Controlling pressure is fundamental in hydraulic systems, ensuring safe and efficient operation by preventing over-pressurization and matching output to load requirements. While system pressure is dynamically influenced by the load, setting maximum pressure limits and standby pressures is a key aspect of pressure control. This is often achieved using pressure control valves, such as relief valves or, in the case of load-sensing pumps, specific control valves integrated into the pump itself.
For hydraulic pumps with load-sensing capabilities, setting the pressure involves a specific calibration procedure. This procedure primarily focuses on calibrating the pressure limit or standby pressure maintained by the load-sensing control when there is no significant load demand.
Setting Pressure on a Load-Sensing Hydraulic Pump
Adjusting the pressure limit on a load-sensing pump requires a systematic approach involving key valves. According to standard procedures, the calibration process emphasizes starting with the load-sensing mechanism.
Here is a typical step-by-step process based on common practices for setting the pressure limit on such a pump:
- Isolate the Pump's Outlet: To create a condition where pressure can build against a closed path (known as "deadheading" the pump), you must isolate the pump's outlet. This is often done by closing a manual hand valve located downstream of the pump. This simulates a high-pressure demand without flow.
- Prepare the Pump Controls: Ensure the pump-loading valve, which might influence pump flow based on system demand, is de-energized. With the pump-loading valve de-energized, its control effect is minimized, allowing the pressure setting procedure to isolate the function of the load-sensing control.
- Focus on the Load-Sensing Valve: The core of the adjustment lies with the load-sensing valve. The instruction is explicit: always adjust the load-sensing valve first. In the deadheaded condition with the loading valve de-energized, pressure will build in the system. The level it reaches at this point is determined solely by the current setting of the load-sensing valve.
- Adjust to Desired Pressure: With the pump deadheaded and the pressure stabilized at the load-sensing valve's current setting, you can now adjust the load-sensing valve to the specific desired pressure level. This sets the maximum standby pressure or the control pressure reference for the load-sensing system.
This procedure calibrates the pump's internal control to maintain the specified pressure limit when flow is minimal or blocked, which is crucial for system protection and efficiency.
Summary of Pressure Setting Steps
The process can be summarized in the following steps:
| Step | Action | Purpose | Key Valve/Component |
|---|---|---|---|
| 1. Prepare for Adjustment | Close manual hand valve | Deadhead pump, create pressure build-up condition | Manual Hand Valve |
| 2. De-energize Loading Control | De-energize loading valve | Isolate load-sensing control adjustment | Pump-Loading Valve |
| 3. Identify Current Setting | Pressure builds up | Show current load-sensing pressure setting | Load-Sensing Valve |
| 4. Calibrate Desired Limit | Adjust load-sensing valve | Set the target pressure limit | Load-Sensing Valve |
Important Considerations:
- Always consult the manufacturer's specific manual for your pump model, as procedures and component names may vary.
- Ensure safety precautions are followed when working with hydraulic systems under pressure.
- This procedure sets a limit or standby pressure. During normal operation, the actual pressure will be determined by the load and flow demands, regulated by the pump's load-sensing controls relative to the load signal.
