Paint the inside of the table, console, or panel each year to protect
Rate Controllers. Rate-of-flow controllers may be either direct-acting or
indirect-acting. Maintenance procedures for both types follow:
Each week, clean exterior, check for leakage through
diaphragm pot, and lubricate or tighten packing to stop any existing leakage. Also,
make sure that both the diaphragm and the control gate move freely between zero
differential and the open and closed positions.
At regular intervals, remove and disassemble the diaphragm
pot, including the rubber diaphragm. If the water does not cause tubercles, this
operation may only need to be performed once every 3 to 5 years.
Every 3 years, disassemble and service the controller gate
and mechanism. Inspect the venturi throat. Paint or apply protective coating, as
Each week, clean the outside of the controller, adjust the
packing, and 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 and other foreign matter. Also, be sure
that the piston has free vertical travel and does not bind. Replace the packing if
Each year, disassemble, clean, and lubricate the pilot valve.
Remove foreign matter from the piston with a cloth. Do not use an abrasive to clean
the piston. Make sure that the piston is moving freely. Disconnect and clean the pilot
valve piping and strainers; make sure that no foreign matter enters the pilot valve
during the cleaning operation. Check for leaks or cracks in the diaphragm.
Gages. Indicating and recording instruments mounted on the operating
table or control panel may include a filter rate controller, loss-of-head gage, flow-rate
gage, water level, backwash flow rate meter, wash water rise indicator, and summation
gage for total filter output.