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Cryogenic Vessel Design Specification

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Cryogenic Vessel Design Specification

Cryogenic Vessel Design Specification

Sruthish

(Mechanical)

(OP)

23 Jan 18 15:35

I have seen one of the datasheets for cryogenic vessels specifying the vessel shall be designed for allowable temperatures of -196 Deg C as the minimum and -20 deg C as the maximum. I believe that this implies the vessel can withstand a lowest temperature of -196 Deg C and a maximum temperature of -20 Deg C. Please suggest whether my understanding is correct. If it is, then it means that the vessel cannot withstand temperatures higher than -20 Deg C. Then how can we fabricate and store the vessel before commissioning at ambient temperatures, which are certainly higher than -20 Deg C? Once we fill the vessel with cryogen, the temperature will reduce to very low values, say -196 Deg C. But still, does it make sense to consider the maximum allowable temperature as -20 Deg C for design? Please clarify my doubt.

RE: Cryogenic Vessel Design Specification

EdStainless

(Materials)

23 Jan 18 15:53

How would you ever get it above -20 filled with liquid gas? It is only rated for use in service up to -20. In fabrication and storage, it can be just about any temperature, but the design loads and conditions only apply for the temperature range given.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Cryogenic Vessel Design Specification

pradipgoswami

(Materials)

23 Jan 18 16:10

Cryogenic vessels are usually fabricated either from Austenitic stainless steels (304L, 316L) or aluminum alloys. For a design temperature of -196 Deg C, austenitic stainless steels would be default choices. These steels are quite stable with respect to mechanical properties (especially Charpy impact) from +400 Deg C to -196 Deg C. Hence, no concern.

Pradip Goswami, P.Eng.IWE
Welding & Metallurgical Specialist
Ontario, Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299

RE: Cryogenic Vessel Design Specification

keyen

(Mechanical)

23 Jan 18 18:24

Pradipgoswami, why did you specifically mention 304L and 316L and not, for example, 304, 316, 304H, or 316H?

RE: Cryogenic Vessel Design Specification

victorpbr

(Mechanical)

23 Jan 18 19:54

Sruthish, what is the fluid it is containing? I`ve seen a similar specification before; the justification was that the vessel was designed for LOX/LIN/LAR but also refrigerated CO2. So, when using LOX/LIN/LAR, the maximum temperature would be -196C, and when using refrigerated CO2, the maximum temperature would be -20C. They do that to make sure the pressure inside does not exceed the designed value. When temperature increases, so does the pressure because the liquid starts to boil, so they used it as reference for when using CO2.

RE: Cryogenic Vessel Design Specification

metengr

(Materials)

23 Jan 18 20:31

Quote:

I believe that this implies the vessel can withstand a lowest temperature of -196 Deg C and a maximum temperature of -20 Deg C.

Correct

Quote:

If my understanding is correct, then it means that the vessel cannot withstand a temperature higher than -20 Deg C.

Only applies to in-service conditions where the vessel is under pressure.

Quote:

But still, does it make sense to consider the maximum allowable temperature as -20 Deg C for the design?

Yes, it does because the vessel can be pressurized internally up to -20 Deg C in service, and this must be taken into account for design purposes.

Cryogenic vessel materials can be either 304, 304L, 316, or 316L. Typically, the H grades would be for elevated temperature service because of the demand for elevated temperature creep strength.

RE: Cryogenic Vessel Design Specification

Sruthish

(Mechanical)

(OP)

24 Jan 18 01:08

EdStainless, I totally agree with you. It's just a rating temperature. But the same point you made in your reply makes my question more specific. The design loads and conditions apply only for the temperature range given. So if the calculations take a higher temperature as -20 Deg C, then it clearly means that this vessel, when subjected to the loads or conditions of ambient temperature, may have some problems. Although in actual conditions, it won't have any problem because the vessel is fabricated of SS 304. Surely it will withstand higher temperatures. My concern is whether the specified temperature is right or wrong? What will be the problem if we design the vessel considering at least ambient temperature as the maximum allowable temperature?

RE: Cryogenic Vessel Design Specification

LittleInch

(Petroleum)

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24 Jan 18 10:19

Commissioning cryogenic vessels is an interesting procedure, usually involving cold gases to allow the metal to come down to its operating range gradually before introducing cold liquid. The datasheet should include an empty, zero pressure, ambient temperature condition case, so revert to whoever supplied the datasheet or just add that particular case into the design cases being studied. Perhaps the datasheet provider thought that this was bleeding obvious, so omitted it from his cases?

Remember - More details = better answers
Also: If you get a response, it's polite to respond to it.

