Elimination of common faults in gear pumps
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Gear pumps of the CB-B type are widely used in dump trucks and construction machinery, serving as essential components in various operating mechanisms. However, like any mechanical system, they are prone to certain common faults. Below are detailed causes and troubleshooting methods for reference.
1. **Vibration and Noise Issues**
(1) **Air Ingestion**
Air entering the pump can cause vibration and noise. This often occurs when the flatness of the pump body or cover does not meet specifications, leading to air leakage at the contact surfaces. If the gland is made of plastic, it may deform due to temperature changes or damage, allowing air to enter. To resolve this, the pump body or cover should be ground on a flat plate using a "8" shape pattern or a surface grinder, ensuring flatness within 5μm. For leaks at the gland, sealing with epoxy resin can help. Additionally, if the oil level is low or the suction pipe is not fully submerged, the pump may draw in air. The oil should be refilled to the correct level, and the return pipe should be submerged below the oil surface to avoid negative pressure. If the pump is installed too high above the oil level, adjust its position accordingly. A clogged or undersized oil filter can also increase suction resistance and lead to air intake. Clean or replace the filter with one that has an appropriate size and diameter to prevent both air ingestion and noise.
(2) **Mechanical Causes**
Vibration and noise can also result from mechanical issues. Misalignment between the pump and coupling can generate unwanted noise, so the coupling should be adjusted properly. Dirt or contaminated oil inside the pump can cause wear on gears and other components, leading to noise. In such cases, the oil should be replaced, the filter reinforced, and the pump disassembled for inspection. Severely worn gears should be repaired or replaced. Worn or damaged parts, such as gear tooth profiles, end face roughness, or bearing issues, can also contribute to noise. These parts should be replaced or reconditioned to restore proper function. Axial clearance that is too small can cause internal leakage and reduce flow, so the clearance should be adjusted appropriately.
(3) **Other Factors**
High oil viscosity can also cause noise, so using oil with the correct viscosity is essential. Additionally, if the oil temperature is too high, it can lower viscosity and increase internal leakage, reducing output flow. It's important to check for seal damage and ensure the oil has the right viscosity. Reversing the pump can also cause operational issues, so the direction of rotation must be verified. Low engine speed can further reduce flow, so the root cause should be identified and corrected.
2. **Insufficient Output Flow**
Poor flow can be caused by a variety of factors, including high oil temperature, incorrect oil viscosity, improper installation, or insufficient engine speed. Ensuring the oil is at the right temperature and viscosity is crucial. Also, checking the pump’s rotation direction and confirming the engine speed is adequate will help maintain optimal performance.
3. **Poor Rotation**
Poor rotation can be caused by tight clearances, dirt inside the pump, incorrect assembly, misalignment, or un-demagnetized parts. Adjusting clearances, cleaning the pump, correcting assembly procedures, and ensuring proper alignment can all improve performance. If the needle roller sleeve is faulty, it should be replaced. Blocked outlets should also be cleared to allow smooth operation.
4. **Overheating**
Overheating can occur due to poor rotation, incorrect oil viscosity, excessive friction between internal components, or inadequate cooling. Addressing these issues through proper maintenance, oil selection, and cooling system checks can help prevent overheating.
5. **Main Part Repair**
(1) **Gear Repair**
Gear teeth can be worn or damaged, requiring repair or replacement. Light wear can be addressed with fine sandpaper or an oil stone, while severe wear necessitates replacement. End face wear should be carefully ground to maintain parallelism and perpendicularity within 5μm. The meshing orientation of the gears can also be changed to extend their lifespan.
(2) **Pump Body Repair**
Wear on the inner cavity of the pump body, especially on the suction side, can be repaired by rotating the body or using plating techniques to restore the surface.
(3) **Bearing Race Repair**
Worn bearing races should be ground or replaced to ensure smooth operation. Proper grinding and alignment are essential to maintain precision.
(4) **Shaft Repair**
Shafts that have worn due to contact with bearings can be buffed or reworked. If severely damaged, chrome plating or rework may be necessary. Keyway alignment and coaxiality must be maintained to ensure proper fit and function.
By following these troubleshooting steps and maintenance practices, the performance and longevity of CB-B gear pumps can be significantly improved. Regular inspection and timely repairs are key to preventing major failures and ensuring reliable operation.