How to analyze the failure of the vane pump control valve?

How to analyze the failure of the vane pump control valve? The fuel is supplied by the main fuel pump, and the fuel bypass valve of the main fuel pump adjusts the fuel quantity of the unit, thereby controlling the change of the load. So how to analyze the failure of the vane pump control valve? The following summarizes the failure problems of the vane pump control valve:

Failure and cause analysis of vane pump control valve

Electro-hydraulic converter (or servo valve), when the current signal of the input coil changes, the torque motor drives the armature and the flexible tube to move, causing the flow on both sides of the first-stage injection pipe to change, and then changing the second-stage The pressure at both ends of the spool valve drives the spool valve to move, so that the oil cylinder enters or exits the oil, thereby driving the fuel bypass valve to work.

There are two main failure phenomena of the fuel bypass valve of the vane pump control valve:

  1. During the start-up process, the fuel flow FQL deviates from the flow input signal FSR after ignition, and the flow is too large, causing the over-flow protection action to fail to start. Sometimes there is no flow or the flow is very large and the startup fails;
  2. The other is that during normal operation, the fuel flow FQL deviates from the flow input signal FSR instantaneously, and the fuel flow rises or falls within a few seconds, but recovers within a few seconds. When the fuel flow drops, the load drops and resumes immediately, and generally no tripping occurs. When the fuel flow increases, the load increases, which may cause the exhaust temperature to be high and the tripping occurs.

Selection of lubricating oil for vane pump control valve

  1. The lubricating oil in the gas turbine is in an extremely harsh high-temperature oxidizing environment. The temperature that the babbitt bearing can withstand is as high as 120 °C, but the temperature of the sealing air around the bearing is higher, where the oil film temperature can reach 130 °C, and some even have the highest temperature. There are 140 ~ 150 ℃, which have reached or exceeded the temperature limit of mineral oil and additives. Combined with exposure to sealed air, the oxidation of the oil is very violent;
  2. Just because the biggest challenge encountered by gas turbine lubricating oil in operation is high-temperature oxidation, the high-temperature oxidation resistance in gas turbine lubricating oil specifications is the most worthy of attention. The federal oxidation test can better reflect the anti-aging and anti-sludge properties of oil at high temperatures. In the federal oxidation test, five metals were added to the oil as catalysts (copper, silver, aluminum, magnesium, iron), and the aging was carried out at 175 ° C with airflow for 72 h;
  3. The test report reports the change of viscosity, the increase of acid value, the content of sludge, etc. after oil aging. The oil has undergone the most severe high-temperature oxidation resistance test in this test. Routine tests pay more attention to viscosity and acid value, but for the gas engine lubricating oil to be used as vane pump oil, the threat of sludge to the vane pump controller should be paid enough attention to.

How to change the oil of the vane pump control valve

  1. In order to remove the remaining old oil, sludge, sediment, paint film, and other impurities in the maintenance process to the greatest extent, after cleaning the oil tank and pipeline, repeatedly flushing with flushing oil, re-cleaning, and then using working oil After flushing and draining, add new working oil. When changing the oil, try to drain the old oil as much as possible to reduce the pollution to the flushing oil. Discharge when the oil temperature is 60~70℃, remove the oil accumulated in the large container such as the oil tank and the cooler, open the low valve and pipeline joint, and replace all the filters.
  2. During the flushing process, try to form a turbulent flow, and the oil temperature should fluctuate between 30 and 80 °C. Install a filter screen on the oil inlet and oil return pipe. When the pressure difference of the filter screen is too large, it should be replaced in time. When heating oil, the temperature should not exceed 88℃, the surface temperature of the heater should not exceed 120℃, and the surface temperature of the heater should not exceed 66℃ when the oil circulation is stopped.
  3. The cooler circulates alone, and sensitive components such as servo valves and bearings are bypassed. When the working oil is flushed, the oil temperature should be controlled at 60 ~ 70 ℃. After the oil change, the oil sample was extracted for comprehensive testing and compared with the new oil in the barrel.

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