small valve free pass

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Do small valves 2" and below get a free pass? I say NO …


Somebody on the job smarter than me says:


"Per API 500 Section 9.1.5, Areas surrounding small valves do not need to be classified since the definition of small valves is not provided by API. Valves 2" and smaller are considered small valves, except for Hydrogen service, where only valves smaller than 2" are considered small because of the increased hazard associated with Group B materials."


I think it always depends on the environment, the product and ignition source regardless of the piping size. What say you?
 

rbalex

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To answer the initial question, small valves don't get an automatic "free pass"; however, the real question is, "What constitutes a 'closed piping system'?"

I'm going to cite NEC Section 500.5(B)(2)
Informational Note No.2: Piping without valves, checks,
meters, and similar devices would not ordinarily introduce
a hazardous condition even though used for flammable liquids
or gases. Depending on factors such as the quantity
and size of the containers and ventilation, locations used for
the storage of flammable liquids or liquefied or compressed
gases in sealed containers may be considered either hazardous
(classified) or unclassified locations. See NFPA 30-
2012, Flammable and Combustible Liquids Code, and
NFPA 58-2014, Liquefied Petroleum Gas Code.
Note it DOES NOT say, "Piping with valves, checks, meters, and similar devices ..." should be considered classified sources.

From NFPA 497[2017]:
5.6.4 When classifying buildings, careful evaluation of prior
experience
with the same or similar installations should be
made. It is not enough to identify only a potential source of
the combustible material within the building and proceed immediately
to defining the extent of either the Class I, Division
1 or Division 2; or Class I, Zone 1 or Zone 2 classified areas.
Where experience indicates that a particular design concept is
sound, a more hazardous classification for similar installations
may not be justified. Furthermore, it is conceivable that an
area be reclassified from either Class I, Division 1 to Class I
Division 2, or from Class I, Division 2 to unclassified, or from
Class I, Zone 1 to Class I, Zone 2, or from Class I, Zone 2 to
unclassified, based on experience
.[rbalex: underlines and bold are mine]
I won't cite them all, but API RP500 makes similar "experience" statements throughout.

My personal opinion is that "closed piping" has no intentional designed paths to the atmosphere, such as relief valves or ports AND has sufficient pressure ratings for valves, flanges, etc.
 
feedback

feedback

Thanks for the feedback. I should have mentioned that all valves are threaded connections and threaded bonnets so the source points at the valves are the threaded connections. The source points are the connections that set the boundary limits.

Al
 

rbalex

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Thanks for the feedback. I should have mentioned that all valves are threaded connections and threaded bonnets so the source points at the valves are the threaded connections. The source points are the connections that set the boundary limits.

Al
That would have indeed been useful information. I would note however that process, mechanical, and piping designers aren't usually too keen on creating commonly or naturally "leaky" mechanical systems though; i.e., are the threads intentionally designed to be paths to the atmosphere for volatile process fluids. Nevertheless, certain mechanical seals are prone to leak over time though. This is where the "experience" as mentioned earlier, as well as known maintenance practices, come into the overall classification evaluation process.
 

MrJLH

Senior Member
Location
CO
Noticed you are referencing section 9 of API 500. Are you in a refinery?

Did you look at API 500 10.15.1.1? I just got out of a discussion about this.
 
small valves classification

small valves classification

This is the API section quoted for the decision not to use small valves as a source point depending on the commodity:

API 500 9.1.5 Experience has shown that the occurrence of flammable material liberation from some operations and apparatus is so infrequent that it is not necessary to classify the surrounding areas. An example of such an area is an adequately ventilated location where flammable substances are contained in suitable, well maintained closed process piping systems that include only the pipe, fittings, meters and small valves.
 

MrJLH

Senior Member
Location
CO
API 500 10.15.1.1 Control Panels Containing Instrumentation


Can you give me heading of the section you are looking at? Thanks


Al

Looking at API now 10.15 refers to Screwed Connections, Flanges, Valves, and Check Valves. But I guess since you are in a refinery, which I wasn't expecting.
 

kwired

Electron manager
Location
NE Nebraska
Yes, in a Northern California refinery. I'll review your API ref. Thanks
refinery may have classified area on outside of closed piping system.

This is different than say a typical closed system gas line with solenoid valve to a boiler in an otherwise non classified area.
 

cbass123

Member
Location
Utah
Occupation
Electrical Engineer
API RP 500 Annex D, Section D.5.7 used to be called "Flanges and Valves" from what I've found, but is now just called "Flanges". I think you would want to assign a hazard radius for all process control valves in a refinery. A 5 or 10 ft. radius per D.5.7 seems appropriate. However, looking at section 9, it doesn't seem right to slap a 50 ft. radius on every valve either.

If I'm classifying locations at a drilling site, and can give control valves an 18" radius per 10.15.2.1, it doesn't seem like there should be a 48 ft. discrepancy just because one valve is at a refinery, and the other is at a production site.

Does anyone have a good method for assigning a radius to a control valve in a refinery?
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
API RP 500 Annex D, Section D.5.7 used to be called "Flanges and Valves" from what I've found, but is now just called "Flanges". I think you would want to assign a hazard radius for all process control valves in a refinery. A 5 or 10 ft. radius per D.5.7 seems appropriate. However, looking at section 9, it doesn't seem right to slap a 50 ft. radius on every valve either.

If I'm classifying locations at a drilling site, and can give control valves an 18" radius per 10.15.2.1, it doesn't seem like there should be a 48 ft. discrepancy just because one valve is at a refinery, and the other is at a production site.

Does anyone have a good method for assigning a radius to a control valve in a refinery?
Seeing as how this is a year and half old thread you may get better response by asking the refinery guy directly. You can try to PM rbalex.
 

rbalex

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Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
I'm going to repeat post #2
To answer the initial question, small valves don't get an automatic "free pass"; however, the real question is, "What constitutes a 'closed piping system'?"
...
My personal opinion is that "closed piping" has no intentional designed paths to the atmosphere, such as relief valves or ports AND has sufficient pressure ratings for valves, flanges, etc.
A properly designed valve with a proper pressure rating has no release rate.

Referencing API RP500 Section D.2 and Figure D.2: what isn't shown in Figure D.2 is a "'Zero' Mass release rate". (Yeah, I know that zero is less than 10 gal/min, but if you have any discernable "release", you have a bigger problem than determining a hazard radius) That is, a "closed piping" system would have a 0' hazard radius.
 
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