Hose barbs are a common feature on fittings and connectors. However, several key factors need to be considered when designing these. This column discusses how all barbs are not created equal.
Q: I have an application that requires me to design a molded hose barb. What key factors should be considered?
A: Sealing a length of flexible tubing on a barb seems like a straightforward process. Create a barb and shove the tubing over it. However, anyone that has worked with hose barb and tubing, whether on their home irrigation system or a complex medical device knows that not all barbs are created equal.
There are three key factors to consider when specifying a hose barb for your application: outer diameter, sharpness, and the manufacturing process.
The outer diameter or OD of the barb relative to the inner diameter (ID) of the tubing is the first key factor to consider. The larger the OD, the more stretch on the barb which will increase the pull off force of the barb. Need more pull off force? Then increase the OD. However, the tradeoff is higher assembly force, so balance is critical.
The second factor is barb sharpness. The sharper the barb the more holding force as the barb grips the tubing. A sharper barb will help increase pull off force without requiring an excessively large OD, which would increase the assembly force.
The OD and the sharpness are the key factor in tubing pull off resistance. Some may say the number of barbs matter, but if the barb is poorly made, it doesn’t matter how many you have, the tubing will pull off. Assuming they are made well, with the correct barb size and sharpness, single hose barbs tend to work better with soft stretchy tubing, and multiple barbs tend to work over a broader range of durometers, especially with stiffer tubing materials.
Finally the manufacturing process can play a significant role in the performance of a hose barb. Advanced manufacturing techniques can create multiple sharp barbs, but cheap tooling will result in rounded barbs and poorer performance. Parting lines on molded parts are natural leak paths so these must be minimized or avoided if possible.