While ‘small’ is a relative term, it can describe the physical size of metering equipment, which may weigh as little as 39 grams or a low flow rate. As with all metering pumps, flow rates can be highly variable, especially depending on the specific applications.
Small liquid pumps such as these may be used to transport a wide variety of fluids when compatible apparatus is used. Coolants, blood, oil, corrosive agents, fuel, chemicals, acids, medicine, water, adhesives and liquid metals name just a few of the materials handled by metering pumps in the daily operations of several industrial and commercial facilities. These pumps provide the unique ability to cyclically introduce a consistent amount of fluid into a continuous-flow stream ensuring homogeneity.
With reliable and reproducible pumping actions, small metering pumps can exhibit a coefficient of variation as low as 0.1% allowing their use even as the internal force behind artificial hearts. While medical applications abound, small metering pumps are found throughout chemical, biomedical, pharmaceutical, electronic, mechanical, fluid engineering, food and beverage processing, lubrication, automotive, laboratory, analytical and agricultural industry.
All metering pumps, large or small, can be divided into two main categories based upon the means of metering or precision measuring the fluid that is expelled over a given period of time. Either the length of the stroke may be changed in order to pull in and push out a given amount of fluid, or the frequency of the cycle is altered. Those pumps with variable stroke are known as variable displacement constant speed pumps while those that manipulate cycle speed are called fixed displacement variable speed pumps.
As the latter type is more compact-able, it is more popular in small metering pumps. Specific types of pumps beyond this main grouping include diaphragm metering pumps, peristaltic pumps, piston metering pumps, chemical metering pumps and bellows pumps. Each offers a unique method for effectively achieving continuous precision fluid transfer. It is important to take into account several factors in pump selection. First and foremost the materials used in pump construction must be compatible with the chemical compounds flowing through them.
Common materials include ceramics, aluminum, stainless steel and durable plastics. Additional considerations for small metering pumps of any design or configuration include minimum and maximum flow rates, maximum operating pressure and temperature, accuracy, efficiency, power source, voltage and physical dimensions such as height, length and width as well as overall weight.