Driving Heavy Equipment Efficiency with Hydraulic Steering Systems

A steering control unit (SCU)—often called an orbitrol or hydrostatic steering unit— is a core component in many off-road and mobile machines. It delivers smooth, low-effort steering by using hydraulic flow instead of mechanical linkages.

How does a hydraulic steering unit work?

A steering control unit (SCU) is commonly used on tractors, loaders, forklifts, telehandlers, and other mobile machinery. Internally, the unit combines a rotary valve and a rotary meter, and connects to the steering wheel via the steering column.

When you turn the steering wheel, oil from the hydraulic pump is routed through the rotary valve and metering section to either port L or R (depending on the direction of steering). The rotary meter delivers oil to the steering cylinder in proportion to the wheel rotation, giving consistent and responsive steering control.

Steering Unit Diagram — A steering control unit (orbitrol) routes and meters oil to the steering cylinder based on wheel input.

Quick takeaway

The SCU does two jobs at once: it directs flow (left/right) and meters the oil volume so steering response matches steering wheel movement.

What’s the difference between open-center and closed-center steering units?

The difference between open-center and closed-center steering units is mainly about how hydraulic fluid behaves when the steering is not being used, and how the overall hydraulic circuit is configured.

Comparison: open-center vs closed-center

Feature	Open-center system	Closed-center system
Flow at rest	Constant flow	No flow
Pump type	Fixed displacement	Variable displacement or load-sensing
Efficiency	Lower	Higher
Complexity	Simpler	More complex
Multi-function support	Limited	Excellent
Typical use	Basic equipment, lower cost	Advanced machinery, high-performance

Do hydraulic steering units require external power?

Hydraulic steering units do not require external electrical power. They run on hydraulic power, usually supplied by an engine-driven pump.

Power source

Powered by pressurised hydraulic fluid from a pump.
The pump is typically mechanically driven by the engine (belt, gear, or shaft drive).

No external electrical power required

These systems are purely hydraulic.
The orbitrol directs oil to steering cylinders based on steering wheel rotation.
Manual fallback: many designs offer limited steering if pump pressure is lost, using internal “hand pump” action within the steering unit (capability varies by model/system).

Can hydraulic steering units provide feedback to the steering wheel?

Hydraulic feedback is the reactive force felt at the steering wheel due to pressure changes in the circuit. Whether you get “steering feel” depends on the steering unit type.

Steering unit type	Feedback to steering wheel?	Steering feel	Self-centering
No reaction	❌ None	Disconnected	No (unless geometry provides it)
Reaction / load-reactive	✅ Yes	More natural feel	Yes (when load tends to center)

Rule of thumb

If it’s labelled Non-Reaction / No Reaction, it won’t provide feedback.
If you want feedback, look for a Reaction or Load-Reactive steering unit.

Which steering unit is right for my machine?

Choosing the right steering unit depends on the machine application, your hydraulic system type, and the steering behaviour you want. Use the guide below as a starting point.

1) Machine type and application

Machine type	Common steering unit requirement
Tractors / agricultural vehicles	Load-sensing, reaction or non-reaction units
Forklifts / telehandlers	Compact, low-displacement, often non-reaction
Construction equipment	Robust, high-displacement, often reaction units
Utility vehicles / ATVs	Lightweight, responsive, usually non-reaction
Road vehicles	Precision steering, often closed-center with feedback

2) Hydraulic system type

The steering unit must match your hydraulic circuit design.

Open center: constant flow, simple systems (common on light/medium duty machines).
Closed center: flow on-demand, used in more sophisticated systems.
Load sensing: efficient systems that adjust flow/pressure based on steering demand.

3) Reaction vs non-reaction

Reaction units: allow steering feedback (“road feel”) back to the wheel; useful where operator feel matters. Common in construction and some road-going machines.
Non-reaction units: isolate the steering wheel from kickback; prevents wheel movement when loads act on the cylinder. Often preferred for off-road/agricultural use.

4) Displacement (cc/rev)

Displacement determines how much oil is metered per steering wheel revolution. It influences how quickly the wheels turn for a given steering input. Choose displacement based on steering cylinder size and the steering speed/effort you want.

5) Mounting and port configuration

Check mounting flange type (e.g., SAE, DIN) and bolt pattern.
Match port sizes and thread types (BSP, SAE, Metric).
Confirm shaft type / steering column interface.

Construction vehicles using hydraulic steering — Hydraulic steering is common on construction and mobile machinery where durability and control are essential.

Are hydraulic steering systems suitable for high-speed vehicles?

Hydraulic steering systems are not naturally suited to high-speed vehicles due to reduced road feel, slower response compared to modern EPS systems, and potential safety risks. However, they can be engineered for certain specialist high-speed applications with the right design features and fail-safes.

Hydraulic steering is often used in specialised vehicles such as heavy-duty trucks, airport fire engines, military transports, and off-road racing vehicles. These systems may use reaction-type steering units, closed-center/load-sensing hydraulics, and redundancy (backup pumps or mechanical overrides) to improve safety and performance.

What information do I need to order a replacement steering unit?

To order a replacement steering unit, gather the following key details to ensure compatibility:

Category	Details
Identification	Model, serial number, manufacturer
Specs	Displacement, reaction type, center type, porting
Mounting	Bolt pattern, flange, shaft type
Application	Machine model, usage environment
System info	Pressure, flow, pump type

Ordering tip

If you can, send photos of the unit (nameplate, ports, mounting face, and shaft) alongside the specs above. It’s often the fastest way to confirm an equivalent replacement.

Do hydraulic steering units come with built-in load sensing or priority valves?

Some steering units do come with built-in load sensing and/or priority valve functions—especially on modern/OEM-style systems. However, not all units include these features, so always check the specific model details and your circuit requirements before ordering.

Steering unit alternatives and equivalents

Find the perfect match: our steering units are cross-compatible with major brands, built for easy interchangeability, trusted durability, and competitive pricing.

	BPB1	BPB2	BPB3	BPB5	BPBS1	BPBS2	BPBS5	BPBS5T	VLSA	(D) YXL
DANFOSS	OSPB ON	OSPB OR	OSPB CN	OSPB LS (OLS)	OSPC ON	OSPC OR	OSPC LS (OLSA)	OSPC LS (OLS)	OLSA	OLS
M+S	HKU…/4	HKU…/3	HKU…/7	HKU…/5T	HKUS…/4	HKUS…/3	HKUS…/5D	HKUS…/5DT	PRD (D)	PRT

Why buy hydraulics from Flowfit?

Premium quality: We supply hydraulic steering units made from top-grade materials for durability in demanding applications.
Comprehensive range: A wide selection of agricultural and mobile hydraulic components.
Customisable solutions: Tailored power units and hydraulic solutions to meet unique requirements.
Free UK shipping: Free UK shipping on orders over £250.
Global shipping: Serving customers across the UK and worldwide.