Have you ever had a hose “bubble” right behind, or very near, the fitting?
Your hose assembly is extremely vulnerable nearest the fitting. Therefore, it is very important to select the proper fitting to match the hose and application.
Let’s look at a rubber 300 psi multipurpose air and water hose and review the two most common reasons this may happen.
Fitting too aggressive
Many distributors have a crimper for their hydraulic hoses and will crimp a hydraulic fitting with its barbed end onto a rubber multipurpose hose, sometimes, without issue. However, you need to select the proper fitting to match both the construction and pressure rating to the hose. (FYI – a hydraulic style fitting is not recommended for use on a standard air and multipurpose hose).
If the barbs on the fitting are too aggressive, they will bite through the tube causing a leak path. Material being conveyed through the tube will find the path of least resistance, and when the pressure builds up, air or water will escape through this leak path to form a bubble behind the fitting.
Or, the material will wick its way through hose by following the reinforcement, and where ever the cover is compromised, and that’s where the bubble will form.
You may think you need a more aggressive fitting for a hose with a high working pressure. However, the best course of action is to check with a reputable fitting manufacturer for a suitable fitting recommendation and coupling procedure.
Another cause of a hose failure right behind the fitting is because this is where the greatest amount of flexing and stress is put on the hose. If the hose bends at the point where the stem of the fitting ends, there is an opportunity for the stem to cut into the tube of the hose, and causes a similar scenario, where material migrates through the leak path and a bubble is formed.
Using a bend restrictor, spring, or strain reliever can reduce the amount of wear at this vulnerable point.
What to do
If you question whether the fitting or crimp is incorrect, or if the hose has a manufacturing defect, it is essential you return the end of the hose with the fitting intact to the manufacturer or fabricator of the hose. They need to see how the fitting was installed, then examine the tube of the hose where the fitting was in contact, to identify the problem and recommend a solution.