Steam traps - Hoffman no 18

Koan

The house I am moving into has Hoffman no 18 traps on the radiator returns (2 pipe). Looks like both Tunstall and Barnes and Jones make replacement guts. I discussed with a pro the Tunstall parts in a Hoffman 18 and he explained that when they do it they replace the cover and it says "Tunstall". Indeed one trap does say this. Here are my questions:
1) Is it necessary to get a new Tunstall TA-CVR-1411 cover when installing a TCHF-1411 capsule in a Hoffman 18?
I got the impression from the pro this was needed, but Tunstall said not needed. Maybe they did to know which ones they worked on.
2) Is the Barnes and Jones #2211 just as good a part as a capsule for the Hoffman 18?
3) If I had to replace the Hoffman 18 with an all new part, what would be used?
I can't seem to find a new Hoffman No. 18, but the 8C, 9C, 17C, & 17K all look the part.
4) Any tricks I might need to know??

I appreciate any help I can get in learning about this stuff - Thanks!

Sailah

1.) I do not believe the Tunstall requires a new cover but I would trust them to answer that definitively. Ours uses the stock cover

2.) I won't pass judgment on who makes a better trap. We feel that our phosphor bronze diaphragm is better suited to mechanical movement than a welded stainless bellows. We make both but it's our opinion that the stainless work hardens over time and is more prone to cracking. Again, our opinion.

3.) To replace the Hoffman with an angled radiator trap you can chose from a variety of manufacturers. Their 17C, our 122A, Tunstall makes a 1/2" trap, Watts 1G (old Illinois 1G) etc.

However I would not recommend replacing the trap unless you feel it's leaking somehow. I believe all the others are making their traps overseas except Tunstall and I know we make ours (Barnes & Jones) here in Massachusetts from start to finish. The quality of the overseas elements is terrible.

So keep the trap you have, it's cheaper, you won't risk breaking pipe and it will be a better repair. You gain nothing other than shiny brass to swap out a trap.

To renew a trap, get 2 crescent wrenches and grab the hex on the bottom of the trap with one, and put the other on the cover. Hold equal pressure back on the bottom wrench as you unscrew the cover. If you don't you risk ripping the tailpiece out of the radiator and now you have a mess.

Remove the element, the 18 has an integral seat. Drop the new element in, maybe a touch of anti-seize on the thread covers (no pipe dope and no Teflon tape) and screw cover back down.

That's it. Any questions you are welcome to call me at the office if I can be helpful.

Sailah

If you can't get the cover off, lightly rap with a ball peen hammer around the cover. Lightly. The percussion of the rapping will loosen the grip on the threads. If that doesn't work, you can heat with a torch the female part of the trap (body) until it is 300 degrees then take an ice cube and cool the cover. The thermal differential breaks the bond as well.

We use an impact wrench at the factory.

nicholas bonham-carter

Have you verified that the traps are not working?
follow the route the air takes to escape, and make sure the route is open.
Don't forget to check any cross-over traps as well.keep the pressure down with a vaporstat, verified by a low pressure 0-15 ounce gauge.--NBC

Steamhead

Sailah said:

We use an impact wrench at the factory.

We use an impact wrench on the job!

SWEI

https://www.milwaukeetool.com/power-tools/cordless/2764-22

Sailah

Yeah that would work lol. Might be a little overkill for a couple rad traps

Gordo

@Koan. It is largely true that you don't need a new cover with a new element with either the Tunstall or the B&J units for the Hoffman #18. For this trap, the new cover can be thought of as a sign unto others that follow after you that the trap in question has been rebuilt and has the model number for the part therein, should a replacement part be needed.

The covers are sold only a bit above their cost to manufacture as they also serve as proud advertising for their respective companies in solid American brass.

As to getting the #18 cover off, I'd use a 1-1/4" box wrench and strike it with a 40 oz plastic dead blow hammer, whilst holding back with another wrench on the hex on the bottom of the trap. Put a cheater bar on that hold back wrench and hold it in place with your ankle. Hold the 1-1/4" box end down on the trap cover tightly with one hand and strike with the dead blow the other end of the wrench. Two or three wacks and the cover should be loose.

