DC Boiler Operator cheat sheet

Sensible heat raises temperature without phase change; latent heat is absorbed or released at constant temperature during a phase change such as water boiling to steam at saturation conditions.

Saturation temperature rises with pressure: at atmospheric pressure water boils near 100 °C (212 °F), while at 1 000 kPa (about 145 psig) saturation temperature is roughly 184 °C (363 °F).

The three T's of combustion are time, temperature, and turbulence (mixing); a deficiency in any one produces incomplete combustion, visible smoke, or high carbon monoxide.

Theoretical air is the minimum air required for complete combustion; excess air is the amount supplied above theoretical, expressed as a percentage of theoretical air.

Flue gas CO2 falls and O2 rises as excess air increases; typical targets are 10–15 % excess air for gas firing and higher for oil or coal, confirmed by a flue gas analyser.

Stack loss is the dominant heat loss in a boiler; it grows with higher flue gas temperature and higher excess air, so both are held to practical minimums.

Boiler efficiency by the indirect (heat loss) method = 100 % minus the sum of stack, moisture, radiation, and unburned-carbon losses; the direct method compares steam energy output to fuel energy input.

Heat transfer in a boiler occurs by radiation in the furnace, by convection in the tube banks, and by conduction through the metal wall; scale on the water side adds a large resistance.

One boiler horsepower equals 9 810 W (33 475 Btu/h), roughly the evaporation of 15.6 kg (34.5 lb) of water per hour at 100 °C from and at 100 °C.

A safety valve protects against overpressure and must be sized to discharge all steam the boiler can generate at the maximum firing rate without pressure rising more than 6 % above the set pressure.

The lowest set safety valve on a battery of boilers limits the maximum allowable working pressure of the whole battery; the highest-set valve is the first to open.

A try cock (gauge glass test cock) verifies water level independently of the gauge glass; a three-way gauge glass valve allows blowing the glass clear while keeping the water column in service.

The water column and gauge glass connections must be blown down regularly because sludge and debris plug the lower connection and give a false high level.

A fusible plug, where fitted, is located at the crown sheet or upper firebox and melts to warn of low water and overheating; it is not a substitute for low-water cutoff.

A steam drum internals package includes the steam separator and scrubber; carryover of water into the steam line is reduced by adequate steam space, low water level, and controlled dissolved solids.

A blowdown valve must be of the slow-opening type on the boiler shell, with a quick-opening valve downstream; the boiler-shell valve is opened first and closed last.

A feed check valve prevents backflow from the boiler to the feed line; a feedwater stop valve isolates the boiler, and a feedwater regulator maintains level.

A bottom blowdown line is sized for the boiler's evaporation and must discharge to a safe location; a surface blowdown line draws from the water surface where dissolved solids concentrate.

Before lighting off, purge the furnace and gas passages with at least five air changes (commonly 30–60 s of forced draft at full airflow) to clear any accumulated combustible gas.

Cold startup sequence: verify water level, open air vents and drains, warm the boiler slowly, establish draft, light the pilot, prove the flame, then bring the main burner on and raise pressure gradually.

Warm-up rate is limited to about 55 °C (100 °F) per hour for thick-walled drums to keep thermal stress and differential expansion within safe limits.

On a cold boiler, the main steam stop is kept closed until pressure is raised; the header is warmed through the bypass before the stop valve is opened slowly.

Normal shutdown: reduce firing rate, blow down the water column and gauge glass, secure the burner, purge, close the main steam stop, and maintain water level while the boiler cools.

A low-water condition is treated by securing the burner immediately and verifying level with the try cocks; water must never be added to a boiler whose crown sheet or tubes may be uncovered until the metal has cooled.

A sudden rise in stack temperature with unchanged firing indicates internal fouling, baffle damage, or tube leakage and warrants a shutdown for inspection.

Boiler water level should be held at the normal operating line, typically the centre of the gauge glass; a level that cannot be seen in the glass means the burner is secured at once.

When two boilers are on a common header, the incoming boiler is paralleled by opening its stop valve slowly after its pressure slightly exceeds header pressure.

Scale is precipitated hardness (calcium and magnesium) on hot surfaces; it has low thermal conductivity and causes overheating, tube failure, and efficiency loss.

External treatment removes hardness before the boiler (softener, demineraliser, reverse osmosis); internal treatment precipitates or conditions remaining impurities inside the boiler.

