First I will start with the basics. A hydraulic torque is designed to exert torque on some sort of fastener. The goal can be to quickly and securely fasten or loosen various nuts. They apply an amount of torque to a lubricated fastener beyond what a human could muster, usually in conjunction with an impact socket. They were first introduced in the 1960's, but have evolved considerably since that time due to manufacturers constantly updating and advancing their designs. This has lead to the modern hydraulic torque wrench, one which is light due to exotic alloys, having a smaller nose radius to increase the number of spaces it will fit into, possessing multi-position reaction members, and you can even now run multiple tools off of one power pack simultaneously. Today's modern torque wrenches are optimized for efficiency and flexibility in their uses.

What makes a hydraulic torque wrench work is that it generates torque using only hydraulic means, it is self ratcheting, and it must have an accurate way to measure the amount of torque applied to the fastener. A holding pawl design is popular amongst most manufacturers to lock the wrench in position, but each have some claim that there design is superior. I say whichever one works, works. These wrenches typically have an accuracy rating of +/- 3%, with a high repeatability rate. This makes them suitable for large bolts that need a high degree of accuracy. The biggest advantage of a hydraulic wrench doesn't have anything to do with performance, but with those who use them - these torque wrenches are significantly quieter than similar output pneumatic impact wrenches. That is a benefit that you can't measure in strength, repeatability, or work output increases - it is about the health of those who use it.

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