Drilled holes thru the pressure vessel side along the length

[somebodyfromworld]

Hello,

Is there any specific chapter in ASME BPVC VIII regarding these kind of holes. Please take a look at the enclosed simplified sketch. Pressure vessel looks like a cylinder with two caps threaded into it. I have to make two holes through the cylinder along its length and i'm not sure how far they should be from the center and what is a limit for diameter for those holes.

Could anyone advise me where i should look for a standard for those kind of holes?

 

[XL83NL]

As I think of it ... from a pressure perspective point of view, the holes indicate where youre pressure boundary ends, so what your wall thickness for code calculation is.
Therefore (depending how you look at it), the diameter of the holes doesnt make a difference, if you have a 'fixed' wall thickness which is determined by the material between the vessel's internal chamber and the holes.

 

[somebodyfromworld]

thanks for a reply,

holes have an atmospheric pressure, and the boundaries for internal pressure end on the oring grooves. Wall thickness is not fixed so i can increase it. But I'd like to find an optimal wall thickness and the distance of the holes from the main axis.

 

[prex]

From a stress point of view, you can simply subtract the hole diameter from the wall thickness. But from a code perspective, I think that this situation is not treated, so, if you are bound to code rules and you need to place the holes closer to the inner wall than the min.req.thk., then you'll need to go through U-2.

prex
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[somebodyfromworld]

Thanks, could you be more specific with this "U-2", not sure what you mean

 

[XL83NL]

ASME Section VIII, Division 1, paragraph U-2.

 

[racookpe1978]

This is one of those cases where "slide rule" approximations are inadequate, and a formal FEA analysis is warranted.

How many units? What is your penalty if the wall fails? (Compare that investment in a formal FEA analysis and second check with the failure cost. On the other hand, if you are only building one, and the "cost" of increasing wall thickness is less than the cost of a FEA analyst time, then make a thicker wall. Say you need 10,000 psi for a lab test. Weight is no object, you are making only one, and the total pressuer vessel is less than 2 liters in volume. Make a thick wall.
Say you are making a 4000 fuel pressure regulator assemblies for an aero application where you need to fly the thing. Every ounce is important, and fabrication cost is important, but the design time is divided among many units. Analyze it, don't make any assumptions about wall stress.

 

[saplanti]

The design seems to be very odd at the thread and seal area. I do not think that this design will work and will not hold the internal pressure.

What is the purpose of the the 2 holes in the wall thickness of the cylinder? As it seems there is no purpose at all. If you provide the holes on the flanges at the same orientation, there may be 2 stud bolt can be used for additional safety.

How do you pressurise the cylinder in this orientation?

I guess, if you are the designer, you need to solve all these first.

 

[somebodyfromworld]

The sketch is very simplified, and that is not a normal pressure vessel. Originally this will be a downhole equipment in the oilwell. I have to design it according to ASME anyway. The hole thru that cylinder will be a passageway with atmospheric pressure. I just want to design that hole according to ASME if there is a rule for those holes. If there is no such rules in ASME then I run it thru Ansys.