Many maintenance procedures for a flash type distilling plant are similar to the maintenance pro-cedures required for a submerged tube plant. Both types of plants are subject to air leakage, saltwater leakage, and malfunctioning of pumps and other auxiliary equipment. Some of the more important maintenance problems will be discussed in the following paragraphs.

AIR LEAKAGE.Since all parts of the distilling plant are designed to operate under a vacuum except the circulating, feed, and freshwater lines, extreme care must be taken to prevent leakage of air which might seriously interfere with the proper operation of the plant. The brine overboard and distillate pumps take their suction from points of relatively high vacuum. Air leakage in the piping to these pumps is particularly objectionable and must be eliminated. A small amount of air entering these lines, even though it is insufficient to affect the distilling plant vacuum, may cause the pump to lose suction. Leaks in the lines to the pump suc-tion gages must never be overlooked.

An 8 to 10 psig, low pressure hydrostatic test should be applied to the entire system in accord-ance with the PMS, and at any other time when there is an indication that air leakage may exist. The saltwater circulating pump can be used to apply the pressure.

PUMPS.Proper operation of all pumps is essential for the successful operation of the dis-tilling plant. The effect of air leakage into the suc-tion line of the pumps has been discussed in the preceding paragraph. Proper operation of the water-sealed gland lines and proper mainte-nance of the glands themselves are necessary for dependable operation of the pumps. General in-formation on the operation and maintenance of pumps is found in Engineman 3 & 2, NAVED-TRA 10541 (current edition). However, for details of any specific pump, consult the manufacturers technical manual.

SALTWATER LEAKAGE.Saltwater to distillate or saltwater to condensate leaks at any of the various tube bundles will be immediately indicated by an alarm bell and a red light which shows at which cell a conductivity increase has occurred. These cells are located downstream from each tube bundle. Tube leaks usually result from damaged or corroded tubes or from im-proper expansion of tubes into the tube sheets. Faulty tubes may be sealed with plastic tube plugs or may be removed and replaced in accord-ance with standard Navy procedures, as given in chapter 9581 of Naval Ships Technical Manual.