Figure 206 ACME Thread dimension

[OKCMET]

I'm in the process of modifying a relief valve we manufacture to have an outlet for this particular hammer union. It's for a 4" union and so far I have only been able to find that the ACME thread is 4-3 modified. I can't find any dimensions for this type of thread to give our machinists. Has anyone been able to find a website that has thread dimensions outside the narrow scope included in the machinery handbook?

Also, I'm a little concerned about setting this up where the hammer nut connects the pipe to the valve(acme threading being on the valve). Looking at it, wouldn't the angle between the two pieces possible cause a leak path since flow would be in the same horizontal direction as the angle?

 

[flash3780]

Why not just reference the ASME standard? ASME B1.5-1997, I believe.

 

[btrueblood]

" the ACME thread is 4-3 modified."

Without knowing what exactly has been modified, you are stuck. Request more clarification from the manufacturer, or get a sample part in so you can inspect it and make a mating thread.

"Looking at it, wouldn't the angle between the two pieces possible cause a leak path since flow would be in the same horizontal direction as the angle? "

The picture you showed has an o-ring seal on the conical union face, not clear where your leak path concern arises. I don't have any concern about the direction of the union taper angle for leak tightness, at least for an intermittent flow from a relief valve. Might be an erosion concern over time, but unless the valve/union is passing fairly abrasive flow, I wouldn't worry about it (and the good news is, it just means the customer will have to keep coming back to buy more valves when these open up).

 

[OKCMET]

We don't actually have B1.5 and we don't change change acme threading enough to justify getting it. (We sell MAYBE 4 of these valves a year and they're usually standard.)

I figured I was going to need to contact a supplier but I was hoping I would be able to find a chart with more sizes on it.

Thanks for the input. I'm at least in a better direction than I was before.

 

[Cockroach]

No magic here, that's a WECO Hammer Union or equivalent. I built many of these using a course Acme thread, typically 4 TPI.

Just go down to your local oilfield supply store and buy one off the shelf. They're cheap since made hundreds at a time in China. You could measure it up and then turn out a better product for internal use only.

Done.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[OKCMET]

Thanks for the responses. I've pretty much decided to just order one of the three piece unions because the customer hasn't specified which end they are needing and then I'll have it welded on. This will probably be the only time we end up selling the valve with this particular outlet so I'm trying not to waste too much time in design/production.