Still no joy? Then go to the impact.

The Steam Whisperer

Also, if the system runs in vacuum, you cannot use the Hofmann traps, they are now only rated for pressure use.

Koan

First and foremost, I must express my deep gratitude to everyone who responded.

@Sailah from Mahsachusetts,
Thanks for the information. I remember materials classes so your comment about Phosphor bronze not strain hardening as much as Stainless might make sense. It would be an interesting experiment, though the environment might be hard to re-create! I hope I do not have to resort to the blue wrench to remove the lid, but I have let it work its magic before. I do have an air compressor and an air impact wrench if needed.
@Gordo - thank you - I have removed suspension components with the same techniques of using two BAWs (Big _ss Wenches) before I got an air impact, or even when the air impact did not deliver enough torque. Thanks for letting me know the change of cover is a signal not a requirement. Knowing I need a 1&1/4 in socket and or wrench is very helpful.

@nicholas bonham-carter your comment: "Have you verified that the traps are not working? follow the route the air takes to escape, and make sure the route is open."

- Sorry my friend but I must ask how to do this. I understand the logic, but pragmatically do not know how to test for this.
My understanding is that it is actually fairly difficult to test a steam trap, and I ma not well-versed enough to test a return line
I think Dan wrote somewhere that traps are hard to test, and the best way was to attach a nipple and valve and open them to see what comes out. I am all ears for any other test procedure.

"Don't forget to check any cross-over traps as well."
Good call - I think there are two of these that I forgot

"keep the pressure down with a vaporstat, verified by a low pressure 0-15 ounce gauge.--NBC"
we are at 3-5 Oz pressure usually.

@SteamWhisperer - this is a two pipe low pressure vapor system. I do not know if it runs under any vacuum. I understand the basics - steam cools, can create a vacuum, everything wants to go to the vacuum because that's what things do. At this point it may be a moot issue as I am not planning on replacing the traps unless I break one. But I think you are saying the Hoffman 18 could function where
a 17C could not. Just in case, how do I tell?

Thank you all

nicholas bonham-carter

Where did you find that great photo?
Traps should be only condensate hot, but not steam hot on the discharge. Perhaps Sailah can elaborate on this, but feeling the pipes can tell you a lot.
I would start first with the crossover taps, and see if they are steam hot, then follow the return piping back up to find the guilty party. Replacing the trap elements would be so much easier, than the whole trap. Sailah's elements come with his advice which is priceless!!--NBC

Koan

@nicholas bonham-carter Thanks! Don't remember where the photo came from, but it seems to go with steam Heat . We have a few cool radiators, so those traps are suspect. I assume they can stick closed, and if the air doesn't get out of the way the steam can't get through. If they fail open the steam goes right through and no joy there either.

Can anyone( @Sailah ) comment on the normal failure mode - do radiator steam traps more often fail and stay open or fail and stay closed?
Thanks! KW

Gordo

@Koan: In our experience, the #18 mostly fails fully or partly closed. Fully closed is easy to find - no heat. Partly closed is harder to determine... the trap is acting like a restrictive orifice and the radiator may heat up enough to be comfortable but not enough for the steam to get into the dry return and cause mischief. If the valve leading to the radiator has a restrictor built in, like the Hoffman #7 radiator valve, the #18 trap, or any trap for that matter, will never see steam due to it being fully condensed in the radiator and the trap won't cycle out to failure.

The cross-over traps have most likely failed and if they are #18s failed closed. I would remove them completely and install the B&J 122. I would consider their "super trap" version (122A-ST) as that trap will see steam every cycle. Have plenty of 1/2" pipe nipples and fittings (90s, street 90s, couplings, etc) handy.

Gordo

Just want to point out that on most other first time trap rebuilds, the cap replacement, if called for in the company's literature, is necessary. The Hoffman #18 is one of the very few exceptions.

vaporvac

So does having Hoffman Traps mean that he probably has a Hoffman system with the differential loop , as does @Jamie Hall ?

The Steam Whisperer

That\s right. The 18 may be fine in vacuum, but I believe any new Hofmann is not. You can double check the box to be sure.

