shopper1732
Mechanical
When does a Pressure Vessel become a Pipe and vice-versa?
Is there a minimum diameter for a Pressure Vessel?
Is there a minimum diameter for a Pressure Vessel?
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Pressure Vessel vs Pipe 5
- Thread starter shopper1732
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Well, one way to define is the code that it's built to, if any.
Piping code = piping
PV code = PV
No code = call it what you want
While I am not aware of any real minimum dia. for a PV, vessels 6" dia and smaller are excluded from the scope of Sec VIII, Div 1, for example. Other codes may have different limits.
Also piping is primarily for transport of fluids, while PV's typically process them in some way, such as changing temps, separating, etc.
Hope this is helpful, no doubt somebody else can give you something more definitive.
Mike
Piping code = piping
PV code = PV
No code = call it what you want
While I am not aware of any real minimum dia. for a PV, vessels 6" dia and smaller are excluded from the scope of Sec VIII, Div 1, for example. Other codes may have different limits.
Also piping is primarily for transport of fluids, while PV's typically process them in some way, such as changing temps, separating, etc.
Hope this is helpful, no doubt somebody else can give you something more definitive.
Mike
Indeed as far as i know, the piping codes (at least the oens i am familiar with such as B31.3 & B31.4) have originated from ASME code and there is a close relation between them.
In any case heat exchangers, filters, scrubbers, and any equipment that is connected to a piping system with one or more objectives other than just transportation of fluids are PV's. Hence i agree with SnTMan.
In any case heat exchangers, filters, scrubbers, and any equipment that is connected to a piping system with one or more objectives other than just transportation of fluids are PV's. Hence i agree with SnTMan.
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shopper1732
Mechanical
Thank you.
I am getting old.
I was trying to remember if it was 4" or 6" or what.
In this age of electronics, I do not have access to the section VIII or B31's except via computer.
It takes all day to search and I go blind mousing and screen-looking at damn PDF's
So, thanks again.
I did not complicate the question with reference to in-line (piping) devices such as static mixers, but my faulty memory says that they are exluded too.
I am getting old.
I was trying to remember if it was 4" or 6" or what.
In this age of electronics, I do not have access to the section VIII or B31's except via computer.
It takes all day to search and I go blind mousing and screen-looking at damn PDF's
So, thanks again.
I did not complicate the question with reference to in-line (piping) devices such as static mixers, but my faulty memory says that they are exluded too.
shopper, I agree, there is NO substitute for a paper Code book. Much easier to flip back and forth, especially with the way they put three pages of figures in the middle of the paragraph you're trying to read. When I need to look at the (electronic) Code book, I just print that section. Eventually I'll have the whole thing.
Mike
Mike
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Pressure Vessels are defined in ASME Section VIII, Div 1 introduction....
"Pressure Vessels are containers for the containment of pressure either external or internal. The pressure may be obtained from an external source, or by the application of heat from a direct or indirect source, or any combination thereof..
This seems clear to me for pressure vessels - size has nothing to do with pressure vessels.
Piping is a pressure-retaining component that conveys fluids.
"Pressure Vessels are containers for the containment of pressure either external or internal. The pressure may be obtained from an external source, or by the application of heat from a direct or indirect source, or any combination thereof..
This seems clear to me for pressure vessels - size has nothing to do with pressure vessels.
Piping is a pressure-retaining component that conveys fluids.
I think the line is blurry. Sometimes, a pipe can be a vessel and vice versa.
Here is another example: You can all decide.
I have a 50 scfm instrument air receiver. Most people would agree that it is a pressure vessel (100 psi).
I have a 16" pipe, schedule 40, of sufficient length to give me 50 scfm equivalent volume. Most people would agree that it is a pipe (100 psi).
I can use the two interchangeably, if I have to.
The air receiver falls under ASME Sect. VIII. The Pipe in my my case falls under CSA Z662.03.
It's a tough call.
My colleague and I still don't know what the right answer is.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
Here is another example: You can all decide.
I have a 50 scfm instrument air receiver. Most people would agree that it is a pressure vessel (100 psi).
I have a 16" pipe, schedule 40, of sufficient length to give me 50 scfm equivalent volume. Most people would agree that it is a pipe (100 psi).
I can use the two interchangeably, if I have to.
The air receiver falls under ASME Sect. VIII. The Pipe in my my case falls under CSA Z662.03.
It's a tough call.
My colleague and I still don't know what the right answer is.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
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- #10
Ashereng,
I agree that the line is blurry, but if an inline component is simply fabricated from standard pipe and piping components then it should be possible to design and fabricate to a piping code.
I have seen some pig launchers/receivers though designed to B31.3 and others to ASME VIII, so sometimes it seems to come down to personal choice.
Once one has to start rolling plate and pressing dished ends, then to my mind the component is definitely a pressure vessel.
