How to Prevent Air Bubbles in Syringe Barrel Dispensing

Keeping Air Out of Your Fluid Improves Deposit Accuracy and Repeatability

Are you experiencing oozing, drooling, or a little ball of material forming at the end of your dispense tip? If all of your dispenser settings are correct, this is likely a result of entrapped air. To prevent air from impacting deposit consistency when dispensing from a syringe barrel:

• For low-to-medium viscosity fluids, hold the barrel at an angle
  
  If you’re filling a syringe barrel with a low-to-medium viscosity fluid, be sure to hold the barrel at an angle to prevent air bubbles from forming. Plus, only fill the syringe to a maximum of 2/3 full regardless of the fluid’s viscosity. And be sure to use a piston to help keep air out of the fluid while dispensing.
  
  Another Useful Tip: Fill the syringe and insert the piston. Hold the syringe with the tip end facing upward and tap the syringe. Air bubbles will rise to the top. Next, remove the tip cap and push the piston slowly upward to remove large bubbles.

   

  
   
• For medium-to-high viscosity fluids, use a centrifuge
  
  When thicker fluids contain entrapped air, bubbles will compress and expand after each dispense cycle. You'll end up with oozing, a major cause of inconsistent deposits. Using a centrifuge to remove air prior to dispensing is the best fix.
  
  Keep in mind that prepackaged fluid is often degassed so this may be a bigger benefit if you're filling syringes at your facility. A centrifuge can be used to degas fluid syringes that you fill onsite.
  
  
  
• Store syringes in an upright position (with the tip cap facing down)
  
  Storing filled syringes this way overnight allows air pockets to rise to the top. For some fluids, you may need to pinch the barrel where the piston sits and push the piston down with the end of a pencil to purge any air that has risen.
  
  
  
  
  
  Another Useful Tip: Fluids prepackaged in syringe barrels are not always paired with the best piston for your application. This can cause inconsistent deposits. Optimum SmoothFlow pistons come in a variety of styles to optimize each unique dispensing process. Make sure the piston installed is the right one for your application.
  
  One Last Tip: Keeping air lines shorter than 5 feet is another way to minimize the risk of trapped air.

Tom Muccino

Tom Muccino is a Regional Sales Manager at Nordson EFD. He manages the sales team located in the Midwest to the West Coast of the U.S. and Canada. Tom has more than 30 years of fluid dispensing expertise. He joined Nordson EFD in 1987.