Throttling valves used in the seawater circuit will regulate the amount of water passing through the seawater side of the freshwater cooler. The throttling valve in the seawater circuit should be adjusted so that it regulates the minimum flow

Figure 7-16.-Conventional type of thermostatic valve operation.

of seawater through the cooler while not exceeding a discharge temperature of 130F to reduce the effects of errosion and to prevent scale formation on heat transfer surfaces. Where throttling valves are incorporated in the seawater circuit and a thermostatically operated valve is included in the freshwater circuit, the throttling valves serve only to provide a constant flow of seawater or to close the circuit completely. Temperature is then controlled by direction of flow by the action of the thermostatically operated valve in the freshwater circuit.