Non-ASME relief valve on code-stamped vessel 4

[barnesed]

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?

 

[pleckner]

@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.

@Ashereng:

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]

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:

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?

jt

 

[dcasto]

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]

dcasto-

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...

From

http://www.dir.ca.gov/Title8/6857.html:

(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.

jt

 

[pleckner]

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]

Appearances can be deceiving. Have a look at Note 1 on page 7...

http://www.tycoflowcontrol-na.com/ld/KUKMC-0396-US.pdf

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]

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]

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.