Measuring the compressor fad flow (free air delivery) is a challenging task. The fad measurement method adopted by the compressor manufacturer in the factory is usually limited by site conditions and is not feasible or applicable. However, this task is not difficult if appropriate flow measurement tools and mathematical methods are used.
The basic function of the air compressor is to compress the air after sucking in the ambient air, and then discharge the compressed air into the compressed air network. The performance index of the compressor is reflected in the rated power of the compressor and the fad performance description given by the manufacturer. However, if you have completed the field measurement, you will find that sometimes this is not the case. In fact, the following simple questions can be used to judge the performance of the compressor: how much power does the air compressor consume? How much compressed air does the air compressor output? What is the specific shape of the pressure distribution curve?
In order to answer these questions, we must make relevant measurements at the production site. In general, measurements are divided into two categories:
Temporary performance measurements are usually used after the installation of new equipment or before the compressor purchase decision. The purpose is to analyze the performance of the compressor to provide performance comparison.
Long term performance monitoring is used for real-time monitoring of compressor performance to reasonably arrange equipment maintenance or host overhaul.
Standard definition of fad
Flow refers to the volume of gas measured per unit time, but the gas volume is easy to compress or expand and changes with temperature. In addition, the humidity (water vapor) and density (air quality per cubic meter) of the air inhaled by the air will also change with altitude and temperature. In order to ensure the consistency of measurement, the industry has introduced a series of international standards, such as ISO 1217. This standard specifies the acceptance test standards for positive displacement compressors (including rotary screw compressors).
ISO 1217, Section 3.4 Article 1 provides as follows:
The actual volume flow of the compressor refers to the volume flow of gas compressed by the compressor and discharged at the standard exhaust position, which is converted to the full temperature, full pressure and full component state of the inlet standard suction position.
This is to convert the actual gas volume discharged by the compressor into the free air state in the compressor inlet. Therefore, fad refers to the total free air entering the compressor measured at the exhaust port of the compressor. Fad uses volumetric flow units, such as m3 / min and L / s.
ISO 1217 allows all types of flow meters to first calculate the mass flow of air and then convert the flow into the volume flow of intake according to the air density in the compressor inlet. Ideally, real environmental conditions are used, but for convenience, ISO 1217 recommends the following environmental conditions under acceptable actual conditions:
·Pressure = 1 pa absolute
·Temperature = 20 ℃
·Relative humidity = 0%
Finally, the flowmeter corrects the volume flow value according to the humidity of the air inlet, the condensate flow upstream of the flowmeter and the speed of the motor. Tip: the fad data provided by the compressor manufacturer can be measured under different inlet conditions. Therefore, it is recommended to refer to the compressor data sheet rather than simply look at the data displayed on the nameplate when evaluating the performance of the compressor.
Compressing air to a higher pressure requires more energy. In Zerlion air compressor, the air loss and working air volume increase with the increase of pressure. Only in this way can the compressor motor overload under high voltage. For example, the operating speed of rotary screw compressor is different at the pressure of 8 PA and 10 PA.
Post time: Dec-22-2021