Screw compressors almost occupies most of the market share of air systems above 22kW, with a nominal pressure of 0.7～1.0MPa. Leading to this trend is the improvement of its performance and reliability, as well as reduced maintenance and lower initial costs.
Nevertheless, the double-acting piston compressor is still the most efficient compressor. The rotor shape of the screw reduces the high efficiency range of the screw compressor. Therefore, a better rotor profile, improved processing and innovative design are the key factors of the screw compressor.
For example, a low-speed, direct-drive screw compressor can provide a discharge pressure of 0.7MPa and an air volume of 0.13-0.14m³, which is 90-95% of the double-acting piston compressor. For most users, unless some occasions where energy consumption is particularly considerable, due to its higher initial investment (purchase price), the more efficient double-acting piston compressor is often not cost-effective due to the long payback period of the investment.
A well-maintained screw compressor can provide operation for 10 years or more. At the same time, its control system with fault diagnosis and processing capabilities can indicate the oil change gap based on the operating temperature, which also improves the reliability and life of the compressor .
maintain
For maintenance costs, screw compressors have advantages over piston compressors. Double-acting piston compressors have shorter maintenance intervals than screw compressors. The valve, piston ring and other wearing parts on the piston compressor require periodic maintenance.
The main maintenance of screw compressor is oil, oil filter and oil separator. Sometimes, the replacement of screw rotor air and inspection side equipment requires considerable costs, but they can usually work for 10 years or more.
The standard screw compressor assembly has a controller based on microprocessor or electrical control. These controllers enable the screw rotor to maintain load 100% of the time. One of the main functions of the controller is to adjust the air flow so that the machine can run at the highest efficiency under full load, partial load and no-load conditions.
Some screw machine controllers have many other useful control functions, such as operation monitoring, shutdown warning and maintenance reminder.
A unit equipped with a well-operated and maintained double-acting piston compressor is beneficial to operation. This kind of equipment can be coordinated and distributed, using regular repairs and maintenance to become a successful compressed air system.
lubricating
According to different lubrication conditions, piston compressors can be divided into two types: lubricated and non-lubricated. In a lubricated unit, lubricating oil is introduced into the compression cylinder to reduce the friction between the cylinder and the piston ring. Under normal circumstances, a well-lubricated piston ring can last for several years, and the application of advanced materials can extend the life of the piston ring in a dry-type unit to more than 8000h.
The cost between lubricated and non-lubricated piston engines is a factor worth considering. In some cases, oil-free compressed air or gas is required. The initial investment of a non-lubricated unit is 10-15% higher, and there is little difference between energy consumption and efficiency. The biggest difference lies in the maintenance required for the two types of units. Cost, the maintenance cost of an unlubricated unit is four times or more than that of a lubricated unit.
The unbalanced force and heavier weight of the piston compressor are the main influencing factors in the installation cost. Usually, the piston unit requires a heavy base and a thick foundation. Of course, the compressor manufacturer will provide the relevant data needed to build the base.
Although the initial investment and installation cost of the piston compressor is more than that of the screw compressor, the life of the piston compressor under good maintenance can be 2 to 5 times longer than that of the screw compressor.
For decades, the piston compressor has become a reliable heavy-duty machine. With the advancement of technology, while providing high-quality air, the maintenance cost of piston compressors has been greatly reduced. In units with a nominal pressure of 0.7～1.0MPa, whether it is compressed air or other gases, the piston compressor is still the best choice.
Post time: Dec-03-2021