Re[2]: Q:Selecting workshop heater

> Date: Tue, 19 Dec 2000 14:00:13 -0600 (CST)
> From: "Terry L. Ridder" <terrylr@...>
>
>i would think twice about having a propane cylinder
>inside a building. if the workshop is connected to
>the house in anyway i would never do it. keep the
>propane cylinders outside. run either black pipe or
>gas rated copper pipe. (copper pipe brazed not silver
>soldered is the better choice in my opinion.)
>
>national fire preventtion association-58 does allow
>for copper pipe. it also clearly states that propane
>cylinders should never be inside a residential house.
>
>in case anyone would like to know why not to keep
>a propane cylinder in a building search the web
>for 'bleve' (boiling liquid expanding vapour explosion).
>if you ever see a propane bulk tank or cylinder bleve
>you will understand. many volunteer fire fighters have
>been killed attempting to put out propane tank fires.
>instead of just letting the tank burn itself out they
>make the mistake of hitting the tank with a jet of water.
>the bulk tank does not like this and thermal shock causes
>the tank to rupture. near instant decompression of the

Not true. When the flame impinges on the container and there's liquid on
the other side, the propane simply boils and cools the container wall. Once
the liquid is below the flame impingement area of the container, the vapor
on the other side gets hot, the container heats until it fails. The near
instantaneous pressure drop causes the remaining liquid to flash into vapor.
This vapor is what makes the spectacular fireball. The best thing to do
with a fire near a tank is to apply a steady stream of water to keep the
tank cool. This is typically done with deck guns that can be set up and
then run unmanned.

>tank causes the propane to flash boil creating an expanding
>vapour cloud near ground level (since propane is heavier than air)
>the expanding vapour cloud ignites with explosive force.
>pieces of the propane bulk tank or cylinders become shrapnel.

Railroad tank cars have been tossed well over 1/2 mile.

>any shop fire is bad enough if there are propane tanks in the
>shop it will be catastrophic. 99% of the time the building will
>be leveled by the explosion. if this is ever the situation
>with anyone please tell the fire department to fall back and
>keep the fire from spreading. this will also keep them from
>going into the building and getting themselves killed when
>the cylinders bleve.

That's a good reason to install a sprinkler system. On new construction it
only adds 1-2% to the construction cost. Even a limited area system is
better than nothing. Some insurance companies will discount the fire
insurance premium if there's a sprinkler system. There's even a new type of
residential system that combines the domestic water system with the fire
suppression system using a matrix of plastic tubing.

Ken
:-)