design pressure, MAP, MAWP, hydrostatic test, horizontal vessel 5

[Mike-Carlson]

Hello everyone,

I have a couple of questions about designing of a horizontal pressure vessel (to be more specific, a pipeline pig receiver) according to ASME Sec 8 div 1. TL to TL length is 12010 mm and, ID is 76.2mm, lethal service, operating pressure is 127.2 barg and operating temperature is 35/52 C:
1- How should I specify the design pressure, MAP and MAWP?
2- Should the vessel be hydro-statically tested in the horizontal condition? if so how should I specify the hydrostatic pressure?

Thank you!

 

[LittleInch]

1st off, a pipeline pig receiver is NOT a pressure vessel. Therefore you need to go back to why this code has been chosen and chose which ever pipeline code you're working to.

They (pig traps) are specifically allowed for within the pipeline design codes as part of the pipeline and other than the end closure, they are not subject to ASME VIII design.

The key reason, apart from unnecessary cost, is that the ID of the minor barrel is a lot smaller than the pipeline ID due to the different way pipeline codes work from ASME VIII. This is not a good idea for a pig trap. If you absolutely cannot persuade someone to use the correct design code then at least make sure the ID of the trap equals the ID of the connecting pipelines ( might need a special forged component)

Pipelines work by using a single design pressure for design of components.

yes, normally tested in horizontal position. Find it difficult to believe that the height of the vessel is actually measurable / has any impact when you're looking at a DP of 127.2 barg

This is a 3 inch pig receiver 12 m long !!!! or was that a typo and you meant 762 - 30" sounds a lot more like it...

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[Mike-Carlson]

Thank you @LittleInch . It was very helpful. You're right, it is a 30 inch pig receiver. Sorry!
Just to be clear about the pressure, the operating pressure is 127.2 barg. Does it mean that the design pressure should be also set to 127.2 barg?
Also do you have any comment regarding what the hydrostatic pressure should be in this pig receiver?
Thanks!

 

[JohnGP]

Design pressure should be set at least 10% above MOP, in my opinion, but should not be less than the pipeline design pressure. Hydrostatic test pressure should be the same as that set for the attached pipeline.

The receiver can be designed as a pressure vessel (and is often done that way), and in that case, hydrostatic test pressure should be in accordance with the pressure vessel code.

 

[r6155]

@ JohnGP
Different pressure test may be in pipeline and pig receiver, depends of code applied for each one.

Regards
r6155

 

[LittleInch]

"The receiver can be designed as a pressure vessel (and is often done that way)," Not if the pipeline engineer sees it it doesn't, only when someone from a wholly plant piping background gets involved.

Apart from the extra design and construction costs & mismatch on ID, you then end up with annual inspections and re-testing which you don't get if you just use a pipeline design code.

"Different pressure test may be in pipeline and pig receiver, depends of code applied for each one." - I disagree. The pig trap is part of the pipeline, which is why it should be designed to the same code and the same design / test pressure. That is another reason you don't split codes at this point.

I missed the Operating pressure bit.

You cannot determine the design pressure from the operating pressure. You need to find out the design pressure of the pipeline from a design basis document. You can't guess or calculate. Might be 140 bar, might be 200. E.g. Normal operating pressure at the far end of the pipeline might be 5 barg, but design pressure > 127 barg.

Hydrostatic pressure should be same as the pipeline to which it is attached. See the pipeline design code / design basis for what this pressure is.

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Also: If you get a response it's polite to respond to it.

 

[JStephen]

LittleInch, just curious on the ID comment. Are you assuming that a 30" pipeline is always 30" ID, but a 30" vessel is always 30" OD?

 

[zealotjj]

LittleInch's comment on ID probably based on the fact that the wall thickness required based on ASME VIII calculation will always be higher than pipeline code calculation (using the same MAWP/DP). The smaller ID may cause various problems; pipeline inspection for roundness using gauge plates will not be possible for example.

 

[marty007]

Pipelines are often fabricated from... pipe.

Pipe is normally specified on an OD basis.

The calculated required thickness from pipeline codes is often lower than the calculated required thickness from pressure vessel codes.

So, if you buy pipe with the same OD, and design to the different codes, you will have a different ID.

In this case, the OP would likely end up with a pig receiver with a smaller ID than the main pipe line. This could be a recipe for binding or other such problems...

 

[LittleInch]

Both replies correct. Although the IP states "ID is 762" , i.e. 30". now he might have meant OD, I don't know, but you can get some big differences in ID between pipeline design and materials and piping / pressure vessel, especially for large diameter high pressure stuff.

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

 

[JohnGP]

LI, I'm not saying launchers/receivers should be designed as pressure vessels, just that I have seen it done that way. Obviously there are issues to be managed, and for high pressure stuff particularly, the small barrel section would need to be manufactured to suit the pipeline.

