PRESSURE RELIEF VALVE

857 070 49 PRESSURE RELIEF VALVE is basically your hydraulic system's safety net, kicking in to dump excess pressure back to tank when things get too high. It keeps your pumps, hoses, and cylinders from blowing seals or worse, especially when you hit a hard spot in the rock or if another valve sticks closed. Think of it as the last line of defense, making sure the whole system doesn't overpressurize and damage itself.

When this valve starts to go, you'll often notice the rig acting sluggish or just not getting the power it should, especially during heavy operations like collaring or tramming uphill. Sometimes you'll hear a constant 'hiss' or 'whine' from the valve itself, even when it shouldn't be actively relieving pressure. You might also see your pressure gauges fluctuating wildly, or the drill feed just won't hold steady, drifting down even when it's supposed to be locked in place. It's a clear sign that pressure isn't being managed correctly.

Replacing one of these isn't usually a huge job, but make sure you check the spring and the valve seat for any scoring or debris when you pull the old one out. That's a common oversight, and a little piece of grit can cause a brand new valve to leak internally. Also, always double-check your pressure settings after installation; don't just assume it's good to go right out of the box. A quick test with a calibrated gauge can save you a lot of headaches and downtime later on.