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tedd's avatar

Fellow fluther chemists, and/or machinists, how would you solve this?

Asked by tedd (14073points) June 15th, 2011

Work question for you. One of our gas analyzers has a clog at the bottom. Without going into too much boring detail, basically at the bottom of the combustion chamber there is a cup with a hole in it. That hole connects to an S shaped metal tube that’s about 6 inches in length, and welded to the bottom of the cup.

About the S shaped tube: We believe it is brass, coated in some kind of other metal (possibly steel but we’re honestly not sure). Its flexible, but not very, and banging it against corners of tables (for reasons I’ll explain later) will leave little “chip” marks on the outside of the tube. The tube is an S shape, but now think of it in 3 dimensions. The top curve of the S is twisted 90 degrees, so if you were looking at it on a flat plane such as an S on paper, the top curve would be twisted out towards you. At the dead center of the S there is a smaller offshoot tube in an L shape, that connects to the center of the S through the smaller line of the L.

We have a blockage in the S tube, and we believe we’ve narrowed it down to somewhere between the offshoot L-tube and the bottom of the S (or the cup at the bottom of the combustion chamber). Using a makeshift snake we were able to scrape out chunks of molten metal and carbon, but unfortunately we can get no more to come out. We’ve tried poking it continuously with wire of various sizes, using our makeshift snake (a pair of small high tension springs), banging it on the table in the area of the clog to loosen it, sonicating it in a methanol bath for 30–45 minutes, firing high pressure air through it, blasting as much high pressure water through it as we could… and we are at a loss.

We have a flow, but its nowhere near as fast as it should be. We are considering trying to dissolve the blockage but are not sure what to use. This is where the question comes in. We’re afraid to use acid (we have high purity sulfuric, nitric, chloric, fluouric, etc) because we fear we may damage the tube. Do you guys have any ideas as to what might dissolve the clog, yet not hurt our tube?

(late breaking news from our analysis of the blockage we pulled out…. the blockage was roughly 40% Sn, 20% W, 8–9% Cu, and ~20% Fe)

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8 Answers

lillycoyote's avatar

Depending on how sharp the curves are in the tube you might be able to get the rest of the blockage out with a power drill and the proper bit and speed using a flexible shaft attachment similar to this or these.

Edit: also, depending on what kind of shaft you might want to tape some heavy guage wire to it so you have more control.

Anyway, just a thought.

thorninmud's avatar

What is the apx. ID of the S-tube?

The_Idler's avatar

Well, as the largest component is Sn, wouldn’t the blockage become softened enough to loosen/get out, at a higher temperature than Sn mp?

Brass and steel won’t melt at that kind of temperature (232degC).

Obviously you will not be at the mp of W & Fe, so the whole mass will not melt, but it should become much softer around 300–400degC, and that temperature will not melt the pipes, even if they are made of brass, so you might have better luck pushing it out…

Tropical_Willie's avatar

I like @The_Idler ‘s answer., except for the Tungsten mp being so high. That’s a weird alloy or slag.

lucillelucillelucille's avatar

Try super-cooling it with dry ice,then attempt to manually clear it as you did earlier.Cooling and thawing may break it away from the wall.
Good luck ;)

tedd's avatar

@The_Idler I didn’t think of MP outside of the analyzers. I’ll have to think about how I can accomplish it. We don’t do much with mp so we have an oven that can probably get about that hot, but its not easily controllable.

@Tropical_Willie Its definitely slag. We don’t run anything remotely close to this alloy, but we do run all of those separately. My assumption is over time they collected, building the clog we have now.

tedd's avatar

@thorninmud approximate inside diameter of the S tube is maybe ¾ inch. Between ½ and ¾ probably (I’m not at work so I can’t measure it). The L tube offshoot is significantly smaller, 3–4 mm probably.

(and yes I’m aware I just used metric and imperial, lol)

thorninmud's avatar

I think I’d try pinpointing the location of the blockage (there might be enough iron in the slag that you could locate it by sliding a rare-earth magnet along the tube), then using a C-clamp to pinch the tube at that location, just enough to make it slightly oval in section. Then pinch it again at 90 degrees from the first pinch to restore the round. Might fracture the clump, or break its grip.

Good luck, and keep us posted!

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