With reference to starting air receivers, explain why they should be drained frequently and describe the procedure for inspecting their internal surfaces, indicating possible defects?

flowchart TD
    A[Start: Isolate receiver] --> B[Depressurize & drain completely]
    B --> C[Open manhole/inspection door]
    C --> D[Internal visual inspection]
    D --> E{Defects found?}
    E -->|Yes| F[Record: corrosion, pitting, cracks, scale, oil residue]
    E -->|No| G[Check relief valves & fusible plugs]
    F --> G
    G --> H[Test drain lines clear]
    H --> I[Close up, pressure test if required]
    I --> J[Log in maintenance records]

• Drain reason: condensate and oil carry-over creates fire/explosion risk in the air system
• Drain frequency: regularly; cooler drains open automatically on stop and timed cycle while running
• Access: inner surfaces must be examinable and cleanable; manhole large enough for entry where practicable
• Protection: efficient drains, relief valves, fusible plugs required
• Inspection scope: internal examination for corrosion and pitting; relief valves overhauled and tested; all valves opened for inspection; drain lines proven clear
• Possible defects: corrosion, pitting, cracks, scale, oil residue, moisture accumulation
• Test alternative: if too small for entry, hydraulic test at 1.5 × max working pressure
• Stamping: test authority, test pressure, working pressure, date, surveyor’s initials over access hole
• As EOOW: verify drains clear, log inspection, report defects to Chief Engineer, ensure relief/fusible devices functional