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WHAT IS A CHEMICAL FEED PUMP?
A guide to learn about chemical feed pumps, also known as metering pumps, at Burt Process Equipment. Peristaltic and diaphragm are two types of metering pumps.
A chemical feed pump, also known as a chemical dosing pump, is a compact positive displacement pump that injects a precise amount of chemical or other substance into water, gas or steam. It is typically part of a chemical feeder system that comprises a pump or multiple pumps, storage tank, pipes and control panel. There are different methods and types of pumps that can be used, but the general procedure is to draw a preset amount of the chemical into a holding container and then inject it into a pipe or tank that holds the water or other material to be dosed.
Basic Parts of a Chemical Pump for Dosing
Whether these are water treatment chemical feed pumps for a municipal water supply or chemical pumping used to process industrial waste water, the pumps will have certain standard components. Dosing pumps are typically small and are powered by an electric motor or air actuator.
- Chemical Feed Pump – available in chemically resistant plastic, stainless steel or rubber. The mechanics depend on the type of pump.
- Tank or Container – holds the material for dosing.
- Injector – a one-way valve at the point of chemical injection.
- Dosing Line – reinforced hose or rigid plastic tube. Stainless steel is used for hot water, steam and high pressure operation. The dosing line may include pressure relief, bleed and air release valves.
- Foot Valve – a one-way valve that is placed in the product drum and attached to the suction line to keep the pump primed. A float switch may be attached to activate an alarm when the fluid level runs low.
- Control System – turns pump on and off at specific times and ensures accurate dosing. This might be a simple switch or timer, or a full control system with various sensors and variable flow rate control.
Types of Chemical Feed Pumps
Chemical dosing pumps that are used for water treatment fall into the following categories: centrifugal pumps, piston pumps and displacement style pumps (peristaltic and diaphragm pumps). The specific application will dictate the best pump to use.
- Piston Pumps – Can be used in very high pressure environments, so they are frequently used for reverse osmosis systems and other water reclamation processes.
- Centrifugal Pumps – Have impellers that help move the fluid toward the discharge port. Since they can pump large amounts of water, this type of pump is often used for water recirculation.
- Displacement Pumps – Can be used as a chlorine pump and to inject other chemicals for water treatment.
Diaphragm Pumps vs. Peristaltic Pumps
Both peristaltic and diaphragm pumps are positive displacement pumps, moving a fixed amount of fluid by trapping and forcing it into a discharge tube or pipe. However, there are important differences between the two.
A peristaltic pump, also called a squeeze tube pump, works by pushing chemicals through a flexible tube into the fluid flow stream. Unlike a diaphragm pump, they don’t use any valves or check balls, making them more suitable for chemicals that contain particulates as well as slurries, air and gasses. For delicate fluids, peristaltic pumps are preferred, since the gentle squeezing won’t cause damage. They are also self-priming.
A diaphragm pump is better for cleaner fluids. Diaphragm pumps are also recommended for high pressure and high output applications, which can both cause excessive wear on peristaltic pumps. A diaphragm pump is also better at handling high temperatures
