The number of substances that can be used in double diaphragm pumps is long and varied. Lets just look at five of them and what they are used for. There are a lot of industries that use this kind of pump. Just to name a few metal fabricators, petro chemical and mining industries use these pumps.
Wastewater processing is often done in a flow process. As the water is getting ready to be treated it needs to be pumped into the area where the treatment will take place. After the treatment is completed the cleaned wastewater needs to be pumped out of the treatment area. These pumps use positive displacement to remove liquids and prevent back flow. This is very important in almost any process because you don't want the untreated or unprocessed liquid to flow into the area being treated. Once treated the water needs to stay on the treated side.
Ink and paint are often used with double diaphragm pumps (all-flo.com/applications.html). Ink has small particles and paint can have large particles that can wear on the pump parts. Depending on what is being pumped the particles will not affect this type of pump. Using a base paint pumped to another vat where the color is added and than pumped on to a last vat to be pumped into containers.
In a mining setting the pumps could be pumping excess water out of the mine or the waste water from the mining operation. The pumps make sure there is no back flow and that the water does not fill back in on the mining operation.
Petro Chemical processing from start to finish goes through several processes depending on what end product they are producing. These processes can move crude oil from the product coming out of the ground to the final product of gasoline. Double diaphragm pumps are used in a lot of the movement of the oil from one location of processing to the other.
The paper making process using a number of corrosive materials that need to be pumped from one vat to another. Double diaphragm pumps are more than capable of pumping most kinds of corrosive materials. From the trees to whatever kind of paper the company is making the pumping of the corrosive materials needs to move to the next stage.
Some of the other materials that double diaphragm pumps are used for are acids, chemicals, concrete, coolants and combustible materials. These are very versatile pumps.