Peristaltic Dosing
Dosing with a pump that drives the liquid by squeezing a flexible tube with rollers; the product only touches the inside of the tube.
A rotor with rollers or shoes presses the tube against a housing and, as it turns, pushes forward the liquid trapped between two compression points. As the tube recovers its shape, it draws more product from the container. The flow rate depends on the internal diameter of the tube and on the speed or running time of the rotor, so the dose is programmed as a running time or a number of revolutions. As there are no valves or metal parts in contact with the liquid, it is suitable for acid, alkaline or oxidising products, provided the tube material is compatible with them.
It is the most common pump in industrial dishwashers and washing machines: the machine sends a signal and the pump injects detergent, rinse aid or additive for the programmed time. The tube is the wear part: with use it loses elasticity, the flow rate drops and the actual dose decreases. That is why the pump must be calibrated on installation, the flow rate checked periodically and the tube replaced according to use. Compared with a venturi, the dose does not depend on water pressure; compared with diaphragm pumps, it usually tolerates lower discharge pressure.
Instaquim products whose technical data sheet states their use with a peristaltic dosing pump:
- Oximatic (stabilised hydrogen peroxide; pH 2.5; 2-6 g per kg of dry laundry): bleaching agent for laundry washing, using an automatic peristaltic dosing pump.
- Oximatic + (oxygen-based bleaching agents 5-15 %; pH 1 %: 2.0; 2-6 g per kg of dry laundry): bleaching agent for laundry washing, using an automatic peristaltic dosing pump.