Machining Orifice Radius

[regestjl]

I have a 2ft long 1" SCH 80 pipe (stainless steel) that is flanged on one end and capped on the other. Near the capped end, I have an 0.051" diameter orifice that is drilled radially through the pipe wall. The flow goes from the inside of the pipe, through the vessel, and into a tank. I need to lower the pressure drop through this orifice but I can't change the overall diameter of the orifice due to design constraints. I was going to try to put a radius/chamfer on the inlet of the orifice which is on the inside of the pipe.

My options so far are to
1. Drill a larger hole through the pipe on the opposite side of the orifice to gain access to it's inlet side. Use a larger drill bit to put a chamfer on it. Then fill the access hole with weld.

2. Cut the section of pipe out and slice it radially to gain access to the inlet. Put the chamfer on it. Then seam and circumferentially weld it back together.

3. Find a tool (like a router) that can pass through these holes from the outside and put either a chamfer or radius on the inlet (prefferably a radius). I haven't found anything yet but have heard that there may be such a thing.

Anyone have any guidance or experience trying to do something like this? Are there tools that could do this radius on the ID of the pipe accessing from the OD? I've thought about using a smaller grinder bit, sliding it through the hole from the outside and angling it to put a chamfer on it but with the thickness of the pipe and size of the bit needed, I imagine I'd just snap a bunch of bits without doing much good. Plus, I can't really get the geometry for the orifice that I want that way.

Any thoughts?

 

[STYMIEDPIPER]

If your Code permits depending on pressure & temp

Drill existing orifice slightly larger than required
Use dummy plate same thickness as pipe
Chamfer and drill orifice as required in dummy plate
Weld dummy plate to OD of pipe similar to a reinforcing saddle

 

[regestjl]

Thanks for the response. Actually, my orifice consists of 8 side by side orifices. By cutting out the pipe, machining, and re-welding, (option 2) I'm essentially doing what you suggested. I guess I'm looking for a way/tool to avoid having to re-weld my pressure boundary like that.

 

[MikeHalloran]

- Machine the orifice you want into the tip of a stainless machine screw, say #8 or bigger.

- Drill and tap the existing orifice to accept the machine screw.

- Run the machine screw in far enough to make the tip flush with the inside.

- Break off the screw proud of the outside and grind it flush.

- Use a TIG torch and young eyes to make an autogenous seal weld at the periphery of the screw threads on the outside, or at least make a little puddle to tack it in place.







Mike Halloran
Pembroke Pines, FL, USA

 

[hydtools]

We have created orifices using hex socket pipe plugs. You could drill and tap the pipe for NPTF threads. Use 1/8 NPTF stainless pipe plug with the drilled and chamfered orifice. You then have an internal wrenching orifice plug. No need for welding.

Ted

 

[Compositepro]

Try these guys.

http://www.birdprecision.com/orifices/

 

[hydtools]

You might try Nobur to see if they can make a custom tool for the small diameter. The smallest standard tool appears to be for .090 diameter.

http://www.cogsdill.com/pdf files/usdeb_nobur.pdf

Ted

 

[Broach]

Any chance to make a 2nd hole same size and tap into your extension?