OSPC-LS Hydraulic Orbitrol Control Unit

Load sensing hydraulic steering control unit is an important element in the load sensing steering system. Together with fixed displacement pump, various displacement pump with constant pressure or load sensing pump(variable displacement pump with flow, pressure joint compensated) supplying oil, it can make up different loading sensing hydraulic steering systems. BPBS5 series can be used together with modulary mounting priority valve.

Above figure shows components composition of power steering system on the vehicle with the Orbitrol. This is an example of the simplest steering system. The oil from Pump flows into "P"-port of Orbitrol and then the quantity of oil in the proportion to the rotations of Steering Wheel flows into Steering Cylinders via "R"-port at right turn and via "L"-port at left turn. It is clear by this figure that there is no mechanical connections between the part of steering input (Steering Wheel, Steering Column and Orbitrol) and the part of steering output (Steering Cylinders,Linkages and Steered Wheels). Accordingly, there are many advantages for designing of vehicles. The Orbitrol is used principally for hydrostatic power steering systems of industrial vehicles, construction vehicles and boats, but it can be used for some servo-type applications or any applications where visual positioning are required.

ORBITROL is a hydrostatic - fully fluid linked - Power Steering Control Unit with epoch-making design. "Hydrostatic (or fully fluid linked)" means there is no mechanical connections between the steering control unit, the pump and the steering cylinders.

Troubleshooting of Metering Pump

PROBLEM	CAUSE	REMEDY
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.	1. 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.