mechanical seal for VS4 pumps 1

[mirghaffari]

Dear all,
I have two question:

1-Could you please help me to select the suitable mechanical seal for VS4 pump for sour croud oil?
Some belive that because in VS4 the liquide level in sump is below the discharge flange, mechanical seal is not required.
Do you agree?

2- if both vs1 and vs4 handle our application wich one do you select? Vs1 or vs4?
Best regards

 

[1gibson]

1 - Dry gas seal if you need to prevent vapors in suction area from escaping. Otherwise, no seal required.
2 - Continuous duty and/or part of a real process, VS1. Intermittent duty and/or just draining a sump (flow control not important) VS4.

 

[mirghaffari]

Thanks 1gibson,

But our flow is sour oil and all of our pumps are equiped with singel mechanical seal. In this case we need to drain the sump intermittent. I dont khow what is the dry gas seal in suction side. Could you please explaine
Thanks.

 

[JJPellin]

A VS4 pump (vertical wet pit pump) does not require a mechanical seal. The point where the shaft passed out of the cover is not at discharge pressure. If you want to have a vapor tight installation, you can use a dry gas seal as 1gibson suggests. For this application, most of our pumps use double lip seals with grease between them. Others use a packing gland with two rows of braided packing with grease in between. These options would be much cheaper than the dry gas seal. And if the vapor space of the pit is vented through carbon canisters, the lip seals or packing can easily pass a VOC sniff test.

A VS1 pump (vertical turbine pump) always requires a mechanical seal. The point where the shaft passed out of the pump is under full discharge pressure and flooded. For a pump of this type in sour crude, we would require a pressurized double seal (API Plan 53) as a minimum to meet environmental requirements.

Given the choice I would prefer a VS4 pump in order to eliminate the need for mechanical seal and a seal support system and to reduce the possibility of a substantial leak.


Johnny Pellin

 

[mirghaffari]

thanks JJPellin and 1gibson for your kind attention.

well noted

 

[mirghaffari]

Dear 1gibson,

this only for my information, could you please explaine why we use VS1 for continuse application? is it possible we use VS4 for process or continuse application?
what isyour reason for selection these pumps?

thanks

 

[mirghaffari]

Dear 1gibson,

this only for my information, could you please explaine why we use VS1 for continuse application? is it possible we use VS4 for process or continuse application?
what isyour reason for selection these pumps?

thanks

 

[1gibson]

VS4 curve shape is generally very flat, it is difficult to determine what flowrate is based on differential pressure, pump will be damaged if it does not operate at appropriate flowrate. VS1 curves will generally be steeper, so it is easy to adjust flow and have a good idea of the flowrate by checking the differential pressure across the pump.

VS4 efficiency is usually very low compared to VS1, so for continuous service the utility costs will be too high.

VS4 are good at emptying sumps using level switches (high level pump turns on, low level pump turns off) and they are cheaper than a VS1. Beyond that, if you have a "real" process that requires a specific head and flow, with some flexibility in adjusting the conditions, then you want a VS1.

 

[mirghaffari]

Dear 1 Gibson,

Your response is always a good guide for me. thanks for your help

 

[1gibson]

No problem, glad to help.

 

[gilus02]

This thread raises a question for me. The main difference between VS4 and VS5 is the shaft length? I mean if we want to lift liquid from a deeper sump we use VS4?

In addition I think in a sump pump we have three possible location of leakage (whether gas or liquid):
- Mounting Plate
- Back Liner Seal
- Impeller Thread Seal

The mentioned sealing systems (double lip seals) is proper for which of them? What shall we do for preventing the fluid leakage from these three locations?

Thank you all!

 

[Reifleman2]

FYI: There are also dry running wet seal options that can last a very long time under the right conditions. A graphite impregnated carbon primary ring on a silicon carbide or tungsten carbide mating ring will last forever when there is not any actual sour crude at the seal faces.