The receiver would most likely be tested at its point of manufacture, and would not need to necessarily take part in the pipeline testing.

I see the issue with MAWP - I sort of assumed that OP Mike was involved with both the receiver and the pipeline. But that may not be the case. Presumably there is a launcher in the system as well, with the same design conditions. Just to reiterate then, design pressure must match pipeline design pressure, and minimum test pressures must be in accordance with the relevant codes, if different.

 

[zealotjj]

Well, with proper justification, engineers can decide on any construction code they like, and they may also take exception on certain requirement and rules. I guess that's one way to be creative!

Possibly the extra thickness from PV codes is desired for the CA, since the owner may expect high internal corrosion rate from the service fluid (which, to me, will be much better addressed by fixing the plant operation).

To answer the initial questions:

1) Receiver MAWP = Pipeline DP
2) HT Pressure = 1.3*DP according to ASME VIII

 

[LittleInch]

I realise I've gone off the scope here, but it is an important issue.

There is no valid reason, IMHO, why anyone would choose to use a design and construction code which offers no advantages to another design code but has operational issues and cost and inspection issues, i.e. ASME VIII versus your pipeline code.

I've heard of people trying to design pig traps to ASME VIII, but normally this is simply a lack of understanding, knowledge and experience of alternatives which are much more suited to the design and operation and cost a lot less. the same applies to when people try and design it to B31.3 - again an incorrect application of the design code mainly caused by a lack of understanding about the scope and application of different codes.

The extra thickness of ASME VIII vessels is irrelevant to a CA, which should be no different or even less than the pipeline. I've seen people argue for a lower CA on the pig traps than the pipeline as, in general, nowadays they are normally isolated or disconnected when not in use.

We all agree on the MAWP / DP of pipe pipeline bit though.

I note the OP has disappeared from this thread(!)

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

 

[r6155]

(OP)has mentioned lethal service.
Lethal service is clear under ASME VIII Div.1. Which is the pipeline code for lethal service?

Regards
r6155

 

[LittleInch]

"Lethal Service" is covered by most pipeline codes as a material designation which leads to different design factors and separation, especially for different types of gas.

It's not handled in the same manner as it is in 31.3 or ASME VIII.

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Also: If you get a response it's polite to respond to it.

 

[r6155]

@ LittleInch
Please, can you mention one pipeline code including the term lethal?
Thank you.

Regards
r6155

 

[LittleInch]

That's why I put it in speech marks. Pipeline codes tend to use the word "toxic"

I'm not a PV man so not sure what the definition of "lethal service" is other than the normal use of the words

Interestingly, neither of the ASME pipeline codes appear to cover toxic fluids, only hydrocarbons, ammonia and similar gases. 31.8 limits itself to "gas" which is defined as a gas suitable for use as fuel, and 31.4 has an "including but not limited to" clause, but doesn't create any listing one way or the other for toxic fluids.

ISO 13623 specifically covers toxic liquids and gases by designations of their category (Cat B and Cat E) as does BS PD8010

ASME B 31.3 category M is closest to your "lethal" description with
(b) Category M Fluid Service: a fluid service in which
both of the following apply:
(1) the fluid is so highly toxic that a single exposure
to a very small quantity of the fluid, caused by leakage,
can produce serious irreversible harm to persons on
breathing or bodily contact, even when prompt restorative
measures are taken

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[r6155]

Thanks LittleInch

We are in problems with LETHAL. I think that an international definition must be established

A lot of comments are in eng-tips forum, search LETHAL

ASME VIII Div.1 ENDNOTES 65
By “lethal substances” are meant poisonous gases or liquids of such a nature that a very small amount of the gas or
of the vapor of the liquid mixed or unmixed with air is dangerous to life when inhaled. For purposes of this Division,
this class includes substances of this nature which are stored under pressure or may generate a pressure if stored
in a closed vessel.

Thank you again

Regards
r6155

 

[LittleInch]

Pretty close to Cat M in 31.3

I don't know how you would actually gain approval for such a pipeline through public access areas which is a different issue, but I know there are chlorine lines and similar which run around industrial areas and similar outside plant fencelines.

I think there are a lot more things which need to have a definition than that - seems clear to me.

Still doesn't mean you design a pig trap to ASME VIII though....

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

 

[marty007]

I have done a fair amount of work with chlorine systems (saw a beautiful green cloud during one start-up). The crazy thing is that it's often classified by the operators/owners as non-lethal.

I saw one organization go so far as to state in their design requirements that chlorine was not considered lethal, but that all equipment was to be designed as though it was. Basically they understood how nasty it was, and wanted to build their plant recognizing this, but I don't think they wanted to deal with jurisdictional issues that would arise if you actually called it lethal.