Which Is Better? — Screw Compressor VS Piston Compressor

Author: May

Jun. 13, 2024

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Tags: Minerals & Metallurgy

In the air compressor market, screw air compressors and piston air compressors stand out as the two predominant models. Practitioners in the field often leverage this comparison to advertise and promote their respective advantages to users.

 

Piston air compressors, having entered the market early, initially secured a substantial market share. On the other hand, screw air compressors, though introduced later, brought a high level of intelligence to the market.

 

A noticeable trend is the gradual replacement of piston air compressors by screw air compressors, and this transition is consistently advancing. It is anticipated that, in the near future, screw air compressors will find broader applications in industrial production, leading to a continuous increase in their market share.

 

When deciding between a rotary screw air compressor and a piston compressor, it is crucial to understand their similarities and differences to determine the most suitable option for optimal equipment performance.

 

Compressors play a pivotal role in the daily operations of many companies, with a clear demand for their applications. The widespread use of compressors extends across various gas fields, and while both types are utilized, air compression holds the lion's share. Currently, stationary screw air compressors command approximately 40% of the air compression market, while piston air compressors account for 21% (calculated in US dollars).

 

Screw Air Compressor


What Is the Difference Between Rotary and Piston Compressor?

 

Different Structures:

The screw air compressor's organizational structure comprises the oil screw main engine, electric motor, oil and gas separator, oil pipeline system, cooling system, gas pipeline system, and electrical control system.

In contrast, the piston compressor is composed of a compressor main unit, cooling system, regulating system, lubrication system, safety valve, electric motor, and control equipment.

 

Different Features:

Screw air compressors offer several advantages, including low vibration, no requirement for anchor bolts to fix on the foundation, low motor power consumption, minimal noise, high efficiency, stable exhaust, and absence of wearing parts.

Typically, the compressed gas from a piston compressor does not contain oil under normal circumstances, eliminating the need for a degreasing device.

However, the piston compressor comes with certain drawbacks such as higher motor power consumption, less stable exhaust pressure, elevated exhaust temperatures, increased noise levels, higher maintenance workload, and greater maintenance costs.

 

Different Types of Failures:

Screw air compressors experience minimal faults, requiring routine maintenance involving the replacement of the air filter, oil filter, and oil-gas separator for normal operation.

On the other hand, piston air compressors face distinct challenges. Issues arise from incomplete oil scraping and inadequate sealing, causing oil to migrate towards the packing device or even the piston ring, resulting in oil presence in the compressed gas. Additionally, these compressors exhibit elevated exhaust temperatures, reaching as high as 200 ℃ at times. Cooling inefficiency due to blockages, oil-stained piston rings prone to wear, valve flap leaks, and cylinder wear are common problems associated with piston air compressors.

 

Which Is Better Rotary or Piston Compressor?

Performance Comparison:

Reliability:


Piston air compressors exhibit low reliability due to numerous parts, a high vulnerability to wear, substantial maintenance requirements, poor operational reliability, a short lifespan, and an overhaul interval typically around 8,000 hours.

In contrast, screw air compressors boast high reliability with few parts, no wearing components, minimal maintenance demands, dependable operation, an extended lifespan, and overhaul intervals ranging from 40,000 to 80,000 hours.

 

Additional reading:
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Dynamic Balance:

 

Piston-type compressors suffer from unbalanced inertial forces, resulting in significant machine vibration and noise. Foundations are often necessary for smaller machines and above to mitigate these effects.

On the other hand, screw-type compressors have no unbalanced inertial forces, allowing for steady, high-speed operation. They are characterized by a compact size, lightweight design, and the ability to function without the need for a dedicated foundation.

 

Pressure Stability:

 

The reciprocating air compressor has a discontinuous exhaust, causing airflow pulsation, unstable pressure, and easy to cause pipeline vibration. A large-capacity air tank is required.

The rotary screw air compressor has a uniform exhaust, no airflow pulsation, stable pressure, and no need for large-capacity air tanks.

 

Air Quality:

 

Reciprocating air compressors have poor air quality and high exhaust oil content, which cannot meet the higher requirements of users, and post-processing costs are high.

The oil-injected screw compressor can achieve excellent air quality, with an exhaust oil content ranging only between 1-5 ppm. This meets the elevated standards of users and effectively reduces post-processing costs.

 

Price Comparison

Piston-type air compressors come with low production requirements, translating to lower prices. In contrast, screw-type air compressors demand advanced production technology, leading to higher prices compared to piston-type counterparts.

 

Stress Adaptability:

Piston air compressors demonstrate versatility across a broad pressure range and can attain the required pressure regardless of the flow rate, reaching up to 350Mpa in industrial settings.

Oil-injected screw air compressors, however, are limited by the rigidity of the rotor and bearing, making them unsuitable for high-pressure applications, with exhaust pressures generally not exceeding 3 Mpa.

 

Capacity Adaptability:

Piston-type compressors exhibit robust adaptability with a wide displacement range unaffected by pressure variations.

Rotary compressors face limitations for miniature applications due to their reliance on gap-sealing gas. Generally, rotary compressors deliver optimal performance only when the volumetric flow exceeds 0.2m3/min.

 

Operation and Maintenance:

The piston air compressor operates with a low degree of automation, requiring continuous supervision by an on-duty operator. In contrast, the screw air compressor boasts a high degree of automation. Operators do not need extensive professional training and can achieve unattended operation.

 

Conclusion:

Considering the factors discussed above, the piston air compressor emerges as the optimal choice when prioritizing price. Opting for piston-type air compressors is advantageous in reducing maintenance and production costs, enhancing economic benefits, simplifying equipment management, and contributing to environmental protection by minimizing pollution.

However, recognizing the imperative need for increased efficiency and reliability, the inevitable trend in advancing development and strength lies in transitioning to high-efficiency screw compressors to replace piston-type air compressors. The construction of an advanced and economical air compressor station aligns with this evolving trend, further enhancing overall performance.

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