BZZ1 50 Hydraulic Steering Unit

BZZ1,BZZ2,BZZ3 series SCU offers the advantages as follows:
This kind of SCU series can help you reduce the machinery cost without mechanical linkage device, and can offer reliable and light structure.
This kind of SCU series can operate more flexible with light steering torque.This kind of SCU series can offer emergent manual steering in case of engine failure.This kind of SCU series can be steering at the continuous speed with less steering torque.This kind of SCU series can offer various hydraulic system and different mounting choice.This kind of SCU series can link various steering pump and hydraulic steering system.

Hydraulic Steering Unit (BZZ1, BZZ2, BZZ3)

Hydraulic steering control units (BZZ)
BZZ1, BZZ2, BZZ3 Hydraulic steering control units(SCU), new design,   better performance. Widely applied to low speed and heavy load vehicles E.g. construction machinary, forklift, tractor, harvester and helm control etc.

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
BZZ口-E50* 50 4 16 2.5 4.72
BZZ口-E63* 63 5 4.85
BZZ口-E80* 80 6 5.00
BZZ口-E100* 100 7.5 5.27
BZZ口-E125* 125 9.5 5.43
BZZ口-E160* 160 12 5.75
BZZ口-E200* 200 15 6.08
BZZ口-E250* 250 19 6.48
BZZ口-E280* 280 21 6.78
BZZ口-E315* 315 24 7.13
BZZ口-E400* 400 30 7.78
BZZ口-E500* 500 38 8.67
BZZ口-E630* 630 48 9.72
BZZ口-E800* 800 60 11.18
BZZ口-E1000* 1000 75 12.80

Note 1: represents Function Code, BZZ2 can be chosen for SCU with the displacement of 50-200mL/r. BZZ1 or BZZ3 can be chosen for SCU with the displacement of 50-1000mL/r. 
Note 2: “Flow” that we suggest to use is the flow of 1.25 times as much as that at the steering wheel’s rotation speed of 60 r/min. If the design of the system can't meet the requirements, the flow is allowed to be adjusted a little bit. 



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 

Heavy turning of wheel. 1. lnsufficient oil pressure or no oil
  • pressure at all.
    a. Pump not operating.
    b. Pump defective.
    c. lncorrect pump rotation.
    d. Pump worn.

2. Relief valve sticking when open orthe valve pressure is  too low.

3. Blocked Ls orifice or dirt particles delaying spool          movement in flow amplifier.

4. Very high implement system pressures acting on EF      port.

5. Misplaced anti-cavitation ball in steering unit.



  • a. Make the pump operate.
  • b. Repair or replace the pump.
  • c. Alter direction of pump rotation.
  • d. Replace the pump.

2. Repair, clean and reset the reliefvalve.

3. Remove and clean the whole system.Change all filter    elements.

4. Contact your dealer for help underthese special            circumstances.

5. Dismantle steering unit and repositionor replace anti-  cavitation ball.

"Motoring" - steering wheel turning by itself. 1. Leaf springs have sagged and thus have reduced elasticity or no elasticity at all (broken springs rotherwise).

2. Squeezed   spool/sleeve.Possible
insufficient spool/sleeve clearance.
1. Replace leaf springs in control unit.

2.Contact your dealer.In the meantime,
lower the relief valve setting.

Repeated steering wheel corrections required.
lmpossible to make steering go to neutral or right on own accord.

1. Leaf springs without elasticity or broken.

2.Steering column out of alignment with steering unit.

3. Insufficient clearance between steering column and coupling.

1. Replace leaf springs in control unit.

2.Align steering column with steering unit

3. Adjust the clearance.

Backlash. 1. Splines of cardan shaft worn or broken.

2.Leaf springs without elasticity or broken.

1. Replace cardan shaft.

2. Replace leaf springs in steering unit.

Shimmy - abnormal
vibration of steering (tire pattern can cause vibration)
1. Air accumulation in steering system.

2. Worn mechanical connections and wheel bearings.

3. Leaky dual shock valves and suction valves or broken springs.
1. Bleed the cylinders and find the source of the air          accumulation and have it removed.

2. Replace worn parts.

3. Repair or replace dual shock valves,suction valves or    the springs.
The steering wheel can be turned continuously without turning the wheels.

1. No oil in the tank.

2. Steering cylinder piston seals leaking badly.

3. Shock valve failure.

1.Fill system with clean oil and bleed the system.

2.Repair or replace cylinder(s).

3. Remove shock valves and repair or replace, then reset pressure level.
The operator cannot feel resistance when the steered wheels turn to the stops. 1. Shock valves are set to approximately the same setting as steering PRV.

2.Dirt particles causing shock valve erratic operation.
1. Adjust shock valve settings to at least 500 psi (34 bar) higher than steering PRv setting.

2.Clean system and fill with clean oil.
steering wheel in both steering wheel in both directions. 1. lncorrect setting of cardan shaft and gear wheel setting (timing). 1. Adjust setting (timing).

Kickback from system. 1.Dirt particles delaying spool movement in flow amplifier.

1.Remove and overhaul flow amplifier.
Sample test oil to determine contamination source. Clean system,change filter elements and fill withfresh oil.
Slow steering. 1. lnsufficient oil to the steering unit due to defective or worn pump.

2. Weak or damaged priority valve spool bias spring.
1.Replace the pump.

2. Check or replace spring.
The steering wheel does not pass to neutral 
position - tendency to "motor."
1. Dirt particles between spool and spring.

2. Squeezing between spool and sleeve caused by a too-high system pressure.

3. Leaf spring broken or without elasticity.

4.Mechanical binding in steering column.
1.Clean spool and sleeve, or replace steering unit.Clean entire system.

2.Adjust pump pressure to the correct value at steering PRV.

3. Replace with new springs.

4. Correct and adjust where necessary.
When turning the steering wheel, the steered wheels are
activated in the opposite direction.
1. The hydraulic hoses to the steering cylinders have been reversed.

2. Incorrect mounting and setting of cardan shaft and gear wheel set.
1. Correctly connect the hoses.

2.Correct the setting.

Steering power too low (possibly to one side only). 1.Pump pressure too low.

2.Malfunctioning shock valve.
1.Correct the pump pressure or adjust the steering PRV in the flow amplifier valve.

2.Remove and repair or replace shock valve.
Leakage at input shaft,end cover on gear wheel set. 1. Defective shaft seal.

2. Screws have come loose.

3. Defective discs or O-rings.
1. Replace shaft seal.

2. Tighten the screws to 266 in-lb (3 N-m).

3. Replace discs or O-rings.


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


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