ASME STAMP- ABOVE 14.7 PSIG ONLY 1

[Mechy]

I am not in the field of pressure vessels. The question is why a vessel rated for less than 14.7 psig, not required to have an ASME stamp. Is there less chance of injury etc ??

There could be a vessel holding a high "volume" at 14.7 psig and a veseel holding very less volume at 14.7 psig. Does this make a difference. Why the volume is not taken into account along with the 14.7 psig ??

 

[prex]

As you correctly stated, it is a matter of public safety.
The choice of not limiting the size is in fact questionable (other national codes do provide such limits), but that's it, at least at the moment. prex

http://www.xcalcs.com

Online tools for structural design

 

[abbver98]

The safety threshold of construction taking into account all parameters (dimensions, pressure, fluid, …) is evaluated by practices. We know that in pressure vessel the energy = Fluid energy + Wall energy (that behaves as a spring). When an explosion occurs, the work of gaz is like : W = C.P.V. where P : pressure, V: Volume and C : contant depends on gaz. You see in this formula that the pressure and the volume intervene in the safety of the vessel.
In other hand, the deformation energy of a cylindrical vessel is like : E=V.(P^2).D/2.e.E where D: diameter, e:thk and E: Young Modulus. V, P and D/e (wall flexibility) intervene in the safety of the vessel.

 

[CHD01]

This is a bigger subject than I have time to repsond to. But let us just say that we have API standards for the construction of low pressure ( < 15 psig) storage tanks. Most tanks designed to the API standards tend to be for large tanks used for liquid storage. For > 15 psig it is a REQUIREMENT to design to the ASME Code. Costs usually prohibit building large tanks (about 20 ft diameter is the break point) designed to the ASME Code for > 15 psig. Again, I have designed to the ASME Code for a tank as large as 20ft x 20 ft - but even here the design pressure was < 25 psig. The more you learn, the less you are certain of.

 

[vesselguy]

Another fun discussion.

I understand that for simplicity to provide a break for the Codes and Standards, the wise ones deceided API-620 shall cover everything less than 15 psi-2psi and let ASME cover everything above that. And of course, if it is covered under ASME code than it requires ASME stamp. Is there a better reason? I too like to know.

As for the question of whether volume is taken into account or not, our Canadian jurisdictional law and regulations for some Provinces stipulate rules that include volume and pressure as part of the rules to determine whether it needs to be registered. Thus it implies requirements for stamping and third party inspection. I heard some jurisdiction in State side is like this too. Right?

 

[CHD01]

Except for a tiny bit of knowledge about Ireland and UK; I'm not familiar with other than US regulations. On your other question, I too do not know. The more you learn, the less you are certain of.

 

[ghopkins]

ASME Section VIII, Class 1 stamp for pressure vessels is not required in AZ, CT, FL, LA, MT, NM, SC, SD, and WV. Unfortunately, pressure vessels are not covered by a Federal Law - yet - States are currently given jurisdiction. ASME Section X (fiberglass) is only required in about 60% of the states. If you ask me, I would think fiberglass pressure vessels should be code stamped more so than steel vessels.

The question of stamping requirements below 15 psig may be answered soon by the US Chemical Safety Board. Please see following links:

http://www.chemsafety.gov/news/2002/n20020804.htm

http://www.chemsafety.gov/news/2002/n20020904.htm

http://www.chemsafety.gov/news/2002/n20020903.htm

A very bad accident (mostly due to company negligence) may prompt the government (OSHA) to require all vessels with hazardous chemicals to have some kind of stamp or certification as an extra precaution in addition to normal preventative maintenance.

ASME does have a standard (not code - yet) for fiberglass vessels that are full vacuum to 15 psig. I only know this because I specify and build vessels to this standard (as well as Section X). It is called RTP-1 (&quot;RTP&quot; stamp). Some of my customers require an ASME stamp (corporate directive) whenever its available - even if the pressure is below 15 psig. This not only insures them a better product if they have no corporate specifications, but the lawyers like it since it could reduce liability if there ever was a problem.

Also reference these sites:

http://www.osha.gov/SLTC/pressurevessels/index.html

http://www.americanchemistry.com

The OSHA site combined the the Responsible Care Initiative of the American Chemistry Council will probably some day be combined into a federal law for all containment equipment.

ghopkins@rl-industries.com

Hope this helps,
Greg

 

[CHD01]

Thanks Greg, by the way you can add Texas as a non-code state. The more you learn, the less you are certain of.

