The pumps are used to pump non-compressible fluids from one area to another. A diaphragm pump is one of the most famous types of the pump from the category of positive displacement pump. It is also called a Membrane pump. This type of pump uses a diaphragm to pump the fluid. This article deeply explains the diaphragm pump working, types, and its applications.
What is a Diaphragm Pump?
A pump that uses the reciprocating action of a flexible diaphragm to pump the fluid is known as a diaphragm pump.
The diaphragm is commonly made of Teflon, thermoplastic, rubber, or other flexible material. There are valves (globe valves, flap valves, butterfly valves, check valves, or any other type of valves) on both sides of the diaphragm.
The diaphragm of the pump is installed inside a compression chamber. The diaphragm divides the chamber into two sections. One section of the chamber is linked to the inlet, while the other section is linked to the outlet of the pump.
As the diaphragm flexes, it produces a pressure difference between the two portions of the compression chamber. Due to this pressure difference, the fluid flows from the external source to the chamber through the inlet and discharges from the outlet.
These types of pumps have the ability to easily control high, medium, and low viscous liquids and slurries with high solid content.
This pump can also be made from various body materials and membranes to handle a variety of harsh chemicals such as acids. Therefore, diaphragm pumps are ideal for multiple industrial applications, including wastewater treatment, pharmaceuticals, food and beverage, and chemical
Working Principle of Diaphragm Pump
A diaphragm or membrane pump is a positive displacement pump that uses two flexible diaphragms that move forward and backward to form a temporary vacuum through the pressure difference. This vacuum uses to introduce or discharge the liquid from the pump.
The diaphragm acts as a partition wall between liquid and air. The working principle of the diaphragm pump is given below:
First Stroke: –
The two diaphragms are linked via a shaft through the central part in which the air valve is placed. The air valve uses to force compressed air behind the first diaphragm and moves it away from the middle section.
The first diaphragm creates a pressure stroke that expels fluid from the pump. Simultaneously, the second diaphragm performs the suction stroke.
The air behind the second diaphragm is released into the atmosphere, and atmospheric pressure forces the fluid to the suction side. The suction valve pushes out of the seat, and fluid flows through the ball valve into the pump’s fluid chamber.
Second Stroke: –
As the first pressurized diaphragm reaches the end of its stroke, air transfers from this diaphragm to the back of the second diaphragm through the air valve.
The pressurized air pushes the second diaphragm away from the central block, and the first diaphragm is pulled into the central block.
In the second section of the pump chamber, the outlet ball valve is pushed out from its seat, while the first section of the chamber has the opposite situation. When the second stroke completes, the air valve pumps air behind the first diaphragm, and the whole cycle repeats.
For a better understanding, watch the following video:
Read also: Different types of Pumps
Types of Diaphragm Pumps
The diaphragm pumps have the following major types:
- Air-Operated Double Diaphragm Pump
- Motor-Driven Pump
- Solenoid Pump
- Wanner Hydra-Cell Pump
- Hydraulic Pump
1) Air-Operated Double Diaphragm (AODD) Pump
Air-operated Double Diaphragm (AODD) pump is the most common type of diaphragm pump. It utilizes compressed air to flex the diaphragm and move the liquid. It has two pumping chambers with two diaphragms.
AODD pump has a discharge check valve, a diaphragm, and a suction check valve for each pumping chamber. The air is supplied from one chamber to the second assembly chamber through an air distribution system that may install inside the pump.
The systematic operation of air transfer from one assembly chamber to another chamber causes the liquid to flow from one chamber to the drainpipe by filling the other chamber with liquid. As a result, the pump has a pulsation in the discharge flow. This pulsating flow may reduce by using a pulsation damper in the delivery pipe.
They are famous because of their easy maintenance, high reliability, and versatility.
2) Solenoid Diaphragm Pumps
It contains a solenoid that is used to flex the diaphragm forward and backward. This pump has a compact design and low cost. They can only handle low flow rates. Therefore, they are best suitable for analytical and medical industries.
