6 replies to this topic

[ali]

hi Dear friends,

We have a number of reciprocating pumps in our vacuum distillation unit. As i mentioned, our problem is associated with not filling the suction side of some pumps due to leakage. how can we be notified the leak zone and handle this problem.

thanks

[Art Montemayor]

Ali:

There is a problem in understanding your post.

You state: "As i mentioned, our problem is associated with not filling the suction side of some pumps due to leakage". The problem is you haven't mentioned anything prior to that statement. If you did, it was deleted. Can you describe specifically what your problem is?

Do you mean to say that your positive displacement pumps are failing to pump because suction liquid is not getting to the pumps due to some leakage? Where exactly is that leakage happening and why is it being tolerated? Is this something new to an existing unit? Or is this a recent happening? Why are the leaks taking place?

[ali]

Ali:

There is a problem in understanding your post.

You state: "As i mentioned, our problem is associated with not filling the suction side of some pumps due to leakage". The problem is you haven't mentioned anything prior to that statement. If you did, it was deleted. Can you describe specifically what your problem is?

Do you mean to say that your positive displacement pumps are failing to pump because suction liquid is not getting to the pumps due to some leakage? Where exactly is that leakage happening and why is it being tolerated? Is this something new to an existing unit? Or is this a recent happening? Why are the leaks taking place?

Dear friend.
You are right. The problem I guess is associated with the strainer and around it. Recently, we have filled the suction side of the pump with a hose pipe. Howevere, the problem is still running because the atomospheric pressure overcomes the vacuum inside the line.

[sgkim]

Ali:

Your posting seems quite much confusing.

(1) What are those reciprocating pumps for?
For feeding liquid to the vacuum still, for discharging the liquid product form the still to atmosphere, or for vacuum generation?
(2) What do you mean by the word "leaks"
Does the word mean that "air flows from atmosphere to the suction of reciprocating pump and then to the vacuum still" ?,
or "air flows from atmosphere to the discharge of the reciprocating pump and then to the suction side of the pump" ?
(3) What does the phrase, "the atomospheric pressure overcomes the vacuum inside the line" mean ?
(4) How did you fill the suction line with a hose pipe? Did you fill the line with liquid with your reciprocating pump on or off? with or without venting the suction line?
(5) Where has all the LIQUID gone that filled with the "hose pipe"?

sgkim

[ali]

Ali:

Your posting seems quite much confusing.

(1) What are those reciprocating pumps for?
For feeding liquid to the vacuum still, for discharging the liquid product form the still to atmosphere, or for vacuum generation?
(2) What do you mean by the word "leaks"
Does the word mean that "air flows from atmosphere to the suction of reciprocating pump and then to the vacuum still" ?,
or "air flows from atmosphere to the discharge of the reciprocating pump and then to the suction side of the pump" ?
(3) What does the phrase, "the atomospheric pressure overcomes the vacuum inside the line" mean ?
(4) How did you fill the suction line with a hose pipe? Did you fill the line with liquid with your reciprocating pump on or off? with or without venting the suction line?
(5) Where has all the LIQUID gone that filled with the "hose pipe"?

sgkim

1- for transfering the liquid from reboiler to still
2- air from atomosphere to suction
3- It means that the air push the liquid from suction
4- with another reciprocating ppump and without venting the hose pipe
5- to the bottom of the tower

thanks

[sgkim]

sgkim
[/quote]

1- for transfering the liquid from reboiler to still
2- air from atomosphere to suction
3- It means that the air push the liquid from suction
4- with another reciprocating ppump and without venting the hose pipe
5- to the bottom of the tower

thanks
[/quote]


I can hardly understand your system yet.

(1) You wrote "from reboiler to still". Then you might have two columns "A" and "B"
Your system configuration as follows, then is this CORRECT ?
(Vac or atmospheric) tower "A" reboiler-->hose pipe (suction)--> reciprocating pumps--> (vac. or atmospheric) still "B"; Which is laid under vacuum "A", "B", or both?

(2) "Air from atmosphere to suction" means the "SUCTION" is open to ATMOSPHERE.
Why does the suction of the reciprocating pump open to ATMOSPHERE ?
You mean to say that the suction side of the pump leaks severly?

(3) You wrote ".. air push the liquid from suction".
Does this mean that LEAK (from atm to suction hose pipe) AIR lifts up the suction check valve of the pump and passes thru the pump, lifts the discharge check valve and eventually to the tower "B" under vacuum ?

(4) "with another reciprocating ppump and without venting the hose pipe" means you connected the other stand-by pump in SERIES (i.e. Tower A-->Reboiler A-->another reciporcating pump B--> pump A(suction) -->Reboiler A --> Tower A bottom). Is this what you want to say?
Why do you use the HOSE PIPE for the suction of the reciprocating pump and for VACUUM service ?

(5) The 'tower' in the phrase "to the bottom of the tower" indicates tower A ?

Without understanding the problem correctly, no solution would be expected. Please explain your system more clearly or attach the system sketch.

Stefano

[djack77494]

Ali,
If I understand your problem correctly, then your leakage is of AIR into your pump suction piping system which is operating under high vacuum. I know of no solutions to your problem beyond saying that you must work to eliminate the leaks.

I can offer a few suggestions that may mitigate the impact of the problem. Your system should be welded to the maximum degree possible. Locations such as your strainer covers require a lot of attention to ensure they form a leaktight seal. Use good quality gaskets and tighten per the manufacturer's recommendations. Try to run your suction near the maximum level to increase the pressure in the piping.
HTH,
Doug