BALANCE LEAK OFF LINE

[shashankTurbomachine]

We all know that BLO is required in multistage between bearing pumps(BB2/3 and 5)

BLO is a line in which some flow is taken from discharge side(balance drum on BB5,throttle sleeve on BB2/3) and routed back to suction

This flow from final stage of pump has some undergone some heating beacuse of pump inefficiencies thus this flow may flash to vapor and may cause some distrubance to suction.

BLO routing is always done thru bottom of suction becasue of saving in length of pipe and least amount of P.E.(i.e., static head)
which otherwise if routed from top will have liquid fleshing.


I want to know the thumb rule for this flow.
I know this flow is generally 2-5% of total flow.Hence the rated flow shall be chosen accordingly. AS we increase rated flow in case of warmup flow and RO.

Kindly thro some light on above.

A well phrased question has answers in itself!!!

 

[mk3223]

As suggest, it can be a good question for the Pump Vendor.

 

[JJPellin]

I have never heard of a rule of thumb for balance line flow. I checked two of our largest barrel pumps and found flows at about 5% of rated flow. Not all balance lines run in the bottom. Both of the pumps I just checked have the balance lines on top (top suction, top discharge pumps). I have never heard of any issues with flashing from the balance line flow, even with pumps running near minimum continuous stable flow. With a reasonable NPSH margin, I see no reason to expect any flashing to occur.

Johnny Pellin

 

[Artisi]

Johhny P, I wouldn't worry too much, the OP is always stating the obvious, on fishing trip, or airing "knowledge".

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[MechEngineer2012]

shashankTurbomachine:
I work for a pump company and I have never heard about the term "BALANCE LEAK OFF LINE" or "BLO". I understood what you are asking by reading the definition you provided. We call it simply "Balance Line". Just for your information!