Manufacturers of Authentic Reproductions of Historical Railway Components in 3½", 5", 7¼" & 10¼" Gauge Specialising in Vacuum Brakes & Trackwork
Upcoming Events
PNP Railways will be the
7¼" Gauge Society Annual Gathering at
The City of Newport Model Engineering Society
Friday 18th & Saturday 19th September 2026
Select - Collection at the 7¼" Gauge AGM when placing your order.
Please note: PNP Railways will be attending Friday and Saturday only.
All pre-orders must be collected before 4.00 pm on Saturday 19th September.
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:
Height: 1″
Width: ½″
