Difference between piston and centrifugal air compressor

In the industrial field, engineers often face a tangled problem: whether to choose piston or centrifugal air compressor? To distinguish them accurately, we will teach you to distinguish piston air compressors and centrifugal air compressors thoroughly from five aspects.
Difference between piston and centrifugal air compressor
First, the working principle
Piston air compressor (positive displacement type): The crankshaft is driven by the motor, so that the piston moves back and forth in the cylinder, and the gas is abruptly “squeezed” into the pipeline. Its compression is achieved by volume reduction.
Centrifugal air compressor (power type): The motor drives the impeller to rotate at a high speed (the speed is tens of thousands of revolutions at every turn). After the air is sucked in, the gas is violently “thrown” to the edge of the volute by centrifugal force, which is extremely fast, and then the speed is converted into pressure by the diffuser. Its compression is realized by kinetic energy conversion.
Second, small displacement and high pressure vs large air volume are stable
In terms of output characteristics, the division of labor between them is clear. Piston air compressor is good at providing small and medium flow of compressed air. However, due to the mechanical characteristics of the reciprocating motion of its piston, the air flow discharged by it has a pulse feeling, which belongs to intermittent air supply, so it is usually necessary to equip a larger air storage tank to stabilize the air flow.
On the contrary, centrifugal air compressor is a leader in the field of super-large flow, designed for large-scale continuous production. It can provide extremely smooth and pulse-free continuous airflow.
Third, structural characteristics and key points of operation and maintenance
Piston air compressor:
Structural complexity: It contains a large number of precision kinematic pairs (piston rings, air valves, bearings, etc.), and its mechanical structure is relatively complex.
Wearable parts: Piston rings, valve plates of air valves, sealing fillers, etc. are regularly replaced, and the maintenance frequency is high.
Cooling mode: mostly air cooling or water cooling, and the cylinder head, cylinder body and other parts need heat dissipation.
Installation foundation: due to the large inertia force, it is usually necessary to strengthen the concrete foundation and damping pad.
Centrifugal air compressor:
Structural complexity: the core components are rotor (shaft+impeller) and stator (casing, diffuser), which are compact in structure but require extremely high manufacturing accuracy.
Wearable parts: relatively few, mainly concerned with bearing life and sealing system.
Cooling mode: interstage coolers (water cooling or air cooling) are often used to ensure that the gas temperature can be controlled after each stage of compression.
Installation foundation: the requirements for foundation are relatively low, but it is sensitive to centering accuracy and pipeline stress.
Fourth, the operation and maintenance experience
In the actual use scenario, the sensory experience and operation and maintenance costs of the two are quite different. Because there are many mechanical friction parts such as piston, connecting rod and air valve in piston air compressor, it is noisy and vibrates strongly during operation, so it usually needs independent machine room or sound insulation treatment. In addition, it has more wearing parts and relatively high maintenance frequency, but its initial procurement cost and energy efficiency performance are friendly to small and medium-sized enterprises under low load or intermittent work.
Because the centrifugal air compressor mainly relies on the high-speed rotation of the impeller, its running vibration is very small, its noise is low, and its internal moving parts (mainly bearings and impellers) are few, and its daily maintenance workload is small, so it is suitable for occasions that require extremely high stability of the environment and gas source (such as food, medicine and electronics industries).
Fifth, the application scenario is big PK
The scene of choosing piston air compressor: small factories and CNG filling stations that need ultra-high pressure (such as above 30bar), small gas consumption with large fluctuation and limited budget.
Scenarios for selecting centrifugal air compressor: large chemical plants, steel plants, pharmaceutical factories, large air substations, etc. with huge gas consumption (usually more than 20m3/min) and oil-free and 24-hour continuous operation.
The above is an introduction to the difference between piston air compressor and centrifugal air compressor. If you need intermittent air source with small flow and high pressure, and the budget is limited, piston air compressor is a classic choice. And if you are faced with the continuous large-flow gas demand of large-scale factories, and have strict requirements on airflow stability and environmental noise, centrifugal air compressor is an irreplaceable industrial behemoth.