Common applications for a motor pump unit are:
• Liquid transfer in terminals and bulk plants;
• High flow dispensers;
• Combined pumping and metering systems;
• Mobile pumping units.
• The equipment essentially consists of the following components:
A) Positive displacement rotary vane pump with mechanical seal and built-in adjustable by-pass valve (this valve is designed to release excess flow rate generated by the pump).
B) Electric motor sized according to the specific pump equipment.
C) Drive gear or belts and pulleys drive.
D) Safety casing.
E) Pump unit steel base plate.
The electric motor coupling is available in the following two versions, according to the unit type:
1. with antistatic trapezoidal belts and cast iron pulleys with variable diameter according to the capacity required;
2. with parallel axis reduction unit and gears case hardened in oil bath; the reduction unit is coupled to the pump by elastic precision joints exhibiting suitable features based on the torque and on the installed motor power.
Once you have determined the desired capacity so as to choose the motor pump unit model, it is necessary to calculate the delivery head at which it should work in order to select the required power.
The pumps used in the units have a very low NPSH value; this means they can also suck from tanks not deep underground. Such capacity depends on both the pump features and type of sucked fluid (density and vapor tension) and above all, on how the system is built up. With regard to suction pipe, we recommend using a larger size than the pump inlet. Following the indication in the chart, you will ensure a good suction fluid speed rate not exceeding 1,5 ÷2 m/sec. On the other hand, on delivery pipe , no increased size is generally required.