A pneumatic valve located near the handbrake on a freight car, used exclusively on heavy mountain grades. When manually set by the train crew before descending, it holds a specific amount of pressure in the brake cylinder even when the engineer releases the automatic brakes. This keeps the train's speed in check while the brake pipe and auxiliary reservoirs recharge with fresh air.
The dispatcher says we've to stop at the summit and set up twenty retaining valves before we head down the hill.
Setting retainers requires a crew member to physically walk the train and turn the valve handle on each car before descending a steep grade.
Also heard as
- retainer
Related terms
Brake pipe
The air line running the full length of a train that charges and controls every car's brakes.
Triple valve
The core control valve in a railway air brake system that charges, applies, and releases the brakes.
Runaway train
A train or cut of cars rolling out of control without an operator able to stop it.