February 2023 Volume 5

MAINTENANCE

Evaporative tower systems, consisting of a recirculating pump, heater, sump pump, fans, and cooling fins, require more maintenance than dry types. Yearly maintenance is the same as for dry tower systems plus the following: • Lubricate the pump(s), motor, bearing and bushings. • Check seals and gaskets for leaks. • Remove dirt that has accumulated in the sump pump and reservoir. • Check to ensure that the sump pump heater is functioning properly. This is especially important because the heater prevents freezing of the sump pump water during winter operation. Suggested water quality requirements for both dry and evaporative cooling towers are 100 ppm total water hardness (CaCO3), 200 ppm total dissolved solids, 20 - 300 K mho/cm, 10 ppm suspended solids and 7.0 - 7.5 ph.

• Tighten loose connection using only a screwdriver; never overtighten. • Visually inspect for overheating (discoloration) of bus connections, SCRs, diodes, and other components including transformer and capacitor connections, and tighten using appropriate tools. Do not over- torque SCRs. If the system has mechanical contractors, inspect the contact pads and springs, and adjust or replace worn components. • Perform an infrared scan of the internal components looking for hot spots. Include mechanical gear boxes and control panels as well to find hot spots.

Power Supplies and Heat Stations The power supply and heat station, which are the most expensive parts of a production induction heating system, are the most likely to be ignored. Maintenance requirements and frequency schedules

The infrared image of a transformer shows the center winding being hotter than the outer windings. Yearly inspection: • Test all door interlocks. Check the OEM manual as each manufacture has its own requirements for this particularly important safety test. • Inspect the power supply and heat station using infrared thermal imaging, which identifies hot spots and provides information that can be used to identify potential problems during operation. • Check power-supply battery backups used for logic memory; most batteries require replacement annually, while others have a five-year life. Check the OEMmanual. • Check water-cooling hoses. Hoses become brittle and are susceptible to leaks and complete failure. Depending on factors, such as ambient heat and humidity, water-cooling hoses may need replacement every five to ten years. Use only the same type of nonconductive hose as originally supplied, and never shorten the length of any hose when replacing it.

are given below. Daily inspection:

• Inspect inside the cabinet for water leaks, drips, and condensation. This must be done with the cooling pump on, at the beginning of the shift after the unit has been idle all night, and again at the end of the shift while the system is warm. If tightening a hose clamp cannot stop a leak, replace the hose. Never reduce the length of a hose; hoses have a specified length and may have loops to prevent electrical conduction and subsequent electrolysis of the copper tube at the end of high voltage dc potentials. • Test the ground leak detector; see the OEMmanual for details. Monthly inspection: • Check for loose connections of all ribbon connectors and wires on terminals.

FIA MAGAZINE | FEBRUARY 2023 15