Differential pressure sensor on flammable gasses

Brian123

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Sep 2007
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Has anyone used a sensor like this on flammable gasses like natural gas? I have an orifice plate installed in a gas line that I'd like to monitor via PLC. Right now, it has hose barbs and shutoff valves suitable for connecting a handheld meter to get a reading.


For monitoring air supplies, I usually mount these sensors in the same enclosure as the PLC and use hose and bulkhead fittings to bring the pressure sensing lines to the sensor. I'm guessing it's a bad idea to bring flammable gasses into an electrical enclosure in the same fashion. How is this situation usually handled? Mount the sensor outside the enclosure? Upgrade to a (way more expensive) sensor?

Thanks!
 
Has anyone used a sensor like this on flammable gasses like natural gas? I have an orifice plate installed in a gas line that I'd like to monitor via PLC. Right now, it has hose barbs and shutoff valves suitable for connecting a handheld meter to get a reading.


For monitoring air supplies, I usually mount these sensors in the same enclosure as the PLC and use hose and bulkhead fittings to bring the pressure sensing lines to the sensor. I'm guessing it's a bad idea to bring flammable gasses into an electrical enclosure in the same fashion. How is this situation usually handled? Mount the sensor outside the enclosure? Upgrade to a (way more expensive) sensor?

Thanks!

It's not a problem to obtain an instrument rated for use with NG, but I personally wouldn't bring gas lines into my PLC cabinet. What is gained by doing that? It's easier and more effective to minimize the tubing length and extend the wiring length for the instrument instead.
 
You can not use plastic pipes with natural gas in a fixed installation or take the gas to an electrical cabinet (high risk of explosion)

The transmitter should be preferably similar to the one on the photo, mounted near the measuring orifice and using metal pipes.

differential-pressure-transmitters-250x250.jpg
 
It's not a problem to obtain an instrument rated for use with NG, but I personally wouldn't bring gas lines into my PLC cabinet. What is gained by doing that? It's easier and more effective to minimize the tubing length and extend the wiring length for the instrument instead.

Hmm, maybe I'm asking the wrong question. Perhaps I should have asked what options are available around the price range of the linked sensor that would be suitable for NG.

I've only ever used this type of sensor for air pressure monitoring. In the few instances I've used them, it ended up being easier to run tubing to the control cabinet then to mount the sensor locally and run wiring to it.

Just tossing around some ideas in my head for a future project and being too lazy to do actual research, I guess :ROFLMAO:
 
I've only ever used this type of sensor for air pressure monitoring. In the few instances I've used them, it ended up being easier to run tubing to the control cabinet then to mount the sensor locally and run wiring to it.

It may be easier and less expensive to route plastic tubing than to run armored cable or conduit, but you can't do that with NG. Ask your distributor about instruments rated for use with NG. They aren't uncommon.
 
Has anyone used a sensor like this on flammable gasses like natural gas? I have an orifice plate installed in a gas line that I'd like to monitor via PLC. Right now, it has hose barbs and shutoff valves suitable for connecting a handheld meter to get a reading.


For monitoring air supplies, I usually mount these sensors in the same enclosure as the PLC and use hose and bulkhead fittings to bring the pressure sensing lines to the sensor. I'm guessing it's a bad idea to bring flammable gasses into an electrical enclosure in the same fashion. How is this situation usually handled? Mount the sensor outside the enclosure? Upgrade to a (way more expensive) sensor?

Thanks!
what are you trying to accomplish? monitoring the flowrate of a gas line or monitoring pressure on a gas line?
 
Piping natural gas through plastic tubing is not only against the advice of others, it is not allowedd by NFPA code. Beware the liability.

National Fuel Gas Code NFPA 54-2006 ANSI Z223.1-2006

5.6 Acceptable Piping Materials and Joining methods

5.6.4 Plastic Pipe, Tubing, and Fittings.
5.6.4.1 Plastic pipe, tubing, and fittings used to supply fuel gas shall be used outdoors underground only and shall conform to ASTM D 2513, Standard Specification for Thermoplastic Gas Pressure Pipe, Tubing, and Fittings. pipe to be used shall be marked "gas" and "ASTM D 2513."

Various ASTM standards are cited for other piping metallic materials-of-construction that are listed in NFPA 54.

The class of industrial grade pressure transmitters recommended above are designed for threaded connections for suitable metallic piping.
 
So the area where the orifice plate is installed is probably a hazardous area?
You have the following options:
1. Install an explosion proof transmitter.
2. Install an intrinsically safe transmitter and associated loop.
3. Install your transmitter in an air purged box. This will introduce further requirements to monitor the air purge and take appropriate action should the purge be compromised in some way. (these systems are generally a pain in the butt).
4. Don't install a transmitter.

The cost of a certified transmitter will generally be fairly expensive compared with the one you indicate.
 
The electrical material for measurement and control in natural gas installations, such as transmitters, valves, pressure switches, flow counters, etc. does not need to be Ex-proof but the space where it is installed must be ventilated with openings to the outside of a minimum section that the standards indicate.

Just use a normal process differential pressure transmitter like a Siemens or a Rosemount 3051 and install it in a support near the orifice and use metallic tubing.
 
The electrical material for measurement and control in natural gas installations, such as transmitters, valves, pressure switches, flow counters, etc. does not need to be Ex-proof but the space where it is installed must be ventilated with openings to the outside of a minimum section that the standards indicate.

Just use a normal process differential pressure transmitter like a Siemens or a Rosemount 3051 and install it in a support near the orifice and use metallic tubing.

The reason why it doesn't need to be Ex in your opinion is precisely because the place has to be ventilated enough where a leak would never achieve the minimum ignition mixture with air.
Is the standard for NG different than IEC600079?
 
I agree completely with cardosocea. As you are in the USA I would seriously consider checking out the NFPA 70 on electrical installations with respect to gas systems installations and and the requirements are clearly given there.
 
Areas with Natural Gas regulating, measuring and also combustion equipment in which I worked for many years are not considered areas with risk of explosion, therefore that IEC600079 norm is not applicable.

In fact, electric and electronic devices for use with GN that brands such as Kromschroeder or Eclipse sell are not Ex-Proof
 
Last edited:
what are you trying to accomplish? monitoring the flowrate of a gas line or monitoring pressure on a gas line?
I was looking to monitor the flowrate in a natural gas supply line to a furnace. I was hoping to detect changes in total flow over time in an automated way. The furnace itself is under 1 million BTU/h input. If the sensors were reasonable in cost, I could expand the monitoring to each of the 8 burners individually.
 
Piping natural gas through plastic tubing is not only against the advice of others, it is not allowedd by NFPA code. Beware the liability.

National Fuel Gas Code NFPA 54-2006 ANSI Z223.1-2006

5.6 Acceptable Piping Materials and Joining methods

5.6.4 Plastic Pipe, Tubing, and Fittings.
5.6.4.1 Plastic pipe, tubing, and fittings used to supply fuel gas shall be used outdoors underground only and shall conform to ASTM D 2513, Standard Specification for Thermoplastic Gas Pressure Pipe, Tubing, and Fittings. pipe to be used shall be marked "gas" and "ASTM D 2513."

Various ASTM standards are cited for other piping metallic materials-of-construction that are listed in NFPA 54.

The class of industrial grade pressure transmitters recommended above are designed for threaded connections for suitable metallic piping.

Sorry for the confusion, everyone. I wasn't intending to imply that I would be using plastic or rubber to connect natural gas lines to a sensor. I do appreciate the references though, from everyone!
 

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