Troubleshooting Coupling Failures

In this week’s Primed Insight, Graeme Thomas explains the 3 Most Common causes behind coupling/fitting/hose failures as well as how to remedy them.

Welcome to this week’s Primed Insight. My name’s Graeme Thomas. I’m a director at Blastone and we had a call from some customers. Two different job sites last week where their hose and couplings were coming apart in the field, which can be very dangerous.

So, what I’d like to do is review the three most common issues we see and make sure that you can eliminate them from your job site. The first is incorrect selection of the coupling and hose, a non-mating set.

I suggest you go to the Bluestone catalogue on page 132 to 137, it has the correct selection tables for the hose, the coupling, the gaskets and the screws. If you don’t have a copy, please contact us and we’ll happily send you one.

The second common reason for hose coupling failure is incorrect hose fitting. There’re two things to look out for. The first is that the hose must be cut clean and square. We supply hose cutting tool for this and we do not recommend the use of a saw or a handheld knife.

Next is that the hose must be pushed right up to the shoulder and check that it’s up against the shoulder. If it’s not up against the shoulder you will have premature failure.

The next area to pay careful attention to is the screws. This may seem very simple but it’s very important because they’re going into a soft rubber substrate and the amount that they are screwed in is very important for the integrity of the coupling.

It’s common for them to be put in and then the rubber to be stripped out which creates a premature wear point. The rubber is designed to seal against the screw and if I strip out a piece of that rubber, I’ve got an early failure point.

The other common mistake is to bring the screw in until it meets the shoulder but no further, that of course, has pushed the rubber down into a dimple inside the hose which you can feel with your finger and it still hasn’t fully bitten into the hose. So, you need to continue to turn the screw, one to two more rotations until that dimple is pulled back up inside the hose and it is properly bedded into the rubber. This will secure the hose to the coupling so it can’t come off.

Third most common cause of hose coupling failure is either incorrect handling of the hose or incorrect placement. It’s important to remember that the hose coupling interface cannot be used to take the strain of whipping on startup or of the weight of the hose.

So, wherever hose is suspended it needs to be restrained each side of the coupling. Most common wear that we see that is on either bridges or running up a vertical structure such as scaffolding.

Each time there’s a coupling joint restrain it back to the structure either with a strap or a rope each side of the coupling. And then when we’re moving hose, maybe in a Dockyard maybe in a blast yard, it’s important that the hose is not dragged along by machinery such as a skid steer loader or a forklift, but it’s coiled up and then moved. Because again the coupling will have too much force applied and can come apart and lead to premature failure.

Thanks for watching this week’s Primed Insight.

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