Adjusting Hydraulic Pump Pressure on CAT 312 Excavator

[MikePhua]

Hydraulic systems are at the heart of modern excavators like the CAT 312, which is widely used in construction, demolition, and other heavy-duty applications. A well-functioning hydraulic pump ensures that the excavator’s boom, bucket, and arm operate smoothly under heavy loads. However, as with any complex machinery, there are times when the hydraulic system might not function at its best, often due to incorrect hydraulic pump pressure.
Adjusting hydraulic pump pressure is crucial for ensuring that your excavator performs optimally and operates efficiently. A well-calibrated pump allows for proper lifting, digging, and other hydraulic functions, while incorrect pressure settings can lead to sluggish operation, overheating, or even system failure. In this article, we will explore how to adjust the hydraulic pump pressure on a CAT 312 excavator, why it’s important, and what issues might arise if this adjustment is not done correctly.
Understanding Hydraulic Systems in Excavators
Before diving into the specifics of adjusting the hydraulic pump pressure, it’s important to understand the role of the hydraulic system in the CAT 312 excavator. Excavators use hydraulic systems to generate the force needed to perform tasks like lifting, digging, and moving material. The hydraulic pump is responsible for generating high-pressure fluid that powers the various components of the machine, including the boom, bucket, and swing functions.
The CAT 312 uses a closed-center hydraulic system, where the pump continuously circulates hydraulic fluid to the various parts of the machine. This system is more efficient because it provides consistent pressure, and the hydraulic fluid is always available to the machine’s components.
The hydraulic pump pressure controls the speed and force of these movements. When the pressure is too high, it can cause damage to the hydraulic components, while too low pressure can lead to weak performance, reduced lifting capacity, and slow response times.
Symptoms of Incorrect Hydraulic Pump Pressure
Before making any adjustments, it’s important to recognize the signs that indicate the hydraulic pump pressure needs attention. These symptoms include:

• Slow hydraulic movement: If the boom, bucket, or arm responds slowly or hesitates to move, it might be due to insufficient hydraulic pressure.
  
• Overheating: If the hydraulic fluid temperature is abnormally high, it can signal that the system is under too much pressure, causing excessive friction.
  
• Weak lifting capacity: If the machine struggles to lift heavy loads or if the lifting force is inconsistent, this could be a sign of low hydraulic pressure.
  
• Unusual sounds: A whining or buzzing sound from the hydraulic system can indicate a problem with the hydraulic pump or a pressure imbalance.
  

How to Adjust Hydraulic Pump Pressure on the CAT 312
Adjusting hydraulic pump pressure requires a careful, methodical approach to ensure the system functions optimally without risking damage. Here’s a step-by-step guide to adjusting hydraulic pump pressure on the CAT 312 excavator:
1. Safety First

• Before performing any maintenance, ensure the excavator is parked on level ground with the engine turned off.
  
• Engage the parking brake and remove the key from the ignition.
  
• Wear appropriate safety gear, including gloves and goggles, to protect yourself from hydraulic fluid or debris.
  

2. Locate the Hydraulic Pressure Relief Valve

• The hydraulic pump pressure is typically controlled by the pressure relief valve located near the hydraulic pump assembly.
  
• In the CAT 312, you can find the relief valve near the pump on the engine compartment. Consult your service manual for the exact location and diagram for reference.
  

3. Prepare the Pressure Gauge

• You’ll need a hydraulic pressure gauge to measure the current system pressure. Connect the gauge to the hydraulic system at a point that can provide an accurate reading, such as the test port on the pump.
  

4. Start the Engine and Warm Up the Hydraulic System

• Start the CAT 312 and allow the hydraulic system to warm up for a few minutes. This ensures that the hydraulic fluid is circulating properly and at operating temperature.
  
• While the machine is running, operate the boom, bucket, and other hydraulic controls to ensure the system is under load.
  

5. Check the Current Hydraulic Pressure

• With the machine at idle, observe the reading on the pressure gauge. The correct hydraulic pressure will vary depending on the model and year of the CAT 312, but generally, the operating pressure should be between 3000 and 3500 PSI (pounds per square inch).
  
• If the pressure is lower than the desired range, this indicates that the hydraulic pump is not generating enough pressure. If it’s too high, there could be excessive strain on the system.
  

6. Adjust the Pressure Relief Valve

• If the pressure is out of range, you’ll need to adjust the pressure relief valve to the correct setting.
  
• Use the appropriate tools to turn the adjustment screw on the relief valve. Turning it clockwise will increase the pressure, while turning it counterclockwise will decrease it.
  
• Make small adjustments at a time and recheck the pressure to avoid overshooting the target.
  

7. Recheck the System Pressure

• After making the adjustments, operate the hydraulic system under load again to ensure the pressure remains within the correct range. Double-check the pressure reading on the gauge.
  

8. Test the Excavator

• Once you’ve achieved the correct pressure, test all the hydraulic functions—boom, bucket, arm, and swing—under load to ensure smooth and consistent operation.
  
• Monitor the system for any unusual noises or signs of overheating, which could indicate an issue with the pressure setting.
  

Common Issues When Adjusting Hydraulic Pressure
Even with careful adjustments, there are a few issues that can arise when setting hydraulic pump pressure. Here are some common problems to watch out for:

• Leaking Seals: When adjusting hydraulic pressure, check the seals around the pump and relief valve. If the pressure is too high, it can lead to leaks, which reduces system efficiency.
  
• Incorrect Calibration: Over-adjusting or under-adjusting the pressure can lead to a poorly calibrated hydraulic system, affecting the excavator’s performance.
  
• Pressure Spikes: A sudden increase in hydraulic pressure could stress the system’s components, leading to damage or failure if the pressure relief valve is not set correctly.
  

Conclusion
Properly adjusting the hydraulic pump pressure on your CAT 312 excavator is essential for maintaining the machine’s efficiency and performance. Whether you’re facing issues like slow hydraulic response, weak lifting capacity, or overheating, adjusting the pump pressure could resolve these problems and extend the lifespan of your machine.
Remember that maintaining the right hydraulic pressure not only ensures smooth operation but also reduces wear and tear on the system, preventing costly repairs in the future. Regular checks and adjustments to the hydraulic system should be part of your routine maintenance to keep your CAT 312 performing at its best.
For those who are not comfortable performing this task on their own, it is advisable to consult with a trained technician to ensure the adjustment is done correctly and safely.