An insufficient flow of circulating water is indicated if the temperature of the water rises more than 20F in passing through the condens-ing section of the distiller condenser. The last-effect shell pressure is directly dependent upon the distiller condenser vacuum. The vacuum is dependent upon the temperature and quantity of the circulating water, and the proper operation of the air ejectors. Too low an overboard discharge temperature of the distiller condenser circulating water is accompanied by efficiency losses in the distilling plant. The overboard discharge temperature should be kept as high as possible, without exceeding the desired 20F temperature rise through the distiller condenser. In addition, limiting the quantity of circulating water tends to prolong the service life of the tubes and tube sheets. When troubles occur which are not caused by improper operating procedures, an inspection should be made of the condenser cir-culating water system to determine the cause of faulty operation.

Preventive maintenance procedures should be carried out to ensure that the circulating water pump is maintained in good material condition. The maintenance and repair procedures for this pump are similar to those for the other pumps of the plant.

Routine procedures should be carried out to ensure the proper setting and maintenance of the back-pressure regulating valve. If this valve is not functioning properly, the valve should be disassembled, the valve parts replaced, and the necessary repairs to the valve made, before its faulty operation interferes with the operation of the distilling plant.

To ensure that the condenser circulating water system is clean and free from scale and foreign matter, the piping should be inspected at regular intervals. The operators of the distilling plant should inspect and clean the strainers, in accord-ance with the PMS, to prevent accumulations of foreign matter from interfering with the proper operation of the plant.

Improper Drainage

Failure of the distilling plant to produce designed output when the pressure above the orifice is 5 psig and the first-effect tube nest vacuum is several inches of mercury always indicates improper drainage of the distiller con-denser or of one of the evaporator tube nests subsequent to the first effect. Complete flooding of the flash chamber gage glass is also a positive indication of improper draining of the condenser, but the fact that the level appears to be in the gage glass or below is not necessarily an indication of improper drainage because air leaks at the gage glass fittings may indicate a false liquid level. A temperature difference of more than 5 F to 10F between the last-effect shell temperature and the temperature of the distillate at the distillate cooler inlet is another indication of improper drainage; however, the fact that the temperature difference is within the proper range does not necessarily indicate proper drainage. Scale deposits are unlikely to form in the distilling condenser tubes if the plant is properly operated and a full flow of circulating water is maintained. However, if scale deposits do occur, the tubes must be cleaned.

Venting of the vapor side of the distiller con-denser is continuously accomplished by the air ejector. Venting of the saltwater side of this and other units of the distilling plant need not be con-tinuous. While starting the plant, and once every watch thereafter, the vents on all saltwater heads should be opened until all air is expelled and a solid stream of water appears, then the vents should be closed.