Column Style Steel Radiator, difficult to seal threads
I'm picking up the torch on this one, although I see others have struggled with a similar issue without apparent resolution, for example:
I have a number of Hudson Reed Radiators sold for the US market, along with their thermostatic valves. The valves are connected by a compression end onto a radiator tail that is threaded on the radiator side. The radiator tails bottom out and don't seal. The manufacturer has replaced the radiator several times under warranty, but their support never responds to my inquiry of how the radiators are threaded, bsp or npt. I attempted to connect two npt fittings, the shorter one clearly did not seal, the longer one did, kind of, but the connection seems imperfect. Sometimes it happens, but I have a feeling these are BSP female internal threads. From my research online, it appears that in places where BSP threading is used, it is very uncommon to produce a BSPT(tapered) female internal thread or coupling. Instead a BSPT(tapered) male fitting is paired with a BSP straight threaded female internal thread, which apparently will seal, while the reverse(straight male thread and tapered female) will not. In the US, npt female threads are common, and I'm unaware of whether an NPT male would seal with an NPS female. I'm considering trying to order a 15mm x BSPT radiator tail and hope it has a longer tapered thread than the one provided with the Hudson Reed valve. However I'd likely have to order from Europe, and it's hard to see how long the threads are. I'd love to hear any advice or ideas on how to get this to seal well. Thanks!
Comments
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Don't they seal with a gasket on the face?
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Hi, thanks for the quick response. Apologies, but I accidently posted before finishing my post. It's my understanding that BSPP(straight thread) male will seal to BSPP female with a gasket or o-ring. However, the fittings supplied have a flange the same diameter as the thread, so there is clearly no room for a gasket of any sort, nor did it come with one, and the directions do not discuss one. It may be possible to order a radiator tail that does seal with a gasket, although I'm not sure whether that type of seal will last as long as a thread seal, though I would certainly prefer it to the leaky connection I now have. The leak corrodes the radiator and destroys the paint. However as discussed above, I think it's supposed to seal as a BSPT tapered thread to BSPP female thread. What do you think makes sense here?
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I think they use hemp in the threads in europe. you can also use the setting type thread sealant the other thread mentions.
Even with tapered threads you need to use pipe dope or teflon tape for them to seal under normal conditions.
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Many BSP connections are sealed with Loctite thread locker. 545 and 272 are what we use at the factory. Sometimes Loctite and a nose gasket.
Hemp or Loctite 55 string may work, but it is not a pretty look.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Thanks Matt. I try to use a high quality tape and/or dope when I make threaded connections. In this case, I used the Oatey pink tape which is indicated for water, but is quite a bit thicker(perhaps similar to the yellow gas tape) than the slightly cheaper white tape that is common. Other tapes I like include megatape and blue monster tape. But even when I use the cheap white tape, I have enough experience that I never have a problem, it's just a little easier with good tape and worth it to me. After experiencing the difficulties making a good seal, I tried added dope as well as tape, which I have seen can help with a difficult joint. In this case I used Megaloc, which I believe to be a high quality product, and never had a problem with before. Some videos of UK plumbers show a thread sealant product that looks more like a string than a tape. I didn't think it would make a ton of difference where dope was also used, do you think it might?
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The loctite 55 is teflon string. you can also use ball wick which is thin cotton string and can make threads with larger gaps seal along with teflon dope.
Er I guess loctite 55 is actually nylon with a dope in it.
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Ah ok, that's interesting. I did not realize these products were used or recommended to seal plumbing joints. I'm a little hesitant to use the red loctite, since it's possible the radiator may need to be removed for service, or to paint behind it, and heating the joint to 500 degrees F might damage the paint.
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Is loctite 55 designed to seal a straight threaded joint?
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Hydronic Alternatives has fittings to deal with the BSP connection problem. Phone support was fantastic.
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Handle with care, it is for smart installers and daring professionals. Do you see yourself in that category? :)
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream
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A tapered thread on both sides, with a little tape or dope, it works just great. It's not difficult to machine. The connections are pretty forgiving. Do plumbers in Europe really go from job to job hemping and stringing these joints? I honestly don't know, I'll try the product. If that's how it works then fine. But normally I have viewed tape and compound as a helper, or a backup, I thought the threads should mostly seal themselves.
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well you can read several threads with like 5 pages about this but the conventual wisdom is there is a spiral gap between the peak and valley of tapered threads that needs something like dope to fill in that gap and seal it.
