The MS9001E gas turbine generator set operates in a simple cycle configuration, with a base load of 180 kg/h of heavy fuel oil at a power output of 13.8 MW and a pressure ratio of 12.3. The overall design features the No. 2 bearing positioned between the compressor and turbine, while the No. 3 bearing is located in the turbine exhaust diffuser. The compressor inlet guide vanes are adjustable via the 9OTV-1 control system. Fuel delivery is managed by the main Fuel Pump, with the fuel bypass valve—controlled by 65FP-1—regulating fuel flow to maintain load stability. However, since the second half of 2002, the 65FP-1 valve has experienced multiple trips due to internal failures, leading to startup delays or unstable fuel levels.
The 65FP-1 is an electro-hydraulic converter, also known as a servo valve. When the input current signal changes, the torque motor moves the armature and flexible tube, altering the flow through the first stage nozzles. This change in flow affects the pressure on both sides of the second-stage spool valve, which in turn controls the fuel bypass valve. Common failure symptoms include excessive or insufficient fuel flow during startup, causing protection trips or failed starts. During normal operation, brief deviations in fuel flow can lead to load fluctuations, sometimes resulting in high exhaust temperatures and trips.
Upon disassembling the 65FP-1, significant sludge and varnish buildup were observed on the oil filter and metal surfaces. These deposits, which appeared as a hard, brown, translucent layer, were identified as the primary cause of the valve’s malfunction. Although standard lubricant tests (viscosity, cleanliness, acid value) met specifications, further analysis revealed that the oil had reached critical sludge levels. Specifically, the Millipore sludge test results showed values of 4.21 mg/100mL and 6.12 mg/100mL in May 2002. In early 2003, TURBO GT32 lubricant was introduced as a replacement, and the issue with 65FP-1 was resolved. However, the No. 7 unit continued to experience problems until its oil was replaced in April 2003, after which no further issues occurred.
Gas turbine lubricating oils operate under extremely harsh conditions, particularly in high-temperature oxidation environments. Bearings can withstand temperatures up to 120°C, but the surrounding sealing air may reach 130–150°C, exceeding the thermal limits of conventional mineral oils. Oxidation is a major concern, as it leads to sludge formation and can severely impact hydraulic control systems. The Federal Oxidation Test, which simulates high-temperature aging with metal catalysts, is essential for evaluating oil performance. TURBO GT32, formulated with XHVI base oil and high-temperature additives, demonstrated superior resistance to sludge generation compared to mineral oils.
During oil change procedures, it is crucial to thoroughly remove residual oil, sludge, and contaminants. The process involves draining old oil, cleaning the tank and piping, rinsing with flushing oil, and finally introducing new working oil. Key steps include maintaining turbulent flow during flushing, controlling oil temperature below 88°C, isolating sensitive components, and conducting comprehensive oil analysis post-change.
In conclusion, regular lubricant testing—especially for oils used in hydraulic systems—is vital. The Millipore sludge test and rotary oxygen bomb test should be prioritized. When sludge content exceeds 5 mg/100mL, oil change should be performed promptly to prevent accelerated degradation. Due to the high-temperature exposure, it is recommended to separate gas turbine oil from hydraulic oil to reduce contamination risks and simplify maintenance.
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