A compressor is a device that uses to compress gas or air so that it can transfer from one place to another. Compressors most widely use all over the world in different industries. Most compressors are used in pneumatic systems. There are multiple types of compressors, and a diaphragm compressor is one of them. In the previous article, we discussed different types of compressors; therefore, in this article, we will mainly discuss the diaphragm compressor.
What is a Diaphragm Compressor?
A diaphragm compressor is a famous type of compressor from the category of reciprocating compressors. The diaphragm compressor is also called a membrane compressor. A diaphragm compressor uses a rotatory diaphragm to compress the air or gas. The rotatory diaphragm helps to deliver the air or gas inside the compression chamber and apply the required pressure to deliver the air in the desired area.
The diaphragm compressor has a hydraulic piston system with tight sealing so that ionic fluid can’t mix with the gases. In this compressor, the air is compressed by a flexible diaphragm instead of an air inlet element.
The reciprocating diaphragm is powered by a crankshaft and a connecting rod mechanism. During the diaphragm compressor working, the compressor box and the diaphragm make contact with the working fluid (e.g., gas or air). Therefore, this compressor is best suitable for transferring explosive and toxic gases.
The diaphragm or membrane must be too much reliable that it can bear the pumped gas’s strain. It should also contain sufficient heat resistance and sufficient chemical properties.
Diaphragm compression is the best choice for situations where complete separation of the seal is needed. Mostly Diaphragm compressors use to handle radioactive, explosive, flammable, toxic, or rare gases.
Diaphragm Compressor Working Principle
A diaphragm compressor has the following two systems:
- Pneumatic force system
- Hydraulic system
The working cycle and structure of a diaphragm compressor are given in the below diagram.
During the working of the diaphragm compressor, each revolution of the piston delivers a certain amount of hydraulic oil to the membrane or diaphragm. This oil helps the membrane to move upward and downward; due to this movement, the membrane compresses the air or gas.
During the suction stroke, as the piston reaches BDC (bottom dead center), the compensating pump delivers a very low quantity of oil through the check valve in the oil head to permit the piston ring to leak. As the membrane approaches the oil head, the suction gas stops flowing inside the head.
When the piston begins to move toward TDC (top dead center), the pressure of the internal gas becomes higher than the pressure of the external gas, which shuts the inlet valve; after that check valve also shuts because there is no more need for hydraulic oil delivery by the compensating pump.
The pressure of the oil and gas increases at once until the hydraulic oil forces the membrane to make contact with the gas head. After the membrane contact with the gas head, delivery stroke starts.
A pressure relief valve is attached to the oil head, which uses to maintain the internal oil pressure. This valve opens, and the extra oil returns to the crankcase.
When the oil returns to the crankcase, the pump piston starts to move toward the BDC (downward stroke), due to which the pressure of the external gas becomes more than the pressure of the internal gas, and the outlet valve shuts.
Due to the closing of the outlet valve, the gas available in the gas head starts expanding from the outlet pressure to the inlet pressure. As the internal pressure of gas touches the external gas pressure then the outlet valve opens, and the gas is released. After this process, the whole cycle repeats.
Due to the harsh operating environment of the diaphragm or membrane compressor, mechanical noise can easily contaminate the AE signal. In general, the frequency of mechanical noise is less than 10 kHz.
For a better understanding the diaphragm compressor working, watch the following video:
Read More: Working of Reciprocating Compressor
Schematic Diagram of Diaphragm Compressor
The schematic diagram of a diaphragm compressor is given below:
- A flexible membrane is fixed with its circumference.
- Dielectric layers are placed on the metal electrodes to avoid electrical short circuits when the membrane comes into contact with the chamber surface.
- The metal electrode layer deposits on the surface of the chamber and the membrane
- A molded chamber has two identical halves that completely close the membrane. Gas enters the chamber through the inlet port, and an outlet valve controls the flow of delivery gas and the pressure rise.
Read More: Different types of Compressors
Diaphragm Compressor Parts
The major parts of the diaphragm compressor are given below:
- Check Valve
- Overpump Valves
- Piston
- Connecting rod
- Hydraulic Injection Pump
- Crankshaft
1) Body
The body of a diaphragm compressor is a significant part of the compressor placement, which generally consists of a crankcase (frame), a body, and a medium body.
The damper is attached to the machine body to guide and position the transmission components like externally connected cylinders, oil, crankcase lubrication, electric motors, and other units.
During compression process, the compressor body must withstand the forces of the pistons and gases, the inertia forces of the moving parts, and transfer all or part of its weight to the base.
2) Cylinder
It is an important part of all compressors. The diaphragm sucks air or gas from the outside and delivers it inside the cylinder. Due to the high gas pressure, the cylinder has high technical requirements such as the complex structure and the variable direction of heat exchange.
