Fluid Dispensing 101: How to Fill a Syringe Barrel

A Simple Guide on How to Properly Fill a Syringe

How much have you thought about the process of filling syringe barrels? Have you considered there could be a different process that could eliminate trapped air, resulting in more accurate deposits?

In this blog post we’ll explain the two different ways to fill a syringe, how to select the best filling system based on how you get your fluid packaged, and helpful tips on how to get rid of air bubbles prior to dispensing.

Watch this video to learn more.

Bottom Filling

Bottom filling is beneficial with non-pourable fluids because it reduces the introduction of air bubbles, which can ruin deposit consistency and impact process control. With bottom filling, it’s easy to fill syringes without introducing air bubbles. Whether you get your fluid packaged in a caulking tube, cartridge, pail, or tank, we have a syringe barrel filling solution for you:

1. Our Atlas 940 Series filling system simplifies bottom filling from a caulking tube. This solution accommodates 3cc to 70cc syringes and includes a weighted indicator to show the maximum fill line at about two thirds full.


2. Our Equalizer is perfect for 2-part epoxies that are packaged in 50mL cartridges. This dispensing tool easily downpacks two-component materials into a single syringe barrel. Just make sure you order the transfer kit and follow these instructions for filling.


3. For materials packaged in 5-gallon straight wall pails, we suggest our manual pail pump to easily fill barrels for low-volume applications. Note that this method is best for greases and sealants and does require someone to manually bottom fill.


4. For very thick materials packed in cartridges, we offer a wide range of Atlas 920 Series barrel loaders to choose from based on the size of the cartridge you’re filling from.

Note: Even with bottom filling you may introduce air bubbles into your fluid if you don’t carefully manage the fill rate. If that happens, you can use a centrifuge to eliminate air bubbles prior to dispensing. Removing air helps your dispensing equipment deliver more accurate deposits and less rejects.

Top Filling

When working with thin fluids that are pourable, we recommend top filling. Some important things to remember is to have the tip cap sealed tightly so it doesn’t leak. Using a funnel when pouring fluids into a barrel is important, especially with glues that could otherwise adhere to your adapter if the fluid touches the top of the barrel.

Note: Top filling is more likely to introduce air bubbles than bottom filling. If you see bubbles in your fluid, first try purging them through the dispense tip by holding the barrel with the tip pointing up and applying back pressure to the piston.

Helpful Tips

Regardless of whether you’re top filling or bottom filling, it is important to keep a watchful eye on where the piston meets the fluid line. When you’re bottom filling, you need to keep a constant force on the piston as it’s being filled to prevent air pockets from forming. You may also have to adjust the speed of the fill to avoid air entrapment. When you’re top filling, gently squeeze the sides of the barrel as you’re inserting a piston so that air bleeds past it instead of getting trapped underneath.

Overall, the goal is to be able to fill a syringe with as little air as possible. You need to first identify what fluid you’re working with to identify if you should be bottom filling or top filling. Then think about how your material is packaged, which will help you find the best filling system. Lastly, it is important to keep an eye on where the piston meets the fluid, so you can adjust the fill rate and pressure on the piston to prevent air entrapment. This will set you up for better dispensing in the future.

For more details about Nordson EFD’s Optimum dispensing component systems, download this guide.

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.