ESAB Knowledge center.

Plasma Maintenance

March 21, 2014

Clean the torch body

  •  Remove the torch parts and examine the inside of the torch.
  •  Check for any signs of mechanical damage to threads.
  •  Clean the inside of the torch with electrical contact cleaner and a cotton swab.
  •  Disconnect the torch from its mounting tube and slide back the tube to reveal the torch/lead fittings.
  •  Make sure there are no leaks or damage to any of the connections.
  •  Blow out any accumulated metal dust.

Clean the torch leads

  • Wipe down or blow off the entire length of the torch leads to remove accumulated metal dust and dirt. (Metal dust can cause dissipation of the high voltage needed to start the plasma arc.)
  • Check for any kinked or worn hoses, exposed wires, cracked fittings, or other damage.
  • Check high frequency shielding for proper connection to earth ground.

Clean out the power supply  

  • Blow out any accumulated metal dust from the power supply using clean, dry, shop air.
  • Metal dust can cause damage to power supply components especially PC boards.
  • Contactors, relays and spark gap assemblies can also malfunction due to excess buildup of metal dust.
  • Check air filters on the power supply housing; replace as necessary.

Check torch cooling system

  • With water cooled torches check the coolant stream in the tank for signs of aspirated air or reduced flow. Make sure the return flow is at the specified gallons per minute.
  • Check flow switches on the return line to make sure they are functional. These prevent operation of the torch with low coolant flow, preventing overheating.
  • Check coolant filters and pump screens and clean or replace as necessary.
  • If available use a conductivity meter to check coolant resistivity.
  • The reading should not exceed 10 micromhos for most systems.
  • Coolant should be flushed and replenished every 6 months.

Check water quality  

  • Secondary water quality is particularly important with water injection torches.
  • Water hardness should not exceed 8.5 ppm or 0.5 grains.
  • Hard water causes mineral deposits to build up on nozzles leading to shortened life.
  • Use a commercial water softener if necessary.
  • Water quality in water tables is also important.
  • If the water in the table is heavily contaminated with slag and metal dust, it can cause hard starting of the plasma torch. It may also cause rust accumulation on the cut pieces necessitating more rework.

Check plasma gas quality

Plasma gas quality is critical to maintaining good parts life and cut quality.

  • To check air quality hold a clean paper towel under the torch while purging air through the system in the "TEST" mode.
  • Make sure there is no sign of contamination. Shop air systems are especially prone to contamination problems.
  • Check for water, oil mist, or particulate contamination.
  • Filters should be checked once a week; moisture traps should be emptied whenever they begin to accumulate water.

Clean machine and surrounding area  

  • Rails, gears and racks should be kept spotlessly clean.
  • Use a degreasing agent and an abrasive pad to remove grease, dirt, and metal dust.
  • Lubricate gears with dry lubricant such as graphite powder.
  • If bearings have grease fittings, lubricate them.
  • Rail sections should not be lubricated. Lubricants will attract contaminants leading to excessive wear.

Level and align rails  

  • Rails should be periodically checked and adjusted for levelness using an accurate level.
  • Check joints where rail sections meet with a piece of tool steel or other precision straight edge, feeling for any misalignment.
  • Filing may be needed to eliminate any difference in alignment not corrected through leveling.
  • Alignment of the rails is also important to prevent drag on drive motors.
  • Distances between the rails should be constant across entire length of system.

Align and adjust gears and bearings  

  • Gears should be in near perfect alignment to gear racks; they should not overlap above or below the rack.
  • Adjust gear alignment until no play is felt between gears and racks. These adjustments should be made for both rail and cross drives.
  • Alignment bearings should have minimal play between them and rail or cross rail surfaces.
  • These bearings are usually mounted on an eccentric.
  • Adjust until no light can be seen between bearing and rail surface.
  • Do not over-tighten. With drive gears disengaged, roll the beam across rails to make certain there is no binding.
  • Adjust accordingly until the beam rolls free with minimal vibration and very little resistance.

Posted in Welding Equipment , Tagged with Plasma

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