The Dreaded Abrasive Clog

The most common issue any water jet user will likely encounter is the infamous abrasive clog. It is unfortunate whenever a clog in the abrasive system forms. I would like to share how the abrasive system works, how to resolve a clog in the easiest way, and how to avoid clogs as best as possible.

How Does the System Work?
Essentially, there is a controlled amount of abrasive guided through the Abrasive Drawer output. That metered amount is then pulled into the cutting head through a venturi effect created by high pressure water exiting the head. The diagram below is a great illustration.

  • No High Pressure Water = No movement after the output.
  • Clog in the Hose = No movement after the output.
  • Clog in the output = No movement at all.

How to Resolve Abrasive Clogs?
Essentially, there are three possible clogging locations. I will list them from 1-3, with 1 being the most common and 3 being the least likely.

  1. Hose Clog - Disconnect the abrasive hose from the cutting head and the catch under the Drawer. Blow compressed air through the hose from the drawer end up. The end inside the tank should flail around wildly when the clog has been pushed through. Compressed air is the best in order to get all moisture and wet sand out.
  2. Drawer Clog - Empty the Abrasive Drawer of dry abrasive. Find the center drop piece, manually open the pinch valve and lightly blow compressed air through the drop tube. Be careful to manually open the pinch and use light air - the drop tube is rubber and can tear under harsh conditions.
  3. Nozzle Tip Clog - Unlikely as this is due to too much abrasive or too many small grains of abrasive entering the tip. To resolve this, measure the abrasive flow from the drawer output. Make sure it is within spec. Afterwards, clear the clog in the tip by inserting it upside down in the cutting head and performing a Nozzle Purge.

How to Avoid Clogs?

  • Use Barton ALLTEK HPA 80 Mesh.
  • Make sure the cut bed is level to the cutting head.
  • Utilize plenty of tabs to hold materials to the bed.
  • When using thin flexible materials, make sure the middle of the material does not bow upwards at any time. The bubbling water under the material will push upwards.
  • When using the black height tool, swivel it side-to-side underneath the cutting head to give yourself spare height between the material and nozzle tip.
  • Measure the abrasive flow-rate. Make sure it is within spec (130-150 g/min).
  • Make sure the input water gauge stays in the green during the entire cut.
  • Verify the high pressure orifice is in good condition.
  • Check that the nozzle tip is fully seated into the cutting head.

I get backflow all the time and it makes our Wazer very unreliable. For any cut lasting longer than 10 minutes, I assume it’s going to fail at some point during the cut due to backflow / loss of abrasive flow. I am at a total loss for the underlying cause.

All of the recommendations in this article are followed, and our nozzle tip is not coming into contact with the material (we have been setting it extra high to avoid this, and it still happens). Our abrasive flow rate coming out of the drawer is within spec. The nozzle kit is brand new with good orifice health. Pump pressure is good at 4000psi. Inlet water pressure is good (70-85psi) and stable. For what other reasons could we be experiencing backflow on a regular basis?

Hi @tk4b! Welcome to the Forum!

If you are practicing all of the points listed above, it is certainly odd to see such consistent abrasive clogs. The next time it happens, I recommend trying to identify exactly where the clog starts and ends. Perhaps the abrasive being used is not within normal specs. (Bad batch, not dry, etc.)

Check the following locations -

  • Remove the nozzle tip from the cutting head and look inside.
  • Feel along the length of the abrasive hose. Start from the cutting head and work back.

If we can identify exactly where the clog is or isn’t, that may help narrow down the root cause of this issue!

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I also get backflow when cutting stained glass. I found that the glass is thicker in spots causing the head to get too close to the glass. So I move the head around before setup to see the highest point and set it there. After I had figured that out it works fine.

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