Metal tubing fluid lines are sized by what criteria?

• A. Inner diameter only
• B. Wall thickness and outside diameter
• C. Length only
• D. Material type

Answer: (B)

Metal tubing fluid lines are sized primarily based on wall thickness and outside diameter. This is essential because the wall thickness contributes to the strength and pressure rating of the tubing, while the outside diameter is crucial for ensuring compatibility with fittings and other components in the fluid line system.

Understanding the wall thickness is important for applications that involve high pressure, as it affects the tubing's ability to withstand the internal forces from the fluid pressure. Additionally, the outside diameter is necessary to guarantee that the tubing can be securely connected to valves, connectors, and other fittings, which often have specific requirements for size compatibility.

The criteria of inner diameter alone does not provide a complete picture, as it omits the influence of the wall thickness. Length and material type, while factors in fluid line systems, do not define the sizing of the tubing itself, making them less relevant in the context of this question.