Pressure vessel with large lid

[pietje]

We have to design a small pressure vessel (-10°C - 30°C, 50bar) based on a 4" pipe. The client wants to be able to take of the lid numerous times. He thought it would be nice to do this by welding a welding neck flange on top and close it with a blind flange. Well, I learned that you should always renew the gasket everytime you remove the blind flange. I don't think it is practical and wonder if there aren't any better solutions to be able to often open and close the vessel...

 

[TGS4]

What you are looking for is a quick-actuating/quick-operating closure. There are many companies that offer such a device. These are permitted in the Codes.

Good for you for noting that the gasket needs to be replaced every time!

 

[pietje]

Yep, I found some, but what I forgot to mention is that a small, long tube will be inserted through the lid. Therefore it can't be a hinged closure. Any ideas?

 

[TGS4]

There should be some quick-=opening closures that aren't hinged, especially in that small size. Call one of the manufacturers.

 

[pietje]

Okay, I have done some research and I can't find any practical solutions for us.

I am now thinking of using a standard asme flange and put an O-ring groove on the raised face. Is this allowed?

 

[doct9960]

Have you looked at T-bolt closures?

https://www.tubeturns.com/products/t-bolt-closures/

 

[pietje]

yep, but they are hinged and therefore we can't install a long tube in the lid that sticks into the vessel. I think it is a bridge too far for us to design and fabricate one ourselves.

I must tell you b.t.w. that my knowledge of the codes (PED in this case) is limited.

The idea of using a O-ring may be the best attainable solution for us. Only thing I have doubts about is that the surface of the blind flange is easily damaged/roughened up when handled without care and therefore the chance of leakage is large. Even I create a blind flange that has plug on it to create an axial seal, putting it in roughly can damage the surface of the hole. There is no room to put on a guiding mechanism for the flange.

I am a bit out of ideas...

 

[doct9960]

pietje,

The T-bolt closure was just to give you an idea. Hint: Pipe Cap + T-bolt + O-ring.

They can be designed without using hinges.

 

[chicopee]

Why not have the T-bolt closure without the hinge as stated by doct9960?

 

[racookpe1978]

It would be a complex machining issue, and would not use standard round flanges, but you could make an oblong, elliptical, or rounded end PV cover and lid. Twisted sideways, the PV cover then goes into the PV, rotates 90 degrees, then lifts "out" towards the PV lip. The internal pressure seals the PV cover against the PV lip, and all you need is a cam type lever to lift the PV lid uou against the sealing surface when there is no internal pressure.

De-pressurize the vessel, lift the cam lock, push in the PV lid into the vessel, twist and you can remove the lid with its thermometer intact. (Check clearances in 3D before fabrication.)

 

[pietje]

thanks for all your ideas.
The project leader just informed me he wants the standard flange with an O-ring. Other solutions are just too expensive and time consuming for now.
My question: does the PED (or ASME) prescribe anything about the use of an O-ring?

 

[Compositepro]

You can make a metal "gasket" with o-ring grooves in it.

 

[XL83NL]

Maybe a bit late, but its good to remember PED isnt a design code, just a directive. It only yells you what the requirements are for pressure equipement, not how to design it.
For design, youll need a design code, like ASME. Keep in mind not all design codes have conformiteit with the PED upfront, therefore require extra measures. Harmonized standards, like EN 13445 however, have conformity with the PED upfront.

 

[GenB]

ASME SCT. VIII,1. O RING ALLOWED.

 

[moltenmetal]

The o-ring groove in a standard B16.5 flange pair is allowed and has been done many times. Presumes that the temperature and pressure are within the limits of the elastomer you've selected. Will reduce your gasket seating stress greatly such that you may be able to use eyebolts (effectively big wingnuts) on the studs so you don't need a wrench to open them. This type of closure is commonly done on filter housings, although the studs are usually swingbolts in that case and there isn't a full body flange.

Another popular option is a tri-clamp closure, but you'd have to move to 4" or 6" tubing to use it- they are not made in pipe sizes.