Oxygen pitting is prevented by mechanical deaeration plus a chemical oxygen scavenger such as sodium sulfite or hydrazine; sulfite is not used where steam is taken for food processing.

Caustic embrittlement (stress corrosion cracking) is avoided by keeping caustic alkalinity within limits and by using phosphate treatment rather than high-hydroxide programmes.

Carryover is controlled by maintaining dissolved solids below the limit set by the boiler's TDS controller and by avoiding sudden load swings and high water level.

Conductivity is used as a proxy for dissolved solids; the continuous blowdown rate is adjusted so boiler water conductivity stays within the manufacturer's or standard's limit.

Bottom blowdown removes sludge and sediment from the lowest point; it is done with the boiler under load and in short, repeated openings rather than one long opening.

Blowdown percentage can be estimated as feedwater TDS divided by the maximum allowable boiler water TDS, multiplied by 100; higher blowdown means higher fuel and water consumption.

Feedwater pH is normally held mildly alkaline (about 8.5–10.5) to protect steel; excessively high pH attacks copper alloys in the feed system.

A flame safeguard (programming) control supervises purge, pilot proving, main flame proving, and lockout; it must go to lockout on flame failure and require manual reset.

Flame detection uses flame rods (ionisation) on gas or UV scanners on oil and gas; a fouled scanner or grounded flame rod causes nuisance lockouts and must be cleaned and checked.

A low-water fuel cutoff trips the burner when the water level falls below the lowest safe level; it must be tested while the boiler is firing, not only with the burner off.

High steam pressure and high water temperature limits are separate from the operating controller; they are manual-reset safety limits set above normal control points.

A high gas pressure switch and low gas pressure switch protect the burner train; both are proved before and during firing and lock out the burner on trip.

The burner management system enforces the prepurge, pilot proving period, main flame proving period, and post-purge; bypassing any of these interlocks is prohibited.

Safety valve set pressure is verified by the valve's tag and by a pop test, not by the pressure gauge alone; a valve that weeps or fails to reseat is repaired or replaced.

A combustion safeguard with a lockout must not be reset more than the manufacturer allows without investigating the cause; repeated lockouts indicate a real fault, not a nuisance.

Jurisdictional inspection intervals are set by the local boiler code; a common pattern is annual internal and external inspection with a certificate posted at the boiler.

An internal inspection requires the boiler to be cooled, drained, isolated, and locked out, with valves tagged and the space verified safe before entry.

Hydrostatic test pressure is normally 1.5 times the maximum allowable working pressure for a new boiler; the test is done with the safety valve removed or gagged only under controlled conditions.

Scale thickness above about 0.8 mm (1/32 in) on a heating surface is a reason to clean; even thin scale measurably raises metal temperature and fuel use.

Records to keep include daily water level and blowdown logs, flame safeguard tests, safety valve pop tests, water treatment test results, and inspection certificates.

A safety valve that has been repaired must be reset and sealed by a qualified valve shop, and the set pressure recorded; field adjustment by the operator is not permitted.

Tube failures are traced to cause: low water, scale, corrosion, thermal fatigue, or vibration; the failed tube is plugged or replaced and the cause corrected before return to service.

Combustion efficiency testing with a portable analyser records O2, CO, CO2, and stack temperature; trends over time reveal fouling and burner drift better than a single reading.

Sensible heat changes temperature without a phase change; latent heat is absorbed or released at constant temperature during boiling or condensation.

Saturation temperature rises with pressure, so a boiler at 1 000 kPa boils water near 184 °C while one at atmospheric pressure boils near 100 °C.

Complete combustion needs the three T's: time, temperature, and turbulence (mixing); any shortfall produces CO, smoke, or unburned fuel.

Theoretical air is the minimum for complete combustion; excess air is the extra supplied, expressed as a percentage of theoretical air.

As excess air rises, flue gas O2 rises and CO2 falls; a flue gas analyser is used to trim excess air to the lowest value that keeps CO low.

Stack loss is the largest boiler heat loss and increases with flue gas temperature and excess air, so both are held to practical minimums.

Indirect efficiency = 100 % minus stack, moisture, radiation, and unburned-carbon losses; direct efficiency compares steam energy output with fuel energy input.

One boiler horsepower equals 9 810 W (33 475 Btu/h), about 15.6 kg of water evaporated per hour from and at 100 °C.

