Hydraulic-powered brake system

New dual-circuit hydraulic brake system

The effectiveness of hydraulic brake systems in agricultural trailers has been proven on countless occasions. This is also true for the breakaway safety function, which for years has been servicing trailers that travel at speeds of up to 40 km/h. These positive experiences are being carried over into the next stage of development.

The new dual-circuit hydraulic brake system, with its additional line, provides users with an element of security that surpasses any of its regular functions. For the driver, the system is also a reassuring visual feature, both on the towing vehicle and on the trailer.

Tractors with dual-circuit hydraulic brake system


Towing vehicle:

A new trailer brake valve secures the oil pressure supply of both standardised brake connectors:

­During operation, the brake line, with its already-recognised male connector (standardised as per ISO 5676:1983), increases the brake pressure from 0 to 150 bar, pressure which continues to be used by the customary single-circuit brake to operate the service brake on the trailer.

The new, additional line, with its male connector coupling (as per ISO 16028:2006 /DIN 10), maintains a continuous, constant pressure of 15–35 bar. A drop in the pressure in this line will cause the trailer to brake automatically.

An electrical connector (as per ISO 7638-2, 5/7 pole ABS plug) should be installed on the towing vehicle, in order both to monitor the trailer electronically and to be able to tow trailers with electronic braking systems.

Intelligent trailer brake valves on the towing vehicle are downward compatible and can accommodate both older single-circuit or new dual-circuit brake systems.

On the trailer:

The central element on the trailer in the figure below is the new ­dual-circuit emergency brake valve (NBV16). All the necessary functions are performed from this single unit, which includes the brake line, the additional line, the breakaway function, and the auxiliary brake with pressure reservoir, as well as the automatic load-dependent braking system (ALB) and reservoir emptier.

The system displayed below ensures that trailers can also be towed by those towing vehicles which only have one hydraulic brake connector. The parking brake is activated mechanically from the trailer’s brake linkage.

The electrical connection is used for the system monitor, the immobiliser and the power supply for the automatic braking system. It is possible to route the brake line and the additional line to the second trailer.

Example on a R3a tandem vehicle

Hydraulic brake schema for trailers

1. Hydraulic dual-circuit emergency brake valve with ALB and reservoir 4. Electrical system monitoring with ABS plug 7638-2
2. Load sensor for ALB (automatic load-dependent braking system) 5. Mechanical emergency brake
3. Brake line and an additional line for the 2nd trailer  

Other features and advantages:

  • Braking is automatically triggered by pressure from the reservoir as soon as the pressure in the additional line drops.
  • Breakaway system: Ensures the automatic braking of the trailer when the brake lines are ripped from the couplings mechanically.
  • Provides the pressure reservoir with a constant supply of oil.
  • Monitors the pressure level in the reservoir electronically, and relays low values to the brake monitoring system in the tractor.
  • Allows for the direct installation of a pressure control valve, which subsequently allows for the newly-prescribed ALB controller to be added to the vehicle in a compact and space-saving manner.
  • Along with a sensor on a sprung axle, controls the NBV16 automatically and in proportion to the brake pressure.
  • The reservoir pressure can be released manually, before the trailer is switched off and the brake lines are uncoupled.
  • If the coupling is incomplete, the brake pressure in the reservoir will work as an immobiliser.

Transitional provisions:

The deadlines for registering new vehicles with single or dual-circuit hydraulic trailer brake systems are specified in the EU regulation. It should be noted that vehicles already equipped with brake systems that meet EU standards can be put into circulation in Switzerland and EU-countries. For tractors, the grace period expires in 2020. The deadlines for trailers are yet to be fixed.



Documentation about the regulation from brake systems for agricultural and forestry vehicles

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Flyer - Brake system for agricultural and forestry vehicles

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Hydraulic-powered brake system

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