A.13.1 Brief description of the fault
A company has repeatedly encountered the problem of high oil consumption in screw compressors. After adding 201 lubricating oil, the oil level sometimes cannot be seen in a week. Under normal circumstances, the air compressor needs to be refilled once after running for 2 months. High oil consumption in air compressors is one of the common fault phenomena of air compressors.
A.13.2 Cause analysis
(1) First, check whether there is oil leakage or oil seepage on the surface of the machine's pipes.
(2) Check whether the water cooler is leaking. The method is to stop the operation of the air compressor, close the water inlet and return valves of the cooler, open the cooler drain port, drain the accumulated water and observe whether there is lubricating oil flowing out. Generally, if there is residual pressure in the air compressor system, the cooler will leak and lubricating oil will be discharged from the leak point.
(3) In most cases, the high oil consumption of the air compressor is caused by the oil fine separator. The rupture of the oil fine separator is the most common oil leakage phenomenon. There are many other reasons that have been introduced in the previous chapters. The following introduces several specific cases.
A.13.3 Actual case analysis
Case 1: The oil separator of a company's screw air compressor consumes a lot of oil, affecting the normal operation of the machine. After checking the pressure, temperature, current, loading and unloading data during the operation of the machine, no abnormalities were found, and the return oil pipe was hot.
After the machine was shut down, the minimum pressure valve and the return oil pipe check valve were checked, both of which were normal. After opening the oil and gas barrel cover, it was found that the return oil copper pipe originally fixed on the oil and gas barrel cover fell off from the welding point, and the oil level was at 2/3 of the height of the oil separator.
Due to the fall-off of the return oil pipe welding point, the oil accumulated at the bottom of the oil separator core after separation could not be sucked back to the machine head, resulting in the condensed oil droplets being carried away with the air flow.
Case 2: After the newly replaced oil separator of a company's screw air compressor was used for 3 days, the oil consumption was too high and the machine tripped due to high temperature. The return oil pipe, check valve, minimum pressure valve and the use of the machine were checked and no abnormalities were found. When the machine was running, the oil content at the air outlet was detected to be high, and it was basically determined that the problem was related to the oil separator. In the process of removing the oil separator, the real reason was found to be poor sealing. Because the oil separator used in the air compressor is a flangeless structure with two ends, the machine's own steel plate seals the bottom of the oil separator, and the top is sealed by the oil and gas barrel cover, so that a sealed space is formed inside the oil separator. The oil and gas mixture after the initial separation must be separated by the oil separator before output, and the ternary rubber pads at the upper and lower ends of the oil separator and the machine's own steel plate seal are displaced, resulting in poor sealing. Part of the oil and gas mixture is directly output from the gap at the seal without oil separation, resulting in excessive oil consumption and reduced oil volume. When the machine's circulating cooling oil volume is insufficient, high temperature is generated and the machine is shut down.
The displacement of the ternary rubber pad is caused by the loosening of the nut fixing the oil separator. After recalibrating the position of the ternary rubber pad, add a flat washer and a spring washer to the fixing nut, tighten the nut with appropriate force, and then add another nut to tighten it to ensure that the seals at both ends of the oil separator are intact. It runs normally after starting up.
Case 3: A company's newly replaced oil separator ran out of oil after less than one day of use. After inspection, it was found that this type of oil separator was originally used for a European brand air compressor with a displacement of 12.8m³/min, but the maintenance company used it on a Japanese brand air compressor with a displacement of 20m³/min. The maintenance company explained that since the size of this type of oil separator was more suitable for this model, it was adopted.
In addition to size matching, the selection of oil separators also needs to consider whether the processing volume matches, whether the flow rate of the gas in the oil-gas separation tank matches the filter material used by the oil separator, as well as the oil intake and exhaust volume of the machine head, the diameter of the oil-gas co-pipe, etc. These are all factors that need to be considered. Combined with the on-site usage, another matching oil separator was customized, and it ran well after installation.