A safety valve must pass all the steam the boiler can make at maximum firing without pressure exceeding 6 % above set pressure.

On a battery of boilers the lowest-set safety valve governs the maximum allowable working pressure of the battery, and the highest-set valve opens first.

Try cocks verify water level independently of the gauge glass; three-way gauge glass valves allow the glass to be blown clear while the water column stays in service.

Water column and gauge glass lower connections plug with sludge and give a false high level, so they are blown down on a regular schedule.

A fusible plug melts to warn of low water and overheating; it supplements but never replaces the low-water fuel cutoff.

Steam drum internals include the separator and scrubber; carryover is reduced by adequate steam space, controlled water level, and limited dissolved solids.

The boiler-shell blowdown valve is slow-opening and is opened first and closed last; the quick-opening valve downstream is opened last and closed first.

A feed check valve prevents backflow from the boiler into the feed line, while the feedwater stop valve isolates the boiler for maintenance.

Surface blowdown draws from the water surface where dissolved solids concentrate, while bottom blowdown removes sludge from the lowest point.

Before lightoff, purge the furnace and gas passages with at least five air changes, commonly 30–60 s of forced draft at full airflow.

Cold startup order: verify water level, open vents and drains, establish draft, light and prove the pilot, then bring on the main flame and raise pressure gradually.

Warm-up is limited to about 55 °C (100 °F) per hour on thick-walled drums to keep thermal stress and differential expansion within limits.

On a cold boiler the main steam stop stays closed until pressure is raised; the header is warmed through the bypass and the stop is then opened slowly.

Normal shutdown: reduce firing, blow down the water column and gauge glass, secure the burner, purge, close the main steam stop, and hold water level while cooling.

On low water, secure the burner at once and verify level with try cocks; never add water to a boiler whose crown sheet or tubes may be uncovered until the metal has cooled.

A sudden rise in stack temperature at unchanged firing points to internal fouling, damaged baffles, or a tube leak and calls for shutdown and inspection.

When paralleling boilers on a common header, open the incoming boiler's stop valve slowly once its pressure slightly exceeds header pressure.

Scale is precipitated calcium and magnesium hardness on hot surfaces; its low thermal conductivity causes overheating, tube failure, and efficiency loss.

External treatment removes hardness before the boiler (softener, demineraliser, reverse osmosis); internal treatment conditions what remains inside the boiler.

Oxygen pitting is prevented by deaeration plus a scavenger such as sodium sulfite or hydrazine; sulfite is avoided where steam contacts food.

Caustic embrittlement is avoided by limiting caustic alkalinity and by using phosphate treatment instead of high-hydroxide programmes.

Carryover is controlled by keeping dissolved solids below the TDS limit, avoiding load swings, and not running the water level high.

Conductivity is used as a proxy for dissolved solids, and continuous blowdown is adjusted to hold boiler water conductivity within the standard's limit.

Blowdown percentage is roughly feedwater TDS divided by maximum allowable boiler water TDS, times 100; more blowdown means more fuel and water use.

Bottom blowdown removes sludge from the lowest point and is done in short, repeated openings with the boiler under load, not one long opening.

Feedwater pH is held mildly alkaline, about 8.5–10.5, to protect steel; excessively high pH attacks copper alloys in the feed system.

A flame safeguard control supervises purge, pilot proving, main flame proving, and lockout, and must lock out on flame failure with manual reset.

Flame detection uses ionisation flame rods on gas and UV scanners on oil or gas; a fouled scanner or grounded flame rod causes nuisance lockouts.

The low-water fuel cutoff must be tested while the boiler is firing, because a stuck float or probe may only show up under actual low-water conditions.

High steam pressure and high water temperature limits are manual-reset safety limits set above the normal operating controller's setpoint.

High and low gas pressure switches protect the burner train and lock out the burner on trip both before and during firing.

The burner management system enforces prepurge, pilot proving, main flame proving, and post-purge; bypassing any interlock is prohibited.

Safety valve set pressure is confirmed by its tag and a pop test, not by the pressure gauge; a weeping or non-reseating valve is repaired or replaced.

Repeated lockouts are investigated rather than reset repeatedly, since they usually indicate a real fault in flame detection, fuel pressure, or air supply.

Inspection intervals come from the local boiler code, commonly annual internal and external inspection with a certificate posted at the boiler.

Internal inspection requires the boiler cooled, drained, isolated, and locked out, with valves tagged and the space verified safe before entry.

