4.4.3 - Effective flow rate
The effective flow rate is lower than the theoretical flow rate due to leaks due to fluid compressibility, fluid
leakage through the valves, system deformability.
The ratio between theoretical and effective flow determines the volumetric efficiency of the pump, which
on average can vary from 70 to 98% depending on the machines and the conditions of use.
This efficiency varies based on the size of the pump, the type of pump head (piston or diaphragm), the
liquid to be pumped, the viscosity of the liquid, the suction and discharge pressures, etc.
4.5 - Pump description
The pump consists of:
Reducer unit: Reduces the number of motor revolutions to that required for dosing, by
transforming the rotary motion into a reciprocating rectilinear motion by
means of an eccentric shaft, with a slide and return spring.
Gearbox transmission: Aluminium flexible coupling.
Adjustment: Piston stroke from "0%" to "100%" is obtained by turning the knob on the
screw that partialises the slide return, either with the pump stationary or
in motion.
Hydraulic pump head: Sucks the liquid from the inlet valve and pushes it through the delivery
valve.
Electric motor: Three-phase or single-phase (CVE – ex proof – Gr. B14 – Cl. F- 50/60
Hz- IP 55 or higher
Pump body: Die-cast aluminium.
Hydraulic parts: Plastic or metal materials based on product compatibility.
4.6 - Dosing pumps SR series
They are spring-return dosing pumps with helical gear reducer/worm screw enclosed in a die-cast
aluminium gear reducer body. The helical gear is placed on the eccentric shaft supported by ball bearings
and lubricated in an oil bath and the worm screw is connected to the electric motor by a joint.
The movement of the mechanism is given by the eccentric shaft with helical gear that moves a slide in the
pressing phase, the suction phase is given by the spring that ensures the return of the slide allowing the
suction phase of the pump.
The stroke adjustment is made with an adjustment handle which, by screwing or unscrewing it, adjusts
the stroke of the slide.
The pumps can be equipped with both electrical and pneumatic regulation.
The electric motors installed range from 0.18 kW to 0.75 kW depending on the size of the pump.
The pump heads that can be combined with the spring return mechanism are:
▪ type A with piston pump head
▪ type D direct diaphragm
▪ type B with hydraulic diaphragm
▪ type BR with hydraulic diaphragm with recirculation valve
type SD with double hydraulic diaphragm with interposed liquid and recirculation valve
Operation can be single or multiple. The pipe connections are of the threaded or flanged type.
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