Hydraulic torque wrenches are designed to tighten or loosen fasteners which require large amounts of force to achieve the proper preload. In contrast to hydraulic tensioning devices which directly stretch a bolt, these wrenches apply a turning force, or torque to a nut or bolt head which causes the bolt thread to advance. Some hydraulic torque wrenches use impact sockets, while low clearance wrenches use interchangeable heads for different nut sizes. This video describes the operation of a typical system. Systems may vary, so it is important to use the specific operating instructions for the wrench and pump that you are using. A typical system consists of a wrench body, sockets or heads, hoses, and a source of hydraulic pressure. Be sure that all parts of the system meet the specifications of the wrench manufacturer, inspect all components for damage before use. To begin, inspect the hoses and make sure that the fittings are clean and tight. Dirt and debris in the system may damage the pump, valves or wrench. Loose fittings may leak or burst. If a leak occurs, shut off the pump and depressurize the system. Never grasp a leaking hose. The pressurized fluid may cause serious injury. Choose the proper size socket or wrench head. To install a drive head on this wrench, slide the body onto the head until it is fully seated. Then push in the retaining pin, making sure that it is completely engaged. Next, make sure that the pump is off and that the system is depressurized, then connect and tighten the hoses. This pump unit has three control switches, an odd off switch on the unit itself, and two switches on a control pendant. Let's look at the function of each. The main switch, located next to the motor, controls all power to the system. It must be in the on position for operation. The pendant houses a three position rocker switch and a momentary push button. Pressing the run side of the rocker starts the pump and sends pressure to the wrench for tightening or loosening. The rocker must be held in this position, since it is spring loaded to the center. The center position releases pressure and retracts the wrench piston, causing the wrench head to ratchet back for the next torque cycle. The pump is running when the switch is in the center position. The stop position turns off the pump. The set button is used when adjusting pump pressure. The torque applied to the fastener depends on the pressure developed by the pump, so pump pressure must be adjusted to provide the proper torque value. This pressure and torque table applies to several wrench models. In this demonstration, we will use Model TWLC2. The bolt torque range is 600 to 650 foot-pounds. A pressure setting of 4000 psi will exert 630 foot-pounds of torque at the wrench. To adjust pressure, be sure the system is fully connected, then turn on the pump switch. Press the run switch to start the pump and press and hold the set button. Turn the adjustment knob until the gauge shows the correct pressure. Place the wrench on the fastener. Be sure that it is fully seated and that the reaction pad seats firmly. Low clearance wrenches have a reaction pad designed to brace against an adjacent nut. Whenever possible, this pad should contact a flat, not a corner. The pad is a pinch point, so keep hands away from the wrench when applying to it. Square drive wrenches use a reaction arm that can be rotated to a secure position. Adjust the arm so that it is braced firmly against the structure. Using the pump control, advance the wrench so that it rotates the nut. When the wrench reaches the end of a stroke, pump pressure will peak. Retract the wrench that apply pressure for another stroke. Continue this cycle until the nut stops turning. When the nut is fully torqued, pressure will peak and rotation will stop before the wrench comes to the end of a stroke. This is called stalling. To ensure that the nut is torqued, retract the wrench and apply another forward stroke. If the nut does not move, the torque procedure is finished. Using hydraulic wrenches to loosen a fastener can be difficult, depending on how badly it is corroded. A bolt with light rust may require up to three times the tightening torque pressure to break free. Be sure that the tooling and reaction surface are strong enough to bear this loading. Once the nut is free, use an impact wrench to remove it. Never strike the wrench or fastener when loosening. This may cause wrench damage or injury to the operator. Be sure to review the specific operating instructions for all system components before using any hydraulic torque wrench. Thanks for watching.