Figure 8-14. - Standpipe.
When cracks appear in prestressed concrete tanks, the problem should be referred to the erecting company for recommendations, even if the guarantee has expired or does not cover maintenance.
Every 6 months, joints should be checked for leakage at the juncture of the floor and the walls, and for loose or missing filler, debris, or trash. They should be cleaned and repaired as necessary.
Every 6 months, the roof should be inspected for the condition of the covering. Are roof hatches and other covers locked? Are the screens on the overflow or at other locations in place? They should be cleaned as necessary.
Where the tank rests on an earth embankment, it should be checked for erosion from the lack of full sod or vegetation coverage, and for damage from burrowing animals, improper drainage, ponding water along the base, or leakage through the embankment or along the outlet piping. When leakage exists through the embankment, the tank should be drained and the bottom inspected for failure or cracks.
UNDERGROUND STORAGE. - If storage tanks are constructed belowground or are surrounded by an earth embankment, the semiannual inspection and repair comprise only the interior walls, roofs, accessories, and embankment. The inspection procedures and maintenance operations are the same as described above for ground level storage facilities. When the earth embankment, surrounding soil, or interior of the tank shows evidence of tank leakage, the earth may need to be excavated and repairs made on the walls.
ELEVATED STORAGE. - Concrete storage tanks elevated aboveground require the same inspection and repairs as outlined above, where applicable.
Usually, outside contractors maintain and repair steel tanks. At times, though, you may have to perform various inspection and maintenance duties, such as those discussed in the following section.
GROUND LEVEL STORAGE. - Annually, after the winter season, steel storage tanks should be inspected for ice damage, watertightness, and structural conditions. Twice each year, the maintenance procedures set forth in the following paragraphs should be followed.
Tanks walls (exterior and interior) and bottom (interior) should be inspected semiannually for rust corrosion, loose scale, leaky seams and rivets, and for the condition of the paint (both inside and out). Maintenance procedures to adhere to are as follows:
1. Replace rivets, or patch-leaking areas, and follow by cleaning and painting.
2. Check painted surfaces for rust, corrosion, cracking, peeling, alligatoring, caulking, fading, or complete loss of paint. Empty the tank and examine the interior paint, as corrosion is more likely on the inside. When the interior needs painting, arrange to take the tank out of service. Paint the tank interior as often as the exterior (more often if the stored water is corrosive); unless the tank is equipped with cathodic protection.
Make certain that the paint used will protect the metal against corrosion,. Consult the applicable guide specifications for paint selection and application.
Use only new coat if the previously applied coat is in fair condition. Bare spots of steel should be painted with a spot or patch coat before the finish coat is applied. When the condition of the old paint is bad, use a complete primer coat.
Every 6 months, the roof and its appurtenances - screens on overflows, hatches, and manholes, as well as the condition of the paint, should be inspected. Maintenance procedures to adhere to are as follows:
1. Make certain that hatch covers and manholes are in place and locked and that screens are in place to prevent the entrance of birds, insects, and animals.Continue Reading