A type of positive displacement pump, a diaphragm pump uses a flexible membrane (diaphragm) as its main pumping element to move and pressurise fluid. Diaphragm pumps are used for low-flow, low-pressure, applications, and can be used to pump many types of gases, liquids, and slurries.
It is important to understand that the diaphragm pump is named after the diaphragm that it utilises for pumping fluid. Similar to other pumps, such as gear pumps and piston pumps, the name of the pump usually corresponds to the specific part responsible for the pumping action. The naming convention also applies to valves, which are commonly named after the disc used to control the valve’s opening and closing, such as ball valves and gate valves.
Key Components of a Diaphragm Pump
A diaphragm pump consists of a limited number of primary components, which include:
- Non-return valves (both suction and discharge)
- The chamber responsible for the pumping action
- Suction manifold
- Discharge manifold
Diaphragm pumps are commonly operated using compressed air, but they can also be powered by electricity or mechanical means. Electrically operated pumps rely on electric motors, while pneumatically operated pumps utilise an air distribution valve.
How exactly does a diaphragm pump operate?
Diaphragm pumps rely on compressed air, electrical power, or mechanical action to function. In this case, we will focus on the use of compressed air, which is the prevalent method for operating diaphragm pumps. There are two main types of diaphragm pumps: single and double diaphragm pumps. However, the double diaphragm pump is more commonly used due to its enhanced efficiency resulting from its double-acting motion.
It is helpful to understand that double-acting pumps expel fluid in both directions, while single-acting pumps only discharge fluid in one direction. Hydraulic pistons and pneumatic rams commonly employ either a single or double-acting design.
Diaphragm Pump Operation
In the general domain, for a knowledgeable audience, with a neutral formality, the intent to inform, the provided text can be paraphrased as follows: Compressed air, typically at a pressure of 6-7 bar (87-101 psi), is connected to a double diaphragm pump using hoses or piping. An air distributor, also known as a pneumatic piston, supplies compressed air to the space behind one diaphragm while air is simultaneously released from the other diaphragm.
This is achievable because both diaphragms are attached to a shared shaft. When one diaphragm moves, the other follows suit. The released air is usually directed out through a muffler, which serves the purpose of reducing the noise produced by the pump and preventing high-pressure bursts of air from being intermittently released.
When air is released, the diaphragm involved will contract and take on a concave form. Conversely, when air is supplied, the same diaphragm will expand and become convex. These changes in diaphragm shape generate either positive pressure (when convex) or negative pressure (when concave) within the pumping chamber. As a result, fluid is either drawn into or discharged from the pump due to the pressure differentials in the pumping chambers. To maintain flow in a single direction, non-return valves are utilised within the pump.
Types of Materials Used in Diaphragm Pump Construction
The pump casing is commonly made from aluminum or a polymer-based material such as PTFE. Aluminum is used to keep the pump lightweight, while polymer materials provide corrosion resistance. Diaphragms can be produced using materials such as rubber, thermoplastic elastomer (TPE), or polytetrafluoroethylene (PTFE).
These flexible membranes are commonly used in various industries, including the manufacturing sector, to create a hermetic seal and control the movement of fluids or gases. In particular, industrial diaphragm pumps utilize these diaphragms to transfer and regulate the flow of liquids or gases in a wide range of applications, from chemical processing to wastewater treatment.
Pros and Cons of Diaphragm Pumps
Diaphragm pumps are highly adaptable and find applications in various industries due to their versatility. They are utilised in a wide range of applications, including:
- They are highly suitable for functioning in corrosive surroundings or for pumping corrosive liquids, as their components can be specifically selected for corrosion resistance.
- The pump can be produced in a way that is intrinsically safe, meaning it does not act as a potential ignition source when operated in an environment that is explosive or flammable.
- The device can function properly even when it is partially or completely immersed, as long as the air exhaust is positioned above the liquid surface.
- Self-priming refers to the ability of positive displacement pumps to prime themselves, and this property extends to diaphragm pumps as well.
- These pumps are lightweight and portable because of their small size.
- Consisting of only a few components and demanding