2. Check for excessive wear of moving parts, including gears.

3. Flush and back blow the sludge withdrawal line by using high-pressure water or compressed air.

NOTE

Do not allow the waterline to be cross connected to the drinking water supply system.

4. Check the plows or rakes and straighten them if necessary.

5. Check the motor condition, couplings, and service shear pins.

6. Clean equipment and paint as necessary.

When the equipment has an overload alarm, check it for operation. If the alarm sounds at any time, shut off the equipment, locate the source of trouble, and correct it. Under no condition should the alarm switch be nullified to provide continuous operation. If the overload is caused by a sludge buildup leading to cutout of the starter switch or pin shearing, the tank must then be drained and the sludge flushed out.

Conveyor-Type Collector Basins

As with the revolving-sludge collectors, specific maintenance procedures in conveyor-type collector basins are in the manufacturer's instructions. Maintenance procedures on the tanks and structures are the same for this type of sedimentation basin as they are for the circular-type basin. Generally, the maintenance procedures for gears, chains, sprockets, reducers, and so on, are also the same as those for circular-type basins.

Cathodic Protection

Where stubborn water problems exist in water supplies, the sedimentation tank equipment may be protected by cathodic protection. Cathodic protection is a method of protecting metal surfaces from corrosion through the use of a direct-current voltage. The voltage is applied so that the current tends to flow from the direct-current source through the soil or water to the metal surface to be protected. This flow of current applies electrical energy that reverses the natural process of corrosion.

There are two well-known methods of cathodic protection: the impressed current system and the galvanic anode system. The impressed current system requires graphite rods and an external power source to establish enough voltage. The galvanic anode system, which requires no external power supply, uses metallic anodes, such as magnesium, zinc, or aluminum.

Cathodic protection systems may be maintained by activity personnel or by service contract. The field engineering officer will provide guidance in developing maintenance procedures or in contracting for such services.

IMPRESSED CURRENT SYSTEM. - Make inspections and necessary maintenance repairs at monthly intervals. The steps for the inspection include the following:

1. Check exterior of enclosure for rust, corrosion, or mechanical damage; check hinges and locks for inadequate lubrication, rust, or other deficiencies; check wiring and fastenings and rectifier for broken or damaged insulation, and for rust or corrosion on conduit; and, check exposed wires and cables and all electrical connections for insecurity, frayed or broken insulation, and other deficiencies.

2. Check interior of enclosure for rust, moisture condensation, loose wiring, and signs of excessive heating. (Do not put hand tools inside the enclosure.)

3. Check anode suspensions for rust, corrosion, bent or broken suspension members, frayed or broken suspension lines or cables, loose bolts, loose cable connections, and frayed or broken wiring.

4. Whenever necessary, replace or repair any item which will not pass inspection for continued service, and paint switch cans and exposed rectifier housing and other electrical gear as necessary.

GALVANIC ANODE SYSTEM. - The only maintenance required for a galvanic anode system or a sacrificial anode system is monthly inspection and potential tests to determine when replacement of anodes is necessary and to ensure continuity of the electric circuit. The procedures that apply are as follows:

1. When an abnormal decrease in current output (or potential of the protected structure) occurs, the 8-9