Tools and Equipment Maintenance
Equipment that is neglected fails in the middle of a firing or a batch. The exam tests routine checks and the diagnosis of common machine and kiln faults.
Routine checks
- Wheel: check the wheel head for wobble, listen for bearing noise, clean the splash pan, check belt tension and the foot pedal. Never grease where clay dust will cake.
- Pug mill: check vacuum pump oil and filter, clear the auger, never leave clay to set in the barrel.
- Kiln: vacuum the floor and element grooves with the kiln isolated, check the door seal, thermocouple, relays and contactors, and record element resistance.
- Spray booth: clean or replace filters, check the fan.
- Hand tools: dry after use, oil steel tools lightly, sharpen trimming tools, store wooden ribs flat.
Element resistance check
Resistance rises as a resistance element ages, so power output falls. Measure with a multimeter, kiln isolated and cold, and compare with the maker's figure.
Worked example
A 240 V element rated 3.0 kW should read R = V² ÷ P = 240² ÷ 3000 = 57 600 ÷ 3000 = 19.2 Ω. Measured at 22 Ω, actual power = 240² ÷ 22 = 2 618 W, about 13 % below rating. The kiln will still fire, but slowly and unevenly. Replace the whole set rather than one element, because mixed ages create cold zones.
Traps
- Testing elements with the kiln live.
- Replacing only one element in a set.
- Storing plaster moulds damp or stacked - they chip and lose absorption.
- Fitting a relay or fuse of the wrong rating; it fails again within weeks.