FOLLOW UP ON CLOSED THREAD"UNIDENTIFIABLE SERIUOS PROBLEM"

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dave h

Member
Location
Bergen, New York
AFTER COUNTLESS HOURS / DAYS OF TRYING TO SOLVE THIS PROBLEM, WE THOUGHT WE FINALLY HAD IT FIGURED OUT BECAUSE THE LIGHTING SYSTEM WORKED FLAWLESSLY FOR 5-6 WEEKS.
On a day with a soaking rain there was a soccer playoff game scheduled so the Superintendent of Grounds wanted to test the lighting to be sure there would be no problems. He turned the lights on with no problems then called us to let us know he was running the lights, I asked him to wait for us and let us cycle the lights because the problem only showed its ugly head at shut down. I happened to be away so I sent a well qualified electrician there to do the cycling of the lights. While shutting down the third of six contactors there was a massive explosion. The covers of six contactors blew off the enclosures, the panelboard cover bent outward, a 10x10 3R gutter blew its cover off and bent an inch outward, the nema 1 gutters inside blew open and my employee was hit in the arm with a contactor cover breaking his arm, he will be disabled for the rest of his life.

After a week a forensic electrical inspector was hired to find the problem. Without even being on site the first thing he said was "did you check for gas"!
No one has even suspected gas, but yes that was the problem. A undergroung gas pipe has failed and was seeping into the conduits, through the gutters and into the panels and contactors. When the contactors opened, a spark ignited the gas.

Please to all those out there chasing electrical problems, do overlook the possibility the the problem my not be electrical.
Dave H
 

Sierrasparky

Senior Member
Location
USA
Occupation
Electrician ,contractor
AY carumba,,,,

My prayers go to you and your employee. This will affect you for years to come. I suppose we need to get combustable gas detectors as another tool on the truck.


Why was the gas leaking worse when it was raining?
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Thanks for the follow-up.
I have seen a similar, though not as tragic, situation with ballfield lighting where the ballpark was built on an old landfill site.
Methane from the decay filled the pipes and cause disconnect covers to fly off when switched.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
If it was a heavy gas to start with such as propane, the cooling effect of the rain would force the gas into the piping where it would migrate towards the warmer indoor areas.

Another possibility for a lighter-than-air gas like natural gas would be that a parallel path for the gas to dissipate, upward through the earth to the surface, was blocked by the rain-soaked earth, forcing a higher gas concentration at the level where it leaked into the electrical system. Another question that raises is just how the gas entered the underground electrical piping in the first place if it was intended to be watertight. (And I know that gas tight is tighter than just watertight, but it sounds like there was a pretty substantial leak at very low pressure.)
 
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dave h

Member
Location
Bergen, New York
AY carumba,,,,

My prayers go to you and your employee. This will affect you for years to come. I suppose we need to get combustable gas detectors as another tool on the truck.


Why was the gas leaking worse when it was raining?

the gas leak was always the same, but when the ground is saturated the gas can not escape into the air, so the way out was through the electrical conduits
 

hurk27

Senior Member
I have had one of our workers who drove a ground rod through a plastic gas line at a service to a small building (guard shack) that the gas being on the high pressure side of the meter flowed into the building through the drop pipe into the meter then into the service panel on the other side of the wall, but it was immediately noticeable and luckily the service wasn't energized so there was no ignition but I have to repeat Georges response "WOW" that is a new one for the books, guess we have to make sure we smell in the area of the box as a new trouble shooting method, never though my nose would become an electrical trouble shooting tool:(

Thanks for sharing, and I hope you can send the story to some electrical mags as well as it would be good for this info to be known to all.
 

impresv

New member
Location
western ny
The gas was unscented gas, being it was from a private gas well system they scented it at another location down the line. Only was it was detectable was to a gas meter once the issue was found.
 

WorkSafe

Senior Member
Location
Moore, OK
Dang! Hope your employee is doing alright! I'm sure people are wondering what could be done to prevent something like this from happening again. I don't even want to think about what the odds off this happening again are.

You guys going to have a PID tester available in the shop now, or maybe even the Fire Dept could come test....

Interesting though.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Mark,
What is a PID tester? I have not heard that term in connection with combustible or toxic gas detectors before.
 

hardworkingstiff

Senior Member
Location
Wilmington, NC
I guess this stresses the importance of 300.50(F).

My guess is the conduits were not sealed, but I wonder if ductseal would have been enough to stop the vapors (I don't know what kind of pressure was developed).
 

hurk27

Senior Member
Mark,
What is a PID tester? I have not heard that term in connection with combustible or toxic gas detectors before.

Personal indication device? At work we wear Toxi Pro's and depending on where our job is in the plant might include one that monitors for high LEL's, CO or both, as well as other types of gases, we also have Multi Pro's that can test for many gases at the same time, in the area I work, ours are only for CO gas as it is the only one in our normal work area, it also records our levels we have been exposed to and for how long we stayed in the area as if it hits 200ppm we have to leave the area and report it to our super, for confined work space permits we have gas monitoring done with the Multi Pros that monitor OX, LEL as well as few other gases.

They are made by Honeywell
 
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