Diagnosing and Repairing Weak Hydraulics: Flow Testing a Gear Pump

[MikePhua]

Hydraulic systems are essential in many types of heavy equipment, ranging from excavators to skid steers, as they provide the power needed to operate various components like buckets, lifting arms, and attachments. When a hydraulic system exhibits signs of weakness—such as slower movement, reduced lifting capacity, or inconsistent operation—it's crucial to accurately diagnose the problem and identify whether the issue lies within the hydraulic pump, valve, or another component.
One common culprit of weak hydraulics is the failure of the hydraulic pump, which could be suffering from reduced flow or pressure. Understanding how to properly test the pump's flow and diagnose issues can save both time and money by pinpointing the problem before attempting repairs.
The Importance of Hydraulics in Heavy Equipment
Hydraulic systems are used extensively in construction machinery, agricultural equipment, and other heavy machinery because of their efficiency in converting fluid pressure into mechanical force. Hydraulic pumps are responsible for circulating hydraulic fluid throughout the system under high pressure, providing the necessary force to power the hydraulic actuators, motors, and valves.
The system relies on several components working in tandem:

• Hydraulic Fluid: Acts as the medium for transmitting power.
  
• Hydraulic Pump: Circulates hydraulic fluid under pressure.
  
• Hydraulic Valves: Direct the flow of hydraulic fluid to the right components.
  
• Actuators and Motors: Perform mechanical work by converting hydraulic pressure back into force.
  

When any component within this chain malfunctions, the entire system's efficiency can drop significantly, resulting in weak hydraulics.
Signs of Weak Hydraulics
A weak hydraulic system is usually a result of low pressure or low flow. There are a few telltale signs of hydraulic weakness:

• Sluggish Operation: Equipment moves slower than usual or struggles to lift heavy loads.
  
• Erratic or Inconsistent Movement: Attachments or arms jerk or hesitate during operation.
  
• Unusual Sounds: A whining or grinding noise coming from the pump can indicate low flow or cavitation.
  
• Low Pressure: A significant drop in the pressure reading of the hydraulic gauge could signal pump wear or internal leaks.
  

The Role of the Hydraulic Pump
Hydraulic pumps are crucial because they maintain the system's pressure and flow. A gear pump, which is one of the most common types of pumps used in heavy equipment, operates by moving fluid using gears that rotate within a housing. If the gear pump is malfunctioning, the entire hydraulic system’s ability to move fluid efficiently is compromised.
Common issues with hydraulic pumps include:

• Wear: Over time, internal parts of the pump can wear down, leading to reduced flow or pressure.
  
• Cavitation: This occurs when air enters the pump and causes the pump to lose efficiency, leading to weak hydraulics and excessive noise.
  
• Contamination: Dirt or debris in the hydraulic fluid can clog the pump and valves, causing operational problems.
  
• Seals and Gaskets: Worn seals can lead to fluid leaks, reducing the system's pressure.
  

Conducting a Gear Pump Flow Test
To diagnose issues with a gear pump, a flow test is essential. This test measures how much fluid is being moved by the pump, allowing technicians to determine whether the pump is operating at full capacity.
Tools Needed:

• Flow Meter: Measures the volume of fluid being pumped.
  
• Pressure Gauge: Measures the system’s pressure.
  
• Test Kit: Includes fittings, hoses, and adaptors to connect the flow meter to the hydraulic system.
  
• Temperature Gauge: Ensures the fluid is at the correct temperature during testing.
  

Testing Procedure:

1. Prepare the System: Ensure the hydraulic fluid is at the appropriate level and temperature. The fluid should be clean and free of debris. Turn off the equipment before starting the test to ensure safety.
   
2. Connect the Flow Meter: Attach the flow meter to the pump’s outlet line. Ensure that all connections are secure and there are no leaks.
   
3. Start the Engine: Start the machine and engage the hydraulic system to begin the test.
   
4. Monitor the Flow: Observe the flow rate displayed on the flow meter. Compare it to the manufacturer's specifications for the pump. A significant deviation from the expected flow rate indicates a problem.
   
5. Measure Pressure: While testing the flow, also monitor the system’s pressure with the pressure gauge. Low pressure could indicate pump wear or a restriction somewhere in the system.
   
6. Check for Irregularities: If the system exhibits cavitation (whining or foaming fluid), or if the flow is erratic, these are signs that the pump is damaged and may need to be repaired or replaced.
   

Interpreting Results:

• Normal Flow: If the flow rate matches the specifications and pressure is stable, the pump is operating correctly.
  
• Low Flow or Pressure: If the flow is below specifications or the pressure is inconsistent, it suggests that the pump is worn or damaged.
  
• Cavitation: If cavitation is occurring, it may indicate that air is entering the system, possibly due to low fluid levels, contamination, or a faulty pump seal.
  

Common Causes of Low Flow in Hydraulic Systems
If your test reveals low flow or pressure in the hydraulic system, several factors could be to blame. The most common causes include:

1. Worn Pump Components: Over time, the gears and bearings inside a hydraulic gear pump can wear down, leading to reduced efficiency.
   
2. Clogged Filters or Lines: A clogged filter can restrict fluid flow, reducing the pump's ability to move fluid efficiently. Similarly, clogged hoses or lines can impede fluid movement.
   
3. Fluid Contamination: Dirt, debris, or water in the hydraulic fluid can damage the pump and restrict flow. Regular fluid checks and maintenance are critical to preventing this issue.
   
4. Pump Overheating: If the hydraulic system is running too hot, it can cause the fluid to become less viscous, which reduces its ability to transfer pressure effectively. This leads to weak hydraulics.
   
5. Incorrect Fluid Type: Using the wrong hydraulic fluid can cause poor system performance. Make sure that the fluid type and viscosity match the manufacturer’s recommendations.
   

Solutions and Repairs
Once the flow test has identified that the pump is underperforming, the next step is to determine whether the pump can be repaired or if it needs to be replaced.

1. Pump Repair: If the pump has worn gears or seals, it may be possible to repair or rebuild the pump. This involves disassembling the pump, cleaning it, and replacing any worn-out components. Be sure to use OEM parts to maintain the integrity of the hydraulic system.
   
2. Pump Replacement: In cases of severe damage or if the pump cannot be rebuilt, replacing the entire pump may be the best solution. Ensure the replacement pump is compatible with the equipment specifications.
   
3. Clean the System: After pump repair or replacement, flush the hydraulic system to remove any contaminants. Replace the hydraulic fluid and filters to ensure the system operates optimally.
   
4. Preventive Maintenance: To prevent future hydraulic issues, perform regular maintenance on the hydraulic system. This includes changing the hydraulic fluid, inspecting hoses for wear, cleaning filters, and conducting routine pressure and flow tests.
   

Conclusion
Weak hydraulics in heavy equipment can be a significant issue, but with proper diagnostics, especially through flow testing, you can identify whether the hydraulic pump is the problem. Understanding the symptoms of pump failure, performing a flow test, and addressing the underlying causes of low flow or pressure can save time and money in repairs, keeping your equipment running smoothly. Regular maintenance, including fluid checks, filter replacements, and timely pump inspections, can go a long way in ensuring the longevity and efficiency of your hydraulic systems.