RE: Cryogenic Vessel Design Specification

Sruthish

(Mechanical)

(OP)

24 Jan 18 12:19

Hi Pradip Goswami, I understand your point. The vessel I was talking about is made of SS 304. Obviously, for continuous operation, it can withstand up to 950-1000 Degree C. So, I'm not concerned about the vessel's actual operation .. it will withstand. My concern is if this material could withstand this much higher temperatures, why did the design engineer who made the calculations or datasheet consider only -20 Degree C.? Does it make any sense, or is there any specific point I'm missing regarding the cryogenic point of view?

RE: Cryogenic Vessel Design Specification

Sruthish

(Mechanical)

(OP)

24 Jan 18 13:12

Hi Keyen, It's possible to manufacture cryogenic vessels with 304 and 316 grades. When using 304, it's good to check the strength at lower temperatures with an impact test. But if we are using 316 grade without the impact test, it's safe to use. Anyway, in my opinion, there is no need to go for 304L and 316L etc.

RE: Cryogenic Vessel Design Specification

Sruthish

(Mechanical)

(OP)

24 Jan 18 13:18

Hi Victorpbr, The vessel is designed for LNG and commissioned with LIN. There are no considerations for refrigerated or Liquid CO2.

RE: Cryogenic Vessel Design Specification

Sruthish

(Mechanical)

(OP)

24 Jan 18 13:27

Metengr, Thank you for quoting and answering my questions one by one. The points you mentioned make sense to me. But I would say the vessel design doesn't address the condition of keeping the vessel at ambient temperature. Once they start the operation with cryogen within the vessel, the temperature cannot be more than -20 deg in any case. But if the client who uses this vessel stops the operation temporarily and removes all the cryogen inside the vessel, allowing the vessel to return to normal ambient temperature for some specific purpose, does the vessel design lose its validity then? Correct or not? Please correct me if I'm wrong.

RE: Cryogenic Vessel Design Specification

Sruthish

(Mechanical)

(OP)

24 Jan 18 13:32

Hi LittleInch, I think you said the right thing. The datasheet may have missed the point of ambient temperature. It should have considered the condition of ambient temperature somewhere. In the calcs or docs, the design person should have considered this one. Even though it is safe to use at normal temperature, it shall be shown in the proper documents also.

RE: Cryogenic Vessel Design Specification

Sruthish

(Mechanical)

(OP)

24 Jan 18 13:35

Please see the attached image herewith. I would like to provide more details regarding the design conditions that I was talking about. Please see the attached image herewith.

RE: Cryogenic Vessel Design Specification

Caloooomi

(Chemical)

24 Jan 18 14:39

It would be the allowable temperature during normal operation, i.e., when filled and used for storage. Unless it is being installed in the Arctic, it is going to sit above that when not filled due to ambient conditions. You have a jacketed vessel, the inner vessel contains the cryogen while the gap between the vessel and jacket is insulated and a vacuum is pulled to minimise heat ingress. Additionally, part of EN 13458 is to calculate the maximum allowable working pressure when the inner vessel is filled with warm gas (20 degC). You can always ask for that value from the supplier, but I suspect they have just put the larger of the 2 (comparing with cooled down and storing cryogenic liquid).

RE: Cryogenic Vessel Design Specification

Sruthish

(Mechanical)

(OP)

24 Jan 18 14:57

Thank you so much for reminding me of the point that I missed. As per EN 13458-2, the inner vessel must be designed considering various loads, in which MAP with vessels containing gaseous products at 20 Deg C is also required. Moreover, I found out the client specification for the design. The client datasheet specified -196 to +50 Deg C as the minimum and maximum allowable temperatures. Please see the attached images for the EN code mentioning and Client Spec Respectively. I hope that the design missed these points somehow.

RE: Cryogenic Vessel Design Specification

metengr

(Materials)

24 Jan 18 17:02

Quote:

But if the client who uses this vessel stopped the operation temporarily and removed all the cryogen inside the vessel, allowing it to return to normal ambient temperature for some specific purpose. Is the vessel design not valid in this situation?

No, that is not correct.

RE: Cryogenic Vessel Design Specification

pradipgoswami

(Materials)

25 Jan 18 16:04

There are not many options for materials for cryogenic applications. Sec-VIII, DIV-1, chapter ULT lists all approved materials. 304 or 304L is a designer's call, subject to the fact that the consistency of Charpy impact values is most important @ -196 Deg C, assuming that's the lowest design temperature as per the exhibited datasheet. Selection of welding consumables with zero or maximum 2 FN is desirable for consistent & good impact values at -196 Deg C. Read UHA-51 to that effect. Whether to choose 304 or 304L depends on the need for higher design wall thickness if 304L is used due to the lower allowable stress applicable. If 304 is used as the material for construction, using 308L welding material with the ferrite number stated above should be mandatory. For cryogenic services (@ -196 Deg C), correct material and welding conditions are paramount. Thanks.

Pradip Goswami, P.Eng.IWE
Welding & Metallurgical Specialist
Ontario, Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299

RE: Cryogenic Vessel Design Specification

ironic metallurgist

(Materials)

25 Jan 18 17: