Smart questions
Smart answers
Smart people

Member Login

Remember Me
Forgot Password?
Join Us!

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips now!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

Join Eng-Tips
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Donate Today!

Do you enjoy these
technical forums?
Donate Today! Click Here

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.
Jobs from Indeed

Link To This Forum!

Partner Button
Add Stickiness To Your Site By Linking To This Professionally Managed Technical Forum.
Just copy and paste the
code below into your site.

barnesed (Mechanical)
18 Jun 07 11:20
Section VIII, U-1 states:

"the following classes of vessels are not included in the scope of this Division..."

"(h) vessels having an internal or external operating pressure (see 3-2) not exceeding 15 psi (103 kPa) with no limitation on size [see UG-28(f)]"

For a code stamped vessel with a design pressure of 50 psig and an operating pressure < 5 psig, can a non-code, properly sized (for all scenarios) relief valve set at < 15 psig be used?

Or, because it is a code stamped vessel, must a coded relief valve (which would have a set pressure > 15 psig) be used?
Helpful Member!  pleckner (Chemical)
18 Jun 07 12:37
I've always interpreted this part of ASME as saying that if I stamp it, it then falls within scope. Thus, I need a certified relief device. I have most of the interpretations and have seen no mention that woiuld invalidate my interpretation. So, unless your local municipality allows otherwise, you will need to install a coded valve.

If this is a gas/vapor PSV, then it would be beneficial to have the set pressure as high as possible so that it will be as small as possible (and cheaper).
Helpful Member!  Ashereng (Petroleum)
18 Jun 07 13:46
I interpret the requirement also similarly.

If the pressure vessel is stamped, then it is subject to the code under which it is stamped.

In you case, your vessel is designed to 50 psi, obviously above 15 psi, therefore, you need a coded relief valve.

In general, for me, the operating pressure is immaterial in my mind. What is important is the rated pressure of the vessel. This way, I am sure to protect the vessel regardless of how it is used.

"Do not worry about your problems with mathematics, I assure you mine are far greater."   
Albert Einstein
Have you read FAQ731-376: Forum Policies to make the best use of Eng-Tips Forums?

JimCasey (Mechanical)
18 Jun 07 15:32
Well there IS the consideration that you can't buy a code-stamped valve set for less than 15 psig.  ...Because the code does not apply at less than 15 psi, as you pointed out.  

Suggestion: Buy your low-pressure relief valve, and set a code-stamped 50 psi rupture disc on the pressure vessel.  You're protected from your expected pressure.  You're protected from operpressures great enough to harm the vessel, AND you're pretected from ( ecch ) lawyers.
Helpful Member!  gene2007 (Chemical)
18 Jun 07 19:17
I asked the ASME B&PV Code Committee a similar question a few years ago.  My question was as follows:

Re: ASME Section VIII Division I Boiler and Pressure Vessel Code Paragraph U1(c)2(h). Can a vessel that could be excluded from the scope of the Division because it operates at pressures less than 15 psig, but bears the Code Ustamp only because of owner requirements, be protected from overpressure with low-pressure relief devices other than those bearing either the UD or UV stamp such as spring-loaded or weighted-pallet type devices, or, an “open-to-atmosphere” vessel nozzle?

The ASME Code Committee response was as follows:
“Our understanding of the question in your inquiry and our reply is as follows:  
Question:  for a pressure vessel excluded from the Scope of Section VIII, Division I by the requirements in U-1(c)(2)(h), but that is constructed to the requirements of the Code including the application of the U Code symbol stamp, is it mandatory that such a pressure vessel be protected from overpressure by a UV or UD Code stamped safety relief device?

Reply:  Yes."

So, you see from the Code interpretation, that once you place the ASME stamp on the vessel, you must follow all of the rules, including outfitting the vessel with an ASME Code certified relief device.
pleckner (Chemical)
19 Jun 07 7:16
For reference, I believe @gene2007's question and the committee's answer is in the Interpretations, VIII-1-98-112, Issued March 22,2000.

moltenmetal (Chemical)
19 Jun 07 7:25
Wow:  that interpretation makes absolutely no sense.  I'm shocked that ASME would take such a point of view.  That's one ASME interpretation that I will recommend that vendors take exception to!

