page_title: Hydraulic torque wrench
section_title: Reaction arm free torque wrenches
hierarchical_section_title: Hydraulic torque wrench / Reaction arm free torque wrenches
caption_attribution_description: English: Bolting made safer and easier with reaction washer
context_page_description: A hydraulic torque wrench is a power tool designed to exert torque on a fastener to achieve proper tightening or loosening of a connection through the use of hydraulics. A torque wrench is applied to the nut either directly or in conjunction with an impact socket. Hydraulic torque wrenches apply a predetermined, controlled amount of torque to a properly lubricated fastener.
  The hydraulic torque wrench was invented by George A. Sturdevant in Houston, Texas. The concept of a hydraulic powered torque wrench was first introduced on the market sometime in the early 1960s in a primitive form, and several key advances have been developed by manufacturers since that time which provided major advancements in the technology and usability of the tools far beyond the original concept tool.
  Today's tools offer benefits such as lighter weights, smaller nose radius dimensions for fitting into tight spaces, use of exotic alloys, actuation triggers on the tool itself, multi-position reaction members, 360° × 360° hose swivels, and the ability to run multiple tools simultaneously from a single power pack.
  There are two types of hydraulic torque wrenches: square drive and low profile.
context_section_description: The most dangerous part of a hydraulic torque wrench is the reaction member, often called reaction arm. When torque is applied to the bolt or nut, the reaction member abuts against a stationary object to stop the wrench from turning around the fastener. This reaction force is tremendous and accidents (for example pinched fingers) have happened more than once.
  Since 1994 it is possible to torque tighten bolts without the use of a reaction arm, and thus without a pinch point. This is a great breakthrough in the industry. Reaction arm free torqueing is possible due to the use of a reaction washer, or proprietary castle nut with a built-in sleeve. You must then use the same proprietary equipment to remove the same nuts. The knurled side of the washer holds on to the construction/flange and the bolt or nut turns over a smooth and through-hardened surface. The reaction washer will become a stationary object underneath the nut, eliminating the use of reaction arms.
caption: Bolting made safer and easier with reaction washer.
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