Abstract: A covering has a property of allowing an accretion of snow to slide and comprises a coating layer formed on a surface of a substrate in order to prevent accretion of snow and ice. As for the coating layer, its external surface has such wettability that a contact angle relative to water is 70 degrees or greater, and also has such water sliding property that a waterdrop sliding angle is 40 degrees or less. Alternatively, the external surface of the coating layer has such water repellency that a surface tension is 35 dyne/cm or less, and also has such water sliding property that a waterdrop sliding angle is 40 degrees or less.

Abstract: A method of monitoring the inner surfaces of copper-alloy condenser tubes of a condenser through which seawater flows as a coolant by controlling a ferrous-ion injecting operation to inject ferrous ions into the coolant for forming a protective film on the inner surfaces of the condenser tubes, and a sponge-ball cleaning operation to clean the inner tube surfaces by passing sponge balls through the condenser tubes. During an initial period of exposure of the condenser tubes to the coolant after installation of the condenser tubes in the condenser, the ferrous ions are injected into the coolant to form the protective film on the inner surfaces of the condenser tubes until the polarization resistance of the condenser tubes has reached 10.sup.4 .OMEGA.cm.sup.2. Subsequently, the ferrous-ion injecting operation and the sponge-ball cleaning operation are executed while the polarization resistance and heat transfer rate of the condenser tubes are monitored.

Abstract: A condenser including a plurality of condenser tubes through which a coolant is caused to flow, a device for injecting ferrous ions into the coolant before it passes through the condenser tubes to form a protective film on an inner surface of the condenser tubes, and a device for introducing sponge balls into the condenser tubes for cleaning their inner surfaces. The condenser has a by-pass line extending outside the body of the condenser, in parallel connection with the condenser tubes. The by-pass line has a monitor tube of the same material and size as the condenser tubes, so that the coolant flows through the monitor tube under the same conditions as the coolant flowing through the condenser tubes. The monitor tube is equipped with a device for measuring a polarization resistance of the monitor tube, and a device for sensing a fouling condition of the inner surface of the monitor tube.