Design pressure, relief pressure and operating pressure are distinct from one another.  It is by virtue of the relief pressure, NOT the design pressure, that a vessel is distinguished from a non-vessel!  And "vessels", regardless of their design pressure, which are relieved below 15 psig by a means of relief device sized properly for the applicable relief cases, are no longer "pressure vessels" in Code terms.
pleckner (Chemical)
19 Jun 07 14:37
@moltenmetal, just what exactly would you recommend vendors take exception to? Are you recommending that the vendor disreagard the customer's request to stamp a vessel for a higher pressure than what it is to be used at?

The only thing we are saying is that, left by itself, if the vessel would normally not fall within ASME Section VIII, Div. 1 scope but you have the vessel STAMPED at a design pressure greater than 15 psig anyways (for whatever reason you might have), it must then be provided with an ASME certified relief device.
dcasto (Chemical)
19 Jun 07 16:10
Seems that as owner operator you could ignor the stamp and just do as you wish with the vessel.  You could always go back and use the vessel as you see fit later as long as you are the owner.  As for putting a non  code valve, it can't cost that much more than a code valve.  Then if the maintenance on the relief valve is a issure, only test and inspect it every 5 or more years, again not that much money.

All the things I say here are predicated that the vessel is in private ownership and not located where the general public has access.
Ashereng (Petroleum)
19 Jun 07 16:57
The ASME stamp on a vessel represents to everyone that the vessel follows the ASME code - all of the code. If engineers start recommending to follow one portion of the code, but not another, then the code really isn't a code anymore - like Captain Jack Sparrow said, "More like a guideline." If an ASME stamped vessel is used, then ASME code it is.

Nothing in ASME prevents you from using a non-stamped vessel. Perhaps this is a better solution to the OP?

While it is true that an owner can ignore ASME, and do as they wish, I think the question is why would you, as an engineer, recommend that they ignore portions of the ASME code? I think it is more prudent to say either follow the ASME code because it appplies, or do not follow the ASME code because it does not apply.

"Do not worry about your problems with mathematics, I assure you mine are far greater."   
Albert Einstein
Have you read FAQ731-376: Forum Policies to make the best use of Eng-Tips Forums?

pleckner (Chemical)
19 Jun 07 19:17
Wait a minute. @dcasto, what you wrote implies (and @Ashereng appears to be agreeing) that if a vessel falls within ASME Section VIII, Div. 1 scope the owner does not have to have it Stamped if they so choose not to? I'm hoping that what I read above has just been worded incorrectly or is just a generality; or is this in Texas, which is only one of two U.S. states that stil doesn't "get it".

I can't believe any engineer with any conscience can favor an owner ignoring ASME code and do as they wish. This is exactly the type of thinking (and corporate culture) that got BP into the heap of trouble it is now in!!

And yes, I saw the disclaimer by @dcasto, "All the things I say here are predicated that the vessel is in private ownership and not located where the general public has access."

Sure, you can build non-coded vessels and use them; not an issue (the original OP is about building what would normally be a non-coded vessel but changing it into a coded vessel by having it Stamped). But blatently disregarding code requirements because you choose to? This is just reckless and very dangerous thinking.
pipehead (Petroleum)
20 Jun 07 2:37
So, how did anyone surive at all before any code or standard, I mean we should all be dead eh?  Codes fill in for so any non engineer has access to engineering.  Anyoneone can get a pressure vessel today cheaper and easier because of standards or codes.  I'll defend Texas as a state that must have the most pressure vessels than most countries and I don't read about people dieing there daily because they are not with the program.

