The key difference between Rotary Screw Air Compressors and Reciprocating Air Compressors is the mechanism in which they compress air.
Their distinct features can be understood in terms of:
1) System design
Rotary screw air compressors have a couple of meshing spiral screws called rotors for compressing the input air. While reciprocating air compressors employ pistons moved by a crankshaft for compressing the air.
2) Components involved
With just two moving parts (screws) that have a small gap between them, screw air compressors are not subject to much wear and tear. Even in models where the two screws come in contact with each other, they don’t encounter any friction, which is why they are less likely to break down.
On the other hand, reciprocating air compressors have several moving parts like pistons, piston rings, connecting rods, and inlet-outlet valves due to which they are noisier and may need stocking of spares.
3) Temperature
The internal heat produced by screw air compressors during operation is between 80 - 99 degrees celsius. The heat production is limited, as there is no friction between the screws. The oil or lubricant used between the rotors and casing creates a non-wearing seal that can eliminate the heat with the help of a thermostatically managed fluid circuit.
In reciprocating air compressors, the pistons operate at temperatures between 150-200 degrees celsius. The high temperatures are due to the friction caused by the movement of piston rings against the cylinder walls.
4)Oil filtration
The chances of finding residual oil in an oil-lubricated screw air compressor are very low, because this unit has a three-stage oil filtration system. The oil content is typically below three particles per million (PPM).
However, a reciprocating air compressor does not have an oil filtration system, which is why, its outlet air can be more contaminated than a screw air compressor. The oil content in the air also increases when piston rings and oil rings deteriorate, allowing oil to move up to the compression side.
Individual benefits of both the models -
The top advantages of choosing a screw air compressor are:
1) Continuous air supply
2) Higher duty cycle
3) Better durability
4) Higher overall efficiency
5) Lower ambient noise
6) Higher airflow per rated power
Few reasons why some operators still prefer a reciprocating air compressor are:
1) Very high pressure requirements
2) Spare parts management
3) Lower duty cycle
Keywords
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pistons
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friction
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Components
other hand
crankshaft
outlet air
oil content
Few reasons
residual oil
piston rings
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internal heat
fluid circuit
System design
cylinder walls
top advantages
key difference
Higher airflow
three particles
150-200 degrees
80 - 99 degrees
heat production
compression side
thermostatically
Lower duty cycle
two moving parts
Higher duty cycle
Better durability
high temperatures
distinct features
Individual benefits
Lower ambient noise
inlet-outlet valves
several moving parts
Continuous air supply
meshing spiral screws
Spare parts management
Higher overall efficiency
Rotary Screw Air Compressors
reciprocating air compressor
Very high pressure requirements
three-stage oil filtration system
oil-lubricated screw air compressor
