Clean and lubricate stud threads, hand tighten all nuts. Use a torque wrench to tighten nuts to the required torque. Tighten nuts in an even criss-cross sequence. Torque values may vary depending upon bolt, ambient and operating conditions. Use the lowest torque possible to achieve a good seal for the required operating conditions. Increase torque with increasing temperature/pressure conditions. Use lowest torque with cup washers, gasket joints or in piping which may frequently be disassembled.
Nuts should be re-torque after at least 24 hrs. Recommended torque values should not be exceeded unless necessary to effect a tight seal. Retorque nuts annually. Gaskets are not required unless flanges are mated with a different material e.g. reinforced plastic, reinforced glass, bare metal, ceramic, etc.
Note: The torque values given above are a guide and may be exceeded by not more than 50% of the recommended value to effect a seal. Once this torque level has been reached and a seal has not been achieved, it is likely that there is another cause.
If a leak occurs, loosen the bolt opposite the leaking side slightly and then tighten the bolt on the leaking side by the same amount. This procedure avoids over tightening. If the leak persists, then the flange should be disconnected and the flare seal inspected for damage. Slight scratches can be polished with a fine abrasive paper provided thickness of the lining is not reduced excessively.