Barnes & Jones Hoffman 17C Trap Repair Sales Demo Kit

Gordo

For your viewing pleasure, an old B&J trap repair sales demo kit with a cutaway of the old style Hoffman 17C thermostatic steam trap.
https://www.youtube.com/watch?v=IRHLs17t530

Sailah

What do you mean old? We just had those boxes printed in 1964.

KC_Jones

1964? That's modern.

Sailah

Here's mine in the office

Gordo

@Sailah : Thanks! Your sales kit looks like it's for a type of Trane B1 (integral seat, removable bellows) .

gerry gill

thats really cool Gordo! You always have the best toys!

MilanD

So how old is this one, with only a disc?

Sailah

Not that old. That's the old style Hoffman 17c. The new one is called the Bear Trap and is short and squat like a hockey puck vs ice cream cone.

Gordo

@Sailah : am I right in my understanding that the old style Hoffman 17c and the new style Hoffman 17c, aka "The Bear Trap", both take the same B&J #3500 cage unit, but the new style Hoffman 17c absolutely needs a new B&J #3500 cap as well?

It looks like the old style 17c can just use the old 17c cap, as shown in the video.

Sailah

Gordo said:

@Sailah : am I right in my understanding that the old style Hoffman 17c and the new style Hoffman 17c, aka "The Bear Trap", both take the same B&J #3500 cage unit, but the new style Hoffman 17c absolutely needs a new B&J #3500 cap as well?

It looks like the old style 17c can just use the old 17c cap, as shown in the video.

You are 100% correct. The only reason for the cover is simply to get the height to fit a cage unit in with the spring. The old Hoffmans were taller so they use the factory cover.

MilanD

> @Sailah said:
> Not that old. That's the old style Hoffman 17c. The new one is called the Bear Trap and is short and squat like a hockey puck vs ice cream cone.

How did this trap work without any expansion unit inside? It seems only to have this disc float.

Gordo

@MilanD : If I may, the "disc float" as you call it, was the expansion element. It is totally broken apart. There's was not that much to that thing, really.

That style of 17c element is no longer made by Hoffman, although old stock still exists. It should surprise no one that some of old stock is in our shop ;-) .

A 7/16" wrench can be used to get the remainder of the element stalk from the cap. There was a steel lock-nut washer between the stalk and the cap, but is totally rusted!

The seat is removed with a 3/4" socket.

If the 17c is to be used for a tiny radiator, a Hoffman "durastat" can be installed with that same 3/4" socket. The durastat is notoriously slow in venting, as shown by @gerry gill's invaluable venting charts.

To give a reasonable venting through-put, I'd use the B&J #3500 cage unit to rebuild this puppy.

Sailah

MilanD said:

> @Sailah said:

> Not that old. That's the old style Hoffman 17c. The new one is called the Bear Trap and is short and squat like a hockey puck vs ice cream cone.



How did this trap work without any expansion unit inside? It seems only to have this disc float.

The disc works the same as our cage unit in principle. Inside the disc is a mixture of alcohol and water. This "juice" lowers the flash point of the liquid inside. When steam hits the disc it flashes the liquid which in turn expands. By expanding it pushes the plug up against the seat and seals the trap. When enough condensate has accumulated in the trap body it will subcool the disc slightly. That causes the plug to lift slightly and condensate to drain.

In practice it looks like a steady drip from a faucet, it's not an event like a bucket trap when it comes out in gushes.

I'm not a big fan of discs although they are still made and indeed I use them in the Big Mouth. The reason is simply flexure. The cage unit has more bend points so I personally feel it won't work harden as fast as the disc. The other reason is that replacing a disc doesn't renew the sealing surface of the seat where a cage unit does. In the Big Mouth those concerns weren't needed as the disc stays closed for an entire cycle vs modulating like a trap would. And the sealing surface on the vent shouldn't be seeing dirt and rust like a trap would.

MilanD

Thank You @Sailah. I wasn't aware the disc had the liquid inside. The rest of it also makes sense.