Depending on the brand and model, a dosing pump functions in a variety of different methods. All these methods involve taking a measured amount of a chemical and then injecting that product into a pipe or similar vessel. There are a couple of major parts to a dosing pump setup:
The chemical tank or container. The product that is being dosed,
The foot valve. This is a one way valve that is attached to a suction line. It is placed into the drum of product and allows the pump to remain primed. It should have a weight on it so it remains in the bottom of the drum of product and sometimes it has a float switch attached to it so the pumps has an alarm activate if the product runs out.
The pump itself. This can vary in size and materials but is generally a variety of chemical resistant plastic (PVC, PE or similar), rubbers or stainless steel. It has a suction line attached to the inlet and the dosing line attached to the suction. The mechanics of the pump can vary (see below).
The dosing line this is generally a fairly rigid PVC or PE tube or a reinforced hose. Occasionally in steam, hot water or super high pressure applications the line can be stainless steel. This can have a variety of bleed, pressure relief, air release valves included into it but generally it is just a line.
The injector. At the point at which the product is injected into the product, there is an injector point. This is a one way valve so that when the dosing pump pushes an amount of product into the line it can overcome the pressure in the delivery pipe and allow the product out into the flow. Once a shot of product is released or the pump stops, the one way valve stops the liquid in the delivery line from going up the dosing line and damaging the pump. The injector also has a spout so that the product is delivered into the middle of the flow rather than the side wall. Over time certain products especially acids and oxidisers like chlorine or peroxide can corrode the walls of a pipe if released right at the edge of the stream. Releasing the product into the middle of the stream also creates a vortex which allows the product to mix properly too which is beneficial to ensure a proper reaction takes place.
Control system. Occasionally there is a control system installed to ensure the dosing pump is accurate and turns on and off at particular times. This can be as simple as a timer or flow switch right through to a full SCADA or similar central control system with sensors for pH, chlorine and similar and variable rate control to raise and lower the level being dosed. It may also be integrated into a more complex operations system.