What are the factors that cause lower efficiency of pumps with double volute casing

impeller size

Double suction impellers with diameter ranges from 335 to 550 mm

Volute casing is deviced to convert velocety in pressure head. Volute casings pumps have definit advantages of vider opration range, ideal for series and versatile fluide transfer applications. Double volute and double suction are better options reducung the bearing loads and NPSH requirement.
Infact higher no of streams gives better flow pattern and efficient operation but increasingly frictional losses and therefore required to be balanced. The difuser pumps are miniature of volute with severals of vanes and therefore more efficient but also limited range and suitable for process operation. The selection of pumps must be done keeping in view all these various aspects and is an expert job.
A double volute will be more efficient than single volute but less efficient than defuer designe for BEP operation.

Volute casing is deviced to convert velocety in pressure head. Volute casings pumps have definit advantages of vider opration range, ideal for series and versatile fluide transfer applications. Double volute and double suction are better options reducung the bearing loads and NPSH requirement.
Infact higher no of streams gives better flow pattern and efficient operation but increasingly frictional losses and therefore required to be balanced. The difuser pumps are miniature of volute with severals of vanes and therefore more efficient but also limited range and suitable for process operation. The selection of pumps must be done keeping in view all these various aspects and is an expert job.
A double volute will be more efficient than single volute but less efficient than defuer designe for BEP operation.

Volute casing is deviced to convert velocety in pressure head. Volute casings pumps have definit advantages of vider opration range, ideal for series and versatile fluide transfer applications. Double volute and double suction are better options reducung the bearing loads and NPSH requirement.
Infact higher no of streams gives better flow pattern and efficient operation but increasingly frictional losses and therefore required to be balanced. The difuser pumps are miniature of volute with severals of vanes and therefore more efficient but also limited range and suitable for process operation. The selection of pumps must be done keeping in view all these various aspects and is an expert job.
A double volute will be more efficient than single volute but less efficient than defuer designe for BEP operation.

Volute casing is deviced to convert velocety in pressure head. Volute casings pumps have definit advantages of vider opration range, ideal for series and versatile fluide transfer applications. Double volute and double suction are better options reducung the bearing loads and NPSH requirement.
Infact higher no of streams gives better flow pattern and efficient operation but increasingly frictional losses and therefore required to be balanced. The difuser pumps are miniature of volute with severals of vanes and therefore more efficient but also limited range and suitable for process operation. The selection of pumps must be done keeping in view all these various aspects and is an expert job.
A double volute will be more efficient than single volute but less efficient than defuer designe for BEP operation.

Thanks Mr Sharma. But the point I have found in general that double volute designed based on volute throat area determined as per Lobanoff or Stephanoff, gives rise to shift in best efficiency point to words lower flow (about 10 to 13% shift approx) and efficiency is lowered by about 3 to 4 points. But the efficiency curve is much flatter around the bep flowrate. This effect of lower eff. and shiftment towords lower flow is much more for smaller size HSC (del. size about 100, 125 ,150 mm ). Is there any different design methotology for such volute casings ( double volute).

Normal design procedure is to select the specific speed and choosing the suitable throat area. You can choose different combination of throat area to achieve different characteristics of pump. But it will give maximum efficiency in one particular point. Shifting the BEP point will change the efficiency also. So you may get one best efficiency ( Max ) at one HQ point only. Further improvements can be possible with CFD studies.

In double volute pumps designs, we have to focus outer volute emanating from first half volute and issuing into combined diffuser. This part adds to the friction losses in the additional flow path and head at its exit is lower than the head available at exit of second half volute. thus we have a situation where energy available entry of combined diffuser is different for two streams leading to flow mixing and losses.
A successful pump has therefore to have design of outer and inner casings in such a way that flow energy at entry to combined diffuser is as nearly same in the two parts

In process of converting velocity in to pressure the the turbulance in the flow and loss due to expansion are losing points. Imagine this prossess in capilary would have been most ideal but also expensive due to very high frictional loss. Double volute definetly balances radial load on the shaft and more streamed flow pattern. The shifting of BEP to the left will be there incase the flow passage is reduced and not compensated in double volute design which will infact reduce tangential load on the impeller vanes other geometry.