Technical Articles

Load Sensing (LS) Systems: Calibration, Margin Pressure & Balance Adjustment

Nov 25, 2025•20
#Load Sensing#Mobile Hydraulics#LS Calibration#LUDV

Load Sensing (LS) Systems: Calibration, Margin Pressure & Balance Adjustment

Load Sensing is a dynamic hydraulic control architecture used in excavators, wheel loaders, telehandlers, cranes and forestry machines. LS systems match the pump output to the real-time load requirements, improving efficiency, control accuracy and multi-function performance.

Correct LS tuning requires:

  • standby pressure
  • margin pressure
  • pump–valve balance

Failing to calibrate these parameters causes delay, vibration, flow stealing, overheating, noise and drastic energy losses.

1. LS Operating Principle

Pump pressure (PP) always equals:

PP = PL + Dm
(yük basıncı + margin pressure)

Margin (Dm) enables the compensator spools to keep flow independent of load.

2. Key Components

  • LS pump (variable displacement)
  • LS signal lines
  • compensator spools
  • shuttle valve
  • flow-sharing (LUDV) chambers
  • standby spring/piston

3. Critical Pressures

Standby Pressure

Typical: 18–25 bar
Too low → delay
Too high → heating

Margin Pressure (Dm)

Typical: 18–25 bar
Too low → flow instability
Too high → energy loss and heat generation

4. LUDV (Flow Sharing) Behavior

When pump flow is insufficient, LUDV distributes flow proportionally across all functions.
Thus, no single function steals all the flow.

5. Common Calibration Errors

  • overly high margin
  • LS line leakage
  • clogged LS orifice
  • wrong compensator spring
  • faulty shuttle valve
  • wrong standby adjustment

6. LS Calibration Procedure (Field-Proven)

  1. Check LS signal leakage
  2. Adjust standby (valves neutral)
  3. Set margin pressure
  4. Perform multi-function flow test
  5. Set LUDV balancing
  6. Check heat generation

7. Practical Examples

Example 1: Delay in Excavator Boom

Standby increased from 12 → 22 bar → delay eliminated.

Example 2: Flow Stealing

Margin increased from 8 → 20 bar → functions stabilized.

Example 3: Overheating

Margin reduced from 35 → 22 bar → system cooled by 15°C.

8. Conclusion

Correct LS calibration ensures:

  • smooth multi-function performance
  • energy efficiency
  • longer pump and valve life
  • stable temperature
  • precise joystick response

This guide is part of the Sancoqhub advanced hydraulics series.