Flare Gas Measurement devices
Flare Gas Measurement devices
(OP)
What have been your experience with Flare gas flow meters? Our refinery (2 Plants) has three flares and measures the gas going into the flares stack (GE Sensing) after Water Seal Drums. On the case of one of the Plants, on ocassions of events of high pressures, when both flare gas meters should have read flow, one does and the other doesn't. The one that does, it reads two to threefold the amount being released (per our estimates). What type of technology do you use? Have you considered other technologies? Thanks, Airbus





RE: Flare Gas Measurement devices
Best Regards
Qalander(Chem)
RE: Flare Gas Measurement devices
RE: Flare Gas Measurement devices
RE: Flare Gas Measurement devices
RE: Flare Gas Measurement devices
I've also had very poor results from Ultra sonic meters at low pressures. Especially in a line to a flare where you just don't know what the make-up of the flow is going to be from moment to moment.
I would insert a plate in the flow (about 0.6 beta) and put in pipe taps to sense dP and upstream pressure. It doesn't have to be AGA-3 measurement, and with decent secondary devices you can easily get better than 5% uncertainty. You are going to be hard pressed to beat that in the real world with gee-whiz gizmos.
David
RE: Flare Gas Measurement devices
Whereas actual off-gases from plant shall be checked/measured through multiple basic measurement element like pitot tubes,ultrasonic meter Calibrated& verified in-situ for varied load conditions.
Hope this helps better in way forward.
Best Regards
Qalander(Chem)
RE: Flare Gas Measurement devices
Like an orifice plate, the pitot tube is just another head type instrument. You would require multiple dp transmitters to accommodate the turndown.
As previously stated, thermal mass flow measurements such as FCI with multiple transmitters for range turndown is another technology used. However this project went ultrasonic.
My ultrasonic application is specified to comply with the rules relating to volatile organic compounds (VOCs) in chapter 115 of the Texas Commission on Environmental Quality. I hear that they are not very understanding when things don't work.
The fabricated ultrasonic meter specified for my flow application is to be flow tested in a third party lab at 30%, 60% and 90% full scale with an accuracy requirement 5% flow. Full scale is around 250,000 lb/h. Multiple outputs and Ethernet data may accommodate the low end, perhaps less than 250 lb/h. The transmitter accommodates six 4-20 mA outputs. I anticipate that the Ethernet data would accommodate the turndown better than six analog outputs. We don't plan to bring six mA signals to the DCS. You have to specify everything including the maximum pressure, temperature, range of molecular weights, ... etc. Include transmitters to provide process pressure and temperature to the ultrasonic flowmeter transmitter. My application is specified below three barg in a line sized 20 NPS and with a maximum dp specified below 10 inches of water. The probes are retractible. Our inspectors will test the flow meter per our testing criteria.
I am betting that the ultrasonic flow meter will work. However, I my specification data sheet lacks a specified requirement to work.
RE: Flare Gas Measurement devices
Depending on the pipe size and how far your meter is from the burner (i.e., how much dP after the meter for max flow?) you can get some very large pressure swings as a cascading failure scenario causes several PSV's to open into the line simultaneously. I try to take this max flow into consideration when sizing flare header piping, but I see a lot of documentation where the engineer was really optimistic and/or just didn't do the arithmetic.
David
RE: Flare Gas Measurement devices
RE: Flare Gas Measurement devices
RE: Flare Gas Measurement devices
RE: Flare Gas Measurement devices