Max permissable value of pressure in balance leak off line

[terrorist]

Hi all,
We have a no of installation of barrel type centrifugal pumps I.e. BB5 of different make. All of them have balancing piston type arrangement for balancing of axial thrust. Now when the clearance between balancing piston and throttle bush increases, we get a increase in balance leak off line pressure resulting in more thrust on bearings. So it's very important to monitor the pressure in BLO line to avoid bearings failure.
My que is what is the alarming value of pressure in leak off line. Is there any thumb rule for this.

Thanks

 

[JJPellin]

You need to contact the pump manufacturer with this question. Some balance lines have a device to estimate the balance line flow based on pressure differential. Some, do not. Only the manufacturer can tell you the relationship between balance line pressure, thrust load and thrust bearing design.

Johnny Pellin

 

[terrorist]

Thanks Johny,
Actually somebody was telling me that pressure in the balance leak off line must be 110% of the suction pressure, that's why I thought if there exists any thumb rule on relationship between suction pressure and BLO line pressure.
Thanks.