In thermal power plants, the stability and accuracy of the EH oil servo valve SM4-40 (40) 151-80/40-10-D305 directly affect the operating efficiency and safety of the steam turbine. The servo valve is an electro-hydraulic conversion device whose core components include electromagnets, slide valves, feedback mechanisms, etc. In the steam turbine fire-resistant oil system, it receives electrical signals and converts them into hydraulic power to control the action of the actuator. Understanding these basic components and their working principles is a prerequisite for effective maintenance.

Routine inspection items

Visual inspection: First, check whether the servo valve has damage, leakage or abnormal wear on the outside. Any physical damage may affect its sealing performance and function.

Pressure test: Use dedicated pressure test equipment to check whether the servo valve’s response under different input pressures meets the design requirements. This helps to discover potential problems with internal components.

Temperature monitoring: Monitor the temperature of the servo valve during operation. Excessive temperature may indicate insufficient lubrication or internal component failure.

Current detection: Measure the current consumption of the servo valve during operation. Abnormal current changes may be caused by internal short circuits or other electrical problems.

Detailed parameter analysis

Flow characteristics: The flow output of the servo valve under different pressure differences is measured by the flow test bench. The flow characteristic curve should be smooth and without mutation points.

Response time: Use a high-speed data acquisition system to record the time from the servo valve receiving the electrical signal to the full response. A long response time may mean that the internal damper needs to be adjusted.

Linearity: The output of the servo valve should be proportional to the input signal. Poor linearity is usually caused by internal wear or manufacturing deviations.

Zero offset: The servo valve should remain in the center position without external force. Zero offset may be caused by mechanical wear or misalignment of the feedback mechanism.

Dead zone: Detect the input signal range before the servo valve starts to move from one direction to another. Excessive dead zone affects control accuracy.

Repeatability: The output of the servo valve should be consistent under the same input signal. Poor repeatability indicates the presence of unstable factors.

Troubleshooting steps

Preliminary diagnosis: Based on the above inspection results, form a preliminary fault hypothesis.

Step-by-step verification: Verify the hypothesis one by one, such as by replacing suspected damaged parts or adjusting parameters.

Comprehensive analysis: Combine historical maintenance records and current test data to conduct a comprehensive analysis to determine the most likely cause of the failure.

Repair: Take appropriate repair measures based on the cause of the failure, such as cleaning, replacing parts or recalibrating.

Performance test: After the repair is completed, perform a comprehensive performance test again to ensure that the servo valve is restored to normal working condition.

For the maintenance and troubleshooting of the servo valve SM4-40(40)151-80/40-10-D305, engineers need to not only master its basic structure and working principle, but also be proficient in using various detection tools and methods. Through regular inspections and detailed parameter analysis, potential problems can be effectively prevented and resolved to ensure the smooth operation of the generator set.

Yoyik offers various types of valves and pumps and its spare parts for power plants:
Globe valve WJ41B4.0P
vacuum pump spare parts spring P-2335
hydraulic power PVH131R13AF30B252000002001AB010A
bladder type hydraulic accumulator NXQA-10-31.5
screw oil pump HSNH-280-43NZ
circulating pump F320V12A1C22R
Manual valve EH oil inlet K151.33.01.01G01
pressure seal globe valve WJ15F2.5P
SOLENOID VALVE FOR GOVERNING VALVE SV4-20(15)57-80/40-10-S451
Bellows valves WJ60F-25P
IP stop valve WJ10F-1.6P
valve AGAM-10/10/350-I 34
flow Regulating valve BXF-40
SCREW PUMP E-HSNH-660R-40N1ZM
servo valve FRD.WJA5.021
Carbon brush national 634 size 32 x 32 x 64
Bellows valves WJ15F-16P DN15
Seal wiper Ø 20 shaft 4Pcs M3334
CONTROL OIL RELIEF VALVE DBDS10GM10/5
Bellows valves WJ50F-2.5P