unit; however, protection is not provided when the electrodes are not immersed.
Annually, check the anode condition and replace the anodes as necessary. Also, check the current flow; if it has diminished since the previous inspection, the anode probably needs to be renewed.
Annually, in freezing climates, protect electrodes from ice, which may tear them from their hangings or damage them. If ice formation is severe, turn off the current, remove the electrodes, store them until the freezing season is past, and then reinstall them.
Annually, test the effectiveness of the cathodic protection system in one of two ways.
1. Scrape and polish a spot on the tank wall at a point always immersed. At quarterly intervals, lower the water and inspect the spot; if protection is adequate, the spot will remain uncorroded.
2. Suspend two polished mild steel test plates in the tank at an elevation where they will always be immersed (use No. 6 galvanized steel wire). Ground one plate to the tank wall, but have the other plate insulated from the tank. The extent of corrosion on the grounded plate will come close to the corrosion of the protected tank; the extent of corrosion on the other plate is a measure of the corrosion that would occur if the tank were not protected.
As pneumatic tanks are usually on smaller installations, they may be too small for interior inspection, except for observations through a removable hand plate. The size, therefore, shows the inspection procedures to be followed. Standard inspection procedures are as follows:
Quarterly, inspect the air pump and motor to make certain both are operating properly. Check the operating record to determine the time cycle of air pump operation. If the records show a decreasing time cycle, check for possible air line leaks.
Quarterly, check valve operations; particularly, check the pressure-relief valve. Repair or replace as necessary. Annually, check the tank for signs of corrosion, both internally and externally. If corrosion products are apparent, take the following action:
1. If the tank is large enough to permit the entry of personnel, paint the inside with corrosion- resistant paint, or line it with cement. If the tank is too small to permit entry, consider changes in operation or in chemical treatment to reduce corrosiveness of water. Corrosion is most likely in areas alternately exposed to air and water.
2. Paint the exterior as needed.
Every 6 months, ladders, walkways, guardrails, handrails, stairways, and risers should be inspected for rust, corrosion, poor anchorage, loose or missing pieces, or other deterioration or damage. Standard inspection procedures include the following:
1. Be sure to check ladders inside as well as outside the tank. Replace worn, corroded, or missing parts; check for deteriorated lugs and rungs as necessary; and, make other repairs to ensure safety for the operators. Check revolving ladders on the roof for the condition of connection at the final hookups.
2. Ensure that bolts, screws, rivets, and other connections are tight.
3. Inspect the condition of the altitude valve vault and the valves for proper operation. Repair, clean, and paint all equipment when necessary.
4. Check the water level indicator for improper operation and repair when necessary.
5. Inspect the cathodic protection equipment and repair when necessary (follow instructions given in previous portions of this chapter).
6. At semiannual intervals, check the electrical connections to lights, cathodic protection, and so forth, for breaks in the conduit. Remove the conduit inspection plates and examine the internal connections for tightness and adequacy; also check relays for weak springs, worn or pitted contacts, and defective operation. Repair and eliminate all undesirable conditions.Continue Reading