High Suction Pressure
High Suction Pressure
(OP)
Could somebody please explain to me the reason behind removing the back wear rings and balance holes on a high suction, end suction pump? I know it is to balance thrust force, but how does this happen in theory? By having higher pressure between impeller and throat bush are we not having a higher thrust force going towards the impeller?
Also, if the application is very light, SG <0.4, we want the stuffing box pressure to be close to discharge..should we have a close clearance throat bushing or should we open it up and have an orifice on the plan 13 line to back up enough pressure?
Also, if the application is very light, SG <0.4, we want the stuffing box pressure to be close to discharge..should we have a close clearance throat bushing or should we open it up and have an orifice on the plan 13 line to back up enough pressure?





RE: High Suction Pressure
SUBJECT: Controlling the pressure in the stuffing box area
http://www.mcnallyinstitute.com/04-html/4-10.html
RE: High Suction Pressure
In the example you describe, I would leave a standard throat bushing clearance of about 0.035" on the diameter and orifice the plan 13 flush line to keep the seal chamber pressure high.
Johnny Pellin
RE: High Suction Pressure
Also, by having a higher pressur between the impeller and throat bush, are we not have a net thrust towards the impeller? How does this really balance?
Sometimes I hear they plug only one or two of the balance holes why would they do that?
Thanks for your help folks!
RE: High Suction Pressure
What would you be doing, if you knew that you could not fail?
RE: High Suction Pressure
Some applications restrict the balance holes but do not eliminate them. The only time I have done this is for services in vacuum where I want to maintain positive pressure in the seal chamber. This is trickier. You have to try and balance the leakage across the back wear ring with the pressure drop across the restricted balance holes to try and hold some intermediate pressure between suction and discharge. The balance holes are not likely to change over time. But the wear ring clearance will. So, the flow through the balance holes will change as the pump wears and the seal chamber pressure will also change.
Johnny Pellin
RE: High Suction Pressure
http: