Bottom vacuum high and top vacuum low in vacuum column

[Swetang Patel]

In my plant, moisture removal column has top vacuum of -637 mmhg and top vacuum has -690 mmhg.
In which type of condition top vacuum can be less than the bottom vacuum?
For info, top product is water and bottom product is 2,5 DCA crude ( 2,5 dichloro aniline)

 

[Latexman]

First guess, when a transmitter calibration is not correct.

Good Luck,
Latexman

 

[vt2012]

Latexman is probably on to something. I used to use a highly accurate (and regularly calibrated) digital handheld manometer weekly to verify vacuum measurements from transmitters up and down a critical column. Readings from different instruments rarely matched.

How is vacuum measured? If dP transmitter with impulse tubing, is everything sloped correctly to avoid condensation?

How is vacuum pulled on the column? Is the column packed? Trayed?

 

[0707]

check your vacuum ejectors, see if they are correctly installed.

luis

 

[georgeverghese]

There may be
a)condensation in the vacuum PT impulse line or
b)freezing of DCA - check if heat tracing is working well.

 

[pierreick]

Hi,
Consider the doc attached, if you are dealing with ejectors .
Hope this is helping you.
Pierre

 

[pierreick]

hi,
Another resource to troubleshoot your operation.
Pierre