API MPMS 2.2B:1989 (R2013)

This standard describes measurement and calculation procedures for determining the diameters of upright welded (lap/butt) cylindrical tanks, or vertical cylindrical tanks, with a smooth outside surface and either floating or fixed roofs. This standard should be used in conjunction with API Standard 2550. For external application of the ORLM on insulated tanks, the insulation must be removed. The ORLM may be used on the interior of the tank; however, when the reference circumference on the bottom course is established externally, the insulation at the bottom ring must be removed. This measurement shall conform to the procedures described in API Standard 2550. Abnormally deformed tanks (that is, tanks that are dented or have other visible signs of damage) should be repaired before any calibration is undertaken.