Dunham 197 Adjusting Regulating Fitting: Key/Wrench?

LudgerHentschel

We have an older 2-pipe steam system. Many Dunham parts remain throughout the system.

With information from this forum and the related books, I have managed to restore several parts of the system and it generally works quite well and at very low pressure. Thank you.

The main open issue is that we have several recessed/in-wall radiators/convectors that stay cold.

When I disconnect the supply side of these radiators, steam rises to the opening quickly. When I disconnect the return side, nothing happens. I conclude that there is an obstruction in the radiators or the attached fittings.

On the return side, the steam traps are fine.

On the inlet side, these radiators have what page 51 of Dunham Bulletin 634 calls a "Type 197 Adjustable Regulating Fitting". I suspect the adjuster/valve is clogged. (All the other radiators without this adjuster work fine. I have not yet removed the entire fitting from a radiator. I have only disconnected the supply on the inlet side of the fitting. It seems unlikely that someone turned off all of the adjusters. But crazier things have happened in this house.)

There is a cap on the adjuster. That comes off easily. Recessed inside is what looks like a custom socket with a few parallel fins. Amazingly, you can see the cross-section in the Dunham illustration. (I have tried to attach a picture.) A tool with 3 parallel blades looks like it would fit. Sadly, a single flat screwdriver blade just bends the fins.

My current guess is that there used to be a special key/wrench for these adjusters but I don't have one and have never seen one. Because the adjusters are just an inch or two from the floor and wall, I imagine three short blades attached to a stubby shaft and a small T or round handle. My internet searches for such a tool have been complete failures, so far.

3 questions:

1. Do these "197" adjusters clog (over decades)?
2. Can opening a clogged adjuster restore proper steam circulation?
3. Most importantly, how do I open these adjusters, preferably without removing all of the 197 adjustable fittings?

If I can get these radiators working again, the whole system will operate remarkably close to original spec, as best as I can tell. I would be grateful for suggestions.

Many thanks,

Ludger

Jamie Hall

Well that is cute. I don't suppose that the special wrench is hanging around in the basement somewhere? Odder things have happened...

Or, seems to me that you might be able to MacGyver one by taking a piece of rod which just fit into the opening and carefully cutting corresponding slots to fit over the fins into the end of it?

LudgerHentschel

Unfortunately, I have not been able to find a suitable key in the basement or anywhere else in the house. I have looked out for this for more than a year now.

The idea of making a key seems reasonable -- unless these things trade at flea markets for pennies.

LudgerHentschel

I made a "key" from 17/32" brass rod. The main trick was to extract the first valve stem. A 1/2" screw driver tip was helpful with that.

With the custom key, I managed to open all of the valves on the cold convectors with the Dunham 197 connector. They were so far closed that I conclude they were deliberately turned off. Why that was desirable I don't know.

One of the connectors was missing its external seal/cap. Are there spare parts for Dunham 197 connectors?

Thank you,

Ludger

Jamie Hall

Bravo! I'm glad the improvised tool worked! Spare parts? My google search doesn't even find the convector, never mind parts. But if you can machine that tool...

EBEBRATT-Ed

What about removing the whole works and installing a valve in it's place if there is room??

Jamie Hall

Oh but that Dunham valve will regulate so beautifully.

LudgerHentschel

I have checked with plumbing supply houses locally and over the internet. Still no luck with parts for the Dunham Type 197 connectors.

I and the local supply houses have been unable to determine what kind of threads are on the cap. That has made it difficult to rig up a cap (from a nut and bolt, for example) and presumably would make machining parts very difficult.

If I replace the incomplete connector, I presume it will be with open pipe. The valves are now wide open and everything is fine. The "standard" valves I have found all look like the handle would stick out from the recess if I used them as replacements.

For the moment, I have put teflon tape on the interior valve stem threads. Under normal operation this seems to hold the vapor pressure and 1/2" of condensation. (Those happen to be pretty similar at our vapor pressure.) I would prefer a more reliable solution. I am worried that the vapor pressure might rise briefly on cold days, break the seal, and make a mess. I may get to test this over the cold weekend!

Thank you,

Ludger

medida

Ludger
I have the same system in a 1936 house I just purchased. Do you have a drawing of the tool you made? Also, were you able to find another cap (I have one where the end of the cap came off). What did you use for a replacement washer
thanks
Dean

LudgerHentschel

Dean,

I apologize for my slow reply.

The tool I made is shown in the photo above. Unfortunately, I don't have a drawing with dimensions.

I made the tool after extracting one of the valve stems with a wide, short screw driver. If the stem is lose, this works OK. I had to check several radiators to find one where the screw driver only did minimal, reversible damage. My multi-blade tool is intentionally softer than the valve stems. On the valves that were stuck, I ended up bending the tool but not the valve stems.

I have not been able to find a replacement for the misfit external cap. Fortunately, the existing loose cap has sealed adequately.

Good luck,

Ludger