Trailer Pump Operation and Performance (Part 1 of 3)

By Isaiah Helm, SRS Crisafulli Applications Engineer

Crisafulli pumps are naturally robust, and capable of handling a variety of unscreened water-borne debris and slurry mixtures.  The following table lists the maximum sizes of spherical solids each model can pass without clogging.

Occasionally the pump's speed will have to be changed to get more or less flow and pressure.  A small change in speed can result in a large change in power required.  Increasing the speed by a factor of 2 increases the horsepower requirement by a factor of 8 (2 cubed).  This can be estimated with the Affinity Laws below, taken from the Cameron Hydraulic Data Book (Flowserve Corporation):

H = Heads in feet

Q = Capacities in gallons per minute

S = Speeds in revolutions per minute

BHP = Brake Horsepower

Subscript 1 is for original design conditions.

Subscript 2 is for new design conditions.

Note: The Affinity Laws lose accuracy with larger speed variations.  Consult with the factory when considering speed changes of more than 20%.

A pump's impeller may need to be changed in order to get more flow and pressure or to require less horsepower with resulting less flow and pressure.  SRS Crisafulli offers up to three different impeller styles for each pump size.  They are referred to as Regular Lift, Intermediate Lift, and High Lift impellers.  The difference is their diameter.  For a change from a 16 inch Regular Lift impeller to a 21 inch High Lift impeller, the flow would increase by a factor of 1.3, the pressure by a factor of 1.7, and the power by a factor of 2.2.  This effectively doubles the horsepower requirements without changing the pump speed.

While Affinity Laws exist for diameter changes, they are only accurate for small changes of 5%-10%.  The best way to understand this relationship is to view the pump performance curves for the various impellers offered by SRS Crisafulli.

Request a consultation with one of our Applications Engineers/Specialists.

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