The air flasks and separators of surface ships must be given a surface inspection every 3 months to determine if there is any external corrosion or damage to flasks or piping.

Because of the coating of zinc chromate primer, corrosion is seldom a source of trouble on the internal surfaces of air flasks; however, corrosion may take place on the external surfaces of air flasks and may be sufficiently serious to weaken the material, especially in high-pressure flasks. Surface corrosion usually occurs at points which cannot be easily reached for proper cleaning and painting.

Drainage of air system equipment must be sufficiently frequent to prevent excessive accumulations of moisture and oil. Such accumulations not only cause internal corrosion and fouling of moving parts, but also create a serious hazard since any excessive oil accumulation may result in an explosion.

All high-pressure flasks and separators must be inspected, cleaned, tested, and repainted at prescribed intervals by a repair activity. For surface ships, the initial and subsequent intervals should not exceed 6 years. Although inspection intervals for separator flasks are approximately 3 years, if there is reason to believe that serious corrosion of either the exterior or the interior of air flasks is taking place, before the lapse of the normal interval, the flasks should be inspected and tested at once.

Periodic examinations are essential to deter-mine the condition of air system equipment; these examinations should include not only a complete inspection of the interior and the exterior of flasks and separators, but also ultrasonic inspections and hydrostatic tests. After a thorough cleaning, the flasks which successfully pass the hydrostatic test are given the prescribed internal protective coating, and when necessary, the exterior is painted. Further information on the details of the inspections and maintenance performed by repair activities can be found in chapter 551, section VIII, of Naval Ships Technical Manual.