Between engineering jobs, I spent a few weeks working as a maintenance mechanic in a process plant, mostly outdoors, in upstate New York, in winter. It was, er, educational.
Much of my effort was spent rodding out frozen drain/waste lines.
A lot of extra effort was expended removing elbows to gain access for a rod or a steam lance, and then reassembling the same damn elbows in the same damn place a few minutes or a few hours later, and realizing that the same operation had been done umpteen times in umpteen winters.
If I were laying out that plant from new, I'd specify crosses and plugs instead of elbows or tees, pretty much everywhere, but especially at least on drain/waste/vent lines.
Yes, everything was insulated and steam heat traced. The original build used 3/8" copper tube and brass Swagelok fittings for the heat trace. Copper tube generally doesn't burst when water freezes inside, but it does swell so much that a Swagelok won't fit, so you can't re-use it. We replaced it as we went with 3/8" stainless steel tube (.010" wt, I think) and stainless Swageloks.
From a pure thermodynamic standpoint, you'd think that installing the heat trace tube against the bottom of the process pipe would be best. ... but the copper tube was occasionally crushed between the process pipe and its supports, which of course stopped the steam flow and caused the process pipe to freeze, so we tried to put the new trace lines at five o'clock or seven o'clock.
One of the interesting things I got to heat trace was a vertical cylindrical closed tank maybe 8 feet in diameter and about as tall. To do so, you make a bar ring around the top nozzle, and tie a couple hundred lengths of string or lacing tape hanging down from that so you can tie the heat trace tube in a spiral of ~3" pitch all the way up. The first team just spliced the trace tubes end to end as they were uncoiled, which put tension on the Swagelok couplings as the tube was pressurized, and kept the tube out of contact with the tank shell near the couplings. So I got to re-do it, by putting a u-bend near each end of each length of trace tube, so the Swageloks were in axial compression as the tube was stretched, the heat trace was continuous, and the Swageloks were outside the first layer of insulation, for easier inspection and repair.
That plant also had a large number of flanged process lines, and specified only Heavy Hex Nuts everywhere on those, just so us poor mechanics only had to drag around one set of wrenches. We also used a crapload of Never-Seez, pretty much everywhere, just so we'd be able to separate those flanges in a few years without using smoke wrenches, because there was a lot of flammable and explosive stuff everywhere.
<tangent>
It was a union shop, so I had to apply to join the Teamsters. They had a vote about it, and agreed, only if I were not allowed to attend their meetings. ... like I would want to.
They figured I had to be a Management Spy.
I was.
I had agreed to an exit interview with the Plant Manager.
... at which I recommended the mechanic with the worst 'attitude', Don, should become a supervisor, because his 'attitude' was just a reflection of his frustration about all the stupid things that went on. The guy had a terrific work ethic and great skills, and knew all the best places to hide and goof off.
Several years later, I was pumping gas, again between engineering jobs, and Don came in to buy gas. He had indeed been promoted on my recommendation, and was doing very well, and was very happy, and thanked me profusely.
I wonder what happened to Don; recently the whole place was torn down and cleaned up at the behest of the EPA.
</tangent>
Mike Halloran
Pembroke Pines, FL, USA
