LumaSense Technologies M390 - Manual (Page 21)

M390 Manual Maintenance 21
5 Maintenance
5.1 Cavity Life
The life expectancy of the graphite cavity depends on the time and temperature of operation.
The higher the temperature, the shorter the life spans. At temperatures near 3000 °C the life
expectancy of the graphite cavity is approximately one half-hour. The life span is also affected
by the gas purge purity. The presence of air or water will greatly shorten the life span when
operating. We recommend an occasional visual check be made to ensure maximum system
integrity.
5.2 Safety Interlocks
Automatic shut-down will occur if the water flow fails or reduces below 3/4 GPM or if the gas
flow drops below 4 CFH, or if the region near the cavity exceeds ~200 °C. Reset is automatic for
the water flow and purge gas pressure. Reset must be made manually when over-temperature
causes a shut down. The cooling fans will operate only when the internal temperature is above
40 °C (104 °F).
5.3 Periodic Inspections
Check periodically and upon every start up the following items:
1. Condition of all plastic tubing near the graphite core.
2. Condition of all piping external to the M390. (closed or frozen drain valves, supply
valves, etc.)
3. Quartz tube in center of furnace for cracks.
4. Check for clogged electrode cooling cores by touching water out connections while
furnace is running. If one electrode is very hot when the other electrode is not, a clog is
occurring. The electrode cooling core will have to be removed and bench tested to
determine if flow is restricted.
5. Check all internal plastic tubing and fittings for water and gas leaks.
6. Test low water flow and gas pressure interlocks once per month by temporarily shutting
off water and gas purge for a few seconds. Each one should activate the alarms and turn
off all power to the cavity.
5.3.1 Pyrometer Alignment Check
If, for some reason, the control pyrometer (M668 or M680) is suspected as being out of
alignment, do the following:
1. A high intensity light source is built into the M668 for illuminating the receiving end of
the fiber optic cable. Turn the light on using the key switch on the M668. At this time,
the M668 will hold the last reading prior to actuating the light.
2. Observe the projected image into the cavity. The image should be in the center of cavity.
3. Turn off light using the key switch.
4. If the M390 has an M680 sensor as in the M390L series, the aiming light is not present.
The fiber cable must be disconnected from the M680 and then back illuminated using a
Lumasense Illuminator or other bright light source as light input to the fiber optic cable.