Wikipedia:Reference desk/Archives/Science/2019 February 6

= February 6 =

Plumbing problem
What's the best way to loosen a seized union? I need to loosen one in order to turn around an elbow which is pointing the wrong way -- but in the process of attaching said elbow, the union seized so hard that I can't loosen it with even the biggest pair of wrenches I have. Any ideas? 2601:646:8A00:A0B3:64EB:2E36:2529:F033 (talk) 04:49, 6 February 2019 (UTC)
 * Maybe a blowtorch, or just chisel it off? Abductive  (reasoning) 06:08, 6 February 2019 (UTC)
 * A blowtorch would be too dangerous, and as for chiseling it off, it costs over 100 bucks to replace (and has to be ordered in advance) -- I don't want to ruin it! Could boiling water help loosen it? 2601:646:8A00:A0B3:64EB:2E36:2529:F033 (talk) 07:54, 6 February 2019 (UTC)
 * Depending on the materials, it is probably galled and therefore already ruined. Depending on lots of other things you could use a tube cutter to get it off. A picture would help.   Kees08  (Talk)   08:00, 6 February 2019 (UTC)
 * It's stainless steel, so I don't think it's galled. 2601:646:8A00:A0B3:64EB:2E36:2529:F033 (talk) 09:59, 6 February 2019 (UTC)
 * I take that back -- I just checked and stainless steel is indeed subject to galling. And my attempt to use heat (within safe limits) met with no results, so I think it might be galled after all -- so it looks like I'll have to order a replacement for this brand-new $100+ part!  :-(  (Well, at least they can ship it within 1-2 days, so at least I won't be delayed too long.) 2601:646:8A00:A0B3:64EB:2E36:2529:F033 (talk) 10:35, 6 February 2019 (UTC)


 * Why is a blowtorch dangerous? Heat or naked flame?  Many garages are now (for similar reasons) heating seized nuts and bolts with small induction heaters instead. Andy Dingley (talk) 10:55, 6 February 2019 (UTC)
 * It's the naked flame that's dangerous -- my setup is in a wood-frame building, I don't want any accidents! 2601:646:8A00:A0B3:64EB:2E36:2529:F033 (talk) 11:19, 6 February 2019 (UTC)


 * Perhaps you can use a bigger wrench, or extend your wrench handle to get more leverage. There are custom wrench handle extenders that won't break your tool, or perhaps you can use a pipe to fit over the handle. In my experience overtightening stainless steel nuts on stainless steel bolts can do a cold weld which can be stronger than the bolt shaft. Galvanised iron avoids this as the zinc is much weaker. Graeme Bartlett (talk) 21:40, 6 February 2019 (UTC)
 * Fit a pipe over the wrench handle?! Thanks but no thanks, I won't risk my hand in this manner!  And since the problem was solely due to overtightening, I suspect that galling/cold-welding is exactly what happened -- in which case the threads will break before the thing will loosen! 2601:646:8A00:A0B3:64EB:2E36:2529:F033 (talk) 08:30, 7 February 2019 (UTC)
 * Cut the pipe and join it with a coupling after the elbow is facing the correct way? Rmhermen (talk) 09:27, 7 February 2019 (UTC)
 * My first design actually had a coupling -- the result being, either it was undertorqued and leaking persistently, or else the elbow was pointing the opposite way from where it was supposed to -- hence my decision to replace it with a union! And for the record, I had taken the union off without any problems -- it wasn't the ends that had seized (they cannot seize because they're NPT threaded and I always use Teflon tape on those), it was the union nut (because I foolishly allowed the torque from tightening the valve assembly to be transmitted to it!)  And I've already ordered a replacement union (should be here by Monday, and I'll do it right this time!) 2601:646:8A00:A0B3:64EB:2E36:2529:F033 (talk) 10:09, 7 February 2019 (UTC)
 * I'm glad you came up with a solution in the end. My feeling is that everyone knows that for a plumbing problem, what you need isn't a college degree but a plumber -- it would have disappointed my expectations if we or any science group had come up with something practical and not obviously stupid.  I mean, I think maybe you could sonicate the joint, maybe you could cool the inner pipe with an ice pack while you heat the outer one with a hair dryer or a soldering iron, maybe try to work some gallium into the joint and corrode it apart ... yeah, you want a plumber. :) Wnt (talk) 15:31, 7 February 2019 (UTC)
 * And it just so happens that I'm a chemical engineer doubling as a DIY plumber :-) 2601:646:8A00:A0B3:64EB:2E36:2529:F033 (talk) 03:37, 8 February 2019 (UTC)
 * NPT threads can seize even with PTFE tape. You have to try really hard, but it can be done (see my photo on the galling article of an NPT fitting). - Rocket plumber that sees the handiwork of undertrained technicians. In general with stainless, cleaning threads increases the likeliness of galling. Lube those bad boys up and you should be good to go.  Kees08  (Talk)   08:14, 8 February 2019 (UTC)


 * I am happy the problem was solved, but I cannot let the advice given above stand unchallenged. When dealing with seized metal threads, "use more force" (e.g. longer leverage) is exceedingly rarely a good idea, and never the first thing to try. You risk killing the screw thread for good, and the best-case scenario is you separate the pieces but destroy at least one of them. The first thing to try is lubrication (there's an old flowchart making the rounds of the internet where the path "it does not move, but it should" ends on WD-40).
 * Also, do you have any reason to use a custom-made union? (Unless you live in Antarctica or something, if your local DIY store charges more than $100 for a standard plumbing brass piece, change providers.) Tigraan Click here to contact me 10:59, 9 February 2019 (UTC)
 * This is definitely NOT a "standard plumbing brass piece" -- this is a heavy-duty, high-pressure (1000 psi rating) stainless steel piece made for chemical service (in my case, acids under high pressure!) And that is why it costs so much! 2601:646:8A00:A0B3:64EB:2E36:2529:F033 (talk) 11:30, 9 February 2019 (UTC)
 * If you give me a part number or the size/type of connection it is, I can give you a recommended torque value for it. What lubricant do you plan on using?  Kees08  (Talk)   19:11, 9 February 2019 (UTC)

Inside of cat mouth color
I saw a cat with a bright pink shade with very little purple in it. What might that mean? Inflammation? Sagittarian Milky Way (talk) 20:32, 6 February 2019 (UTC) Stray cat, not veterinary advice. Sagittarian Milky Way (talk) 20:34, 6 February 2019 (UTC)


 * It can be a multitude of things. So even if we were allowed to give a diagnosis, it would be impossible based on this only. You may want to read   for starters. Hope this helps. Dr Dima (talk) 22:10, 6 February 2019 (UTC)


 * A vet could probably give you some possibilities too, though not necessarily for free. ←Baseball Bugs What's up, Doc? carrots→ 10:05, 7 February 2019 (UTC)