A hydrostatic test is normally at 1.5 times maximum allowable working pressure for a new boiler, with safety valves removed or properly isolated.

Scale above about 0.8 mm (1/32 in) on a heating surface warrants cleaning, since even thin scale raises metal temperature and fuel use.

Records to retain include water level and blowdown logs, flame safeguard tests, safety valve pop tests, water treatment results, and inspection certificates.

A repaired safety valve must be reset and sealed by a qualified valve shop with the set pressure recorded; field adjustment by the operator is not allowed.

Tube failures are traced to low water, scale, corrosion, thermal fatigue, or vibration, and the cause is corrected before return to service.

Portable combustion analyser readings of O2, CO, CO2, and stack temperature, tracked over time, reveal fouling and burner drift better than one reading.

Sensible heat raises temperature with no phase change; latent heat is absorbed or released at constant temperature during boiling or condensation.

Saturation temperature rises with pressure: water boils near 100 °C at atmospheric pressure and near 184 °C at about 1 000 kPa.

Complete combustion requires the three T's of time, temperature, and turbulence; a deficiency in any one yields CO, smoke, or unburned fuel.

Theoretical air is the minimum needed for complete combustion; excess air is the amount above theoretical, stated as a percentage of theoretical air.

Rising excess air raises flue gas O2 and lowers CO2; the analyser is used to trim excess air to the lowest value that keeps CO low.

Stack loss is the largest boiler heat loss and grows with flue gas temperature and excess air, so both are kept to practical minimums.

Indirect efficiency is 100 % minus stack, moisture, radiation, and unburned-carbon losses; direct efficiency compares steam output energy with fuel input energy.

One boiler horsepower equals 9 810 W (33 475 Btu/h), roughly 15.6 kg of water evaporated per hour from and at 100 °C.

A safety valve must discharge all the steam the boiler can generate at maximum firing without pressure rising more than 6 % above set pressure.

On a battery, the lowest-set safety valve fixes the maximum allowable working pressure of the battery, and the highest-set valve opens first.

Try cocks check water level independently of the gauge glass, and three-way gauge glass valves let the glass be blown clear while the column stays in service.

Plugged lower connections on the water column or gauge glass cause a false high level, so both are blown down on a regular schedule.

A fusible plug melts to warn of low water and overheating but never replaces the low-water fuel cutoff.

Steam drum internals include the separator and scrubber; carryover is limited by steam space, water level control, and low dissolved solids.

The boiler-shell blowdown valve is slow-opening and is opened first and closed last; the quick-opening valve downstream is opened last and closed first.

The feed check valve prevents backflow from the boiler into the feed line, and the feedwater stop valve isolates the boiler for maintenance.

Surface blowdown draws from the water surface where dissolved solids concentrate, while bottom blowdown removes sludge from the lowest point.

Before lightoff, purge the furnace and gas passages with at least five air changes, commonly 30–60 s of forced draft at full airflow.

Cold startup order: verify water level, open vents and drains, establish draft, light and prove the pilot, bring on the main flame, and raise pressure gradually.

Warm-up is limited to about 55 °C (100 °F) per hour on thick-walled drums to control thermal stress and differential expansion.

On a cold boiler the main steam stop stays closed until pressure is raised; the header is warmed through the bypass and the stop opened slowly.

Normal shutdown: reduce firing, blow down the water column and gauge glass, secure the burner, purge, close the main steam stop, and hold level while cooling.

On low water, secure the burner at once and verify with try cocks; never add water to a boiler whose crown sheet or tubes may be uncovered until the metal cools.

A sudden rise in stack temperature at unchanged firing indicates internal fouling, damaged baffles, or a tube leak and calls for shutdown and inspection.

When paralleling boilers on a common header, open the incoming boiler's stop valve slowly once its pressure slightly exceeds header pressure.

Scale is precipitated calcium and magnesium hardness on hot surfaces; its low thermal conductivity causes overheating, tube failure, and efficiency loss.

External treatment removes hardness before the boiler (softener, demineraliser, reverse osmosis); internal treatment conditions what remains inside the boiler.

Oxygen pitting is prevented by deaeration plus a scavenger such as sodium sulfite or hydrazine; sulfite is avoided where steam contacts food.

Caustic embrittlement is avoided by limiting caustic alkalinity and by using phosphate treatment instead of high-hydroxide programmes.

