retaining valve (English, noun)
expansion: retaining valve (plural retaining valves)
Senses:
topics: engineering
mechanical
mechanical-engineering
natural-sciences
physical-sciences
rail-transport
railways
transport
glosses: A device that retains some air pressure in a train's air brake cylinders even when the automatic brake valve is set to the fully-released position, used on steep downgrades to allow a degree of continuous braking effort to be maintained without depleting the pressure in the train's brakepipe (which would result in the loss of nearly all braking ability, causing a runaway).
Forms:
form: retaining valves
tags: plural