Natural Gas Pipeline Hazardous Location Classification

[rroark0003]

Would a field mounted natural gas pipline meter set be considered a class 1 division 2 location? The piping configuration consists of a Natural Gas well head with piping extending about 10' horizontally. I have a flow meter mounted on the piping above a flanged orifice plate. Also, are seals required for this installation?

 

[kwired]

I am not familiar with this situation but one of the first questions to ask - is there normally gas present other than inside the pipeline?

 

[Smart $]

Would a field mounted natural gas pipline meter set be considered a class 1 division 2 location? The piping configuration consists of a Natural Gas well head with piping extending about 10' horizontally. I have a flow meter mounted on the piping above a flanged orifice plate. Also, are seals required for this installation?

Hazardous locations are required to be documented, so you should ask pertinent parties (at the very least, the AHJ). Short of knowing for certain, I would not hesitate to consider it CID2. Need more details to determine need for seal(s).

 

[rbalex]

From NFPA 497 (API RP 500 has a similar statement):

5.4 Unclassified Locations.
5.4.1 Experience has shown that the release of ignitible mixtures from some operations and apparatus is so infrequent that area classification is not necessary. For example, it is not usually necessary to classify the following locations where combustible materials are processed, stored, or handled:
(1) Locations that have adequate ventilation, where combustible materials are contained within suitable, well maintained, closed piping systems
(2) Locations that lack adequate ventilation, but where piping systems are without valves, fittings, flanges, and similar accessories that may be prone to leaks
(3) Locations where combustible materials are stored in suitable containers

Essentially, a "closed piping system" [5.4.1(1)] is one that has no designed paths to atmosphere, such as relief valves.

 

[Smart $]

...

Essentially, a "closed piping system" [5.4.1(1)] is one that has no designed paths to atmosphere, such as relief valves.

What about the suitability of flowmeter itself? Assume an invasive type, especially since the OP mentioned orifice plate.

 

[rbalex]

What about the suitability of flowmeter itself? Assume an invasive type, especially since the OP mentioned orifice plate.

Assuming all valves, plates, fittings, flanges, etc. have the proper pressure ratings; it is still a closed piping system unless for some reason the flowmeter was designed to deliberately discharge to atmosphere on a reqular basis. That isn't likely with a natural gas line.

 

[rroark0003]

Assuming all valves, plates, fittings, flanges, etc. have the proper pressure ratings; it is still a closed piping system unless for some reason the flowmeter was designed to deliberately discharge to atmosphere on a reqular basis. That isn't likely with a natural gas line.

The piping system is rated properly and is a closed. The only time the piping system will be open is during an orifice plate inspection. However, prior to the inspection the 10' section of 2" piping is vented to atmosphere.

The enclosure containing the electronic circuit boards for the flow meter is approved for a class 1 division 2 location. Currently, we have two cables entering the enclosure, one is LFMC containing the wiring from a solar panel, the second entry is an RTD cable terminated with a CGB. My biggest concern is if seals are required to be installed at the enclosure.

 

[rbalex]

Before anything else, the location must be properly documented. [500.4(A)] This has been an NEC minimal requirement since 1999.

Since venting will be a "normal" practice, there will be both Division 1 & 2 envelopes around the vent’s exhaust. Typically, 1.5’ and 10’ radii, but it will depend on several factors that the documentor will need to research.

Enclosure and boundary seals will depend on the meter's location relative to the classified envelopes.

 

[stickelec]

Would a field mounted natural gas pipline meter set be considered a class 1 division 2 location? The piping configuration consists of a Natural Gas well head with piping extending about 10' horizontally. I have a flow meter mounted on the piping above a flanged orifice plate. Also, are seals required for this installation?

Your flowmeter IOM manual is going to tell you the requirements you are asking about. Typically an RTU designed for natural gas service is going to be rated Div.2 (otherwise it would require long tubing lines thereby violating good measurement practices) and the enclosure is going to be Nema 3R or 4. The enclosure design alone tells you the seals would be of no benefit. Your blowdown will need to be at least 5 ft away from the meter. If you blowdown at the orifice-fitting itself you will raise the classification to Div.1. and likely violate the rating of your RTU. Don't go by what i say, check your IOM manual.

 

[rbalex]

I endorse stickelec's post. I overlooked the remote nature of the installation as indicated by the solar panel. You still need to have the location properly documented.