Carryover is controlled by keeping dissolved solids below the TDS limit, avoiding load swings, and not running the water level high.

Conductivity is used as a proxy for dissolved solids, and continuous blowdown is adjusted to hold boiler water conductivity within the standard's limit.

Blowdown percentage is roughly feedwater TDS divided by maximum allowable boiler water TDS, times 100; more blowdown means more fuel and water use.

Bottom blowdown removes sludge from the lowest point and is done in short, repeated openings with the boiler under load, not one long opening.

Feedwater pH is held mildly alkaline, about 8.5–10.5, to protect steel; excessively high pH attacks copper alloys in the feed system.

A flame safeguard control supervises purge, pilot proving, main flame proving, and lockout, and must lock out on flame failure with manual reset.

Flame detection uses ionisation flame rods on gas and UV scanners on oil or gas; a fouled scanner or grounded flame rod causes nuisance lockouts.

The low-water fuel cutoff must be tested while the boiler is firing, because a stuck float or probe may only show up under actual low-water conditions.

High steam pressure and high water temperature limits are manual-reset safety limits set above the normal operating controller's setpoint.

High and low gas pressure switches protect the burner train and lock out the burner on trip both before and during firing.

The burner management system enforces prepurge, pilot proving, main flame proving, and post-purge; bypassing any interlock is prohibited.

Safety valve set pressure is confirmed by its tag and a pop test, not by the pressure gauge; a weeping or non-reseating valve is repaired or replaced.

Repeated lockouts are investigated rather than reset repeatedly, since they usually indicate a real fault in flame detection, fuel pressure, or air supply.

Inspection intervals come from the local boiler code, commonly annual internal and external inspection with a certificate posted at the boiler.

Internal inspection requires the boiler cooled, drained, isolated, and locked out, with valves tagged and the space verified safe before entry.

A hydrostatic test is normally at 1.5 times maximum allowable working pressure for a new boiler, with safety valves removed or properly isolated.

Scale above about 0.8 mm (1/32 in) on a heating surface warrants cleaning, since even thin scale raises metal temperature and fuel use.

Records to retain include water level and blowdown logs, flame safeguard tests, safety valve pop tests, water treatment results, and inspection certificates.

A repaired safety valve must be reset and sealed by a qualified valve shop with the set pressure recorded; field adjustment by the operator is not allowed.

Tube failures are traced to low water, scale, corrosion, thermal fatigue, or vibration, and the cause is corrected before return to service.

Portable combustion analyser readings of O2, CO, CO2, and stack temperature, tracked over time, reveal fouling and burner drift better than one reading.

Sensible heat raises temperature with no phase change; latent heat is absorbed or released at constant temperature during boiling or condensation.

Saturation temperature rises with pressure: water boils near 100 °C at atmospheric pressure and near 184 °C at about 1 000 kPa.

Complete combustion requires the three T's of time, temperature, and turbulence; a deficiency in any one yields CO, smoke, or unburned fuel.

Theoretical air is the minimum needed for complete combustion; excess air is the amount above theoretical, stated as a percentage of theoretical air.

Rising excess air raises flue gas O2 and lowers CO2; the analyser is used to trim excess air to the lowest value that keeps CO low.

Stack loss is the largest boiler heat loss and grows with flue gas temperature and excess air, so both are kept to practical minimums.

Indirect efficiency is 100 % minus stack, moisture, radiation, and unburned-carbon losses; direct efficiency compares steam output energy with fuel input energy.

One boiler horsepower equals 9 810 W (33 475 Btu/h), roughly 15.6 kg of water evaporated per hour from and at 100 °C.

A safety valve must discharge all the steam the boiler can generate at maximum firing without pressure rising more than 6 % above set pressure.

On a battery, the lowest-set safety valve fixes the maximum allowable working pressure of the battery, and the highest-set valve opens first.

Try cocks check water level independently of the gauge glass, and three-way gauge glass valves let the glass be blown clear while the column stays in service.

Plugged lower connections on the water column or gauge glass cause a false high level, so both are blown down on a regular schedule.

A fusible plug melts to warn of low water and overheating but never replaces the low-water fuel cutoff.

Steam drum internals include the separator and scrubber; carryover is limited by steam space, water level control, and low dissolved solids.

The boiler-shell blowdown valve is slow-opening and is opened first and closed last; the quick-opening valve downstream is opened last and closed first.