3) Small Electric or Motor Driven Pumps
Small motor-driven pumps produce a force of up to 60 PSI and sometimes 100 PSI. There are two different styles of this type of pump:
- The first is the demanding style with fixed force switches that regularly stop and start the pump with accurate force settings. This style is very popular all over the world.
- The second style is a bypass style. Regardless of how much force is applied to the system, the pump of this style will continue to work everywhere. Whenever the outlet valve is closed, it stops the internal flow. However, closing the outlet valve for a few minutes may overheat the fluid and damage the internal part of the pump.
4) Wanner Hydra-Cell Pumps
This is a larger shaft-operated pump that can deliver up to 1500 PSI of pressure, and in some cases, 2500 PSI, and the flow rate is 36 GPM. These pumps are designed by using various metals and elastomers for acid solutions, hot fluids, wettable powders, violent chemicals, abrasives, and mud.
5) Hydraulic Diaphragm Pumps
These pumps contain a hydraulic system to flex the diaphragm. These are famous because of their capability to control high flow rates and high pressure. Therefore, they are best suitable for the oil and gas industry.
Read also: Working of Centrifugal Pump
Characteristics of Diaphragm Pump
- This positive displacement pump can pump flammable, toxic, abrasive, and corrosive fluids.
- It can handle very viscous fluids. The viscosity correction table can use as a tool to prevent the AOD pump from being reduced in size.
- It has excellent self-priming ability.
- The design of this pump differentiates the pump fluid from potentially sensitive internal pump components.
- The maximum efficiency of this pump can reach 97%.
- It uses the production of air pumps for small aquarium filters.
- Internal pump components are often suspended in oil and insulated to extend the life of the pump.
- These pumps are best suitable for corrosive and abrasives solutions
- A diaphragm or membrane pump may use to create an artificial heart.
- It has good idling properties.
- Appropriate for exhaust pressures up to 1200bar
- These pumps have good suction lift features, some of which are low flow rate and low-pressure pumps. Other models can provide higher flow rates depending on the diaphragm’s stroke length and effective working diameter. You can handle slurries and sludge with relatively large solids and particle sizes.
How to Choose a Diaphragm or Membrane Pump
The diaphragm pump is one of the most famous types of pumps that are oil-free. Nowadays, these are used in numerous products to prevent the oil vapor impurity problems that plague many of today’s rigorous processes.
The diaphragm pumps available in the market that does not have seal oil or lubricant in the pump head. That is, a vacuum can be created where the exhaust gases are completely free of oil vapors.
All oil-free or not oil-free diaphragm vacuum pumps have distinct operating properties due to that they are perfectly suited for one application but not for another. A diaphragm pump is no exception.
In the pump choice, it isn’t easy to match the type of pump to your application. But the best way to choose a diaphragm vacuum pump is to compare the pump modes of working in terms of strength, characteristics, and weaknesses with your application which can alleviate some issues.
A diaphragm pump is ideal for pumping large volumes of materials at relatively low pressure. These pumps generally resist wear because they don’t move the piston in the cylinder, but one or more simple rubber diaphragms move left and right to transfer material.
You should follow the below steps for choosing a diaphragm pump:
1) Pump Volume Requirements
When choosing a diaphragm pump, it is essential to make sure that the pump that you are trying to choose operates at 50 percent of its highest potential during normal use.
If the pump is operated at half of its highest capacity, it should run for an extended period without extensive maintenance. Diaphragm pumps should contain their operating capacity (gallons/minute) on the sales sheet or in the deal manual.
2) Type of displacement pump drive
A diaphragm pump has many ways to move the diaphragm backward and forward to allow material to be pumped. The most popular drive options for diaphragm pumps are pneumatic or electrical drive pumps. This drive is important for the safe use of the diaphragm pump, and also it affects the operating position of the pump.
