Daily Preventive Maintenance Checklist
When working with furnace equipment, it is essential to extend the life of your vacuum furnace as long as possible. An effective method for doing so is to adhere to a carefully scheduled.
However, one of the hardest things to know (and keep track of) are all the furnace components you need to review on a regular and/or periodic basis. In an effort to help with this, we have provided a few basic checklists that are grouped by the frequency in which certain preventative maintenance tasks should be performed: daily, weekly, monthly and semiannually.
Inspect the furnace interior for signs of dirt and oil, which can prevent the production of high-quality work.
Inspect heat shields to ensure that distortion has not shorted out an element. Shield distortion is normal due to the alternate heating and cooling of the furnace.
Check the O-ring vacuum seal on the furnace door for grit and dirt that might cause vacuum leaks.
Clean the chamber-door or bottom-head flange and lightly grease the O-ring with a thin coating of high-quality vacuum grease.
DO NOT grease the lip seal. Graphite powder should be used on the lip seal.
Check the oil levels and condition of all pumps (e.g., roughing, booster, holding, diffusion). The roughing pump oil should be circulating. Cloudy or discolored oil may indicate the presence of moisture or other contamination.
Check that the roughing pump is operating at 140 ○F (60 ○C). Adjust pump water miser as necessary [160 ○F (71 ○C) for gas ballasting operation].
Check the temperature and cooling-water profile of the diffusion pump. Verify that the water lines are cool to the touch; it is recommended that they are at or under 85 ○F (29 ○C) at the inlet water supply fitting.
Verify the crossover setting of the diffusion pump (normal range is 60-80 microns).
Verify the vacuum level when the booster is activated. Adjust if necessary (28 to 29 inches of mercury). The adjustable vacuum component can be a vacuum switch, vacuum controller or a backset switch.
Valves & Gauges
During the first vacuum pumpdown of the furnace, make sure all valves actuate in proper sequence.
Check all vacuum gauges to ensure they are properly responding to pumpdown pressures.
Check the settings on the backfill valve switch. Adjust if necessary. These adjustable components are typically vacuum switches.
Check the water flow from each drain line. A reduction in water flow indicates restrictions that must be located and corrected.
Closed Loop System: Check the water lines for leaks and any hoses that appear hotter to the touch than usual; this would indicate a lack of normal flow.
Open System: Visually inspect all water lines for flow and temperature.
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