Power strip failure analysis

A brand-new power strip emitted a loud pop and left a soot mark on my friend's hand when he plugged it into the wall. No devices were attached to the power strip. I decided to take the thing apart to see what failed. The circuit breaker in the household electrical system did NOT trip during this event.

My guess is that a very fine piece of wire bridged the neutral and hot terminals on the switch. When power was applied, the whisker vaporized.

Stainless steel conical beer fermenter Pt.6

I decided to scrap the idea of using my ring burner shown in "part 5" of my conical fermenter series of posts. Instead, I started reading about home-built propane burners for use in small metal-working forges.

These sites were very helpful:
http://www.zoellerforge.com/sidearm.html
http://ronreil.abana.org/design1.shtml
http://www.backyardmetalcasting.com/oliverburner1.html

I decided to follow Mr.Zoeller's design, for which he was kind enough to post a PDF and provide great instructions.




I used an 1/8" NPT brass cap to seal the end of the 1/8" pipe nipple instead of a Tweco Mig tip. I drilled a .035" hole in the center of the brass cap after machining the sides and face smooth.


I used a 3/4" to 3/4" extender as a flare. I cut out the threads on the lathe, leaving a 1:12 taper on the interior surface. I tested the burner briefly before cutting the taper, and I'm not sure how much it really helped. I never tested it without the flare.


This is really a very good design. It can be built from parts found at any hardware store, and it only requires a couple holes to be drilled. The performance seems to be quite good. I do not have any other burners to compare it to, but I am quite pleased. It doesn't like to run at very low pressures. The flame will be drawn back into the tube, and it starts to sputter (as well as heat up the tube). Above 3 or 4 psi, it runs like a champ, and the adjustable air shutter is a critical piece. Without the air shutter, the flame is very lean and might blow itself out. I kept the shutter half-closed, and this seemed to produce a very neutral flame.

I fitted the conical with its valves and added 1 gallon of tap water. The burner is mounted by simply placing it between two short stainless pipes that I welded onto the frame rail. There is currently nothing holding the burner in place except gravity. I'll probably add a pin or strap to prevent the burner from accidentally falling.

Cool!


I achieved a full rolling boil in 20 minutes (1 gallon of water). I started out fairly low with the gas pressure, and gradually increased it, as I saw nothing bad happening.

Stainless steel conical beer fermenter Pt.5

I found a 0-10 psi adjustable propane regulator at Home Depot. It was a closeout item with a price of $4.99! I built a circular burner from 5/8" copper tubing and soldered in some "jet burners" from the ubiquitous 23-jet wok burner.


The 23-jet burner is available in natural gas and propane versions. I ordered the propane version from kitchensupplydirect.com (it was on sale for $20.03 a few weeks ago), but they might have sent me the natural gas version. I suspec this might be the case because the burner runs very rich. Take a look:


The yellow tips on the flames show that there is a lot of excess fuel. The flames are jumping off the burners probably because the mixture is too rich to start combustion inside the burner tube.

I ordered some hypodermic tubing from McMaster and made the jets smaller by press-fitting the hypodermic tubing into the existing jets. This changed the jet size from about .023" to .012". Now, the jets seem to burn too lean, and have a very hard time staying lit. The slightest breeze blows the flame out. When the burner was running too rich, it also could be blown out by slight breezes. I think the burners are not designed very well. The original orientation in the 23-jet burner caused a lot of turbulence to be generated -- it positioned the jets to aim into each other's path. This might have been a required design element to prevent the flames from being blown out.

Anyway, I'm considering a different propane burner design. More later.