3) Pump Material
These positive displacement pumps are available in different materials. In general, the most suitable material choices for available diaphragm pumps include the pump seat and ball materials and the material of the pump body.
There are many things to consider, but common coating options include stainless steel seats and balls and PTFE membrane materials.
Stainless steel is high wear-resistant, but it has a high price. PTFE, on the other hand, has low price than stainless steel but may not tolerate abrasives. In addition, stainless steel tends to be more elastic when it is hot.
4) Pump performance curve for air operated Diaphragm Pumps
Each diaphragm pump has a performance curve that contains many more details about the pump.
The general information covered by the performance curve of the diaphragm pump includes the amount of air (CFM) the pump needs at different levels of operation and the amount of material that can be supplied and transported at different levels of operation.
It is vital for a specific diaphragm pump to know that there should have enough air to operate the pump and that the pump can move the material at the required speed and delivery distance.
It is essential to check that the diaphragm pump under consideration can deliver the required amount of material (the curves will show higher operating speeds, but it should be noted that it is generally desirable to operate the pump at a capacity of up to about 50% to reduce wear). You should have sufficient air to operate the pump within the required distance.
See Also: Different types of Positive displacement Pumps
Applications of Diaphragm Pump
- Mixing Tanks
- Filling Machines
- Paint Filtration
- Pigment Milling
- Filter Press
- 55 Gallon Drum Transfer
- Air Spray – Supply or Transfer
- General Unloading/Transfer
- Powder Coating
- The elastomeric diaphragm can use as a general-purpose dynamic seal, removing numerous restrictions found with other sealing techniques. They can be built leak-free, friction-free, and sensitive to low pressure. With proper material considerations, the diaphragm can be sealed over wide pressure and temperature range without maintenance or lubrication.
Advantages of Diaphragm Pump
- This is an oil-free pump and has less seal.
- It can be used for food design.
- It has excellent wear resistance.
- It has a self-priming ability until six meters.
- It has a large displacement volume.
- This pump has easy maintenance/cleaning.
- It can work without oil for a short time.
- It has a multifunctional design and functions (suitable for most media types).
- The lifting capacity of a diaphragm pump refers to the vertical height at which the pump effectively picks up material. The capacity to pump material up makes diaphragm pumps an excellent choice for moving material out of the area like well or similar conditions.
Disadvantages of Diaphragm Pump
- It has a low operating speed.
- It is not energy efficient.
- These pumps do not deliver fluid at high pressure.
- They don’t handle off-gassing chemicals well; gas-locking of the head can occur.
Difference between the Diaphragm Pump and Peristaltic Pump
The main difference between the peristaltic pump and the diaphragm pump is given below:
| Diaphragm Pump | Peristaltic Pump |
|---|---|
| A diaphragm pump moves fluid by creating suction by a vibrating diaphragm. | A peristaltic pump moves the fluid by squeezing a liquid-filled hose. |
| These have a complex design. | These have a simple design. |
| The diaphragm pumps have more valves than the peristaltic pump. | These have a low number of valves. |
| These have a complex operation. | These pumps have an easy operation. |
| This pump has a check valve. | It doesn’t have any check valve. |
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FAQ Section
Which fluids a Diaphragm Pump can Pump?
The diaphragm vacuum pump can pump the following fluids:
- Powders
- Titanium Dioxide
- Latex
- Adhesives
- Lacquers
- Greases
- Paints
- Varnishes
What are the types of the diaphragm pumps?
- Air-operated double diaphragm pump
- Mechanical diaphragm pump
- Hydraulic diaphragm pump
- Solenoid diaphragm pump
- Wanner hydra-cell pump
What are the applications of diaphragm pump?
The diaphragm pumps are most commonly used for pumping gels, oils, abrasive slurry, creams, smaller solids, dirty water, sticky fluids, pharma product, volatile solvents, and corrosive chemicals.