06 · Inspection & Maintenance
Inspection Checkpoints
Structured inspection checkpoints across three contexts: the running heater (shift rounds), scheduled walkdowns (weekly/monthly), and offline cold-unit entry. Each section tells you where to look, what to look for, and when to escalate.
Scope of this page
This page covers operator inspection — what a qualified operator can observe, record, and act on. In-depth mechanical assessment of tubes and refractory are covered in their own pages: Tube Assessment → and Refractory Management →
Shift-round inspection — running heater
Every operator should complete a full heater walkdown once per shift — not just at handover. Many developing problems (refractory spalling, tube hot spots, draft changes) are visible long before they register on instrumentation. Use your eyes, ears, and nose; instruments confirm what the walkdown finds.
Peephole safety
Always approach peepholes from the side, never directly in front. Open the plug slowly — a positive-pressure firebox can eject hot gas. Wear appropriate face protection. If you smell fuel gas near a peephole plug, do not open it; treat as a potential tube leak until proven otherwise.
Shift-Round Walkdown Checklist
01
Approach — external visual scan
Before entering the heater bay, observe from a distance. Check for visible smoke or unusual colour from the stack. Note any fuel smell in the area. Look for signs of external casing hot spots (paint discolouration, blistering).
02
Stack observation
Observe stack effluent. Clear or light grey = normal. Black smoke = incomplete combustion / excess fuel. White steam may indicate tube leak in convection section. Yellow/brown = high excess air or acid gas. Note wind direction and any stack vibration or pulsation.
03
Casing and structural check
Walk the perimeter of the heater casing. Look for: hot spots or glowing casing panels (indicates refractory failure behind), casing buckles or distortion, soot deposits leaking from joints or expansion seals, corrosion around penetrations. Any casing temperature above approximately
80°C to the touch warrants investigation.
04
Burner platform — fuel system check
At each operating burner: confirm pilot and main flame indicators (if fitted). Check fuel supply pressure at the local gauge — compare against normal range. Inspect fuel lines and connections for any signs of leaks (smell, staining, frosting on gas lines). Confirm spill/drain valves closed.
05
Combustion air register positions
Physically verify register positions match DCS/panel settings. Registers can vibrate partially closed or be left incorrectly set after maintenance. A closed register on a lit burner creates fuel-rich zones and potential CO accumulation. Confirm all registers are secured in their set position.
06
Standby / idle burner status
For any burner not in service: confirm fuel block valves closed and locked, pilots confirmed out (not just assumed). Burner tile should be inspected visually — a cracked or missing tile on a standby burner can cause combustion instability when adjacent burners operate.
07
Flame observation — firebox peepholes
Observe each burner flame through the designated peephole. Note: flame colour (blue = lean/correct, orange = rich/normal, yellow lazy = problem), flame shape and stability (lifting, pulsating, impingement), any unlit burners, flames rolling or touching adjacent tubes. Use peephole glass rated for firebox viewing. Record any deviations.
08
Tube visual — radiant section
Where peephole position permits, scan radiant tubes for: uniform colour (bright orange/red at temperature is normal), any tube with a distinctly brighter or white-hot spot (potential hot spot / overheating), bowing or sagging, tube scale or oxide buildup indicating sustained overtemperature. Full tube assessment methodology in Tube Assessment.
09
Refractory — visible surfaces
Through peepholes, inspect visible refractory wall and floor for: spalled or fallen sections (debris on firebox floor), cracks wider than approximately
6 mm or with displacement, brick or castable chunks visible on tube supports or burner tiles. Refractory loss exposes the casing to radiant heat and creates hot spot risk.
10
Draft readings — local gauges
Read local draft gauges at the firebox and bridgewall positions. Compare against DCS readings — significant discrepancy (more than
0.05 inwc) may indicate a blocked impulse line or instrument fault. Verify damper position is consistent with draft readings. Positive firebox draft is a warning condition.
11
O₂ / CO analyser check
Confirm stack or bridgewall O₂ reading is within target range (typically
2–4% O₂ for natural draft; verify against unit-specific target). A sudden drop in O₂ without a corresponding change in fuel rate suggests air ingress path has changed (damper shift, new air leak through casing). CO alarms should be investigated — not reset without cause found.
12
Convection section — external inspection
Inspect convection section access panels and tube penetrations for: soot blowing damage or deposits, steam or water staining (tube leak indicator), casing distortion or hot spots near tube sheets. On units with soot blowers, confirm blower drain pot is functional and draining.
13
Process inlet / outlet temperatures — cross-check
Confirm process flow is established on all coil passes. Compare individual pass outlet temperatures — any pass running more than
15°C above the mean outlet temperature warrants investigation (possible flow restriction, valve position, or pass imbalance). Low flow on a pass with normal firing is the precursor to tube overheating.
14
Process flow — confirm minimum flow not alarmed
Verify process flow instrument is reading and not in alarm. Minimum flow trip setpoints exist specifically because loss of process flow is the most common cause of tube failure. If flow instruments are unreliable, investigate before trusting indirect indicators.
