30 " Propeller Pump -50% Caustic @ 350 degr F

[JimmyA]

I am looking to fit a Spider Bearing c/w 4 support legs behind a 30" Impeller (propeller) in a Caustic Pump.

The pump casing is in fact a 30" truncated 90 degr elbow discharging vertically , and direcly from the Impeller.
Impeller is shaft driven on elbow c/line , fully Immersed at all times.
Requirement is to fit a Cartridge Seal.

Capacity : 28,000 usgpm.Disch Pressure 16 ft. Suction Pressure 23 ft . HP 300.

Shaft is 6 1/4 " diam - Proposed Spider Housing o/d is
9 1/2 " x 12 " long + 4 support legs 1 " thk x 8 " wide.
Bearing liner is RULON 123.

Can anyone advise me how to calculate the REDUCTION in Flow (if appreciable .?) caused due to installation of the Spider ??

 

[saxon]

Jimmy, Use the Pump Affinity Laws, where:

(Q1*RPM2)/RPM1=Q2
where:
Q1=intial flow at initial RPM1
Q2=new flow at new RPM2

P2=P1*(RPM2/RPM1)^2
where:
P2=new head
P1=intial head
RPM1=intial rev/min.
RPM2=new rev/min

This assumes you haven't changed the impellor dia. or the the HP available.

Hope this helps.
saxon

 

[JimmyA]

Thanks CHEMICAL.

My problem is to calculate the 'head Losses' applicable to the components which make up the spider ie parts added to the internal flow path.
Is it possible to do simple x sectional areas for these parts ??

JimmyA

 

[Artisi]

I would suggest that the loss incurred by the "spider" would be negligible, that is assuming the flow path sees the 1" width of the support legs.

An interesting aspect of this modification would be a hydraulic study / design of the "spider", the support legs could be designed in such a way as to act as a flow straightener after the impeller. Worth a thought as it very possible to recover a bit more performance from the pump.

International College
Naresuan University
Phitsanulok
Thailand

 

[JimmyA]

Artisi - Thanks , I had thought about this ie that the 'Legs' will actually assist in -anti swirl- .
But the end user , who is attracted to my repair / mods needs the 'head loss' criteria sorting to pass on to his boss !! (Covering one(s) backside.. )

I am trying to work out appx. x sectional areas of parts for Spider and comparing to losses on eg 30" check valve etc. to put down some figures.
At the moment, my calcs show only negligible change / loss and as I am restoring the Impeller / Shroud clearance to original , I think it is as good as it gets..

RGDS. JimmyA.