarine before I chose to leave the service. It was a terrible mistake to allow a mechanic to work on electrical gear, even crazier to make a voltage check at an energized disconnect. I'm happy to hear that a qualified electrician now supervises; it boils down to training.
Andrew Spies INELUKTBL@aol.com
Response No. 4
I consider myself a relatively safety conscious person, when I get around to having to work on live circuits, performing system diagnostics, I've learned over the years to always have in my pocket a reliable active voltage detector and where necessary a pair of insulated gloves. I also try to have someone on hand to be an observer, or at least to check on me periodically. It never ceases to amaze me the many "professionals" who will tell me that they have to work on live 480/277 systems making or breaking wiring connections so as not to disrupt lighting etc. Having in place an effective closely followed lock-out/tag-out control safety program virtually eliminates the unexpected funeral.
Michael Draggett LDraggett@aol.com
Response No. 5
Interesting story. But we should all remember that being an electrician does not prevent us from contacting live parts under similar situations. And as far as checking voltage with the meter set on ohms--- it is not a matter of IF EVER but WHEN. One of the great items I purchased was a Fluke meter that would not blow up no matter what it was set on. No fuse, no explosion. I am sure others make something similar. When it was demonstrated to me I hardly believed it- but it was true and I am still using the meter.
Of course the real solution would be to wear rubber gloves, safety glasses, flame retardant long sleeved clothing, insulated safety shoes and use rubber mats and blankets. Now try to read the voltage! Perhaps a panel mounted volt meter permanently installed would have prevented the need to open up the live terminals and use a portable meter. And been easier for many people to check the voltage.
Lynn Adams, firstname.lastname@example.org
Response No. 6
I use a Fluke Model # 76 dmm. It has a safety circuit to block out voltage on the ohm circuit and the display flashes and beeps to alert you to your mistake. But beyond that our company has a policy that says when you can't disconnect power before working on a circuit you must use proper" Personal Protective Equipment " (PPE) ie. hot gloves, face shield, buss blankets, and insulated safety mats to stand on. Also a second person must be present (Journeyman level, CPR, and Hot Work trained, with a shepherds hook) as an observer while you are exposed to the live power. In addition a "Hot Work Permit" must be filled out and signed by the supervisor.
This policy has been most effective at eliminating injuries caused by mistake like the one mentioned, however no safety policy can be totally effective until we in the field change our attitudes towards putting ourselves at risk. The first question on the permit form asks "Why is it impossible to turn off the power". With or without a form if we would all set our egos aside and ask ourselves this question before we proceed with the energized work, I think we would do a lot less of it energized. Most of the time we get our work done without incident, but if an incident does happen and you are injured you and your family will ask that question the rest of your lives.
Michael White Mwhite2690@aol.com
Response No. 7
Just remember this. There are old electricians and there are bold electricians, but there
not very many old, bold electricians!
Joseph O. Ellis email@example.com