Sailah

I still need to make video where I show how an element is made but ours are filled with a volatile liquid and then we draw them up hard to a stop under 28" vacuum. They are then sealed. So our normal elements (we call them cage units) work from vacuum to 25 PSIG. We make others to 300 PSIG.

It's possible to make cage units fail open or closed. We usually make fail open cage units for radiator traps. Our industrial customers will often order industrial thermostatic traps with fail closed bellows because of their processes. We sell lots every year to Bath Iron Works in Maine, where they build the Navy Destroyers and the foreman told me why but I can't remember. It was some process application.

Anyways, testing radiator traps is not easy. You can divine a little from the outlet temp but it much more preferable to test to atmosphere. If you don't have the facility to do it I always am willing to do it for heating help members. Who knows you might even get a surprise in the box.

This was a contractor I met in New Rochelle couple weeks ago. He had 200 apartment building, all Trane B2 traps. We date all of our covers and all the cage units in the building were 30 years old, some were still the original Trane bellows. These were his traps I was testing so you can see what is involved.

http://youtu.be/6WVzmIjWqqk

Koan

great explanations. I am starting to really see how all this works. a valve that is to let water pass but not steam requires the water to condense before it returns to the return pipe. So , the best way to see how a trap is working is to actually see what is passing through it.

Koan

wait - not sure I got that right? like drinking from a fire hose

Koan

@Sailah - thank you for sharing this information.
@Gordo - Thank you for the failure mode info - upon inspection I think there are several different traps by different manufacturers. Have ot take an inventory. I think there are two crossovers and I will check to see their make and model. I can see there is an are to getting the crossover plumbing in the right place.
@The Steam Whisperer Thanks for the insight on the Hoffman 18

Sailah

No you have it right. A trap closes in the presence of steam because the volatile liquid flashes to steam at a slightly lower temperature. The steam gives off its latent heat which warms the room and when it gives off the heat it condenses to liquid. This liquid will surround the element and subcool it to where it causes the plug to lift slightly and the condensate drains.

Unlike my video, the actual dripping of a radiator is more of a continuous dripping not like an event.

Koan

@ Sailah - I remember this is why you want the water jackets in a car engine to boil the coolant (but just barely) to cool the engine. It's coming back to me now - latent heat of vaporization - The radiator in a car engine then condenses the steam back to liquid and circulates it back to the water jackets to be boiled again. The phase transformation absorbs heat into the fluid. I assume the latent heat of vaporization is transferred from the steam in the boiler, then as the house radiator condenses the steam back into liquid, the latent heat of vaporization is released into the room. Do I have that correct? Thanks Sailah for all the help!

Sailah

I'm not a car expert but I don't think that a car turns the coolant to steam and then condenses it back down. I believe, and I may be totally offbase here, that a car cooling system contains coolant and water mixture along with a pressure cap to raise the boiling temperature of the coolant. It absorbs the heat from the engine block, sends it over the radiator to cool, and then cycles it back again. I don't believe the coolant goes through a phase change.

Koan

then why is there pressure in the radiator?

SWEI

Water expands when it gets hot. Pressure comes from temperature.

JUGHNE

The pressure keeps the coolant from flashing to steam. That is why you don't open the radiator cap when the engine is super hot, the coolant would come boiling out as steam because of the pressure drop.....some have learned this the hard way. Or have a hose break under the hood and you will see steam come out. But as long as it is pressurized it remains liquid.

Koan

my understanding was that there was phase transformation at the fluid layer next to the cooling jacket, and that is intentional to absorb the latent heat of vaporization into the coolant, then the pressure incurred keeps the boiling point higher so nothing but that thin layer vaporizes... but I could be incorrect. it would make sense though to use the phase transformation to one's benefit to transfer heat from the engine - alas I am getting off topic. Thanks for the comments!

SWEI

Koan said:

my understanding was that there was phase transformation at the fluid layer next to the cooling jacket

On a micro-scale, there often is. It can cause all manner of bad things in Diesels.

Koan

cool beans - thanks! and I appreciate the water main comments as well!