Part 1 - Pump types: an overview
Generally, pumps fall under two broad categories. The first category is centrifugal pumps, where the fluid is moved by rotating an impeller or propeller. The rotation, or centrifugal force, throws the fluid outwards generating the pressure to move the fluid through the piping system. The centrifugal pump is ideal for moving large volumes of low viscosity liquids. For high viscosity liquids, the ability of the centrifugal pump to throw the liquid decreases, affecting its performance. The maximum viscosity that a centrifugal pump can handle is dependent on the impeller design. We have successfully used centrifugal pumps for chemicals as high as 300 cP. Please contact us if you need assistance with your high viscosity applications.
Reference: https://www.pumpsandsystems.com/what-drag-effects-fluid-viscosity-centrifugal-pumps
The second category is positive displacement pumps. These pumps work by changing the volume of the chamber containing the liquid. One sub-category includes rotational pumps such as gears, lobes, or screws, where the meshing together and separation of the parts constantly change the chamber volume, displacing the liquid. Another sub-category works with pistons/plungers, such as piston pumps, plunger pumps, diaphragm pumps, and bellows pumps. One last sub-category involves a squeezing action like squeezing toothpaste, such as peristaltic pumps and tube pumps. Positive displacement pumps are ideal for highly viscous fluids.
Part 2 - Corrosion, hazardous, and explosive chemicals
The types of chemicals used in industrial applications are varied, and many chemicals are hazardous to some extent. Some of the common hazards include the following:
- Corrosive chemicals - include organic and inorganic acids and alkalis such as sulfuric acid, hydrochloric acid, sodium hydroxide, etc.
- Oxidizing agents - can cause or support combustion, including hydrogen peroxide, nitric acid, nitrates, permanganates, etc.
- Flammable chemicals - chemicals with low flashpoints such as acetone, alcohol, gasoline, etc.
- Chemicals that are reactive with water - lithium, sodium, potassium, and other alkali metals and their compounds, strong acids, and strong alkalis.
- Chemicals that ignite with air - mostly fine powders of alkali metals, white phosphorus, metalorganics, nonmetal hydrides, etc.
- Chemicals that are toxic to living organisms and/or plants - most of the above chemical categories are also harmful to organisms. Other chemicals include known carcinogens and poisons.
Almost all these types of chemicals require special care with their handling, and leakage is not allowed. Centrifugal pumps that are designed to be leak-free include magnetically driven pumps and canned motor pumps. For corrosive chemicals, corrosive-resistant alloys or corrosive-resistant plastic materials should be used. Flammable chemicals require explosion-proof or flame-proof motors to prevent accidental ignition. Reactive chemicals should be handled under a controlled environment or within a fully enclosed system. Special care should be taken to ensure proper pump operation to prevent accidental failure and leakage which can cause serious harm to personnel and the environment.
Contact us if you need assistance with selecting a chemical pumps for your chemical application.
Part 3 - Effects of temperature on specific gravity and viscosity
The specific gravity and viscosity of most chemicals do not vary much at different temperatures, therefore, the temperature effects on the chemicals are sometimes overlooked. Generally, the specific gravity of liquids increases with decreasing temperature, which means as temperature decreases, the liquid contracts, making them denser. Similarly, the viscosity of a liquid also increases with decreasing temperature. Viscosity is often described as the liquid’s resistance to flow, so colder liquid flows slower (higher viscosity) while a liquid that has been heated up flows easier (lower viscosity). Specific gravity and viscosity are important for pump selection since it takes more energy to move a heavier liquid or a viscous liquid and should be taken into consideration to determine the power requirements. Any question? Please contact ASSOMA right now.