In the steam turbine control system of a power plant, the LVDT displacement sensor DET-100A is the core component of the throttle valve position feedback. Its measurement accuracy is directly related to the stability and safety of the unit load control. However, pollutants in the oil circuit system are like “invisible killers”. They may penetrate into the sensor or interfere with the magnetic circuit coupling, causing measurement errors or even equipment failures. This article will combine industry practices and technical specifications to deeply analyze how DET-100A can systematically avoid the risks brought by oil circuit pollution through multi-dimensional strategies such as structural design, installation and maintenance, and intelligent monitoring.

I. The “fatal threat” of oil circuit pollution

The impact of oil circuit pollution on LVDT is mainly reflected in three aspects:

1. Mechanical jamming: After the pollutants penetrate into the sensor, they may adhere to the iron core and the coil frame, resulting in increased resistance to the movement of the iron core, jamming or nonlinear displacement signals.

2. Magnetic circuit interference: If the pollutants enter the air gap between the magnetic core and the coil, they will destroy the magnetic flux distribution, distort the induced voltage of the secondary coil, and cause measurement deviation.

3. Electrical insulation failure: Oil pollution corrodes the terminal or coil insulation layer, which may cause short circuit, grounding fault, and even cause servo system malfunction.

A power plant once suffered from metal particle contamination in hydraulic oil, which caused the LVDT core to get stuck and the feedback signal of the valve to fluctuate by 8%, almost causing load loss. This case highlights the potential threat of oil circuit pollution to the safe operation of steam turbines.

II. DET-100A’s “Triple Protection Shield”

As a displacement sensor designed for harsh working conditions, DET-100A has built an oil pollution protection system through the following innovative designs:

- IP67-level protective housing: stainless steel material and rubber sealing ring are used to effectively block hydraulic oil splash and dust penetration.

- Air gap magnetic shielding structure: a non-magnetic isolation layer is added between the core and the coil to prevent pollutants from entering the core area of ​​the magnetic circuit.

- Dynamic sealing design: for the frequent valve action scene, high temperature and oil pressure resistant fluororubber sealing rings are used to ensure long-term sealing reliability.

- Anti-aging coil insulation: Silicon rubber insulation material is used to withstand oil temperature fluctuations and oil corrosion, ensuring the stability of electrical signals.

III. “Golden Rule” for Installation and Maintenance

Even with advanced protection design, the displacement sensor DET-100A still needs to strictly follow the following operating specifications:

1. Installation phase

- Verticality control: The deviation between the core movement direction and the coil axis must be ≤0.5° to avoid oil deposition due to tilt.

- Environmental isolation: Keep away from heat sources and oil splash areas. It is recommended that the installation position be at least 300mm above the tank level.

- Sealing verification: After installation, perform helium mass spectrometry leak detection to ensure that the housing airtightness meets the IP67 standard.

2. Operation and maintenance

- Periodic cleaning: After every 3,000 hours of operation, use compressed air to reversely purge the sensor cavity to remove surface oil.

- Oil monitoring: Regularly test the particle size and acid value of the hydraulic oil to control the source of pollution from the source.

- Full stroke activity test: After each unit start and stop, perform full valve opening/closing operation and observe the linearity of the LVDT feedback signal.

IV. “Precise calibration” of regular inspection and calibration

To ensure long-term stability, DET-100A needs to be inspected and calibrated according to the following cycles:

1. Daily inspection

- Check the tightening torque of the terminal and observe whether the core moves smoothly without abnormal noise.

- Compare the display value of the DEH system with the local mechanical position indicator. If the deviation exceeds ±0.5%, the troubleshooting process should be started.

2. Quarterly calibration

- Use a calibration device that complies with the ASTM E2309 standard to verify the linearity of the sensor.

- Record the temperature compensation coefficient to correct the sensitivity drift caused by oil temperature changes.

3. Fault diagnosis

- If there is a sudden change in the signal or zero drift, first check the sealing of the servo valve oil circuit to prevent oil from penetrating into the sensor cavity.

- Use spectrum analysis tools to identify abnormal vibration frequencies and locate mechanical friction faults caused by oil contamination.

When looking for high-quality, reliable LVDT displacement sensors, YOYIK is undoubtedly a choice worth considering. The company specializes in providing a variety of power equipment including steam turbine accessories, and has won wide acclaim for its high-quality products and services. For more information or inquiries, please contact the customer service below:

E-mail: sales@yoyik.com
Tel: +86-838-2226655
Whatsapp: +86-13618105229

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