Abstract: A safety wrench for coupling and uncoupling hammer union type connections employs a spring biased retractable bolt to apply a blow to the union lug. In use the bolt is retracted rearward to compress compression springs positioned within an internal spring bore in the bolt to a position away from the lug of the union to be rotated. When the bolt is disengaged from the ratchet mechanism, the compression springs rapidly extend to rapidly move the bolt forward to impact the union lug and rotate the union. The bolt may be retracted by a hydraulic or pneumatic cylinder, a hand lever, or a rack and pinion mechanism. Reversing the position of the safety wrench on the union lug will allow the union to be rotated in the opposite direction.