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ASTM D4738 1990 Edition, January 5, 1990
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Standard Practice for Calibration of Upright Cylindrical Tanks Using the Optical Reference Line Method
Includes all amendments and changes through Editorial Change 1, January 5, 1990
Additional Comments: W/D 1995 NO S/S
Page Count:4
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1. Scope

1.1 This practice describes measurement and calculation procedures for determining the diameters of upright welded (lap/butt) cylindrical tanks or vertical cylindrical tanks with smooth outside surface with either floating or fixed roofs. This practice should be used in conjunction with API Standard 2550. There are a few occasions when there may be limitations to the application of the ORLM techniques described in this standard. Specifically, the use of the ORLM is not suitable for:

1.1.1 Abnormally deformed (for example, severely dented or having visible signs of damage) tanks. These tanks are excluded from this practice and should be repaired prior to calibration.

1.1.2 Outside measurement of insulated tanks, For application of ORLM, the insulation must be stripped, if possible. ORLM may be used on the interior of the tank; however, the reference circumference on the bottom course must be measured externally if possible, requiring the removal of insulation at the bottom course. This measurement shall conform to the procedures described in API Standard 2550.

1.3 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

1.4 The values in inch-pound units are the preferred units. The values in parentheses are for information only.