15
Steam and purge connections
Confirm steam connections (firebox purge, snuffing steam) are in correct standby alignment. Isolation valves should be locked in their normal service position. Confirm snuffing steam isolation is operable — this is emergency equipment and must be tested accessible.
16
Fuel gas KO drum — level and drain
Check fuel gas knockout drum level (if fitted). High liquid level in the fuel gas system causes intermittent flame instability and can deliver slugs of liquid to burners — a known cause of flashback. Drain as required. Note if level is trending up (upstream condensation problem).
17
BMS panel status check
At the BMS panel or DCS graphic: confirm no active alarms are suppressed, inhibited, or in bypass without valid PTW. Confirm all flame scanner signals are healthy. Any scanner fault that has been bypassed must have documented authorisation and a maximum duration.
18
Log findings and sign off
Record all observations in the shift log — normal findings as well as deviations. A normal entry reading "no issues" is not useful; record key readings (stack O₂, bridgewall temp, pass ΔT, fuel gas pressure). Abnormalities must be assigned an action owner before handover.
Scheduled inspections — weekly and monthly
Shift rounds catch acute problems. Scheduled inspections look for slow degradation — refractory erosion, tube oxide growth, instrument drift, soot accumulation — that develops over weeks. These require dedicated time and a second pair of eyes.
Weekly
Weekly Inspection Points
Minimum once per week · Logged in weekly inspection record
- —Flame scanner function test — test each scanner's flame-fail response per BMS procedure; confirm relay actuation times are within spec
- —Draft gauge calibration check — compare local gauges against DCS at steady-state; investigate any consistent offset greater than
±0.05 inwc - —Thermocouple comparison — compare all tube skin TCs and process TCs against each other; flag any TC reading more than
20°Cdivergent from expected trend - —Soot blower operation — where fitted, confirm each blower completes a full cycle without sticking; inspect convection casing for blower lance leaks
- —Expansion joint visual — inspect all casing expansion joints for gaps, soot blowout, or displaced ceramic fibre packing
- —Fuel gas pressure regulators — confirm setpoint has not drifted; compare upstream and downstream pressures against expected ΔP
- !Minimum flow trip function — verify the process flow trip transmitter signal matches local flow indication; do not accept transmitter-only verification
- —Stack damper operation — manually stroke damper actuator if fitted; confirm travel is smooth and stops at set positions without hunting
- —Area gas detection — confirm all fixed HC and CO detectors in the heater bay are in service; check for any in bypass or fault state
Monthly
Monthly Inspection Points
Minimum once per month · Engineering review recommended
- —Burner tip inspection — using peepholes or during planned single-burner shutdown, inspect for tip erosion, coking, or tip misalignment; degraded tips cause flame shape problems and maldistribution
- —Refractory thermal imaging — use infrared camera on casing exterior; identify cold spots (indicating refractory bulge or delamination) and hot spots (indicating failure); record and trend against previous months
- —O₂ analyser calibration — two-point calibration with span and zero gas; record as-found and as-left values; a drifting O₂ analyser is a significant operating hazard
- —Tube surface temperature survey — using optical pyrometer or IR camera through peepholes, record skin temperatures across all accessible tube rows; compare against design TMT and trend over time
- —Pressure safety valve (PSV) visual — confirm PSV on fuel gas system shows no signs of weeping or lifting; verify discharge is routed to safe location
- —BMS logic review with instrument tech — review the BMS bypass register; confirm all bypasses are still valid and appropriately documented; remove expired bypasses
- —Casing bolt torque check — on peephole covers, access doors, and burner tiles: check that all fasteners are present and snug; thermal cycling works bolts loose
- —Fuel gas composition review — compare actual fuel gas Wobbe Index / calorific value against the value the burners were commissioned for; significant shifts require burner re-optimisation
- !Process coil pressure drop check — compare measured tube-side ΔP against design; increasing ΔP at constant flow indicates coking; decreasing ΔP may indicate a failed tube or bypass
Offline inspection — cold unit entry
Entry into a fired heater is confined space entry and requires a valid PTW, gas clearance certificate, and isolation confirmation. The inspection below covers what operators and engineers should assess during turnaround or after unplanned shutdown. It is organised by zone.
Entry prerequisites — mandatory before any person enters
(1) Full fuel gas isolation with spades confirmed. (2) Firebox purged and gas-free tested — <10% LEL at all low-point pockets. (3) O₂ confirmed 19.5–23.5%. (4) All process coil passes confirmed drained, purged, and isolated. (5) PTW signed by area authority. (6) Confined space entry standby stationed. Do not enter if any of these conditions are not met.
