BZZ5 Hydraulic Steering Unit

As for load sensing steering system, the steering system and the operational system may use the same pump through the priority valve or the load sensing system can distribute the surplus oil of
the steering system into the operational system. Meanwhile, if the pump with load sensing is used , the load sensing will have obviously productive results.
The LS port of the load sensing steering unit has to connect with priority valve or LS port of load sensing pump, so that the signal of the steering load pressure of the steering unit can be transferred to priority valve or load sensing pump through oil hose ( we suggest that the length of the hose is ≤2 m), to control the oil volume supplied to steering unit by the control system.

BZZ5 Hydraulic Steering Unit 

The advantages of the hydraulic steering control units: 

  • 1.Low cost, reliable. 
  • 2.No load reaction on the steering wheel comfortable. 
  • 3.Manual operation available when the pump doesnt work. 
  • 4.Low control torque, continuous operation. 
  • 5.According to the system, different function and pressure level valves available.
Type Displacement
Max. input 
speed (rpm)
Max. input 
pressure (MPa)
Max. cont. back 
pressure (MPa)
Max. power 
steering torque (N·m)
BZZ5-E 50* 50 140 100 16 1.6 ≤5
BZZ5-E 63* 63 141
BZZ5-E 80* 80 142.5
BZZ5–E 100* 100 145
BZZ5–E 125*  125 148
BZZ5–E 160* 160 153
BZZ5–E 200* 200 158
BZZ5–E 250* 250 164
BZZ5–E 280* 280 169 75
BZZ5–E 315*  315 174
BZZ5–E 400*  400 184
BZZ5–E 500*  500 197 60
BZZ5–E 630*  630 216
BZZ5–E 800*  800 236
BZZ5–E 1000* 1000 262


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