An apparatus for detecting an oil level and a method for controlling the same, an apparatus for detecting oil flow and a method for controlling the same, and a method for controlling oil return using the detected oil level and the detected oil flow are disclosed. The level of oil stored in a compressor is measured at two or more positions. The frequency comparison scheme using two electrodes can correctly detect the level of oil stored in the compressor, a refrigerant state, and the level of mixed oils, and can determine an internal state of the compressor and a normal or abnormal state of the oil return system, such that the oil return control can be actively controlled. The flow of oil in the oil return pipe is detected so as to determine whether the oil is normally supplied in real time, such that a malfunction of the compressor is prevented and a valve state can be checked. The level of oil stored in the compressor is adjusted not only using the oil level detection result but also the oil flow detection result, and the oil return operation can be controlled.

An oil sensor comprising a holder to which an elongated crystal is fastened that is transparent to infrared light and with a refractive index greater than the refractive index of the oil to be examined, whereby a light source is provided in the holder at a first end of the elongated crystal for transmitting light in the infrared spectrum in the elongated crystal, and detector at a second end of the elongated crystal for measuring the intensity of the light, which during the passage through the elongated crystal undergoes total reflection at a boundary plane at least four times in succession in a contact zone where the elongated crystal comes into contact with the oil, wherein the oil sensor is further provided with at least one temperature sensor to determine the temperature of at least one of the components of the oil sensor.

A system for monitoring a piece of hydraulic fracturing equipment such as a positive displacement pump. The system includes a plurality of sensors configured to detect conditions of the hydraulic fracturing pump and a processor that is communicatively coupled to the plurality of sensors and configured to analyze data received from the plurality of sensors. The processor is also configured to predict faults in the hydraulic fracturing pump based on the data analysis. The system also includes a communication interface that is configured for transmitting predicted fault data to one or more devices.

A liquid-cooling fracturing system includes a fracturing device; a power device connected to the fracturing device through a transmission device and configured to provide power for the fracturing device; a cooling medium storage device configured to store a cooling medium for cooling the power device; and a first heat exchange device, the first heat exchange device using cooling liquid to exchange heat with the cooling medium to cool the cooling medium.