Firebox Floor & Walls
High Risk
- Refractory integrity — cracks, spalling, delamination, fallen sections
- Burner tile condition — erosion, cracking, displaced tiles
- Floor debris — fallen refractory, scale, tube oxide deposits
- Wall anchor condition — exposed or corroded ceramic fibre anchors indicate lining loss
- Air register and plenum condition — erosion, corrosion, blockages
- Evidence of flame impingement on walls (dark carbon streaks)
Radiant Coil
High Risk
- Tube bowing or sagging between supports
- Scale or oxide build-up on tube surface — colour and thickness
- Hot spot marks (white scale, roughened surface) at historic high-temperature locations
- Weld condition at return bends and supports
- Tube support condition — cracking, distortion, loss of contact
- Tube sheet and inlet/outlet header visual — leaks, corrosion, staining
Convection Section
Medium Risk
- Finned or studded tube condition — fin erosion, fouling, corrosion under deposits
- Soot accumulation between tube rows — assess blower coverage effectiveness
- Tube spacing — no bridging or contact between adjacent tubes
- Soot blower lance condition — erosion, alignment, nozzle blockage
- Flue gas baffles — warping, gaps allowing gas bypass
- Dew-point corrosion on lower rows — pitting, under-deposit corrosion near inlet
Stack & Damper
Medium Risk
- Damper blade condition — warping, erosion, hinge wear
- Damper seat — confirm full closure is achievable and leak-tight
- Stack lining condition — erosion, delamination, especially around stack base
- Stack base drain — clear and serviceable
- O₂ / CO analyser probe — insertion depth correct, no bridging
- Bird/debris screening at stack top — if accessible
Burner Assembly
High Risk
- Fuel tip condition — erosion, coking, tip geometry
- Pilot assembly — electrode gap, flame rod condition, plug lead condition
- Air register blade condition — corrosion, distortion, drive linkage
- Burner block/quarl integrity — cracks, erosion at throat
- Fuel connection integrity — gaskets, flange faces, threaded fittings
- Atomising steam or air connections — where applicable
Casing & Structure
Lower Risk
- Structural steelwork — corrosion, distortion, weld cracking at connections
- Casing plate — corrosion on hot face (behind lining) and cold face
- Expansion joints and seals — compression, gaps, ceramic fibre condition
- Peephole assemblies — glass condition, frame seating, seal integrity
- Access door frames and hinges — distortion, sealing surfaces
- Instrument connections and thermowells — condition and seating
What to escalate and when
Not everything found on inspection requires immediate action, but every finding must be logged. The table below gives guidance on severity classification and expected response timeline. When in doubt, escalate — the cost of an unnecessary notification is always less than the cost of missed action on a genuine hazard.
| Finding | Severity | Action Required | Timeline |
|---|---|---|---|
| Tube hot spot confirmed (white/bright zone visible) | SEV 1 | Immediate reduction in firing rate; supervisor notification; initiate controlled shutdown if spot worsens or process flow cannot be increased | Immediate |
| Positive firebox pressure | SEV 1 | Do not approach peepholes or burner platform; assess cause from distance; notify supervisor immediately | Immediate |
| Fuel gas leak detected (smell, HC detector alarm) | SEV 1 | Initiate shutdown per site emergency procedure; evacuate non-essential personnel; notify fire team | Immediate |
| Process tube leak suspected (white vapour from peephole area) | SEV 1 | Shut down heater and isolate; treat as tube rupture until confirmed otherwise — see Tube Failure procedure | Immediate |
| Significant refractory fall (large section, tube now exposed to radiation) | SEV 1 | Reduce firing immediately; continuous monitoring; plan for shutdown at earliest opportunity | Within current shift |
| Casing hot spot confirmed by IR or touch | SEV 2 | Engineering review; identify refractory zone; continuous external monitoring; schedule repair at next opportunity | Within 24 hours |
| Pass ΔT imbalance >15°C above mean | SEV 2 | Investigate flow balance; check pass control valves; if cause not found within one hour, reduce firing and notify shift supervisor | Within 1 hour |
| O₂ analyser confirmed drifted or failed | SEV 2 | Arrange calibration or replacement; operate conservatively (higher excess air) until analyser is restored; do not operate without any O₂ reference | Within 24 hours |
| BMS flame scanner bypass without valid PTW | SEV 2 | Notify shift supervisor; restore to normal state or obtain valid bypass authorisation before end of shift; this is a safety system integrity issue | Before shift end |
| Minor refractory cracks (<6 mm, no displacement) | SEV 3 | Log and photograph; monitor for progression; schedule repair at next available turnaround | Next turnaround |
| Soot blower not completing full cycle | SEV 3 | Log and notify maintenance; monitor convection section ΔP for fouling increase; arrange repair within normal maintenance cycle | Routine maintenance |
What to record — minimum shift log entries
A shift log entry of "inspected — all OK" is not acceptable. The following fields should be recorded for each shift walkdown as a minimum. This creates a trend record and protects the operator if a condition is later found to have developed gradually.
Date / Time / Operator
Full name, shift, and time of walkdown completion
Stack O₂ %
Actual reading at time of walkdown (not panel average)
Bridgewall / Firebox Temp
°C or °F as per site standard; note which TC
Pass Outlet Temps
All pass outlets; flag any above +15°C of mean
Fuel Gas Pressure
Header pressure at time of walkdown
Firing Rate / Duty
Actual duty or fuel flow at time of walkdown
Flame Appearance
Normal / describe any deviation from normal
Deviations Found
Describe finding, zone, severity, action taken or deferred
Action Owner
Name of person responsible for any deferred action
Related pages
For detailed tube condition assessment methodology, see Tube Assessment →For refractory repair categorisation and patching procedures, see Refractory Management →