Maintenance operations that should be performed weekly are as follows:

1. Clean the table, the console, or the panel inside and out, using soap and water if necessary.

2. When mechanically operated, check the tension on the cables or the chains, used for connection to the valve operator or for connection to the valve-position indicators.

3. When hydraulically operated, inspect for leaks and stop any leakage; when pneumatically operated, check tubing for possible leakage.

Maintenance operations that should be performed monthly are as follows:

1. Transfer valves (four-way) and handles should be adjusted monthly to make certain that all filter valves open at the same rate. Packing glands should be tightened or new packing added if needed.

2. Transfer valves should be lubricated monthly with grease. They should not be overlubricated; one- half turn of the grease screw (cup) should be enough.

3. The valve-position indicator should be inspected monthly and adjusted to ensure that it reads correctly in all positions.

Maintenance operations that should be performed annually are as follows:

1. The four-way transfer valves in the table should be disassembled annually and any worn parts, seats, or washers should be cleaned or replaced with new ones.

2. The inside of the table, console, or panel should be painted annually to protect against corrosion.

Rate Controllers

Rate-of-flow controllers (fig. 8-5) may be either direct acting or indirect acting.

Maintenance procedures for a direct acting rate- of-flow controller is as follows:

1. Weekly, clean the exterior, check for leakage through the diaphragm pot, and lubricate or tighten packing to stop any existing leakage. Also, ensure that both the diaphragm and the control gate move freely between zero differential and the open and closed positions.

2. At intervals of 1 or more years, remove and disassemble the diaphragm pot, including the rubber diaphragm. When the water does not cause tubercles, this operation may not have to be done more than once every 3 to 5 years. The term tubercles refers to small, more or less hemispherical lumps on the walls of the pipe, which increase the friction loss and, by reducing the velocity, also reduce the capacity of the pipe. Tubercles result from tuberculation, a condition which develops on the interior of ferrous pipelines, caused by corrosive materials present in the water passing through the pipe.

3. Every 3 years, disassemble and service the controller gate and mechanism. Inspect the venturi throat. Paint or apply protective coating as necessary.

With indirect-acting controllers, the following maintenance procedures apply:

1. At weekly intervals, clean the outside of the controller; adjust the packing; lubricate or tighten the fittings as necessary to stop any leakage from the hydraulic cylinder, the controller valve, the piping, or the pilot valve. Make sure that the knife edges seat correctly and are free of paint or other foreign matter. Also, be sure that the piston has free vertical travel and does not bind. Replace packing if necessary.

2. Annually, disassemble, clean, and lubricate the pilot valve. Remove foreign matter from the piston with a cloth. Never use an abrasive to clean the piston. Make certain that no foreign matter enters the pilot valve during the cleaning operation. Check for leaks or cracks in the diaphragm.

3. Every third year, disassemble and service the controller gate and mechanism; inspect the venturi throat and apply protective coatings where necessary. Check the hydraulic cylinders, and maintain them under the manufacturer's instructions.

Gauges

Various types of indicating and recording instruments may be mounted on the operating table or control panel. Here, we will take up one device, the diaphragm-pendulum unit loss-of-head gauge. Where the actuating mechanism is of this type, the general