Let’s say you’re working on some kind of device or component that receives, outputs, or transfers a fluid, such as water or coolant. This could be in an automotive system, a piece of machinery, liquid-cooled equipment, or any other part that has flexible tubing or hoses connected to it.
There are a couple of things you could do.
You could disconnect the hoses and work quickly, hoping that very little liquid spills out all over the place. Or, you could grab pinch-off pliers and clamp the tubing shut so that you can disconnect them without having to deal with a lot of spillage.
Pinch-off pliers shut off the flow through flexible tubing so that you can remove or work on attached components.
Sometimes you will see these called hose pinch pliers.
When designing and building air or water loops for small projects that involve flexible tubing, I will usually incorporate shut-off quick disconnect valves around components that I know will be removed and reinstalled regularly. Even so, I find myself using pinch-off pliers when other components need maintenance or replacing.
Pinch-off pliers can be used on a wide range of flexible tubing, such as vacuum lines, fuel lines, and coolant lines. The larger the tool, the larger the maximum diameter of tubing it can securely pinch closed.
Plastic pinch-off tools are available, but parallel-jawed pliers, such as the SK Hand Tools version shown above, are often a better buy. The jaws swivel, and so you create a parallel pinching force every time.
The kind I use look like the SK version, but under Craftsman and KD Tools branding. A lot of other brands – especially those that manufacture tools for automotive and aerospace industries – offer similar tools.
You can sometimes get away with using other types of tools to pinch off tubing, but unless the jaws are parallel, wide, and smooth like these pliers, you run the risk of damaging and even compromising the tubing.
The Craftsman and KD pinch-off pliers that I use can be hard to open, but I don’t really see that as a downside. After all, if they require a little muscle to open, that means there’s less risk that the pliers will release unintentionally on their own.
These pliers can be used anywhere along a length of tubing to shut off flow at that point, but I generally try to avoid using them right on top of where tubing or a hose is attached to a fitting.
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