6. For every 1000 meters increase in altitude, the air density drops by about?

A. Noise is loud B. Low efficiency C. Maintaining complex D. Low noise and high efficiency Answer: D. Low noise and high efficiency

A. Pressure and temperature B. Oil quantity and pressure C. Temperature and oil quantity D. The answer cannot be determined: A Analysis: The control system of an oil-free air compressor is mainly used to monitor and control the operating parameters of the compressor, such as pressure and temperature.

A. Lubricating oil and oil filter need to be replaced regularly B. Short equipment life C. High energy consumption D. The oil content of compressed air is high. Answer: A Analysis: The oil injection air compressor requires regular replacement of lubricating oil and oil filter, which increases maintenance costs…

A. Poor after-sales service B. The after-sales service network is underdeveloped C. Provide comprehensive after-sales service D. After-sales service is limited to large cities Answer: C. Provide comprehensive after-sales service

A. Price and brand B. Performance, price and brand C. Viscosity and quality of lubricating oil D. Production date and transportation method Answer: C. Viscosity and quality of lubricating oil