Monday, February 02, 2009

Sippican's Thermopylae Of Thermocouples, Part The Third

[Editor's note: We continue the seemingly neverending saga of Sippican welding in the desert. It was uphill both ways in the snow, in the desert, apparently.]

{Author's note: The fancy writing dudes always pooh pooh physically demanding things. Mental toughness is a form of intelligence, if you ask me. There is no editor.}

I've read that it's smells that humans remember the longest, or are the most likely to jog memories. After positing that, the pseudoscientists often talk about Grandma's cookies. Let me tell you about smells.

It smells like exotic bread is baking near the dust collector when you put pine through the drum sander. You know the fine dust is giving you nose cancer and lung trouble so you're almost immune to its charms. Almost. There was this smell once, when I had to renovate an apartment a guy died in. He was in there a good long time, too. It's the smell of the mass grave. That was fun. But nothing can compare to the smell of the abrasive cutoff saw going through steel. It makes brimstone smell like French pastry.

You see, to cut metal like that you don't often use a saw with teeth. It's just an abrasive disc, and you send a shower of sparks and an acrid, burning blast of stink up your nose. It's like snorting sand from the outdoor ashtray next to the door at the place they hold Alcoholics Anonymous meetings. I'll never forget it.

Work started about a half hour before you were scheduled to go to bed, so there was a dreary weariness writ on everyone's face. There was a huddle with everyone looking off into the middle distance, while Larry, the Hawaiian guy with the Long Island housewife afro told us what to do. All the work was tracked on little yellow index cards in pencil. There wasn't a lot to know; outside diameter of the stainless steel tube, length of the finished probe, and what kind of metals were used for the electrodes inside the tube. We made all kinds, but it was mostly J and K types, which are common things made from common metals. By common people, Larry's aureole of hair notwithstanding.

The raw stock to make the thermocouples was coiled to make it easy to store, and simply labeled with a tag tied to the coil with a letter on it. You'd find the coil, which weighed a bit when it was new but was infinitely more appealing than handling the light remainders of the coils. The guys that had worked there awhile never touched the bits and pieces and broke open new coils all the time. Sooner or later someone had to face the short, stainless steel straw, though.

You had to straighten out the coiled pieces by shoving them through a machine called a desuager. A desuager is just a revolving bend. You feed the SS tube through a yoke with three holes. Input output, and the middle. The middle hole is offset from center. The yoke was spun by a motor, and you have to hold on for dear life to the coil as the revolving bend tries to spin it -- and you--all around. It's easy to hold onto the big coils of small diameter tubing, but the scraps of large diameter stuff were almost impossible to hold. You'd clamp the world's oldest Vise-Grip to those and hold on for dear life. More about that later.

So you'd straighten the coil out, and use the abrasive saw to chop them to length. 20 ea K 1/4" 24" is all the work order would say on it. You didn't measure, there were rude markings in pencil on the work bench from the first person who worked there, and you'd use them. Then you got the smell.

It was starting to get hot now. The metal roof sorta glowed with it when the sun started rising up in the sky. So we did what any intelligent person would do. We climbed a ladder to get closer to it.

You see, the shop was set up to handle the largest thing we might sell, not the usual two foot trifle, so you climbed a sort of gangway ladder to a tower where you'd weld. You were working on the tip of the thermocouple, and it had to be oriented vertically. To this day, I can't understand how I climbed up there carrying all the welding stuff and the thermocouples.

The Road Warrior came out shortly after I worked at this place, and I thought they filmed it on location there. It was a barbarous set of circumstances. You'd sit in the kind of chair you'd find at a flea market held outside a torture dungeon, the hot metal roof right over your head. In front of you was a Fred Flintsone looking vise arrangement with brass jaws with a series of holes drilled in it. You'd clamp the thermocouple stock in the appropriate circle, and get to work.

You had to sandblast the insulation out of the tip of the stock to expose the two electrodes inside. And now you had to weld them together. To work, a thermocouple joins two dissimilar metals at one end, sticks that end in the nasty spot full of incredible hotness, and you measure the tiny voltage at the other end with a meter to tell the temperature. The operative term here is: dissimilar.

It's hard as hell to weld identical metals together properly. Welding dissimilar metals is impossible. You do it, but I stand behind the word: it's impossible.

It becomes possible because if you falter once, you will be immediately fired and the other 135 guys that got passed over get their shot. It's possible because if you tarry on the only tower, the other ten guys waiting to do their work while you fumble around will meet you outside after work, and they don't knit for a hobby. You'll lose the only job you can find twenty-five states away from the place of your birth and you won't even have enough money to drive home to be poor there in the snowbanks.

So it's not even possible. It's downright easy.

(to be continued)


Daniel Newby said...

I hope you were using a spot welder. That's the only way to weld the usual thermocouple metals.

The worst thermocouple I ever tried to weld was a micro-coax type. I eventually just gave up. You'd need a microscope and a fancy jig to do it.

River Cocytus said...

Yes, I did notice that 'impossible' tasks - especially in my case driving tasks - become 'extremely facile' in certain situations such as, and not limited to, impending death. Also mutilation and desolation and destitution also seem to work too.