Dosing generally applies to the feeding of chemicals or other liquid additives, in accurately measured small quantities, into a process fluid at intervals to give sufficient time for the chemical to react or show the results. Diaphragm dosing pumps or piston dosing pumps are commonly used. The use of peristaltic or tube dosing pumps is also preferred by some users.
A peristaltic pump is generally preferred by the laundry and catering industries due to the ease of operation and the relatively low cost. These are regarded as the cheapest type of dosing pump for high volume installations where the price of the pump is amortised into the price of the supplied fluid detergent, brightener, softener etc. The peristaltic pump is ideal for measuring the exact dosing for each wash or rinse cycle. Dosing pumps are in reality a metering pump and these terms are used to refer to the same type of pump unit. A dosing pump can be a high pressure pump, however there is a large user base where the dosing of additives is into either no pressure or very low pressure systems.
A reliable dosing pump supplier will offer all types of pumps to suit each application. Acids are commonly dosed into process fluid streams by pumps with the wet component in materials suitable for reliable and safe handling of the specific acids being. The wetted pump chamber is typically PVDF, Poly Propylene, Stainless steel or some other noble metal. Valve seats are also in the same materials with Teflon (PTFE) valve balls and diaphragms making up the most common materials when speaking about diaphragm or piston dosing pumps.
Chemical pumps are available in all types of materials and it is important to specify the acid or alkali or other additives to be dosed.