  I look at people who protect codes as if they the only thing in the world as protectionists. Should all vessel engineers only use COADE software and all others be outlawed, how about no software?  I got on the enlighted list of people that understand what standards are really for when working with some Russian engineers.  I thought that they had third world low life standards.  The engineer pointed out that their piping standards created a more conservative wall thickness than the US and that it allowed greater flexibilty than what we use.  What they really lacked was a standard door or light switch (all doors were custom made and there where 8 different sizes of light switches in every house).  Standards make for easier access, interchangability and should be lower costs, but NOT ALWAYS a safer product.

As for BP, their last accident had nothing to do with vessels.  Personally, I'll use the ASME standards where I am not familir with that portion of engineering (as my Texas PE requires me to and it the Right thing to do), but I'll defend anyone that desires to use any standard they wish to use.
pleckner (Chemical)
20 Jun 07 6:45
ASME is NOT a standard but LAW in all but two U.S. states (I still wonder what is taking those guys so long to get with the program?). I don't believe ASME is even classified as a standard in Texas; they leave that up to the API documents. Standards are there to help engineers interpret and apply the Codes (LAW) in a consistant fashion.

Before the Boiler and Pressure Codes, many people did not survive in many industries, that is why these Codes were developed in the first place. I ask you @pipehead, why OSHA? We didn't all die before they got involved either. If your father or grandfather survived, it was your fortunate luck. Other people weren't so lucky. Even one fatality due to NOT adopting the Codes is one too many.

The BP catastrophy was more due to a corporate culture than to the actual mechanism (and by the way, the fractionator involved is, or was, a vessel). Had the corporate culture been more in tune with process safety, the catastrophy would not have happened. Accidents can and do happen but it is the approach one takes and the way of thinking about process safety that can prevent many "unpreventable" accidents.

So even though the OP was about a vessel, this whole discussion almost boils down to a way of thinking, a "culture" if you will in terms of how to approach process safety.
moltenmetal (Chemical)
20 Jun 07 7:09
I apologize:  where I said "vendors" in my post I meant "owners".

I guess I can understand why ASME would take the position that they do:  you either take the entirety of their code or you take none of it.  You can't continue to call it a code-stamped vessel suitable for registration as such if you choose not to use a code-stamped relief device to protect it.

When a "vessel" is to be used for a service which permits it to be relieved at a pressure below 15 psig, what I recommend is what ASME recommends- to take NONE of their code because it simply need not be applied.  That the vessel in question was originally designed and fabricated in accordance with ASME VIII does not prohibit its later use as an atmospheric storage tank, a tank with a pad pressure of 5 psig relieved with a non-ASME relief device at 14.9 psig, or as a garbage can if you cut off one of its heads.
Armen75 (Chemical)
20 Jun 07 10:25
Does this mean that there are 2 options ?

De-rate the tank and remove the ASME stamping and putting in a non-code relief valve set at < 15 psig

Keep the tank's ASME coding and putting in a certified relief valve.  
the question here would be,considering operation at 5 psig : what would the setting on the RV be, minimum at 15 psig or at the vessel design of 50 psig ?
dcasto (Chemical)
20 Jun 07 10:58
Visit this site and tell us again that ASME is an absolute law
moltenmetal (Chemical)
20 Jun 07 14:17
Armen75:  you would be required, in order to stay out of ASME's domain, to set your relief valve at less than 15 psig, irrespective of the design pressure of your "vessel".  Setting the relief valve at 50 psig renders the "vessel" a pressure vessel as defined by ASME.
Ashereng (Petroleum)
20 Jun 07 14:56

Yes. An engineer may deviate from ASME codes, if in his/her expert opinion, a diviation is warranted. Deviations are not to be taken lightly, but they are allowed. Afterall, that is why we have licensed engineers - to determine what the best solution is.

By the way, I believe ASME is a standard/code/recommended practices/etc. The various laws in the 50 states reference ASME code/standard/recommended practices/etc. ASME is not a judicial branch of the US government last I checked.

Also, in many other jurisdictions, say Saudi Araia, ASME is also referenced. To say that ASME is a law in Saudi Arabia would be incorrect. To say that ASME is also referenced by Saudi law would be more correct.

