Vacuum Limiting Valve

Limiting Valve for Vacuum Brake Systems

This limiting valve is designed for use on steam locomotives fitted with a vacuum ejector. It is used to set and control the maximum level of vacuum within the braking system.

On most miniature railways, the recommended maximum vacuum level is approximately 15″ Hg. Limiting the vacuum is essential because if the vacuum in the reservoir becomes higher than the vacuum that can be produced by the pump or ejector, the brakes may remain applied and fail to release correctly.

By controlling the maximum vacuum level, the limiting valve ensures reliable brake operation and helps prevent issues associated with excessive system vacuum.

PNP Railways limiting valves are compact, easily adjustable, and small enough to be mounted discreetly within the locomotive or tenders.

Product Instructions

Dimensions
Measurements taken with the brass vacuum screw set at a medium adjustment:

Length: 2½″
Height: 1″
Width: ½″