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Oxygen Manifold Fire/Explosion

  • Wednesday, July 10, 2019 8:06 PM
    Message # 7774547

    Earlier this week we got called out concerning a fire/explosion in a Chemetron Series 3000 Oxygen Manifold.  

    The overview of the incident is as follows:

    The manifold went into alarm for "Secondary Bank In Use" when the right bank became empty.  The master alarm was silenced, and the employee went into the manifold room.  The employee put on gloves, silenced the local audible alarm inside the box and then closed the box.  The right bank had two cylinders hooked up one was in use, which was now depleted, and the other full cylinder was in the off position.  The employee then shut the empty cylinder, and opened the full cylinder with the right hand.  The left hand then immediately went up to protect the face from the rapidly expanding fire/explosion.  The employee left the room and went for help.  Fortunately, for all involved, only minor injuries were reported.  There is a sprinkler head directly above the manifold, and it did not go off.  There were smoke detectors in the room.  I saw them being replaced later that morning,  but do not know if they annunciated upon the room filling with smoke.  The fire seemed to self extinguish once the consumables were spent.  It is believed that this all occurred almost instantaneously.  

    The current theory is the ignition source was the typically very hot solenoid.  It was noted by personnel that there was a leak inside the (oxygen) manifold.  The fuel would be the plastic parts.  The pigtail and header looked brand new inside so it does not seem like the ignition source was from the cylinder.

    Any thoughts/input?

    7 files
    Last modified: Friday, July 12, 2019 9:19 AM | Peter "Nick" Linden, III
  • Monday, July 15, 2019 9:13 AM
    Reply # 7780089 on 7774547

    Hello Nick,

    I wanted to wait until I got home where I could look at your pictures on a larger monitor. From looking at the pictures and what I could see the ignition point appeared to be near the regulator. You should find a hole near the back or inlet to the regulator. The high pressure oxygen release then began to consume the back of the cabinet until there was not enough oxygen velocity to consume the metal. Again from what I could make out in the pictures the primary oxygen flow was horizontal from looking at the consumed metal. Oxygen fires are typically a kindling chain type of fire one small thing starts the next item and they continue until there is no more fuel or adequate oxygen to support the combustion of the material. There could have been adiabatic compression (going from ambient pressure to 2000 psi you can see in theory about a 1600 degree rise). that caused material to start burning. You mentioned a leak. High pressure escaping from a small leak can have enough velocity to ignite materials. In carbon steel the rule of thumb is 100 feet per second. So this fire is not necessarily as simple as we had a leak and hot solenoids. Looking at what is burnt and what is missing points you in the direction. However the initial cause of the fire might have been consumed and you can only have theroys. 

  • Thursday, July 18, 2019 9:45 AM
    Reply # 7785689 on 7774547
    Al Moon (Administrator)

    Fire triangle

    Fire triangle

    The fire triangle or combustion triangle is a simple model for understanding the necessary ingredients for most fires. The triangle illustrates the three elements a fire needs to ignite: heat, fuel, and an oxidizing agent (usually oxygen). A fire naturally occurs when the elements are present and combined in the right mixture, meaning that fire is actually an event rather than a thing.

  • Wednesday, May 06, 2020 1:47 PM
    Reply # 8951102 on 7774547

    Al, Thanks for the pictures. I've been trying to convince a couple of clients to replace these older manifolds because they are beyond any expected service life.  Now maybe they will pay attention before they lose their systems.

  • Thursday, May 07, 2020 11:32 AM
    Reply # 8953648 on 7774547

    We all know that this keeps happening with these manifolds and I think they should be pulled from the market before they do real harm.

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