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Thanks. Not challenging the need for tape or dope, I always use them. But in this case I used both on parts all supplied by the manufacturer, and I can't seem to get it to seal. I'm a little skeptical the solution could be that string was supposed to be used, but I'm willing to try just about anything at this point.
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These two will set you up perfectly for the Myson. Or you can be a daring professional. I don't believe that being a daring professional will last indefinitely. They tend to begin a slight drip over time.
https://www.supplyhouse.com/Caleffi-940451-Radiator-Adapter-2-Pack
https://www.supplyhouse.com/Caleffi-437516-1-2-Compression-Fitting-for-Manifolds
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pipe fitters in Europe like the straight thread as every pipe they cut ends up being the correct length. With tapered threads you never know exactly how much the thread make up will change the fit. With the straight thread they can back off to make the fit exact. More like a nut and bolt.
From my visits to jobsites around our factories in Italy, Pex tube or soft copper with either press fittings or compression fittings, is most common. Threaded fittings into radiators with hemp or 55.
New HVAC in commercial work is mainly press/ stainless piping.
Hydraulic piping on construction equipment is commonly straight threads with Loctite locker adapters to flare for hose connections.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
This ^^^^.
The other comment I would make — and it may be unpopular — is that there is no excuse for trying to make up a fitting with one standard of thread on the female half and another different standard on the male half. Even if you are so fortunate that the major and minor diameters are the same somewhere along the fitting, and the thread pitch is the same, it is — at best — poor practice. Those are not the only parameters for threads — groove included angle and crest and bottom radii are others. Use matching fittings, or the correct dies if you are making new threads, or use an adapter.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
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How does this work, I use the 940 adapter and then sweat in a copper tail? Might work, although I was thinking these below would look better if we think a gasket seal is the way to go, which I'm not sure of. Screwfix doesn't ship to the US, may have to find a shop that does or a friend to help. Was trying to avoid using a grey market part since the radiator is sold in the US, but it might make more sense to use the correct part, than a defective one. Another issue would be maybe needing to re-rough the radiator to make space for the fitting, not sure if that would be the case. The specs say it is "1/2" M Radiator". So what is that? Is it BSP, NPT? Tapered? Something else?
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The compression fitting screws to the radiator adapter. It has an o-ring. You don't sweat anything!!
An o-ring seal is always the way to go with straight threads. The radiators are designed for that.
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My limited research seems to agree with that, I read that it is seen as more difficult/expensive to make internal tapered threads than external. Which I interpreted to mean that the male fitting can be threaded too far and it will likely still work, but the internal or female fitting if over threaded won't mate properly. Apparently using a tapered male with a straight female is the accepted solution. And yet, on this side of the pond, NPT fittings mate up just fine every day. I've got the daring loctite 55 on the way, any tips on how to use? I'm a little hesitant to install red or blue liquid loctite, because it may be more difficult to service the joint if I need to. Heating with a torch could damage the paint, and the residual may be difficult to cleanout to re-seal, am I wrong? Thanks for the help.
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[Eastern European accent]
Linen thread. Just like in old country.
[/Eastern European accent]
Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.0 -
Oh I that sounds promising. You think there's any chance I'd find a chrome one? How do I connect to this valve and lockshield? It's a compression with a ferrule, probably either 15mm or 1/2 inch. The bottom piece connected succesfully to 1/2" copper tubing.
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Just to be clear, I'm not trying to do that, I'm trying to avoid it. However it appears that engineers in Europe typically specify a tapered male BSPT with a straight female BSPP fitting. Using a "matching" fitting would mean a either a BSPT fitting if you consider that a match, or a BSPP straight male fitting, which would not seal without a gasket. I'm not sure if it's kosher in the US to seal a radiator with a gasket, might be a question of what the manufacturer of the part and radiator recommend, which is unclear.
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I don't know if it comes in chrome.
You just use 1/2" copper tubing and it sits inside the o-ring. Where you go from there depends on the valve that you have.
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Got it, so I'm basically building up the screwfix fitting. But from parts that we've been able to identify so far in the US.
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Despite the claims I have never had trouble unscrewing red loctite with hand tools although I have never used it on pipe.
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I'd be worried that you could completely rip out the welded boss on a panel radiator. They are nowhere near as strong as a pipe.
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