Pneumatic Double Diaphragm Pumps are a form of positive displacement pump that operates using compressed air. But, how do they work? In this post, you’ll look at how air-operated double diaphragm pumps function.
What is a Pneumatic Double Diaphragm Pump?
An AODD pump, also known as a diaphragm vacuum pump, pneumatic diaphragm pump, membrane pump, or simply a diaphragm pump, is a form of positive displacement pump that uses two flexible membranes to catch and convey pushed material.
Pneumatic diaphragm pumps are commonly used in transfer applications and can handle a range of feeds such as sludges, slurries, abrasive, and shear-sensitive fluids. Although they are durable and simple to maintain, they may be prone to icing and are only suitable for low-pressure applications.
Working of Pneumatic Double Diaphragm Pump
AODD pumps are rather basic. They consist of two chambers separated by a flexible diaphragm. These chambers feature valves (often ball valves) on the left and right input and discharge sides. Both chambers share the same inlet and output.
An external compressor powers the pneumatic double diaphragm pump. This air compressor connects to an air distribution system, which fills one side of a flexible diaphragm before switching to release pressure into the other, filling it.
The alternating inflation and deflation of the left and right air diaphragms produce alternating pressure and vacuum in the pump’s side chambers.
When a chamber’s air diaphragm inflates, the pressure within shuts the valve attached to the intake but opens the ball valve connected to the outflow. The positive pressure within the chamber forces the pumped medium past the discharge ball valve and out of the chamber.
As the air diaphragm in a chamber deflates, the pressure within that chamber shuts the valve attached to the outlet while opening the valve connected to the intake. The negative pressure draws more pumped medium into the chamber, past the inflow ball valve.
As this occurs, the inflow and discharge from each chamber alternate between drawing the pumped medium from the inlet and discharging it via the outlet.
While this process occurs in quick succession, resulting in a rather continuous flow, it can generate pulses, which can be troublesome for some systems. If this is the case, you may need to add dampening downstream.
Because Pneumatic double diaphragm pumps require a compressed air supply, pumping speed is frequently dictated by the differential pressure between the air supply and the pumped fluid. This means that raising the air supply pressure will speed up the pump. However, as the pressure of the pushed fluid grows, the pump’s speed decreases.
If steady flow is necessary, you may need to consider these parameters, as well as pressure and flow controls.
Pneumatic double diaphragm pump mechanisms
Here, you will explore the benefits of utilizing a pneumatic diaphragm pump, but for now, let’s take a brief look at how this sort of pump is controlled.
When compressed air is connected to an AODD pump, it flows via an air motor, which directs the air to push a diaphragm, ‘pushing the liquid out’. The pushed diaphragm is attached to a shaft that pulls the opposite diaphragm and form a hollow on the other side and ‘drawing in the liquid’.
There are one-way valves at the bottom and top of the two cavities, which are often ball valves or flap valves. So, when a cavity is closed, the liquid is pushed up and out, and when a cavity is opened, the liquid is drawn in. This will then alternate between shutting and opening the cavity on the other side. This can happen up to 400 cycles per minute.
Benefits of Pneumatic double diaphragm pumps
Pneumatic diaphragm pumps have several benefits over conventional pumps because of the nature of their pumping action:
- They can transport high-viscosity and abrasive chemicals more efficiently than other pumps. We’ve spoken with folks at tradeshows that use AODD pumps for challenging compounds like diatomaceous earth.
- A pneumatic double diaphragm pump is naturally explosion-proof since it has no electricity and negligible friction.
- They seldom leak. There are no moving seals, just fixed ones between wetted components. Leakage should only occur when a gasket fails or the diaphragm splits.
- They can run dry without causing damage to the pump.
- They are self-priming.
Conclusion
An AODD pump uses two flexible diaphragms attached to a shared shaft to travel back and forth alternately. Operation is based on the availability of a clean compressed air supply and is limited to pumping fluids at pressures equal to or lower than the available air supply. Pneumatic double diaphragm pumps can handle viscous fluids, sludges, slurries, and shear-sensitive fluids.
Frequently Asked Questions
What If my Pneumatic Double Diaphragm Pump fails to function?
If your diaphragm pump cannot work, follow the below tips:
- Check to see whether the air regulator works. If it doesn’t work, replace the problematic pieces.
- Determine whether the fluid pipe is blocked. If it becomes blocked, remove the obstacle.
- If any parts of the Air Driven Double Diaphragm Pump are damaged, please consult a specialist.
How long does a pump’s diaphragm last?
The diaphragm’s life is full of variations. You should inspect diaphragms every 4-6 months in continuous duty applications. Pressure, temperature, moisture, and the kind of gas tested are the most common causes of diaphragm failure.
How frequently should I perform routine maintenance on my AODD pump?
It is tough to provide a broad guideline because it varies based on the application. However, most will benefit from performing basic maintenance once a month. Unlike centrifugal pumps, which may exhibit a drop in performance indicating when replacement and repairs are required, pneumatic double diaphragm pumps will often either work or not function, thus a visual and auditory check will be your best preventative measure of pump issues.
