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The HD-LC helical gear flow meter belongs to the category of positive displacement flow meters, also known as volume-controlled flow meters, and it is one of the most accurate types of flow meters among all such instruments. It is insensitive to flow distortion, can measure non-Newtonian flows, and can reflect the true volumetric flow rate in multiphase flow measurements. Its main components are the metering box and a pair of elliptical gears mounted inside it; together with the cover plate, they form a sealed crescent-shaped cavity that serves as the measuring device. The pressure difference at the inlet and outlet of the flow meter drives the elliptical gear to rotate, and the fluid is discharged after being measured in the initial crescent-shaped cavity. Each rotation of the elliptical gear generates a volume 4 times that of the initial crescent-shaped cavity; therefore, the number of rotations of the elliptical gear is proportional to the flow rate of the fluid. HD-LC helical gear flowmeters: This series of products can be manufactured using various materials such as cast iron, cast steel, and stainless steels 304 and 316L, and are widely used for flow measurement in industries such as chemicals, petroleum, pharmaceuticals, power generation, metallurgy, and instrumentation. Below are an introduction to the seven most common faults of elliptical gear flowmeters and their solutions. I. The elliptical gear does not rotate. Reasons: 1. There are debris in the pipeline; 2. The filter is damaged, allowing debris to enter the device and cause the gear to get stuck; 3. Excessive flow leads to wear of the bearings, resulting in the elliptical gear colliding with the interior surfaces and causing it to get stuck. Treatment methods: 1. Clean the flow meter and pipes; 2. Repair the filter; 3. Replace the bearings to ensure smooth operation with proper clearance. II. The elliptical gear rotates while the pointer remains stationary or moves intermittently. Causes: 1. The rotating fasteners are slipping, damaged, or inflexible; 2. The magnetic coupling is slipping; 3. The index wheel component is stuck. Solution methods: 1. Retighten the fasteners and remove any areas that are not moving freely; 2. Check whether the magnetic coupling is flexible and what its magnetic strength is; 3. Fix any faults in the gear components. III. Large negative error in the flow meter. Causes: 1. Leakage in the bypass valve; 2. Wear or corrosion of the inner wall of the elliptical gear metering chamber or of the bearings; 3. Flow rate below the lower limit; 4. Sliding of the magnetic coupling or periodic faults in the gear system; 5. Actual liquid viscosity being lower than the measured liquid viscosity. Solution methods: 1. Check the bypass valve; 2. Replace the bearings, inspect the gears, and adjust the clearance; 3. Increase the flow rate; 4. Repair or replace the magnetic coupling or gear system; 5. Use a testing fluid with viscosity similar to that of the actual liquid to test the flow meter or make viscosity corrections. IV. Large positive error in HD-LC helical gear flow meters. Reasons: 1. Significant pulsations in the flow rate or presence of gas; 2. The actual viscosity of the liquid is higher than that of the liquid used for testing; 3. When the inlet valve is closed, the medium does not fill the metering chamber completely, resulting in inaccurate measurements. Solutions: 1. Reduce flow pulsation or add a gas separator; 2. Use a test fluid with viscosity similar to that of the actual liquid to test the flow meter or apply a viscosity correction; 3. Regulate the medium flow rate using the valve at the outlet of the flow meter. V. The reading indicated by the secondary gauge is higher than that indicated by the primary gauge. This fault is usually caused by vibration of the signaling blade, and it can be resolved by appropriately adjusting the pressure exerted on the blade by the damping element. VI. The reading indicated by the secondary gauge is lower than that indicated by the primary gauge. Reasons: 1. The fastening screws at the signal-transmitting blade are loose; 2. The signal transmitter has skipped a step. Solution: 1. Tighten the locking screw; 2. Adjust the gap between the signaling blade and the transmitter. VII. The secondary meter does not indicate. Reasons: 1. Open or short circuit in the wiring; 2. Damaged transmitter. Solution: 1. Carefully inspect the wiring; 2. Replace the transmitter. An elliptical gear flow meter is mainly composed of a body, a pair of elliptical gears, a magnetic coupling, a reduction mechanism, high-speed gears, a counter, and a signaling device. In general, the causes and solutions for the possible faults of this flow meter can be found in the above descriptions. If the cause of a particular fault cannot be identified, one can turn to the manufacturer of the flow meter for help in finding a solution. The manufacturer advises you not to disassemble the flow meter blindly in case of problems, as this could lead to irreversible consequences.