In July 1992, Qingdao Petrochemical Plant used 7 electro-hydraulic controlled cold-wall slide valves (referred to as electro-hydraulics) jointly developed by Lanlian Machinery Plant and Beijing Liusan 4 in the technical transformation project of 3.5M t/ a catalytic cracking unit. Slide valve).
The vane pump should have the characteristics of small volume, light weight and excellent performance. However, since the operation in October 1992, there have been many faults such as vibration, noise, pressure, pressure fluctuation, etc., and “automatic operation” is required to switch to “hand” during maintenance. The shaking operation increases the labor intensity of the workers and causes fluctuations in the operation of the device. In order to ensure the safe and reliable operation of the electro-hydraulic slide valve, in the overhaul of the catalytic device in June 1994, we modified the vane pump.
Analysis of the cause of failure of vane pump
When the rotor rotates in the direction of the arrow, the blade gradually protrudes as the rotor rotates in the oil suction zone (lower part of the rotor), and the sealing volume of the blade gradually increases, causing partial vacuum and filling with oil, when the cavity reaches the maximum In the case of the volume, the distribution plate separates it from the suction side to complete the oil absorption process. Then, it is connected to the oil discharge side, the rotor continues to rotate, and the inner curved blade of the stator enters the groove again, and the cavity volume becomes smaller. According to this, the oil is pressed into the oil discharge port to realize the oil discharge process.
In the overhaul, it was decided to make technical modifications to the vane pump in response to the problems. We decided to design the processed distribution plate by itself, the thickness of which is the sum of the thickness of the original rear distribution plate and the thin copper skin, and the thin copper skin is not needed to adjust the gap.
The specific transformation process is as follows:
1) Measure the thickness of the original distribution plate and the thin copper skin, which is measured to be 5.06 mm;
Design a new rear distribution plate whose thickness is equal to the sum of the thickness of the original rear distribution plate and the thin copper skin is 5.06mm.
2) Processing a batch of rear distribution plate according to the drawing, the material is brass. When installing, first measure the gap between the rotor and the rear distribution plate by pressing lead method, that is, put a lead wire between the rotor and the rear distribution plate, and tighten the end cover. Then, the end cover is disassembled, and the thickness of the lead wire is measured with a micrometer. The thickness of the lead wire is the gap between the two, and the rear distribution plate that does not meet the gap requirement is ground to meet the technical requirements.
Through technological transformation, the long-standing problems of the vane pump have been solved. Since the vane pump was rebuilt in June 1994, it has performed well and achieved obvious results, which are embodied in the following three aspects:
Through technical transformation, the problems of vibration, noise, pressure, pressure fluctuation, etc. in the use of the vane pump are solved. The performance of the vane pump meets the technical requirements and ensures the long-term operation of the catalytic device.
The service life of the vane pump is prolonged. After the retrofit, the vane pump rarely fails, and the vane pump is overhauled every year. The vane pump is inspected and found that the rear distribution disc has no wear, which saves a lot of maintenance costs and reduces the device caused by the maintenance of the vane pump. fluctuation.
Avoid the metal of the original design of the thin copper skin
The powder runs to the hydraulic system, so that it contaminates the hydraulic oil or blocks the hydraulic components, ensuring safe and reliable operation of the electro-hydraulic spool valve for a long period of time.
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