3) Check Valve
A check valve is a non-return valve. It stops the air or gas from flowing backward. These types of valves have easy accessibility for replacement, maintenance, repair, or inspection.
Read More: Working of Check Valve
4) Piston
The piston is an important part of the compressor that plays an important role in the compression of gas or air. It moves forward and backward to compress the air or gas.
As the piston moves upward, the pressure inside the compressor becomes high than the external gas pressure, while internal gas pressure decreases when it moves downward.
5) Hydraulic injection pump
The hydraulic pump injects a very low quantity of oil through the check valve in the oil head to permit the piston ring to leak. This oil helps the piston to move back and forth.
6) Overpump sight glass
It gives a visual signal of hydraulic oil in the piston.
7) Inlet and Outlet Valves
The inlet and outlet valves are the essential components of all compressors and pumps. The inlet valve uses to draw air or gas into the membrane compressor. This valve uses to suck air from the outside to inside the compressor.
An outlet valve uses to discharge gas or air from the compressor. As the gas or air pressure inside the compressor becomes equal to the atmospheric pressure then it discharges through the outlet valve.
Read Also: Different Types of Valves
8) Connecting Rod
A connecting rod links the piston and crankshaft of the diaphragm compressor. It transfers the motion of the piston to the crankshaft.
According to the big end of the connecting rod, it is divided into two types:
- Integral connecting rod
- Split connecting rod
The split connecting rod is utilized for the torsion shaft and the crank frame. The end of this connecting rod is attached to a connecting rod screw when assembled with the crank pin.
The split connecting rod can be used in combination with the crankshaft journal to be used for long-stroke refrigeration compressors. A thin-walled bushing is installed on the larger end of the connecting rod. To improve wear resistance, the bearing bush has a wear-resistant alloy layer.
An integral connecting rod uses for the eccentric crankshaft structures. It has an easy installation and simple structure. The eccentric crankshaft stroke is twice the eccentricity, which limits the integrated connecting rod. It may use for small refrigeration compressors.
9) Crankshaft
This is another important component of the membrane compressor. It transforms the reciprocating motion of the piston into rotational motion.
Read More: Working of Crankshaft
10) Diaphragm or Membrane
It is a moveable component that rotates to compress the air or gas inside the compressor.
Advantages and Disadvantages of Diaphragm Compressor
The advantages and disadvantages of diaphragm compressors are given below:
Advantages of Diaphragm Compressor
- The diaphragm compressor provides oil-free compression due to the tightness between the oil chamber and the air chamber
- The duplex device of this compressor has the ability to compress different gases at the same time
- It doesn’t has an issue with the transition assembly
- Statically seal in the gas stream, the diaphragm compressor provides compression without wear & tear.
- Low load on the bearings of the crankshaft
- If the diaphragm fails, it switches itself off automatically to prevent damage.
- It has an easy maintenance
- The exhaust pressure is up to 3000 bar.
- It provides a tight compression of gas.
- Unadjusted high internal pressure saves energy and decreases the price.
- Noiseless operation
- This compressor is free from vibrations and knock
- It saves energy
- Extends the life of the membrane
- Reduce energy costs
Disadvantages of Diaphragm Compressor
- This type of compressor has a short life of the diaphragm.
- It has a low flow rate.
- It can’t self-regulate.
- Valves and piston rings are susceptible to the contamination present in the gas.
Applications of Diaphragm Compressors
- Metal processing
- Flat glass manufacturing industries
- Also uses for the cooling of Power plant turbine
- Filling and off-loading of gases from tube trailers
- Feedstock for pharmaceutical, chemical, and petrochemical activities
- Hydrogen fuel cell station
- Filling gas cylinder and bulk storage tank
- Syngas compression from renewable bases
- Gases for fiber optics, semiconductor, and electronics production
- Gas mixing, blending, and recycling
- For purification of a few specialty gases
- Hydrogenation of palatable oils
- Diaphragm or membrane compressor also uses for the purification of flat glass.
FAQ Section
who invented diaphragm Compressor?
In 1916, Henri Corblin invented the Howden diaphragm compressors “D” series.
What is the difference between Diaphragm Compressor and Diaphragm Pump?
A diaphragm compressor is used for compressible fluids (i.e., air or gas), while a diaphragm pump uses for incompressible fluids.
What are the components of the diagphragm compressor?
- Body
- Cylinder
- Check Valve
- Piston
- Hydraulic injection pump
- Overpump sight glass
- Inlet and Outlet Valves
- Connecting Rod
- Crankshaft
- Diaphragm or Membrane
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