Pressure vessel Design - Splay out concern

Click For Summary

Discussion Overview

The discussion revolves around the design of a pressure vessel, specifically addressing concerns related to the use of a threaded lock ring in place of a bolted end cap arrangement. Participants explore the implications of this design choice on safety and structural integrity under pressure testing, referencing relevant codes and material properties.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • The original design of the pressure vessel uses an end cap bolted to the body, which is not compliant with pressure vessel codes, leading to the need for redesign.
  • The participant proposes using a threaded lock ring instead of a bolted arrangement due to space constraints and the inability to increase the number of bolts.
  • Concerns are raised about the potential splay out of the lock ring during pressure testing, with preliminary FEA indicating localized high stresses despite a calculated deflection of 0.2mm.
  • Material properties for the body, lock ring, and end cap are provided, with specific yield strengths noted.
  • One participant questions the design of the vessel's bottom attachment, suggesting it may also need to be pressure rated if it is not formed-in.

Areas of Agreement / Disagreement

Participants express differing levels of knowledge and concern regarding the design and safety of the pressure vessel. There is no consensus on whether the lock ring will indeed splay out during pressure testing, and the discussion remains unresolved regarding the adequacy of the proposed design.

Contextual Notes

Participants have not fully explored the implications of the localized high stresses and the adequacy of the safety factor. The discussion lacks detailed analysis of the bottom attachment's pressure rating status.

Who May Find This Useful

Engineers and designers involved in pressure vessel design, particularly those interested in compliance with pressure vessel codes and structural integrity under pressure conditions.

krithika
Messages
12
Reaction score
0
Dear Members,
The existing design for the pressure vessel is an end cap bolted to the body which is not designed to any pressure vessel code. Currently I'm trying to qualify this pressure vessel to PD5500 code. Due to the derated allowables in the code i couldn't go with the bolted arrangement, In order to qualify the existing design i have to triple the number of bolts for which i don't have space.

Not left with much options i decided to go with end cap and threaded lock ring ( Please see attachement-BLOGS). The threads i use in the lock ring is stub acme. Although the thread length and lock ring tensile area are good for 300bar ejection load(internal pressure) as per my calculation, I'm more concerned about the splay out of the lock ring. I did some basic FEA from which the deflection i got was 0.2mm but the stresses are localised and quite high. I'm not sure if i can go ahead with the testing with this fine safety factor margin.

Temperature is 20 deg C, but I am not overly concerned about this at this stage.

Material
Body - 65 ksi
Lock ring - 80ksi
End cap - 80ksi.
 

Attachments

  • BLOGS.PNG
    BLOGS.PNG
    64.1 KB · Views: 378
  • 2D Axisymmetric FEA.docx
    2D Axisymmetric FEA.docx
    184.9 KB · Views: 361
Engineering news on Phys.org
So, what is your question ?
 
My question is will the lock ring splay out during pressure testing? Please let me know if you need any additional info.
 
I have no knowledge of this stuff, but I'm still interested in one aspect of the problem. Your drawing makes it appear as if the bottom of the vessel is also attached via a collar rather than being formed-in. If so, is it already pressure rated or are you designing that too?
 

Similar threads

Cubical Pressure Vessel - Maximum Pressure Computation
  • · Replies 5 ·
Replies
5
Views
2K
Designing pressure vessel
  • · Replies 1 ·
Replies
1
Views
2K
ASME compliance in Pressure Vessel design
  • · Replies 16 ·
Replies
16
Views
3K
Submarine pressure vessel design
  • · Replies 7 ·
Replies
7
Views
8K
Radial stress in pressure vessels
  • · Replies 5 ·
Replies
5
Views
24K
Is the Pressure Vessel Design for a Railway Cistern Appropriate?
  • · Replies 4 ·
Replies
4
Views
3K
Seal rotating parts/reduce friction (hand-tight thread)
  • · Replies 9 ·
Replies
9
Views
3K
Designing Pressure Vessel for Heating Air to 500 C
  • · Replies 3 ·
Replies
3
Views
4K
Subsea Pressure Housing Design – Wall Thickness for Stress & Buckling
  • · Replies 13 ·
Replies
13
Views
5K
Pressure Vessel End Cap Deflection
  • · Replies 4 ·
Replies
4
Views
15K