Boiler Safety Inspection Checklist

The external inspection covers all safety devices, controls, and components accessible while the boiler is operating. A thorough external inspection covers the following:

Safety relief valves:

• Verify correct size, type, and set pressure for the boiler's MAWP
• Check for corrosion, mineral deposits, or paint on the valve body and seat
• Confirm discharge piping is properly routed (down and away from personnel areas, no valves or restrictions in the discharge line)
• Verify the valve capacity plate matches the boiler's steaming capacity
• Check the ASME/NB stamp and verify the valve is within its recommended service life

Pressure and temperature gauges:

• Steam pressure gauge: verify against a test gauge, check for stuck needle, confirm the siphon loop is installed and filled
• Temperature gauges (hot water systems): verify accuracy, check for broken stems or fogged dials
• All gauges must be readable from the normal operating position

Water level controls (steam boilers):

• Water column: check for leaks, verify gauge glass readings match actual water level, confirm all valves in the water column connections are fully open and sealed (not throttled)
• Low water cutoff: functional test by blowing down to verify burner shutdown at the proper water level
• Auxiliary (secondary) LWCO if installed: same functional test
• Feedwater system: verify pump operation, check valves, float controls

Fuel train (gas-fired):

• Main gas shutoff valve accessible and properly tagged
• Gas pressure regulator: verify inlet and outlet pressures are within specification
• Main gas valves (typically dual shutoff valves): check for leakage using valve proving system or bubble test
• Pilot gas valve and pilot assembly condition
• Gas train vent valve (between dual main valves): confirm it is piped to outdoors and not plugged
• Manual reset gas cock or valve upstream of the train
• Gas train drip leg and sediment trap

Fuel train (oil-fired):

• Oil supply and return line condition, fittings, valves
• Oil pump pressure and operation
• Oil preheater (for heavy oils): temperature and controls
• Nozzle condition (replace on schedule, typically annually)
• Oil filter/strainer condition

Combustion air:

• Combustion air openings: verify they are unobstructed, properly sized, and have not been blocked or reduced
• Forced draft fan operation and condition
• Air damper linkage and positioning
• Combustion analysis readings: CO2, O2, CO, stack temperature, smoke number (oil). O2 should be 3-5% for gas, 4-6% for oil. CO should be under 100 PPM. Stack temperature should be within manufacturer's specifications.

Flame safeguard:

• Type and manufacturer (Honeywell, Fireye, Siemens)
• Flame scanner or UV detector: clean and properly positioned
• Pre-purge timing: verify proper air changes (typically 4 air changes minimum)
• Pilot flame establishment timing
• Main flame failure response time
• Post-purge operation

The internal inspection is performed with the boiler shut down, cooled, drained, and opened. For fire-tube boilers, this means accessing both the fireside (inside the tubes and combustion chamber) and the waterside (the shell side around the tubes):

Fireside examination:

• Tube condition: look for soot buildup (indicates poor combustion), ash deposits, corrosion, blistering, or bulging
• Tube-to-tube sheet joints: check for cracking, leakage stains, or rolled joint deterioration
• Combustion chamber / Morrison tube (Scotch Marine boilers): check for distortion, cracking at stays, or corrugation collapse
• Refractory condition: cracks, spalling, erosion, or areas where the refractory has fallen away exposing the shell
• Baffles: verify they are intact and properly positioned — missing or damaged baffles cause uneven heat distribution and localized overheating
• Rear tube sheet and reversing chamber condition

Waterside examination:

• Scale deposits: measure thickness and distribution. Scale is the primary cause of tube overheating — 1/16 inch of scale on a tube reduces heat transfer enough to raise tube metal temperature by 150-200 degrees F
• Corrosion: pitting (localized), general thinning, grooving (at waterline), oxygen pitting (small deep pits, often near feedwater inlet)
• Mud and sediment accumulation in the lower shell
• Handhole and manhole gasket surfaces: check for erosion, corrosion, or damage that would prevent a proper seal
• Stay bolts and stay rods (if present): check for wastage, tell-tale hole condition
• Shell condition: general corrosion, localized thinning, evidence of caustic embrittlement

Come prepared with these documents — inspectors check them and their absence reflects poorly on your maintenance program:

• Previous inspection report: The inspector will compare current conditions to the previous report to identify trends (worsening corrosion, recurring deficiencies)
• Operating log: Daily or weekly readings of pressure, temperature, water level, stack temperature, and water treatment test results. Even a simple handwritten log demonstrates attentive operation.
• Water treatment records: Monthly water analysis reports showing pH, conductivity, alkalinity, hardness, sulfite/oxygen scavenger residual, and any corrective actions taken. If you use a water treatment vendor, they should provide these reports at every visit.
• Maintenance records: Documentation of all maintenance performed — burner service, safety device testing, LWCO blowdowns, relief valve tests, parts replaced. Maintenance contracts should produce written reports for every visit.
• Repair records: Documentation of any repairs to the pressure vessel, including R-stamp repair forms (NB-65 or equivalent), engineering drawings, and hydrostatic test records if applicable.
• Boiler manufacturer data: Original installation manual, parts lists, and wiring diagrams. Keep these in the boiler room or in a dedicated building systems file. If you have lost the originals, most manufacturers will provide replacements from serial number records.
• Current certificate of operation: Should be posted near the boiler per state requirements. Have the prior year's certificate available as well.