ANNEX VISupplementary provisions
ANNEX VI Requirements applying to parking braking systems equipped with a mechanical brake-cylinder locking device 1. Definitions For the purposes of this Annex: 1.1. ‘mechanical brake-cylinder locking device’ means a device which ensures braking operation of the parking braking system by mechanically locking the brake piston rod. Mechanical locking is effected by exhausting the compressed fluid held in the locking chamber; it is so designed that unlocking can be effected by restoring pressure in the locking chamber. 2. Requirements 2.1. The mechanical brake-cylinder locking device shall be designed in such a way that it can be released when the locking chamber is again subjected to pressure. 2.2. When the pressure in the locking chamber approaches the level corresponding to mechanical brake-cylinder locking device, an optical or audible warning system shall be actuated. This provision does not apply to towed vehicles. In the case of towed vehicles the pressure corresponding to mechanical brake-cylinder locking device shall not exceed 4 kPa. It shall be possible to achieve parking braking system performance after any single failure of the towed vehicle service braking system. In addition, it shall be possible to release the brakes at least three times after the towed vehicle has been uncoupled, the pressure in the supply line being 650 kPa before the uncoupling. These conditions shall be satisfied when the brakes are adjusted as closely as possible. It shall also be possible to apply and release the parking braking system as specified in point 2.2.2.10 of Annex I when the towed vehicle is coupled to the tractor. 2.3. In the case of brake actuators fitted with a mechanical brake-cylinder locking device, the brake actuator shall be capable of being actuated by either of two energy reserves. 2.4. The locked brake cylinder may only be released if it is certain that the brake can be operated again after such release. 2.5. In the event of a failure of the source of energy supplying the locking chamber, an auxiliary unlocking device (mechanical or pneumatic, for instance) using, for example, the air in one of the tyres of the vehicle, shall be provided. 2.6. The control device shall be such that, when actuated, it performs the following operations in sequence: it applies the brakes so as to provide the degree of efficiency required for parking braking, locks the brakes in that position and then cancels out the brake-application force.