Round Peg in Elliptical Hole

What sort of pressure vessel?

What is the pressure vessel made of?

What fluid is in it, at what temperature and pressure?

What does the vessel's burst indemnity insurance company's Engineer/Surveyor have to say on the subject?

Are you saying your access door is elliptical in shape?

Once you know that you can safely make this modification it will be pretty easy to do.

1- find your tank wall radius

2- make your fitting ( elliptical to round with the proper radius angle set)

3- solidly weld your fitting onto the tank

4- cut out the material from the tank wall inside the fitting (be sure to smooth the edge)

5- install access door/frame to fitting

Good luck.

Thank you,

I guess my concern is how to accomplish step two. I have a collar that is to slide in the hole cut into the side of the tank. The collar is not tapered to match the curve of the vessel. The collar is essentially a tube with the same height around the circumference of the tube.

Thanks to all for the responses. What a community of engineers this is!

So, you have a collar that is tube shaped and is supposed to slide inside the opening in the vessel. Its clearer now, because normally we see plate shaped reinforcement collars, the procedures mentioned above assume that.

In your case, I'd first grind your collas tube to the approximated shape of the external diameter of the vessel, making it set against the diameter. It's not that complicated to adjust and something that you can do in an acceptable manner by using only manual procedures.

So, position your tube against the vessel, and draw with some marker the projection of the tube outer diameter in the vessel. After that, just cut and grind the surface to match the tube outer diameter. Once you do that, any position adjustment will be easy by welding and forming.

BTW, if it's certified pressure vessel, be sure to consult ASME or the applicable code in your area to be sure you are dealing with the correct type of reinforcement collar, if the opening complies with the standard, pressure, thickness, etc OK? Consult an engineer to certify your design, modification or test before entering the vessel in service. It's important, it's for safety, and you may go in jail if you don't do so. Just in case you don't know it.

This gives the gist of the idea, but also consider these factors:

1. Avoid cutting or contouring the collar, unless its internal projection into the main vessel will interfere with something.

2. You can then place the collar against the vessel and with a long enough marking instrument trace the outline of the collar onto the vessel, for an initial cut.

3. Then bevel the cut into the vessel so that a J or V shaped full-penetration weld can be made. As "bhrescobar" points out, there should be a code-qualified procedure that must be followed. Someone will need to verify if any reinforcing pads need to be added according to the rules governing nozzles in vessels.

1. Make a template with the curvature of the tank.

2. Use this template to check the curvature of the collar as you grind it to the shape of the tank

3. The collar can now be used to mark the cut-out on the tank

"The collar is essentially a tube with the same height around the circumference of the tube."

I presume this tubular collar has to meet and enter into the vessel. Yes, the development of the hole will be elliptical.

Do it on drawing board and scale up. Or more practicality, layout the same sized sketch on floor and use the dimintions.

On the floor, describe an arc with the radius of the tank/vessel. Draw the dia of the collar as shown and project it to meet the vessel.

Measure this curved length and this is the horizontal, major diameter of required ellipse. The minor diameter of the ellipse is the dia of the collar.

With this you can mark the shape of the ellipse on the surface of the vessel wall.

Good luck and take care of the safety issues sighted by others.

Hi Allen,

The previous posters are correct about the procedural aspects of any work on a pressure vessel.

Your question though, if I understand it correctly, is how to determine the shape of the ellipse. This is usually done by producing a development drawing - most mechanical draftspersons would be able to do this. The drawing is done full scale, and the shape can be cut of the paper, placed in the correct position and the shape then traced out on the wall of the vessel. To do the drawing you would need to know the outside diameter of the vessel and the outside diameter of the collar. If you can't find someone to do the drawing for you, post the relevant diameters and your contact e-mail address and I'll see if I can do it for you.

This sounds good. I will pursue this route.

If you use a drill you will obtain a circular hole!

Can you post some dimensions for your tank and collar? It's tough to recommend a practical solution when we're not sure if we're dealing with something that can be punched out with a hole saw or what.

If this is a pressure vessel I would HIGHLY recommend discussing the whole procedure with your qualified welder that will be welding the collar back on. [S]He will be able to tell you what kind of tolerances are required and very likely be able to give you some direction on what cutting tools you'll end up using. No point wasting time talking about utopian tolerances available on new machines parts when, in the end, it's a oxy-acetyl torch in a hopefully steady grip that will be doing the work!

The technique you'll require sounds very similar to what they do for "hot tapping" pipelines. A flange/ball-valve/short-tube assembly is welded to the pressurized vessel. On the flange a special mill/drill is attached that reaches through the ball valve and cuts the hole through the pressure wall. The tool is then retracted and the ball valve closed. Once the cutter is unbolted and removed the required fittings can be bolted to the flange.

This does, Thank You.

With a name "pipewelder" and a detailed description like that you'd best be following your instincts on who to be paying the most attention to. Good luck with your project. If you have doubts find a professional.

I'm late to the game, but how about getting a large sheet of butcher paper, tape it to the access door frame and make a rubbing of ithe flange using a crayon or something to make a template. Then cut it out, tape it to the side of the pressure vessel, and lay out your cut. Make your cut keeping in mind that you are not making the cut perpendicular to the vessel surface (only important if the wall is thick).