Back to the OP. If your vessel is ASME stamped, then you should follow ASME - this reduces confusion, and increases consistency; which is also worthwhile.

"Do not worry about your problems with mathematics, I assure you mine are far greater."   
Albert Einstein
Have you read FAQ731-376: Forum Policies to make the best use of Eng-Tips Forums?

pleckner (Chemical)
20 Jun 07 15:09
ASME is only absolute law if the municipality says it is. That's why there are still rouge states out there. They don't want to adopt ASME. Nothing stops a municipality from changing what ASME says and make that law instead.

@dcasto, I didn't see anything in that report on the site you reference that changes anything I've said.

From the OP, I don't see anything that tells us this vessel is "real" but it sounds more like a request for information.

If the vessel is already stamped, then just supply a code certified valve and be done with it as suggested by @dcasto in his first post.
barnesed (Mechanical)
21 Jun 07 8:19
Wow!  I have to say that I didn’t expect the response so far to my original question.  I thank you all for taking the time to read the question and respond!  It has been very enlightening.

I’ve been an Instrumentation/Automation Engineer now for over 30 years now and was originally schooled back then by some very knowledgeable, dedicated engineers who took safety very seriously.  My belief has always been to use a coded relief device on a code stamped vessel, period.  In all that time, I have never been asked to put a non-code relief device, even one set below 15 psig, on a coded vessel.  So when this situation came about, I was surprised, yet curious.  I like to think I am open to alternative points of view.

In this case, a customer has existing, small portable tanks (5 to 50 gal.) that are all code stamped between 95 and 128 psig.  The customer wants these to pressure transfer the contents into another vessel using N2 via a regulator set <5 psig and expected that a small, cheap relief valve set <10 psig would be sufficient.  The basis was that the application was excluded from the Scope of Section VIII, Division I by the requirements in U-1(c)(2)(h).  I disagreed and stated that a coded relief device was required, but I was open to alternative views, thus my post on the forum.  I believe that the Interpretations, VIII-1-98-112, Issued March 22, 2000 in response to gene2007’s question validates my response and that is what I was looking for.  I can understand the argument that if a properly sized (for all scenarios) relief device set at 10 psig is provided, the vessel would be protected, however, I feel I would be doing a disservice and would be exposed to litigation if there was ever a problem, especially with prior knowledge of the Interpretations.

I’m still waiting for additional details from the customer, but aside from regulator failure, there are fire scenarios to consider as these vessels apparently can contain various solvents.  I had expected to have a coded relief device set at the stamped pressures and would be willing to add the cheap relief set at 10 psig for the regulator if insisted.  I’ll reserve final judgment after all details are known.
pleckner (Chemical)
21 Jun 07 13:36
@barnesed: Good for you! And as @dacasto wrote several posts ago, the cost may not be all that much between the lower set pressure non-coded relief device and a coded one.


I'm repeating myself. ASME is only LAW if the local municipality (not Federal government, although I wish it were) makes it LAW, not a standard, recommended practice or guide, and all but two U.S. states have adopted it as LAW, not a standard, recommended practice or guide. By the way, in the case of relief devices, ASME Section VIII, Div. 1 makes a horrible standard; API RP 520 and API Standard 521 do a much better job in that department.

If another country wants to make it their law, they may do so. If they only want to use it as reference, that is their perogative. Many parts of Europe have made their own law, better known as the PED or Pressure Equipment Directive. In many cases, this is even more conservative than ASME!

If the facility is located in a municipality that adopted ASME Section VIII, Div. 1 as LAW, an engineer MAY NOT deviate to a LOWER LEVEL than what the document dictates, period (at the risk of criminal neglegence if something goes wrong). They can be more conservative (safe) but never less.

I hope this subject has been beaten to death enough.

I suggest you pick up the document and read it (have plenty of time and no-doze available) and then read the interpretations that go along with them; I have because of the nature of my work but it isn't a picnic. In some places the document has more speghetti than an Italian restaruant.
jte (Mechanical)
21 Jun 07 14:00
A good discussion, and an often repeated one... Lots of valid opinions out there.