The feed check valve prevents backflow from the boiler into the feed line, and the feedwater stop valve isolates the boiler for maintenance.

Surface blowdown draws from the water surface where dissolved solids concentrate, while bottom blowdown removes sludge from the lowest point.

Before lightoff, purge the furnace and gas passages with at least five air changes, commonly 30–60 s of forced draft at full airflow.

Cold startup order: verify water level, open vents and drains, establish draft, light and prove the pilot, bring on the main flame, and raise pressure gradually.

Warm-up is limited to about 55 °C (100 °F) per hour on thick-walled drums to control thermal stress and differential expansion.

On a cold boiler the main steam stop stays closed until pressure is raised; the header is warmed through the bypass and the stop opened slowly.

Normal shutdown: reduce firing, blow down the water column and gauge glass, secure the burner, purge, close the main steam stop, and hold level while cooling.

On low water, secure the burner at once and verify with try cocks; never add water to a boiler whose crown sheet or tubes may be uncovered until the metal cools.

A sudden rise in stack temperature at unchanged firing indicates internal fouling, damaged baffles, or a tube leak and calls for shutdown and inspection.

When paralleling boilers on a common header, open the incoming boiler's stop valve slowly once its pressure slightly exceeds header pressure.

Scale is precipitated calcium and magnesium hardness on hot surfaces; its low thermal conductivity causes overheating, tube failure, and efficiency loss.

External treatment removes hardness before the boiler (softener, demineraliser, reverse osmosis); internal treatment conditions what remains inside the boiler.

Oxygen pitting is prevented by deaeration plus a scavenger such as sodium sulfite or hydrazine; sulfite is avoided where steam contacts food.

Caustic embrittlement is avoided by limiting caustic alkalinity and by using phosphate treatment instead of high-hydroxide programmes.

Carryover is controlled by keeping dissolved solids below the TDS limit, avoiding load swings, and not running the water level high.

Conductivity is used as a proxy for dissolved solids, and continuous blowdown is adjusted to hold boiler water conductivity within the standard's limit.

Blowdown percentage is roughly feedwater TDS divided by maximum allowable boiler water TDS, times 100; more blowdown means more fuel and water use.

Bottom blowdown removes sludge from the lowest point and is done in short, repeated openings with the boiler under load, not one long opening.

Feedwater pH is held mildly alkaline, about 8.5–10.5, to protect steel; excessively high pH attacks copper alloys in the feed system.

A flame safeguard control supervises purge, pilot proving, main flame proving, and lockout, and must lock out on flame failure with manual reset.

Flame detection uses ionisation flame rods on gas and UV scanners on oil or gas; a fouled scanner or grounded flame rod causes nuisance lockouts.

The low-water fuel cutoff must be tested while the boiler is firing, because a stuck float or probe may only show up under actual low-water conditions.

High steam pressure and high water temperature limits are manual-reset safety limits set above the normal operating controller's setpoint.

High and low gas pressure switches protect the burner train and lock out the burner on trip both before and during firing.

The burner management system enforces prepurge, pilot proving, main flame proving, and post-purge; bypassing any interlock is prohibited.

Safety valve set pressure is confirmed by its tag and a pop test, not by the pressure gauge; a weeping or non-reseating valve is repaired or replaced.

Repeated lockouts are investigated rather than reset repeatedly, since they usually indicate a real fault in flame detection, fuel pressure, or air supply.

Inspection intervals come from the local boiler code, commonly annual internal and external inspection with a certificate posted at the boiler.

Internal inspection requires the boiler cooled, drained, isolated, and locked out, with valves tagged and the space verified safe before entry.

A hydrostatic test is normally at 1.5 times maximum allowable working pressure for a new boiler, with safety valves removed or properly isolated.

Scale above about 0.8 mm (1/32 in) on a heating surface warrants cleaning, since even thin scale raises metal temperature and fuel use.

Records to retain include water level and blowdown logs, flame safeguard tests, safety valve pop tests, water treatment results, and inspection certificates.

A repaired safety valve must be reset and sealed by a qualified valve shop with the set pressure recorded; field adjustment by the operator is not allowed.

Tube failures are traced to low water, scale, corrosion, thermal fatigue, or vibration, and the cause is corrected before return to service.

Portable combustion analyser readings of O2, CO, CO2, and stack temperature, tracked over time, reveal fouling and burner drift better than one reading.