Question 318General Subjects - QMED

The correct answer is D) nominal outside diameter. Tubing is sized by its nominal outside diameter, which is the standard measurement used to identify the size of the tubing. This is the common industry practice and is specified in various standards and regulations related to the use of tubing. The other options are incorrect because: A) Nominal inside diameter is not the primary way tubing is sized, as the outside diameter is the more commonly used and standardized measurement. B) Allowed working pressure is a separate specification that is not directly related to the size of the tubing. C) Cross-section area is not the primary way tubing is sized, as the outside diameter is the more relevant measurement.