Diaphragm Vacuum Pump Working Principle: Diaphragm vs. Rotary Vane

Jump to: Working Principles | Rotary Vane vs. Diaphragm Pump | Why Choose Diaphragm Pump? | Uses and Applications

Diaphragm vacuum pumps are a type of positive displacement pump that uses a flexible diaphragm as the pumping mechanism.

They are commonly used in laboratory settings for low-level vacuum applications (generally on the mbar scale). They can pump gases easily and are often used as a small vacuum source because they require less maintenance than other vacuum systems. However, they are generally limited to low-to-medium vacuum ranges making them unsuitable for processes that demand high or ultra-high vacuums.

Within a lab, diaphragm vacuums can be used in many applications:

• To fix small tools or substrates in place
• For low level gas filtration
• As a vacuum source for vacuum stages
• For degassing and drying porous materials and samples.

Diaphragm Pump Working Principles

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A diaphragm vacuum pump is a dry compressing vacuum pump. Like most vacuum systems, the main pumping mechanism relies on the building and releasing of pressure by varying the chamber volume. Diaphragm pumps achieve this by using a flexible diaphragm as one of the chamber walls.

The expanding and retracting of the vacuum chamber is driven by a rotating or oscillating element rigidly connected to the diaphragm. These systems also require check valves at the inlet and outlet ports to prevent backflow through the pump.

An example process for a single chamber diaphragm vacuum pump is as follows:

1. The rotator/connecting rod pulls the diaphragm away from the inlets, increasing the volume of the chamber.
2. This creates a negative pressure which draws air into the chamber through the inlet port.
3. At a certain point, the rotator/connecting rod will push the diaphragm in the opposite direction, reducing the chamber volume.
4. This will create a positive pressure in the chamber driving the air/fluid out of the exhaust port.

Most laboratory diaphragm vacuum pumps use electrical motors to drive pumping.

Some larger systems often combine two chambers which alternate between negative and positive pressure, to provide more continuous pumping.

Diaphragm vs. Rotary Vane Vacuum Pump

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Rotary vane vacuum pumps can provide stronger vacuums than diaphragm based systems. However, one of the main benefits of diaphragm vacuum pumps is that they are oil-free.

Rotary vane vacuum pumps also use a rotational mechanism and volume-pressure relationships to drive pumping. However, their design relies on rotary vanes. The vanes confine the fluids within segments in the vacuum chamber, and the volume of these segments vary as they travel through the chamber.

There must be minimal friction in this movement, so the contact point between the vanes and walls must be suitably lubricated. Rotary vane pumps need oil to ensure freedom of movement. Therefore, part of maintaining these systems involves ensuring regular oil changes and filter changes.

Diaphragm vacuum pumps are known as dry vacuum pumps. The diaphragm pumps have a hermetic seal between the motor and the compression chamber, so do not require lubricant. A benefit of diaphragm based pumps is they are oil free, so do not require regular maintenance like rotary vane systems.

Why Choose a Diaphragm Vacuum pump?

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There are several advantages to choosing a diaphragm vacuum pump for your applications.

Uses and Applications

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Diaphragm vacuum pumps can handle low to medium viscous fluids, and is a great choice for low-vacuum applications such as:

• Fixing or holding substrates to coating and testing stages
• Low level gas filtration, degassing or drying samples.

Electrically powered diaphragm pumps are not strong enough for uses that require a strong vacuum i.e. for vacuum spin coating, evaporation, creating vacuum chambers, etc. To achieve a full vacuum, you may need a compressed air vacuum system or a rotary vane vacuum.

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