If you’re trying to tighten a fastener, and need to apply a powerful but controlled amount of torque to do so, you’ll want to get yourself a good hydraulic torque wrench. Once you handle your torque wrench calibration, you’ll be able to apply the power of hydraulics and produce a carefully measured and controlled amount of torque.
The original technology for the hydraulic wrench dates back to the 1960s, but designs for modern hydraulic torque wrenches have evolved considerably. They’re available in all shapes and sizes, with profiles that can accommodate turning huge nuts or working in tight, narrow spaces.
Hydraulic torque wrenches have to have three characteristics: they self ratchet, they generate torque using only hydraulics and they have some means of accurately measuring how much torque is generated. Knowing the right way to use hydraulic torque wrenches is important, too, because improper use can damage your equipment. You can get comparable torque out of pneumatic impact wrenches, but hydraulic torque wrenches are best used when you need to be very accurate, but still produce a large amount of pressure.
References: www.titanti.com