Hollow hydraulic torque wrenches are used for mechanical equipment and facilities in metallurgy, electric power, chemical industry, machinery, communications and other industries. The installation and disassembly and maintenance of important bolt connections are mainly composed of rotary joint mainframe, drive head, reaction arm and fixed bolt. Using high-strength light metal, large torque/weight ratio, double acting, high speed, large corner, high efficiency, no other tools are needed when loosening. Tubing rotary joint design, no space restriction, free operation; stable torque output, integrated power head, improve service life.