In your case of the air receiver (I guess you meant 50 scf volume), there is no problem in using a piping system to provide a storage capacity above standard flow related sizing. I can't imagine even the most hardnosed AI insisting on the use of a PV code in such circumstances.
Just my thoughts,
John
I agree that the line is blurry, but if an inline component is simply fabricated from standard pipe and piping components then it should be possible to design and fabricate to a piping code.
I have seen some pig launchers/receivers though designed to B31.3 and others to ASME VIII, so sometimes it seems to come down to personal choice.
Once one has to start rolling plate and pressing dished ends, then to my mind the component is definitely a pressure vessel.
In your case of the air receiver (I guess you meant 50 scf volume), there is no problem in using a piping system to provide a storage capacity above standard flow related sizing. I can't imagine even the most hardnosed AI insisting on the use of a PV code in such circumstances.
Just my thoughts,
John
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moltenmetal
Chemical
ASME VIII and the over-arching Canadian pressure vessel document CSA B51 give definitions for what is a pressure vessel and what isn't. Depending on the nature of the hazard represented by the fluid, the pressure and the diameter, the flowcharts given in B51 will tell you whether the component in question is a pressure vessel, a Category H fitting (for components to be fabricated and sold in multiples as discrete devices), or merely an enlargement in the pressure piping associated with other pressure vessels in the system.
Note also that there are provincial acts which exempt specific situations to ensure that devices such as domestic water heaters and water system expansion tanks are exempt.
The dividing line between vessels and pipe becomes gray as illustrated below:
Let's say we have a piece of 8" pipe connecting two large pressure vessels in a process plant. That would generally be considered a piece of ASME B31.3 piping, even though it is greater than 6" ID and greater than 1.5 cubic feet in volume, and the relief pressure is above 15 psig.
Now let's say that the pipe has a reducer at each end to 4" linesize. Still a piece of pipe, right?
Now let's say that it has reducers at either end to 1/2" NPT or a 1/2" flange, or a Swagelok connector for 1/4" OD tubing. Is this still a piece of pipe? Most people, presented with this piece of "pipe", would conclude it is an ASME VIII vessel, even though it is still no more than an assemblage of piping components.
Even though the codes don't state it in words, what they're concerned about is the volume of stored energy or hazardous material under pressure. The principal enclosures with the largest stored volumes of materials are considered vessels and subject to the rules and codes as vessels, where the lines interconnecting these are considered pipe and subject to the rules and codes associated with pressure piping.
Note also that there are provincial acts which exempt specific situations to ensure that devices such as domestic water heaters and water system expansion tanks are exempt.
The dividing line between vessels and pipe becomes gray as illustrated below:
Let's say we have a piece of 8" pipe connecting two large pressure vessels in a process plant. That would generally be considered a piece of ASME B31.3 piping, even though it is greater than 6" ID and greater than 1.5 cubic feet in volume, and the relief pressure is above 15 psig.
Now let's say that the pipe has a reducer at each end to 4" linesize. Still a piece of pipe, right?
Now let's say that it has reducers at either end to 1/2" NPT or a 1/2" flange, or a Swagelok connector for 1/4" OD tubing. Is this still a piece of pipe? Most people, presented with this piece of "pipe", would conclude it is an ASME VIII vessel, even though it is still no more than an assemblage of piping components.
Even though the codes don't state it in words, what they're concerned about is the volume of stored energy or hazardous material under pressure. The principal enclosures with the largest stored volumes of materials are considered vessels and subject to the rules and codes as vessels, where the lines interconnecting these are considered pipe and subject to the rules and codes associated with pressure piping.
So moltenmetal,back to my example and John's. What is your opinion?
Is the air reciever pipe a pressure vessel or pipe?
Is the pig receiver/launcher pressure vessel or pipe?
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
Is the air reciever pipe a pressure vessel or pipe?
Is the pig receiver/launcher pressure vessel or pipe?
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
In reality it is up to the Regulatory body/agency or Jurisdiction or your insurer of the equipment to determine the applicable Code or Standard. If you happen to be in a location that does not regulate pressure vessels or you happen to be self insured, you decide.
If I was head of the Jurisdiction that regulates boilers and pressure vessels for your hypothetical situation, I would deem them pressure vessels.
If I was head of the Jurisdiction that regulates boilers and pressure vessels for your hypothetical situation, I would deem them pressure vessels.
![[smile]](/data/assets/smilies/smile.gif "[smile] [smile]")
metengr,
Fair enough regarding the pig traps (depending on size I would tend to think of them as inline piping components though). There's no way however that I would consider a length of pipe in a system as being a pressure vessel, just because it had a larger diameter than one may think necessary to transport air from one location to another.
Regarding CSA B51, moltenmetal, I am totally not familiar with that document so cannot add anything there, but feel that if a piece of piping between a couple of vessels looks like a pipe, then it must be a pipe.
