clack valve

plural clack valves

1. engineeringA valve; especially one hinged at one edge, which, when raised from its seat, falls with a clacking sound.

   The feed water enters the back and cool end of the preheater and passes forward to the front and hot end, after which it enters the boiler through a clack valve.

   1959 September, P. Ransome-Wallis, “The British Railways Class "9" 2-10-0s”, in Trains Illustrated, page 420

   1 more example

   The connecting pipe between a locomotive injector and the boiler, through which the water is forced into the boiler against the steam pressure within, is provided with a "clack-valve," which allows the water to pass in the inward direction only and not the outward; this is housed in a "clack-box". No question of "advantages or disadvantages" attaches to the use of a clack-box; it is a necessary part of locomotive equipment.

   1946 March and April, “The Why and The Wherefore: Clack-Boxes”, in Railway Magazine, page 129