Numerous types of level controllers are used in industrial refrigeration practice, two important types of which are shown in Fig. 11.11. The mechanical type in Fig. 11.11a is a simple one applicable for smaller systems. As the liquid level rises, the valve stem closes the port to restrict the flow of liquid. This type of valve provides a modulated rate of flow. A standard type that has been used for many years is the float switch of Fig. 11.11b where the rise in liquid level elevates the float in the float chamber which discontinues the flow of electric current to the solenoid valve to interrupt the supply of liquid to the vessel. The float chamber serves a useful purpose in damping some of the splashing likely to exist in the liquid level in the vessel. The manual expansion valve, as was shown in Fig. 11.2, is always combined with the solenoid valve to reduce the flow rate when the solenoid is open to avoid short pulses of high flow rates which would disturb the pressure in the vessel.