This in no way clarifies the blurriness that exists between what constitutes piping or pressure vessels in some cases (probably because my mind is just as blurred) - sorry shopper1732.
Cheers,
John
Fair enough regarding the pig traps (depending on size I would tend to think of them as inline piping components though). There's no way however that I would consider a length of pipe in a system as being a pressure vessel, just because it had a larger diameter than one may think necessary to transport air from one location to another.
Regarding CSA B51, moltenmetal, I am totally not familiar with that document so cannot add anything there, but feel that if a piece of piping between a couple of vessels looks like a pipe, then it must be a pipe.
This in no way clarifies the blurriness that exists between what constitutes piping or pressure vessels in some cases (probably because my mind is just as blurred) - sorry shopper1732.
Cheers,
John
moltenmetal
Chemical
For those of you not from Canada, I apologize for the regional nature of my post- but these regulatory issues are ultimately subject to regional variations, so I can't comment beyond my knowledge. Your rules may vary!
If the design were for use in Ontario and I was subject to the TSSA Act, the air receiver would be an ASME VIII vessel, whether you chose to make it from pipe or not. It is the major source of hazard from stored energy in the associated system AND it would fall within the definition of an ASME vessel. There is a specific exemption for small air receivers (to exempt the average shop air compressor tank) but I'm far too lazy to look it up.
Designation of mere line enlargements like pig launchers etc. is pretty much at the discretion of the owner. As long as the components were designed and fabricated in accordance with either ASME VIII or B31.3, TSSA would probably be satisfied.
If the design were for use in Ontario and I was subject to the TSSA Act, the air receiver would be an ASME VIII vessel, whether you chose to make it from pipe or not. It is the major source of hazard from stored energy in the associated system AND it would fall within the definition of an ASME vessel. There is a specific exemption for small air receivers (to exempt the average shop air compressor tank) but I'm far too lazy to look it up.
Designation of mere line enlargements like pig launchers etc. is pretty much at the discretion of the owner. As long as the components were designed and fabricated in accordance with either ASME VIII or B31.3, TSSA would probably be satisfied.
JohnGP,
My bad. The CSA came from me - I am currently working in Canada, and hence, the CSA requirement for my pipeline. However, in the US, pipeline would be covered by ASME would it not? In anycase, where to draw the line remains as fuzzy on both sides of the border.
moltenmetal,
The instrument air receiver (ASME pressure vessel kind) typically runs at abut, 120 psi, maybe 150 psi maximum depending on the compressors? This is hardly high pressure.
The instrument air (IA) header that runs around the plant (2" pipe) is at about 120 psi. I don't see the IA header piping posing any more of a stored energy hazard than the receiver. In fact, a receiver should present more of a hazard than the pipe?
By the way, I do agree with both you and metengr - it really comes down to the inspector. However, sometimes, they are wrong too!![[banghead]](/data/assets/smilies/banghead.gif "[banghead] [banghead]")
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
My bad. The CSA came from me - I am currently working in Canada, and hence, the CSA requirement for my pipeline. However, in the US, pipeline would be covered by ASME would it not? In anycase, where to draw the line remains as fuzzy on both sides of the border.
moltenmetal,
The instrument air receiver (ASME pressure vessel kind) typically runs at abut, 120 psi, maybe 150 psi maximum depending on the compressors? This is hardly high pressure.
The instrument air (IA) header that runs around the plant (2" pipe) is at about 120 psi. I don't see the IA header piping posing any more of a stored energy hazard than the receiver. In fact, a receiver should present more of a hazard than the pipe?
By the way, I do agree with both you and metengr - it really comes down to the inspector. However, sometimes, they are wrong too!
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
moltenmetal,
We may be crossing our wires to some extent - I was picturing Ashereng's scenario with the pipe of 50cuft volume as just a section of pipe of increased diameter within a system of air distribution pipework. To my mind designed in accordance with a piping code. I also agree that it is quite likely that a discrete "vessel" would be designed to a PV code (and required to be), even though it may be constructed from standard piping components. No problem. But the line between the two can become blurry as discussed above.
Ashereng, what happens in the US is just as big a mystery to me, but I suspect a similar situation applies - it really depends on how one's AI views the world. I'm sure the same fuzziness exists in all parts of the world.
Cheers,
John
We may be crossing our wires to some extent - I was picturing Ashereng's scenario with the pipe of 50cuft volume as just a section of pipe of increased diameter within a system of air distribution pipework. To my mind designed in accordance with a piping code. I also agree that it is quite likely that a discrete "vessel" would be designed to a PV code (and required to be), even though it may be constructed from standard piping components. No problem. But the line between the two can become blurry as discussed above.
Ashereng, what happens in the US is just as big a mystery to me, but I suspect a similar situation applies - it really depends on how one's AI views the world. I'm sure the same fuzziness exists in all parts of the world.
Cheers,
John
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