NIOSH and OSHA have determined that the IR TLV (threshold limit value) to the unprotected eye is 10 mW/CM2 for time periods greater than 16 minutes. (10 mW is .010 Watts) Continue reading

Plumbing for propane

From LE:

My studio is a separate building and my propane tank and regulator are in a ventilated box my husband built sitting on a ledge attached to the outside of the building. He ran the standard hose that came with the torch (or I my have purchased it separately) through a small hole about a foot from the floor which is about 4 feet to my torch. The small hole has a pvc pipe inserted with the hose running through it and then a wood plate on the ouside and inside holding it in place. The hose also has insulation stuffed around it. Okay, now it all looks fine to us – but the experts out there, are we missing some important safety concern? Thanks in advance!

On the surface, this sounds like a marvelous idea. Make a hole in the wall, line it with PVC, insulate it, and run the rubber hose through it.

Unfortunately, it is an illegal installation. The National Fire Code (NFPA) states that all wall penetrations must be accomplished with hard wall metallic piping. The piping can be copper, black (iron) pipe or stainless steel. There must also be a shut off valve on either side of the wall. On the inside of the wall, the pipe must extend to within 5 feet of the point of use, and if the point of use is further than 10 feet from the inside shut off valve, the line must have an additional shut off valve at that point (torch valves do not qualify).

The danger of leaking propane

In previous articles I have discussed the ins and outs of NFPA 58, that connecting a hot head torch to a bulk tank is against code and therefore illegal etc ad nauseum…but I have not presented any “proof” of exactly WHY it is hazardous to do so.

There is a mathematical formula which converts flow of a particular gas in a line to a volume. Here is the formula:

V = 58 * SQRT((p * (d^5))/(W*L))

Where:
V equals volume flow in CFM
p equals difference in pressure between two ends of the hose in PSI
d equals ID of the hose in inches
W equals weight in pounds of one cubic foot of the gas
L equals the length of the hose in feet. Continue reading