Abrasive Backflow Detect and Clean Abrasive Hose
Backflow is a common occurrence in all Waterjets, where water is unable to exit the nozzle and instead backs up through the abrasive hose. The longer backflow is left unnoticed, the more damage it will do to the abrasive system and the longer the subsequent cleaning. WAZER incorporates a sensor to immediately pause cutting once a backflow is detected, so you only need to clean a small portion of the abrasive system afterwards
Tools Needed
Compressed air source
Safety goggles and respiratory protection.
Paper Towel
Procedure
1. Take a look at the UI screen and make sure the machine paused with “Backflow detected” error message on the screen.
This means the controller registers a backflow event.
2. Move to the left side of the machine, pull out the hopper, and locate the backflow sensor.
The backflow is detected by the backflow sensor attached to the abrasive hose.
The backflow sensor detects a drop in electric resistance across its two terminals and the controller takes that as a backflow taking place.
You will notice there are two similar sections of the sensor. The section with two wires connected to the tank wall is the static discharging section. When abrasives flow through the abrasive hose, a lot of static is built up. The static sometimes gives a false signal to the controller so it has to be discharged. Keep the two wires connected.
3. . Move the bottom of the hopper. Disconnect the abrasive hose from the rubber catcher.
[CAUTION] Put on goggles and respiratory protection
4. Conduct a quick abrasive flow check by pressing the pinch valve.
If the abrasive is flowing steadily as shown in the picture, the catcher and drop tube is not affected by the backflow
If the abrasive is not flowing or flowing very slowly, you will need to clear the hopper by following instructions on this page.
Good Abrasive Flow
No Abrasive Flowing
5. Move to the cutting area. Keep the machine paused, open the door window
6. Disconnect the abrasive hose from the nozzle mixing chamber, inspect the hose tip. You will notice the tip is most likely blocked by wet abrasives.
7. Keep the abrasive hose disconnected, and close the door window.
8. Move to the bottom of the hopper, use a compressed air source (set to no more than 35 psi) to blow into the end of the abrasive hose from the hopper side.
[NOTICE] Make sure the air pressure is set lower than 35PSI (0.25Mpa), otherwise the clogged abrasive hose may puncture.
[CAUTION] Wet Abrasive will come out of the end of the abrasive hose on the cutting head side, and may whip around due to the pressure. As a result, keep the door window closed, and put on goggles and respiratory protection)
9. The abrasive hose may come apart at the backflow sensors, when this happens please follow the diagram below to reassemble it.
10. Keep the compressed air on for another 5 seconds, making sure the hose tip has nothing but air being expelled.
If there is no air, the dry abrasive hose is pinched, kinked, or clogged. Please inspect the hose path and revert back to step 9.
11. Use a compressed air source to blow off wet abrasive in the abrasive side port in the mixing chamber.
12. Reconnect dry abrasive hose end to the rubber catcher, and also the other end to the abrasive side port of nozzle assembly. Make sure O-rings on both ends are seated into their respective holes
Follow-Ups
13. Resume the cutting. Stay with the WAZER for another 2 min to ensure the cut is not paused for backflow again.
If so, please take a look at the troubleshooting article for recurring backflow.
Next Time
Abrasive backflow generally happens due to the following causes:
High pressure system malfunction and pressure dropped
Nozzle assembly touched the workpiece
Abrasive particles clogged the nozzle tip
To address the first cause, pay attention to the high pressure gauge and ensure the pressure stays within the green zone during cutting. If anything abnormal happens, contact customer service.
You can check for a backflow due to HP system malfunction by removing the abrasive hose and running a Nozzle Purge. If water is seen exiting the abrasive hose inlet, a backflow will occur.
To address the second cause, make sure the cut bed is leveled at 4 corners and the cut bed is not dipped or humped in the middle.
This can also be due to the material moving or bending during the cut. Ensure your material is secured to the bed and watch for any pop-ups.
To address the third cause, ensure no water droplets find their way into the hopper, and use the screen to sieve the abrasive while filling the hopper