15 replies to this topic

[Dharak jain]

Vacuum column bottom (Vacuum residue) pump frequently getting low pressure issue. Suction strainer found normal, also temp, level and suction flow is also normal, even discharge pressure and flow is also normal but the suction pressure frequently getting low.
Pump is motor driven and ampere found normal.
What is a issue and how to overcome this problem?

[Bobby Strain]

So, is it a problem?

 

Bobby

[latexman]

If a problem, is it the PT / PT installation, or is that PT just noisy?

[Dharak jain]

Yess, the problem is suction pressure is getting low in actual pump not just like getting alarm on panel(varified in field). And due to that the level of column is increasing and if it gets more and more low it will lead to cavitation.

So in short issue is low suction pressure.

[Pilesar]

My guess is excessive pressure drop in the suction line. Perhaps column internals collapsed to partially cover the outlet nozzle. Maybe some trash got lodged in the pipe upstream of the strainer.

[breizh]

Hi,

I'm with Pilesar, similar issue encounter in the past due to packing collapsing and obstructed the suction line bottom of vacuum column.

Need to shut down and inspect the suction line together with the bottom part of the column, during turn around.

Do you have possibility to investigate using an endoscope prior to shut down.

Good luck.

Breizh 

[Dharak jain]

Hello,
We have 2 parallel pumps but only one of them is facing this issue while other one is running completely normal. Is it possible that the small part of packing is collapsed and stuck in one suction pipe?

[breizh]

Hi,

Definitely Yes.

EDIT : Do you need strainer at the suction of your(s) pump(s)?

Good luck

Breizh

[seuenergy]

hi,

 

When this issue happens? 

If this happens at the initial start up, then it maybe design error.

If this happens after long time running, then I am with Breizh that something may accumulate at the inlet, maybe packing of the column.

[Dharak jain]

We have a strainer at suction line.
And the problem occurs after running of 3 to 4 days.

[Dharak jain]

In our other unit we have completed Turnaround just few months ago. But now again we are facing same issue what are the other possibilities?

[seuenergy]

Maybe the conponent of column should be analyszed. Sometimes the density will change when column performance is not good.

[breizh]

Hi,

I also have experience on this system where thermal cracking of heavies (tars) affects the head at the suction of the pump. You may want to check for the thermal stability of your product.  

 

Breizh

[Dharak jain]

Do have any idea how to check for thermal stability as I am new to these stuff.?

[breizh]

Hi,

We have no idea about your product thus difficult to support effectively. You may need to contact a third-party lab or university to perform the task. Prior to do so you should review the process book of your facility where you may find hints.

One way to check is to measure the loss in weight of the product versus temperature. Typically, this job is carried out in R&D dpt.

My view only

Breizh

[Dharak jain]

Thank you very much for your support, I definitely got some new knowledge from here, thank you again for spending your time and helping me out.