3 replies to this topic

[hiren_d]

Dear All,

 

I am  having one 5 KL SS reactor with MS spiral wound jacket.

 

Its specifications are as below.

 

Design Code ASME sec-VIII div 1,2004 

 

MOC shell: SS316 (SA240 TYPE 316)

MOC jacket: IS 2062 gr A

 

Design temp(Shell): -30 to 170 C 

Design pressure(Shell): 5 Bar - FV

 

Thickness Shell : 10 mm

Thickness jacket: 10 mm

 

 

Design temp(jacket): -40 to 200 C

Design pressure(jacket): 0-6 Bar

 

Corrossion allowance: nil

 

Radiography : Nil

 

Joint efficiency:0.75

 

I would like to utilize this reactor for cryogenic service at -100 C temperature using liquid nitrogen in reactor jacket at  around 2 bar pressure.

 

My questions are

 

1) Can I use the reactor as it is without any modification?

 

2) If modifications required , shall I go with Jacke tor limpet coil?

 

3) What should be preferable MOC for jacket cryogenci service- Mild steel or SS304 or SS316?

 

4) If I go for limpet coil, what should be its thickness  (Sch 40 or Sch 80?

 

5) Any specific welding considerations required for this refurbishment ?

 

Thanks,

Hiren Dave

[Bobby Strain]

This sounds like you should hire someone to do your work. You don't want to use advice from this forum for such an undertaking. For there are codes and standards that you must follow. You must use a competent professional with the proper experience and credentials. Good luck.

 

Bobby

[Art Montemayor]

Once again, in my opinion,  Bobby is 100% correct in his analysis and recommendations.

 

I have struggled and fought with limpet jacket reactors in the past and can tell you from hands-on experience that you have a potential problem in studying and predicting what will be the results when you subject the vessel wall to a differential temperature of over 125 ^oC.  You will experience some complex weld and jacket stresses as the limpet spiral cools faster than the vessel wall.  What will happen structurally with the vessel or the coil is something that is better left in the hands and experience of a qualified mechanical engineer experienced in vessel design.

 

What you propose is just one of the many difficulties encountered with limpet jacketed vessels, and is one of the reasons I have consistently stayed away from them.  I've never been successful in justifying their design and application - from either an economical or practical point of view.  Why are you decided on a limpet design?   What advantages does it contribute to your application?  Any vessel built to contain liquid nitrogen (or similar cryogen) should, from a practical point, be fabricated of stainless steel.

 

I would not recommend you omit 100% radiography on all welds.  Anytime you employ a jacket on a cryogenic vessel, you are going to exhibit tremendous stress points during the initial cool-down(s) - a lot depends on the application.  What is it that you are going to react at cryogenic temperatures?  Or is this an academic exercise?  Your proposal seems weird:

 

As seen in the attached Thermophysical Data, Liquid Nitrogen (LIN) at 2.0 barA exists at temperatures BELOW -190 ^oC.  So how can you claim to have LIN at 2 barA and -100 ^oC?????  Besides, if you intend to employ LIN, then you would be planning on using its LATENT HEAT sink as the cooling medium.  That means you would, in effect, have vaporization occurring during the cooling - your reactor would be a LIN vaporizer and you would require a vapor removal system of some sort or other for it to work.  I don't believe you can apply heat transfer to LIN and maintain it in the liquid phase.  You are going to be generating nitrogen gas at 2 barA and you have to be able to vent it safely.  Perhaps I'm barking up the wrong tree, but a detailed sketch or engineering drawing would certainly clear up a lot of the questions that will continue to arise on this topic.

 

 Liquid Nitrogen at 2 barA.xlsx   25.13KB   39 downloads

[breizh]

Hi ,

 

You may find some interest reading this document .

Hope this helps.

 

Breizh

Edited by breizh, 22 April 2016 - 06:10 AM.