High viscosity fluids generally need more energy to move them than low viscosity fluids

Dynamic Viscosity is stated in Centipoise (cP) it is commonly used because water at a temperature of 20°C has a viscosity of 1.002 Centipoise, most published pump test and performance data is stated "in water"   Below about 300cP, and dependant on fluid type and system detail, roto-dynamic (RD)pumps are generally used eg centrifugal pumps, submersible pumps

Positive displacement (PD) pumps are used for fluids with viscosities usually greater than about 300 centipoise

Positive Displacement (PD) pumps are available in a number of forms. Rotary PD pumps such as gear pumps, progressing cavity pumps,rotary lobe pumps. Reciprocating PD pumps such as plunger piston pumps, mechanical diaphragm and hydraulic diaphragm pumps

Reciprocating PD pumps provide a constant pressure irrespective of flow, this is why they are ideal for dosing and most importantly metering applications


Metering pumps should be considered as precision instruments, used to accurately feed a predetermined volume of liquid into a process or system as in this example

 Metering pump flow-rates can be varied by changing the
 stroke length and / or speed, crucially, such flow-rates
 can be predetermined accurately, with repeatable and
 consistently maintained (within ± 1%) flows

 Ideally, a metering pump should be capable of handling a
 wide range of liquids, including toxic, corrosive,dangerous
 volatile, and abrasive ones, as well as those containing
 concentrations of suspended solids

 
To accomplish this wide range of requirements, many options in design must be available, capacity
method of regulation, liquid-end materials, valve styles, primary drive characteristics, protection and
environmental conditions

Cheshire Pump Company are suppliers of precision metering pumps for your chemical and
process applications, for precision metering and chemical dosing systems we use SEKO SpA
The pumps are available in piston / plunger, hydraulic diaphragm, mechanical diaphragm designs to
very high specification, typically available to API standards with full ATEX approval