Rotary kinetic fluid motors or pumps – Working fluid passage or distributing means associated with... – Passage or casing attached removable liner or wear member
Patent
1987-10-28
1989-07-04
Garrett, Robert E.
Rotary kinetic fluid motors or pumps
Working fluid passage or distributing means associated with...
Passage or casing attached removable liner or wear member
415206, F04D 2942, F04D 2900
Patent
active
048446939
DESCRIPTION:
BRIEF SUMMARY
This present invention relates to an improved hydraulic shape for a casing or liner design for use with centrifugal pumps, and in particular, pumps handling abrasive solids in suspension (i.e. slurry), where the flowrate is significantly less than the best efficiency point flowrate for that pump.
The casing of a centrifugal pump acts as a collector, containing the fluid as it flows from the impeller, diffusing the high velocities and channeling the fluid into the outlet or discharge branch.
Pumps which are designed for handling non abrasive or clear fluids generally have close clearances between the impeller and the casing at the cutwater (of the order of 2-5% of the impeller diameter), as this gives the most efficient design.
Conversely centrifugal pumps designed to handle fibrous or particulate abrasive solids in suspension (slurry pumps) generally have much larger clearances between the impeller and casing to obviate blockages and high local wear which would occur in the case of small clearances. In addition conventional slurry pump casings have generally a constant area discharge neck, with the cross sectional area at the cutwater only 10-20% less than the area at the discharge flange. Designs incorporating large cutwater clearances and constant area discharge necks give adequate overall performance at the pump "Best Efficiency Point" flowrate (BEP).
However at flowrates less than the BEP sever localised abrasive wear behind the cutwater can be a problem. This wear is caused by recirculation and vortexing as fluid which cannot flow out the discharge branch re-enters the volute flowing around the cutwater at an unfavourable angle. Slurry pumps often have to operate at off-design conditions (i.e flowrates not coincident with the BEP) due to process flow variations or mismatching of the pump and duty requirements.
The present invention seeks to ameliorate the above problems by providing a pump casing for slurry pumps which has an improved casing shape in the region of the cutwater and discharge branch, to minimise the localised wear by changing the conventional flow pattern to suit the reduced pump flowrate.
In one broad form the invention comprises a centrifugal slurry pump casing or liner comprising a discharge throat whose area is reduced compared to the area of the discharge throat of the pump operating at the best efficiency point flowrate.
In another form the invention comprises a centrifugal slurry pump casing adapted to be operated at flowrate in the range of 30-70% of the best efficiency point flowrate, said pump casing shape or liner having an extended cutwater which reduces the throat area of the casing to 30-70% of the discharge neck area at the discharge flange.
Further the present invention provides a liner which can be inserted into a centrifugal pump so as to improve the hydraulic shape in the region of the cutwater and discharge branch, to minimise the localised wear by changing the conventional flow pattern to suit reduced pump flowrates.
A preferred embodiment of the present invention comprises a centrifugal slurry pump casing with the cutwater projecting across and partially obstructing the discharge neck so as to give a reduced area for the discharge. Downstream of the cutwater (i.e. further up the discharge neck) and on the opposite side from the cutwater is a bulge or convex protrusion which acts to further guide the flow and reduce the discharge area. The area reduction is primarily in a plane perpendicular to the axis of impeller rotation, so that the width of the discharge neck remains essentially constant from the cutwater to the discharge flange. The overall shape is such that the effective area of the discharge neck at the cutwater (the throat area) is reduced in the order of 30-70% of the area of the discharge neck at the discharge flange.
The invention does not greatly effect the overall pump hydraulic performance and although the BEP flowrate may be reduced slightly, the pump's head-flow characteristic remains basically unchanged. This greatly enhances the application of th
REFERENCES:
patent: 169736 (1899-02-01), Edwards
patent: 1914919 (1933-06-01), Heermans
patent: 2144417 (1939-01-01), Schneible
patent: 3048117 (1962-08-01), Franzen et al.
patent: 3051312 (1962-08-01), Arge
patent: 4113407 (1978-09-01), Grzina
Garrett Robert E.
Pitko Joseph M.
Warman International Ltd.
LandOfFree
Low-flow pump casing does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Low-flow pump casing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Low-flow pump casing will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-849790