Steam Pressure Regulator Valve

pressure regulator
A spring-loaded diaphragm-type pressure-relief valve which governs the pressure of the fuel delivered to the fuel injectors by the fuel pump and returning the excess to the tank.
A device for controlling and maintaining a uniform outlet gas pressure.
A pressure regulator is a valve that automatically cuts off the flow of a liquid or gas at a certain pressure. Regulators are used to allow high-pressure fluid supply lines or tanks to be reduced to safe and/or usable pressures for various applications.

steam
The vapor into which water is converted when heated, forming a white mist of minute water droplets in the air
The invisible gaseous form of water, formed by boiling, from which this vapor condenses
steamer: travel by means of steam power; "The ship steamed off into the Pacific"
The expansive force of this vapor used as a source of power for machines
water at boiling temperature diffused in the atmosphere
emit steam; "The rain forest was literally steaming"

valve
A membranous fold in a hollow organ or tubular structure, such as a blood vessel or the digestive tract, that maintains the flow of the contents in one direction by closing in response to any pressure from reverse flow
device in a brass wind instrument for varying the length of the air column to alter the pitch of a tone
A cylindrical mechanism in a brass instrument that, when depressed or turned, admits air into different sections of tubing and so extends the range of available notes
a structure in a hollow organ (like the heart) with a flap to insure one-way flow of fluid through it
control consisting of a mechanical device for controlling the flow of a fluid
A device for controlling the passage of fluid through a pipe or duct, esp. an automatic device allowing movement in one direction only