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Today I'm going to return to an ever-present problem of hydraulic equipment - oil leaks.

If you're serious about eliminating hydraulic leaks, then the scourge of your hydraulic plumbing is the tapered thread connection - NPT or BSPT.

I'm a big advocate of eliminating tapered threads from your hydraulic plumbing - but I also understand that sometimes, what's ideal is not always feasible.

When they can't be 'engineered out', this is how I deal with them:

First, don't waste your time with thread tape - I only ever use it when there's no thread sealing compound available. I've had best success with Loctite 567 and 577 (my favorite), which are pastes rather than liquids like some of the others.

If you're re-sealing a joint, thorough cleaning of the old adaptor and port is essential. If you're in your workshop, a brush wheel in a bench grinder does a marvellous job on the threads of the adaptor.

But the female threads in the port aren't so easy.

Once you've removed all remnants of thread tape or sealant, the next step is to use the appropriate Loctite cleaner.

Don't skip this step - you'll regret it.

Next, if you're not able to wait the 6 hours or so for acceptable cure strength, apply the Activator 7649 and allow it to dry. If you have the luxury of leaving the joint overnight before pressurizing it, you can skip this step.

Starting two threads back, apply a bead of paste around the entire circumference - completely filling the threads. Do the same with the female threads in the port.

Now torque the joint. And I'll have more to say about correct torque for taper fittings in your next hydraulics email in a few days time.

By Brendan Casey