Time-Specific Vacuum Furnace Preventive Maintenance Checklist to Follow

When you invest in vacuum furnaces, all you want is these to work longer and perform efficiently. This is where preventive maintenance becomes an important aspect to keep up your furnace working fine for years to come.

Talking about preventive maintenance of vacuum furnaces, it is not a one-step process but a through implementation of a wide range of tasks that needs to be done on a daily, weekly, monthly, and semi-annual basis.

So, what are these maintenance steps that you should implement regularly? We take a look below:

Daily Check-List of Vacuum Furnace Maintenance

On a daily basis, you must:

• Analyse the whole of the interior part of the furnace to look for soil and dirt signs, and if there are any take steps to clear these off right away.
• Make sure to look for any missing or broke element retaining wires.
• Inspect the hot zone shielding and elements condition.
• Furnace’s alternate heating and cooling causes distortion of the shielding. Check for this as well.

Weekly Check-List of Vacuum Furnace Maintenance

• Make sure to remove all foreign material from the heating chamber. This cleaning implementation frequency also depends on what is the rate of dirt accumulation on the chamber.
• Use clean, inert gas, or dry air to brush out the dirt. The chamber’s inner part should be cleaned using a damp-free cloth that has been dampened with a suitable solvent.
• Ensure to clean the control cabinet of all the dust and dirt.
• Look for signs of discoloration on heating elements and shield and whenever you see that run furnace clean-up (ideally this should be done once every two weeks).
• Ensure to check the pneumatic lines for any sign of leaks.
• Make sure to insect each of the water drain line individually to not allow any sediment build-up or blockage in components such as circuits, smaller hoses.
• If your furnace includes a pneumatic bank then the related lubricator/filter/regulator is working in fine condition.
• Once every week note down the diffusion pump’s heaters readings – related to amperage and voltage.
• Amperage and voltage readings should also be noted down pertaining to gas blower motor (ideally done at operating pressure to ensure it is in normal range and not above motor rating).
• Note down power control unit (PCU) voltage output readings, which must be aligned and specific as referred to in the PCU manufacturer’s manual.
• Check the pressure switches and ensure these are working fine (make the adjustments if needful).
• Make sure to lubricate the valves once every week by filling the oil or grease cup with oil or grease, respectively, from the pump. Check the manual to refer to the right lubrication method and level.
• You should also lubricate the diffusion pump shaft seal using diffusion pump oil.

Monthly Check-List of Vacuum Furnace Maintenance

• For proper condition and functioning of furnace interior and exterior, ensure to analyse all the safety interlocks whether are working fine or not.
• Inspect for any deterioration concerning heating elements and also thermocouples.
• Check the hot zone ceramic insulations to look if there is any kind of deposit that could be causing any unwanted power drain down the ground, which would result in affecting the heating cycle of the furnace.
• Turn of the transformers and then check it and power terminal connections for how tight it is.
• Also check the tightness of the electrical connection to power feedthrough bars.
• Check for leaks all through the backfill gases’ connection, fittings and lines from the point of origin to the valve assemblies.
• Make sure you flush out the water strainer in the water lines of the furnace.
• Make sure to check the belt tension on the pumps.
• Manifold pressure-relief valves should be disassembled and then inspected for the springs and to ensure the valve bodies are clean.
• Make sure to clean the control cabinet of any dust or dirt.
• Make sure there is no heat deterioration and wear of the secondary power cables.

Every Three Month Check-List of Vacuum Furnace Maintenance

• Inspect every aspect related to the Variable Reactance Transformers (VRT), including resistors, wear condition of the power cables, and for tightness of the cables to and from the transformers.
• The motor amperage ratings shouldn’t be exceeding the limit and so check for the blower blast gate setting.
• Check all the fuses, and the wiring on the junction boxes and the cabinets.
• Check the door alignment and bottom-head alignment related to the tank flange, along with the alignment of the motor and gearbox shafts.
• Check the thermocouples for direction, and response.

Semi-Annual Check-List of Vacuum Furnace Maintenance

• Make sure to go for replacement of load thermocouples, irrespective of how it looks.
• Replace the vacuum-sensing head if you witness a probable malfunction in it (checked through vacuum-indicating instrument).
• If you are having an old furnace then you should clean and lubricate slide-wire and chart drive mechanics.
• Inspect for calibration, temperature and stability, the controls system.

The high temperature furnaces keep working efficiently and for a longer duration the way you keep these maintained following a proper schedule and methodology.