To Main Annealer Page
2005-03-10 Rev. 2006-11-11, 2009-05-02
This tale begins 9+ years before I start working on this page when walking home from the grocery store in November 1995, I spotted a modest refrigerator at the curb. Although bigger than my planned annealer (and a different shape) it will provide a quick solution to what has dragged on too long in making the shell. For the reasons given here, I recommend caution in using these metal shells. Most of the refrig type annealers I have seen had the thicker arched lid from when they used fiberglass or rock wool inside. This is a modern thin shell refrigerator.
Having stripped one of these out for just this purpose, I will never do it again. The problem is that modern frigs are made with a metal outer shell and a plastic inner shell which fits inside. Then the space between the two is filled with liquid insulating foam which expands and hardens AND ALSO GLUES THE TWO TOGETHER.
The only efficient way I found was to break off a saber saw blade short enough
that the down stroke did not hit the metal and cut the plastic shell into
sections about 6" square and then use a long handled scraper to pry the sections
The bottom of the frig was shaped to hold and hide the compressor. After looking at the odd lump for a long time, I realized I could cut it off, remove the panel between the freezer and frig, and use the frig door as a basis for my lid. I used fairly heavy sheet metal I had on hand for a bottom/end. I used thin flashing to extend the lid and this was a mistake; I should have used HVAC weight sheet metal and I have had to reinforce it. I had, some time ago, built a metal extension of the door and installed 1" frax blanket facing 3" of backer board supported by wires across the face. The frax had gotten wet and sagged. I cut a 1/2x1/2" angle iron to length, drilled and pop riveted it across the lid to support the frax and stiffen the lid.
Earlier this year (2005), I hauled the box from where it had been sitting for too long. The boards it was sitting on had sunk in the ground and the back rusted through as well as the holes put there on purpose for inserting foam, etc. I had sketched plans for using frax panels and spacers a couple of times and recently realized I could use insulating fire brick cut to length (3.5") which would have more height than a panel section and weight to stay down.
I began by buying 4 2'x4'x1/2" hard frax panels - $137. Earlier this week (2005-03-07 with a long forecast of no rain) cleaning out the rolls of frax blanket stored inside, and discovering a pile of damp vermiculite I had forgotten although it was put in last year per note and rusted back wall (bottom).
I shoveled the vermiculite out to dry it and screen out the larger pieces of foam and backer board. (2005-03-10) I cut a piece of galvanized sheet metal to size to fit the bottom. Shown with 3.5" long insulating brick pieces and some left over vermiculite.
I cut the first two long side frax panels for a tight fit and the two end panels to fit inside. It was obvious that the backer panels would form a neat floor and keep the side panels from moving in - a problem I had been working on.
I cut 3-1/2" pieces of frax board and used sodium silicate to glue them at the corners and center to keep panels from moving out.
I have two kinds of vermiculite, fine stuff that I bought last year and the coarse that I bicycled out to get. I guess the coarse is a better insulator, but I have the other and will probably mix the two. [According to internet, not so.] [See below] I installed a thermocouple and fiberglass insulation behind the frax board on the left end.
2005-03-11 Drilled for main thermocouple and two wall temp measuring ones and drilled for cutout for heater coil leads. Cut it out and shaped a piece of insulating fire brick to support the leads and bring them out. Found backer board behind frax blanket in lid. Went out in the evening, put frax in the right end and some backer board in the side slots against the walls. I poured out the coarse vermiculite into the box, added some of the fine, mixed, leveled to 3-1/2 inches taking the extra out, added some water glass, stirred it up with a heavy hand gardening fork, packed it down level with a hoe, cut a 1/2" frax board to size and pushed it into place. I mixed the stuff taken out with the remaining fine and shoveled into the side panels. Not enough to fill. Now I have to buy some more. So do I buy just enough to fill out or buy 4 more cubic feet, suck some of the small stuff out and replace it with what is probably a better insulator in the coarse? Not according to the Internet (below) ["Untreated vermiculite has an average insulating value of 0.016 RSI/mm (2.3 R/in.)"; "has a sintering point of 2300o or (1260o C)".]
As the vermiculite got near the top, I placed 8" wide panels down in the slot and glued them with water glass, then added verm to the top, rapping and pushing it down for good fill. (The white cross piece is a temporary brace.) Then the same flaps at the ends.
|Cleaning the rim, applying water glass and folding down the panels completed this part of the job. Must buy electrical connection stuff [03-15] and should clean, sand and paint the shell - yick!|
|The next series of pictures follows the installation of the coil and the burn out. The coil is a replacement coil for a drier, available at appliance repair sources. It measures 19.6 ohms which means 11 amps at 220 volts, 12.75 amps at 250 volts (my current house voltage is 248 in spring with no air conditioning on) The coil, having been stretched to one of the recommended lengths of 49" was pinned to the insulation on the lid using nichrome wire bobby pins shapes. Frax was used to insulate where it crossed the brace and support wires, as well as small folded clay shapes on the wires. This pictures shows after the second heating with black soot from the binder of the insulation.|
image shows the mount for the ends of the heating coil and the thermocouple.
In the inset is the block of insulating fire brick with holes drilled
diagonally, glued into the frame of the lid. Below the inset the wires at
the end of a standard 30 amp 10/4 dryer cord come out of the cord which is
fastened along the side of the lid. The green wire is screwed to the
housing for ground. The black and red wires are held by split bolts to the
straight ends ends of the coil. The white neutral wire is not connected as
yet and will be used for an indicator light.
To the right as we look down at the end, an 8 gauge K-type thermocouple is mounted through the wall (the tip is visible in the 2nd picture below). It will be supported by the corner iron shown loosely screwed in place. The white block is a porcelain connector from the couple to the plug wires. Silicone (GOOP) adhesive was applied at the white tube insulators to keep them from moving. The yellow connector to the right is a standard K-type mini-connector that I use for all my thermocouples, this one attached to a wire couple installed in the wall to measure in the wall temp. To be added are more support for the wires and a wire cage to keep fingers away.
|In this picture are the three boxes mounted on the utility post. Just above the picture is an outdoor circuit breaker box with two single 20 amp breakers and one double pole 30 amp breaker. The grey tube to the right is the end of the underground feed from the house. The white lidded box is fed from the top and contains 2 duplex outlets, one a GFCI also protecting the other. The old annealer and its controller are plugged in there. The overhead lighting is on the other 20 amp breaker. The larger protruding box is an in-use outdoor cover over a standard 30 amp 4 wire dryer outlet. It is fed from the breaker box via a connector behind the white covered box. And finally, the small grey box is the terminus of a signal wire run through conduit from the house when the AC wire was put in, to provide phone, computer, etc. connections. Also ending, just below the picture, is a buried yellow natural gas line, just in case. The 30 amp dryer cord exits the box cover down and to the left. The box had to be modified to take the cord as normally the latch is centered below the outlet.|
|This is the appearance of the box after the second heating. The first heating was to just above the boiling point of water, to burn off crud on the coil and start the drying out process as well as checking clearances of electrical connections. The end of the K-type thermocouple discussed above projects about 2" into the box about half way down. The second heating took the box up to about 750F at which point it stalled, presumably because of heat loss through damp insulation. The third heating got up just over 900F, at which time it was again allowed to cool down. The fourth heating went to 1150 and the brown insulation was again turning white. 2005-03-21|
Contact Mike Firth