Inspection, Maintenance and Testing
Inspection, Maintenance and Testing
This domain tests how operators and inspectors find degradation before failure: external and internal inspection, nondestructive examination, hydrostatic testing, safety-valve testing, and maintenance records. Expect questions on what a test proves and what it does not.
Core rules and concepts
- External inspection checks leaks, insulation damage, supports, expansion, gauge glass condition, and safety-valve condition.
- Internal inspection looks for corrosion, scale, cracks, tube thinning, refractory damage, and debris. The waterside and fireside must both be examined.
- Nondestructive examination may include visual, ultrasonic thickness, magnetic particle, dye penetrant, and radiographic methods. Each finds different defects.
- Hydrostatic testing proves pressure tightness and structural integrity at a specified test pressure, but it does not prove operating performance or safety-valve set pressure.
- Safety valves are tested for set pressure and leak tightness. Jurisdictional rules and NBIC guidance govern inspection intervals and repairs.
Worked example
A boiler has a maximum allowable working pressure of 150 psig. A typical code hydrostatic test is 1.5 times MAWP, or 225 psig. The test gauge should have a suitable range and be calibrated; the boiler should be filled with water at a controlled temperature, vents opened to remove air, and the pressure raised slowly. The reasoning is that water is nearly incompressible, so stored energy is limited compared with a steam or air test. If the gauge reads 225 psig but a safety valve is left set at 120 psig, the test cannot proceed as planned; isolation and proper test procedures are required.
Traps that cost marks
- Assuming a hydrostatic test proves safety-valve set pressure.
- Testing with air instead of water and creating stored energy.
- Inspecting only the fireside and missing waterside corrosion.
- Returning a boiler to service without closing and gasketing inspection openings.