Troubleshooting a Damaged Plasma Nozzle at Startup


WARNING: Plasma cutting system maintenance and repair should only be attempted by those skilled in electrical troubleshooting. Plasma cutting systems use high voltage and direct-current (DC) electricity. Electric shock can injure or kill.

Remember the phrase, proper preparation prevents poor performance? This is good advice for any plasma cutting operators to consider before firing up their torch. In fact, many common troubleshooting issues around plasma cutting, including handling a damaged nozzle at startup, can be identified and potentially corrected in a preventative visual check during setup.

The plasma nozzle itself is designed to optimize the pilot and cutting arcs with very little wiggle room. Therefore, if there’s a problem with the torch not firing, transferring or cutting, the pilot arc is a good place to begin diagnosing the problem. First, check that the arc color is a bright white-blue color and that it sounds smooth and steady when firing. If the arc only fires intermittently and makes a sputtering noise, this may be a case of hard starting.

Hard starting

This is caused when the high frequency can’t penetrate the high-pressure barrier that exists between the electrode and nozzle. To correct this, double-check the factory-recommended settings for gas pressure and flow to ensure that the pressure is at the right level for optimal performance. When the pressure is too high, the pilot arc gets blown out before it establishes itself. 

Clean the hoses and wires

Inspect these for any dirt, damage, loose connections or wear. Keep the hoses and wires clean so they can carry gas and power to the torch efficiently so that no energy is lost. Use an air hose to blow the leads or wipe them with a clean cloth. In addition, clean and re-gap the spark-gap assembly, as dirt and dust can erode the spark-gap electrodes. 

Weak, blue spark at torch or no spark

If the spark at the torch is weak and small, then it’s likely that the pilot arc has no direct current. Check for bad coils in the pilot arc relay or worn contacts or a defective pilot resistor. If there’s no visible spark at the torch at all, you’ll want to double-check that there’s AC power going to your generator or that it’s in good working order. In addition, inspect the capacitors to make sure they aren’t defective or that the spark-gap assembly isn’t damaged.

Ways to avoid premature wearing of your consumables

One common plasma nozzle problem occurs when the orifice becomes blocked, sometimes due to molten material contacting the tip and then cooling down and hardening there, altering the plasma flow. Be sure to keep your torch at the proper distance from the workpiece material after the pilot arc transfers until gradually lowering it as the hole gets deeper.

Excessive piloting, or the amount of time that an arc is initiated before it’s actually transferred onto the workpiece, can result in overall erosion of orifice allowing the arc to diffuse prematurely. An off-center stream will steadily wear down the orifice. As your cutting technique improves, that will also reduce the stress and wear on your torch and other equipment.

Finally, proper inspection, cleaning and maintenance before and after each cutting session can truly extend the life of your equipment, saving you money and wasted time in the shop.


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