But, being mostly ignorant of the details of relief device issues, I'm a bit confused with regard to one issue which was mentioned in this thread:

Quote (JimCasey):

Well there IS the consideration that you can't buy a code-stamped valve set for less than 15 psig.  ...Because the code does not apply at less than 15 psi, as you pointed out.

Is it it really not possible to get a UD stamp on a relief valve set at 5 psi? Seems that this is similar to the fact that I can design/order/fabricate a vessel for a stated MAWP of 5 psi and still get it U stamped, even though it is out of the scope of VIII-1 U-1(c)(2)(h)(1) [note the A05 and A06 revisions for (h)]. Even though a 5 psi MAWP is excluded from the scope, in accordance with U-1(c)(2), ... however, any pressure vessel which meets all of the applicable requirements of this Division may be stamped with the Code U Symbol.

So is it not possible for a relief valve fabricator to UD stamp a valve set for 5 psi? Do the pressure tolerances get involved here? Is this application different from a U stamp?

dcasto (Chemical)
21 Jun 07 15:11
I guess what most people do not realize is that a city or state government can not force you to use ASME on you own private property and that is what a refinery in Denver CO did (a code state), they used their own proceedures and saved $100,000 per year in presure vessel maintenance and repair.

A city or state can mandate on public property or property that is accessible to the public safety of vessels.  It's like getting permits and inspections on your house if you remodel.  The state leaves it up to the county, the county up to the towns on inspections of private homes.  My brother in law worked for a major insurance company and said if you do your own elevtrical work and the house burns down they won't pay.  I asked if he wired up his own ceiling fans and changed his own light bulbs, which he did.  He said oh, thats different, right.

Its a private citizens right to do as he perfeers and assume the risks.  Even OSHA doesn't mandate ASME, its a performance based system, owners risk.
jte (Mechanical)
21 Jun 07 16:55

That may be true for some jurisdictions. In California, you don't have to use the ASME code. All you have to do is convince the chief of the state Pressure Vessel Unit that your way is better or at least equally good. Other states may vary...


(a) All unfired pressure vessels, boilers, and fired pressure vessels shall meet all applicable requirements of the Unfired Pressure Vessel Safety Orders and the Boiler and Fired Pressure Vessel Safety Orders unless the design, material and construction of the pressure vessel or boiler is accepted by the Division as equivalent to the ASME Code.

pleckner (Chemical)
21 Jun 07 18:08
Precisely what I've said. You can be more than ASME but not less.

To answer @jte, to have the stamp applied one must meet all of ASME applicable requirements. This does not just mean the design pressure and size, it also means minimum thicknesses, constructability, nozzles, and other things.

I did a google search and found that Kunkle (owned by Tyco) offers a few models of 'UV' National Borad Certified PSVs with set pressure limits below 15 psig. Ready for this one? Several models appear to have a low pressure limit of 3 psig (Models 912, 913, 918, 919)!
EGT01 (Chemical)
22 Jun 07 1:20
Appearances can be deceiving.  Have a look at Note 1 on page 7...

I believe you will find that other "brand-name" relief valve manufacturers can provide valves set at less than 15 psi but with a similar disclaimer... won't be "code" stamped.
pleckner (Chemical)
22 Jun 07 6:43
It seems so and my error for not investigating furher before shooting off my ..... The models I stated are listed as code valves with allowable minimum pressure but as pointed out by @EGT01, the cataloge indicates that they are non-code at these lower set points.

The best thing would be to talk to the manufacturer.
4Pipes (Mechanical)
22 Jun 07 7:56
What the fuss?  You need a pressure relief device anyway. You need design rules of some form even if its from a text book.  Chances are that a code stamped PSV set at MAWP with smaller vent pipe as somebody above pointed out would cheaper than something bigger and not code stamped.  You'd spend saving, if any, on the extra design effort.  The costs of trying to convince some box-ticking "more than my jobs worth" inspector" could be open ended.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close