Patent ID: 7571667

Claim:
A power tong for use during installation and dismantling of pipes when drilling in the ground, said power tong comprising a drive ring and at least one clamping device where the clamping device is arranged to grip a pipe string, the power tong being equipped with a driving mechanism for rotation of the clamping device about a longitudinal axis of the pipe string, and where the clamping device communicates with a fluid supply via a swivel ring that encircles the drive ring, and a plurality of the clamping devices are gathered in a group, where the group of clamping devices are removable from the drive ring; the clamping device having at least one piston in a cylinder, the piston communicating with the fluid supply via the swivel ring that encircles the drive ring, the cylinder and the piston are double acting, wherein a plus side of the piston is in communication with a first passage in the swivel ring; and a minus side of the piston is in communication with a second passage in the swivel ring.