Integrated Production Unit/Meter Run Process Safety

[akoester]

I'm a Facilities Enigneer, and I recently started working in the Marcellus. A lot of the production units installed in Appalachia have meter runs integrated with the production unit skids (picture attached) - installed on the exterior of the cabinet. Our first generation pad design has the traditional set-up with separate meter houses, but the integrated design would save up significant space on the pads and time/materials for construction. I am working on reviewing the safety of this design. I believe the new hazard would be the potential for flash fire from the gas cloud released when changing the meter orifice plates.

I can quantify the volume of gas released from the chamber of the meter body when changing plates and I have the size of the orifice through which it is vented (1/4") - my question is how to then calculate the radius of flammability from the release to see if there is potential to reach the unit burner? My though was to calculate the release as dispersion from a single relief source. I have been reviewing API 521 section 6.3.2.2 Vapor emission. Would these equations be applicable if the release is indeed a (very short) jet exit?

Anyone else already using this design? Any suggestions on how to correctly evaluate the flash fire hazard?

 

[zdas04]

It is very common to put meter runs inside of production unit enclosure, but mostly people use dual chamber fittings (like a Daniels Senior fitting) instead of simplex fittings. I have no problem with the tiny amount of vented gas from a Senior fitting within an enclosed space. I'd be less caviler with a simplex fitting or an OFU inside, neither seem very house trained to me.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[akoester]

Thanks, David.

We are using a dual chamber currently and plan to use them going forward. There is no way I will get approval for installation inside the cabinets. My I&E TL says that it will be too difficult to change plates in the dual fitting in the enclosed space. Also, my management is convinced that there is a greater safety risk with the gas release inside the cabinet, as opposed to outside. (Though I believe installation inside the cabinet offers better isolation from the burner, if that is the concern.)

Part of the push back from management on any integration is that "this isn't done anywhere else" - have you seen the meters inside the cabinets in the basins out west?

 

[zdas04]

I had 125 wells in the San Juan Basin CBM Fairway where every single meter run was inside the separator enclosure. Other than that there are about 30,000 wells in the San Juan Basin with meter runs within meter houses. I would say that there are something like 10,000 wells in the Piceance Basin with the meter runs inside the separator enclosure. I just looked at my pictures of the Barnett Shale and they focused on water disposal stuff and I don't have a good picture of well equipment. In the Antrium Shale my pictures focused on compressor stations and the incredible amount of snow that was on everything. I could probably find CBM or Tight Gas pictures if that would help, but not Shale Gas. I've uploaded an example from the largest producer in the San Juan that has been in place for nearly 30 years without burning anything down. Guess they were just lucky. This is so normal that I haven't taken any pictures of meters in separator enclosures since I went digital.

Other than nearly every field I've ever worked in (which is a large number of fields), I guess it isn't done anywhere.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[BigInch]

You've got to be kiddng. Have things gotten so, well so.. ? Makes me wonder how the hell we'd ever got a 5000 hp compressor in an enclosed building, with all the potential seal leaks, valve packings and fittings, lube oil vapors, etc. never mind a meter plate fixture. Don't know if they're still doing this today in the Gulf, but we had meter houses offshore that were considered non-hazardous, if the meter house had something like 4 or 5 changes of enclosed air volume with the outside atmosphere every hour accomplished solely by natural ventilation; air inlet vents in the side of the building and a couple of vent turbines on the roof.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek