Air Flow Switch for Glycol Regeneration System
Air Flow Switch for Glycol Regeneration System
(OP)
I am engineer responsible for an offshore installation that processes natural gas. We operate a TEG glycol regeneration system with a gas burner to regenerate the glycol. The burner was originally 'normally aspirated'. Some years ago we replaced the burner, and the controls, and this included a new 'forced draft'system (with duty and standby fans). The control system redesign incorporated a pressure switch to detect that the fans were working. But we were generating so little 'head' that the switch would oftem trip and shutdown the system. We changed the switch and put in a dp switch whereby we detected the pressure upstream and downstream of the fans. The results were no better, and the system oftem tripped on start up (it would detect flow sometime, often not though). Then we installed a heat type flow switch (where you have a heated probe and a non haeted probe and the resistance of the heated probe changes as you get air flows across it). The results were no better (still unreliable). The current 'solution' is another dp switch (very low range) measuring dp across the flame arrestor mesh in the burner inlet box (whwre the mesh acts like an orifice plate). It works, but not always.
So I'm looking for a switch, EExd, that will operate (reliably) to detect flow. The duct is 18", the theoritical flow is 2ft/sec. Can anyone suggest a device.
So I'm looking for a switch, EExd, that will operate (reliably) to detect flow. The duct is 18", the theoritical flow is 2ft/sec. Can anyone suggest a device.





RE: Air Flow Switch for Glycol Regeneration System
RE: Air Flow Switch for Glycol Regeneration System
RE: Air Flow Switch for Glycol Regeneration System
We talked to the heater manufacturer and they said this is a common problem (so why do they design them like that?!) and they suggested replacing the DP switch with a physical flag-type switch, basically a 'wind vane' on a stick. Google "flag switch air flow" to see the kind of things I am talking about. I left that plant before we installed the new switch, and we disabled the DP and just looked at the blower motor status.