 

[ghopkins]

Thanks. My program listed TX as requiring Section VIII, but it had a little asterisk indicating only portions are required... Maybe that means vessels have to be built by code shops, just no stamp applied? Or does it means just to &quot;build to the code.&quot;

My company gets that statement a lot, &quot;Please give us everything but the stamp.&quot; Little do they know that means it does nothing to reduce the cost for shops already certified by ASME.

 

[jte]

ghopkins-

I agree with the fabrication cost issue of stamping or not stamping vessels. Also, I generally favor stamping vessels. However, I also understand the perspective of the &quot;don't stamp it if you don't have to&quot; crowd.

One reason your clients might be requesting &quot;everything but the stamp&quot; is post-construction cost issues. If the vessel is not stamped / National Board registered, the paperwork / authorization for repairs is much less burdensome. In my state, piping may be repaired on line with minimal or no jurisdictional (ie State OSHA types) notification or interference. Putting a temporary repair on a code stamped vessel online is much more burdensome. In addition, inspection requirements may be different. In addition, safety valve requirements are different: Consider a strainer for a 24&quot; pipeline with a 50 psig design pressure. The strainer vendor can sell me one with or without a Code stamp. If I buy one with a Code stamp I must also add a PSV and typically piping to the flare system. Now the PSV costs as much as the strainer and must be serviced on a regular basis so I need a spare PSV in addition. If I buy the same strainer without the code stamp, it is just another piping component...

jt

 

[CHD01]

jte: A couple of points:

1. A non-code repair to a code-stamped vessel can be made; it just is not guaranteed to meet the code any more. So the paper work is no greater unless you want to maintain the stamp - in which case you have to do it anyway.

2. There is now a code exception that does not require a relief valve for every code stamped vessel if it cannot be over-pressured from an external cource. Just quote the ASME Code Exception.

3. The need for a relief valve is determined by the maximum allowable working pressure of the system including vessels; whether the vessel has a code stamp or not. In days gone by, this meant that you had to guarantee a 10% max overpressure for code stamped vessels; but now we have liquid and vapor trim that guarantees that. So only if you are using a liquid trim valve in vapor servifce will you see a change in the relief valve.

4. Finally, there are exceptions diameter and volume wise to the ASME Code; in your strainer example this may eliminate the need for a relief valve; yet if it meets these exceptions; I believe it can still be ASME Code Stamped (I don't have the procedure in front of me right now). ghopkins am I right?
The more you learn, the less you are certain of.

 

[ghopkins]

It appears the discussion has changed course from whether or not to stamp a vessel to whether or not a vessel needs a relief device - the latter of which is a very touchy subject as evidenced in other threads. But as mentioned above, these are very related issues. I hope, however, that people don't make relief requirements and Code stamps excepted in plant design and operating parameters simply because of the cost of implementing safety guidelines. I will be the first to admit that the paperwork and time required to fully comply with federal and state guidelines is quite burdensome and even moreso when ASME vessels and relief devices are involved.

In my previous life, I've designed and specified many relief devices - open pipes, spring valves, and rupture disks just to name a few. At the company I was with, nearly everthing (piping and vessels) had to be protected from over pressure (internal or external). One of the most common problems was thermal expansion of fluids in long runs of pipe - usually blowing out gaskets. Yes, by the rules and codes, relief valves are not required in &quot;pipe&quot; and often times it doesn't make sense to protect every pipe run with a relief valve as it gets way to costly. In general, it depended on the hazards of the fluid. There are other creative ways to relieve pressure - process control programming, ball valves with weep holes, etc.

Now to my current life: I will only claim familiarity to ASME Section X. In this code, Article RG-121 makes a few general statements for items not covered by the code:

1. a &quot;vessel&quot; 6&quot; in diameter and under

2. &quot;piping systems whose primary function is the transport of fluids from one location to anther within a system of which it is an integral part&quot;

3. &quot;piping components, such as pipe, flanges, bolting, gaskets, valves, expansion joints, fittings and pressure containing parts of other components, such as strainers, and devices which serve such purposes as mixing, separating, distributing and metering flow, provided that the pressure containing parts of such components are generally recognized as piping components or accessories&quot;

Lawyers could have a field day with those statements. I'll leave it at that.

ASME Section X also has a few sections dedicated to relief requirements - Part RR &quot;Pressure Relief Devices&quot; and Appendix AB &quot;Nonmandatory Installation and operation.&quot; These make mention of ASME Section IV, Article 4 and ASME Section VIII, Division 1, UG-125 to UG-146. Basically, these state that every pressure vessel must have a location (nozzle) for a relief device. The nozzle must be of proper size and location - yada, yada, yada...

