April 27, 2007



Common Mechanical Purge Gun Problems:


  1. 1. Material leaks when trigger not pulled:


-Coupling block seals leaking. They are either scratched or damaged.


-Leaking material around front of gun. The pattern control disc retainer is not tight.




  1. 2. Low volume of material:


-Restricted mixing module.


-Low spray pressure.




  1. 3. Gun blows air while trigger is pulled. Air escapes around bottom of gun:


-”O” rings in trigger valve shaft are worn or broken.




  1. 4. Low spray pressure:


-Restricted air flow.


-Solids are on isocyanate(ISO)pump rod or in wet cup.


- Regulator is not adjusted properly and/or is not operating correctly.


  1. 5. Trigger sticks:


-Build up of solids on valving rod.


  1. 6. Material steams the dose but does not atomize:


-Low heat; check thermometers and hose temperature setting. Is the hose up to the correct temperature?


-Low spray pressure.


7. Spotting small amount of uncured material on surface of product:


-Worn module.


-Adjust the forward stop.


8. Air leaks from gun valve assembly:


-Worn or broken “O” rings.


9. Cross over:


-Polymerized material in the check valves.


-Cross over is caused by material from one side pushing its way across the mixing module into the other side.


-Never start spraying with large difference in pressure such as one side at a low pressure and the other

at a high pressure.


-Always equalize pressure before spraying.


-A back up into the check valve assembly is a sure sign of a worn check valve. Replace check valve assembly.