PNEUMATIC SYSTEM

A pneumatic system comprises a first compressor and associated first air dryer for supplying dried air to a first set of consumers in a main circuit and a second compressor and associated second air dryer for supplying dried air to at least one further consumer through a subsidiary circuit. A protection valve system is provided in the main circuit between the first air dryer and the first set of consumers. A fluid flow path is provided between the main and subsidiary circuits which is selectively openable or closable by a coupling valve to enable the subsidiary circuit to be supplied with pressurized air from the main circuit or to isolate the main and subsidiary circuits.