I hope this helps a little.

 

[vesselguy]

ghopkins and CHD01,

A very interesting discussion here.
I totally agree FRP vessels should all be build t RTP-1. I have bought many of these vessels in past company. But, the problem is not many FRP fabricators are qualified to RTP-1 but yet are able to build good FRP vessels.

ghopkins, you talk about a table you have which lists the stamping requirements in the States. I'm in Canada but sometimes I have to do jobs in the States. Can you guide me to a site that will list the stamping requirements in all States and the name of the Governing Board there?

Thanks

 

[ghopkins]

vesselguy,

Here's the information. The program you want is titled:
&quot;SYNOPSIS{c} of Boiler and Pressure Vessel Laws, Rules and Regulations&quot;

Please go to the link:

http://www.nationalboard.org/synopsis.html

It will be available for purchase starting in 2003 from the National Board since the Uniform Boiler and Pressure Vessel Laws Society was dissolved. I have the 2001 version as a program and it is very informative. It is the only comprehensive source of information I've been able to locate for information regarding US and Canadian code requirements for States and Provinces. Does anyone else have other sources?

ghopkins

 

[jte]

Well, CHD01, I think we work in different states. In response to your comments:

1) Of course, we could make non-code repairs to a vessel. In my state these would be considered illegal repairs and we would be required to take the vessel out of service by our State OSHA folks. A Code vessel must be maintained as a Code vessel in California. I could also remove the catalytic converter off my car for better performance - but that would be naughty also.

2) The Code excemption which I believe you are referring to is a Code Case - something about handling relief requirements through system design. Again, working in California may be different than in your state: Code Cases are condsidered a supplement, not a part of, the Code. Thus, Code Cases may be only applied with the prior written consent of the State. Guess what! The State hasn't approved the &quot;system design&quot; Code Case for application in California.

3) The system, piping, vessels, etc. must be protected. I agree with you on that. Unless your car-seal open (CSO) all of your block valves, though each portion of the system which may get blocked in must be protected. Even liquid PSV's cost money and must be maintained.

4) I agree with you half way on this point: VIII-1 U-1(c)(2)(i) provides a 6&quot; diameter limit. I don't see a volume limit, though. If you find one, let me know. You are also correct that vessels may be stamped even if they are not included in the scope of VIII-1. This is in VIII-1 U-1(c)(2). However, my strainer example stands. The sticky part for strainers is in VIII-1 U-1(c)(2)(e). However, if we happen to order a strainer with a U stamp, we may not (again, in California, your location may be different) decommission the the strainer as a vessel and keep using it. The integrity of the Code stamp must be maintained.

I agree with Vesselguy - this has been an interesting thread.

jt

 

[CHD01]

jte:

Ref 1) and 2): Interesting comments, while I knew there were variations between states I had no idea California was as restrictive as it is(I don't mean that in a negative way). All states should be like Calif.

Does anyone know of a web site that summarizes state differences in the application of the ASME Code?

Ref 3) I agree generally, but NOT EVERY section of pipe isolated between block valves in liquid service should require a liquid thermal relief valve. To do so in most plants would be to increase the number of relief valves in service many-fold. Instead we evaluate a number of factors for the installation (plant) considering: length between block valves, hazardous rating for fluid, diameter and material of pipe, type of gaskets installed, whether flanges are bolted, pressure rating of pipe versus operating pressure, potenital to completely fill pipe (inlcuding dead-ended pipe, etc) with liquid, probability of flange leakage relieving required rate, consequences of a failure,provision of a gas filled expansion chamber in lieu of a relief valve, whether a fluid is flammable, etc, etc - and then make a determination whether liquid thermal relief valves will be required. By the same token - if length of pipe bewteen block valves is excessive a hazard analysis may determine more than one rv is needed.

Ref 4): Your point is noted, I was referiing to ASME Section VIII, Division 1, Section U-1 in general where depending on the vessel and the material contained there could be volume, pressure or diameter limitations as to whether the code applied or note. Sorry if I confused things.

Regards






The more you learn, the less you are certain of.

 

[CHD01]

I'm sorry ghopkins, I forgot that you already provided a web link summarizing code state requirements! The more you learn, the less you are certain of.

 

[Mechy]

CHD01 and vessel guy's replies seem to answer the question.
I believe &quot;simplicity&quot; was the key word here to divide jurisdictions of API and ASME.