Flange joints should align without excessive stress. When a joint is out of alignment it means that the bolts cannot be installed.
Alignment tools are designed to move the joint precisely until the bolts are able to be inserted. The tools provide the capability of moving the joint until it complies with the piping code for lateral and rotational misalignment.
The ASME Piping code B31.3 (1999 Edition) 335.1.1 9 (c) specifies the following Flange Joint Misalignment Tolerances:
The maximum for lateral or center-line offset is 1.5 mm or less than 1/16”. For rotational misalignment the Piping code specifies that it be a maximum 3 mm or less than 1/8”.
The above tolerances refers to pipe work being connected to pumps, rotating equipment & pressure vessels.