Using the same Gear Pump for different Media Viscosity

The discharge  capacities varies with media viscosity
Example a Gear pump rated to achieve a 3 m3/hr at 200 rpm with media of  3500 CP, if used
for pumping water ,you may get only 0.50 m3/hr or even lesser with the same speed depend
on operating pressure .The higher the delivery head , the higher the hydraulic slip

This is also the same as Rotary Lobe Pumps

This is due to hydraulic slip internally , as water is very low viscosity it tend to slip out between
the gears and only a small percentage of it will be discharged. It also depend on he back
pressure from the piping system

Using low viscosity for metering purpose , a progressive cavity two stage will be bettet option
or High precision Gear Pump which is costly
A reciprocating piston /plunger pump may also be used