101 125 Hydraulic Steering Units

Hydraulic Steering Unit 10 series is integral hydraulic steering unit, the valve body of rotary valve is integral structure, then the steering unit can integrate with cartridge valve, such as the pressure control valve of the integral system.
Hydraulic Steering Unit 10 series is widely used in the steering control system of different kinds of engineering vehicles, such as the steering system of many kinds of industrial and agricultural mobile machinery forklift, loader, road roller, tractor, combine harvester, and the ship helm etc. The steering unit can control the steering cylinder with bigger resistance force by inputting minor force; It’s easier , flexible and reliable; The integral check valve can prevent the system pressure oil from anti-vibration , and prevent from “hit-hand” during the steering operation; Integral pressure control valve can control the operation pressure and the shock pressure of the steering system.

101 Series Hydraulic Steering Units

101-1,2,3 Series Hydraulic Steering Control Units (SCU)

Parameters Type 101-*-***-*
Function Code 1,2,3 1,3
Displacement(mL/r) 50 63 80 100 125 160 200 250 280 315 400
Rated flow (L/min) 5 6 8 10 12.5 16.0 20 25 28 31.5 40
Max. input pressure (MPa) 17.5
Max. cont. back pressure (MPa) 2.5
Weight (kg) 5.70 5.76 5.84 5.91 6.05 6.25 6.45 6.68 6.86 7.06 7.45
Dimension L (mm) 130 132 134 137 140 145 150 156 161 166 176


The installation and use of full hydraulic steering note

1  installation precautions:

  • (1) When installation steering gear must ensure coaxiality with column, must have a gap of 1 mm in the axial direction. 
  • (2) The depth of screw connection to the steering column tightening steering column is ≤15mm.
  • (3) After steering gear installed, must check steering wheel turns to ensure the flexibility of the return position. 
  • (4) Connection pipeline: P oil port connects to the oil supply pump, T oil port connects to the oil tank, and A and B oil ports respectively connect the left and right oil chambers of the steering gear.

2  oil flow rate considerations:

  • (1) The oil supply circuit connected to the P oil port, the oil flow rate in the pipe is recommended to be ≤1.5m/s.
  • (2) The pressure circuit of the oil cylinder connected to the A and B ports is recommended. The oil flow rate in the pipe is recommended to be ≤4~5m/s.

3  other matters needing attention: 

  • (1) The diameter of the steering wheel must not exceed 500mm. 
  • (2) A return filter with a filter accuracy of 30 μm should be installed in the return line of the steering gear. The position of tank is generally higher than installation position of steering gear, and return pipe is inserted below oil level, so oil can be filled only when the manpower is turned, and air can be prevented from entering the oil line.
  • (3) The oil viscosity of steering gear is 17cst~33cst. It is recommended to use low-condensation hydraulic oil. Steering gear allows normal working oil temperature 20°C to 80°C, and the limit working oil temperature range is -30°C to 100°C. Reminder: In case of abnormal oil temperature, steering performance will decrease.
  • (4) After steering system assembled, it shall be tested: clean oil tank before operation, inject hydraulic oil to the max oil level.Loosen cylinder nipple and allow pump to run at low speed until it is out of oil. Remove link,turn the steering wheel so that the piston reaches left or right position, and then fill the tank to specified level. Tighten all thread connections, connect the piston rod, and check if the steering system is working properly.
  • (5) It must be ensured that the oil is clean to prevent the dirt to cause steering failure. Always check the condition of the filter element and the oil. If necessary, give a replacement. 
  • (6) If steering failure, must be carefully check the reason first. The steering wheel must not be pulled hard, and the steering gear should not be disassembled to avoid damage to parts. It is forbidden for two people to turn the steering wheel at the same time. 

Troubleshooting of Metering Pump 

Matter Causes Troubleshooting
Oil leakage between back cover, stator and valves rear cover stator bolt looseness (or uneven force), or O-rings damaged Evenly tighten the bolt to the specified value, replace the seal (special)
Oil leakage at steering shaft shaft seal ring excessive wear or damage Replace the seal (dedicated)
feels light when turn the steering wheel slowly, feelsheavy when turn the steering wheel quickly steering pump oil supply not enough Check whether oil pump is working properly,(Including liquid level,pump efficiency, pipeline patency, etc.)
There is foam in the oil,irregular sound, the steeringwheel turns and the cylinder does not move There is air in the steering system Eliminating the air in the system, Check the suction pipe leaks or not, Orif the return nozzle is below the liquid level
Heavy steering continues to occur Tank fluid is below the specified position Add oil to prescribed height
Heavy oil viscosity Use oil as required
Feel heavy when turn fast and slow, stressless Check valve between P,T failure Check the ball. lf the steel ball is missing, then insert the steel ball; lfthe ball gets stuck dirty,it should be cleaned; In both cases,it isnecessary to check the effectiveness of the sealing tape recovery.
Turns light when the load is light,turns heavier whenincreas the load relief valve pressure lower than steering requirement Adjust relief valve pressure to specified value (no more than 16MPa)
Relief valve stucked by dirt, Or spring failure,Or seal is damaged Clean relief valve (required to check the effectiveness of seal taperecovery), or replace the spring or seal
steering wheel can't auto back to middle position Spring broken or deformation Replacement spring
Steering wheel rotate automatic swing to left or right Rotor and linkage axes are not positioned correctly Stop immediately! Align the teeth of the linkage shaft with rotor splines
No end point Low pressure on relief valve Appropriately increase relief valve pressure
Steering wheel rotates after turning to the end position Low pressure on shock valves Appropriately increase shock valves pressure
when machine is off, turn the wheel, cylinder not move radial clearance or axial clearance is too large between radial and stator Replace rotor and stator
Low viscosity of oil Change oil
Vehicle deviation Or the cylinder is slow when turningthe steering wheel shock valves failure (ball caught by dirty, or spring failure, or seal damage) Clean shock valves,replace spring or seal
pressure of Steering system is able to adjust Spring broken Change spring
not good seals at safety valve make the valve always open replace parts
Valve core stuck due to burr or oil stain Remove, inspect, repair
Poor spool operation Check if the spool is stuck by dirty
Spring bent or too soft Change spring
Oil is not clean, valve plug orifice is blocked Replace the cleaning fluid and unblock the orifice


1. Dust seal ring  15. O-ring  33. Ball 3/16 in
2. Housing, spool and sleeve.
Check valve and the seats for relief and shock valves are locktited. 
16. Distributor plate 34. Rolled pin
3. Ball 8.5 mm [0.33 in]   17. Gearwheel set 35. Ball
4. Thread bushing   18. O-ring 36. Bushing
5. O-ring used with kin-ring (item 6) 19. End cover 38. Spring
6. Kin-ring 20. Washer 39. Kin ring
7. Bearing assembly 22. Special screw 40. O-ring
10. Ring  23. Screw  
11. Cross pin  24. Name plate  
12. Set of springs 30. Complete relief valve  
13. Cardan shaft   31. Spring wire  
14. Spacer 32. Complete shock valve  
Read more!