Industrial piping identification: in chemical plants, oxygen-carrying pipelines are painted with which standard line color for quick recognition and safety?

Introduction / Context:
Color coding of industrial pipelines is a fundamental safety practice. It enables operators and maintenance teams to instantly recognize the service contained in a line, preventing accidental cross-connections and improving emergency response. Oxygen service, in particular, must be clearly distinguished because it strongly promotes combustion and requires strict cleanliness standards.

Given Data / Assumptions:

• Context is general chemical-plant piping color standards used for service identification.
• We focus on line (pipe) color, not compressed-gas cylinder body/shoulder colors.
• The question tests recall of the standard color commonly assigned to oxygen lines.

Concept / Approach:
Standard industrial schemes (widely adopted plant codes) assign blue to oxygen pipelines. While local or national standards can vary in shade or in auxiliary banding, the base identification for oxygen in plant piping is blue, aiding rapid visual identification near manifolds, headers, and equipment tie-ins.

Step-by-Step Solution:

Verification / Alternative check:
Typical plant standards, vendor P&ID legends, and pipe-marking guidelines consistently depict oxygen service with a blue base color and appropriate text arrows/markers.

Why Other Options Are Wrong:

• Yellow: frequently used for flammable gases; not oxygen.
• Black/Green: often used for different utilities (e.g., waste lines, water) depending on scheme.
• Red: commonly fire water, not oxygen.

Common Pitfalls:
Confusing cylinder color codes with pipeline color codes; relying on memory from a different regional standard without checking the plant legend.

Final Answer:
Blue