Betty:
I may be wrong, but what has frequently been a major problem with dP meter readings in the past has been resolved by simply piping (or “tubing”) up the connections to the meter in a manner such that any condensable vapor cannot get trapped in the sensing tubing.
Let’s face it: you have a 100% chance of forming liquid condensed water solution in the tubing if you have installed your dP cell BELOW the sensing points. And, unfortunately, that’s where your instrument technicians like to have the instrument placed for easy access and readings. The best manner to install a dP cell in your specific case is ABOVE the sensing points (which means that you require a ladder and platform on top of the stripper and which may not be your situation) and employ a dP cell that has BOTH the input pressure nozzles located at the BOTTOM of the cell case (never at the top). This allows you to make the pressure tubing connections such that any condensate forming in the tubing always drains down and away from the cell’s diaphagm.
You will note that if your vapor pressure sensing tubing (located on top of tray 17) is going down and to the dP cell, it will collect water condensate (this vapor is essentially pure acid gas + water vapor). This pressure point that the cell is sensing should be LESS than the other pressure (the one below tray 17). Using common sense tells us that if there is liquid in the tubing from the top of tray 17, the pressure sensed by the cell will be MORE than the pressure sensed below tray 17 – just the opposite of what one would expect and (guess what?) a NEGATIVE reading.
Please refer to the attached Rev1 of your stripper sketch. I am speculating because you haven’t given us the detailed, important layout of the instrument tubing and cell, but I may be correct. I’ll let you be the judge.
I don’t know how accurate your sketch is, but I have a lot of trouble accepting what you show. Who designed and built your unit? You show a once-through piping arrangement going to the kettle reboiler when it is totally not required – nor needed. A kettle reboiler – by nature – is inherently once-through. I wonder why you show it that way.
Amine Regen DP Rev1.xlsx 145.28KB
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