NM Boiler Operator key terms

The construction code for power boilers and high-pressure steam equipment. It sets rules for materials, design, fabrication, welding, testing, and stamping; New Mexico requires boilers to be built and stamped to it.

The highest pressure a boiler or pressure part is designed to hold safely, determined by code calculations and shown on the nameplate. Safety valves are set at or below this pressure.

The ASME symbol applied to a boiler nameplate certifying it was built to an adopted ASME section and passed the required shop inspections before shipment.

Metal area with fire or hot gas on one side and water on the other, measured on the water side. It is used to compare boiler capacity and to figure evaporation rates.

A rod or brace that ties two pressure-retaining surfaces together so flat sheets can hold pressure without overstressing. Broken, seeping, or wasted stays are serious defects.

A fitting with a low-melting core, screwed into a crown sheet or similar high-temperature area. If water drops below it, the core melts and releases steam as a warning.

A capacity rating equal to evaporating 34.5 pounds of steam per hour from 212°F water at atmospheric pressure, about 33,475 Btu per hour. It compares boiler output, not engine power.

A strength and tightness test done by filling the boiler with water and raising pressure, commonly to 1.5 times the allowable working pressure for new construction or after repairs.

Bringing a cold boiler up to operating pressure slowly, using low fire and open vents, so metal expands evenly and thermal stress, water hammer, and tube leaks are avoided.

Opening valves at the lowest point of the boiler to discharge sludge and settled solids. It is done under light load, briefly, with the quick-opening valve used first.

Skimming water from near the steam-drum waterline, continuously or in short bursts, to remove dissolved solids and hold boiler water conductivity within limits.

A sharp bang or series of bangs in piping, caused by steam collapsing into condensate or by sudden valve closure. It can crack fittings and dislodge pipe supports.

An automatic device that releases condensate and air from steam lines and coils while keeping steam in the system. Traps that fail open waste steam; those that fail shut flood equipment.

Boiler water droplets or foam leaving with the steam. It causes water hammer in mains, scale on superheater tubes, and contaminated steam for processes.

Tubes that add heat to steam after it leaves the water, raising its temperature above saturation. Superheat improves efficiency and keeps steam dry through the piping.

The calculated air quantity that supplies exactly enough oxygen to burn all fuel, leaving no oxygen or unburned fuel. Real burners need more than this to finish combustion.

Air supplied above the theoretical amount, reported as a percentage of it. Too little leaves carbon monoxide and smoke; too much carries heat up the stack.

The pressure difference that pushes combustion air into the furnace and flue gas out the stack. It may be natural, forced, induced, or a balanced combination.

A hinged flap in the flue that opens to admit room air, holding a steady negative draft in a natural-draft appliance as conditions change.

A burner control package that uses a scanner to prove pilot and main flame and shuts the fuel valves on flame failure. It also enforces purge and trial-for-ignition times.

A timed fan run with fuel valves closed before every light-off, sweeping combustible gases out of the furnace and flue so ignition cannot cause an explosion.

The ratio of a burner's highest stable firing rate to its lowest. A 10:1 burner can run at one-tenth of maximum without losing a stable flame.

Breaking fuel oil into tiny droplets using pressure, steam, or air so it vaporizes and mixes with combustion air. Poor atomization gives smoke, carbon buildup, and an unstable flame.

Automatic adjustment of excess air based on oxygen measured in the flue gas, keeping combustion close to ideal as load and fuel characteristics change.

Water delivered to the boiler, made up of returned condensate plus treated makeup. Its quality controls scale, corrosion, and carryover inside the unit.

A vessel that heats feedwater with steam and strips out dissolved oxygen and other gases, preventing pitting corrosion in the boiler and downstream equipment.

Treated water added to replace steam and condensate that leave the system. It brings in most of the dissolved solids and oxygen that must be controlled.

Hard mineral deposits baked onto heating surfaces. Scale blocks heat flow, overheats tubes, and raises fuel use; prevention is a water-treatment job.

Localized, often deep corrosion caused by dissolved oxygen attacking steel, usually appearing as small pits on tubes and at the waterline. Deaeration and chemical scavengers prevent it.

An ion-exchange vessel that trades calcium and magnesium in makeup water for sodium, so hard scale does not form on boiler heating surfaces.

The maximum concentration of dissolved solids allowed in boiler water, set by the manufacturer or the treatment program and held by blowing down.

A control that stops the burner when the water level falls below a safe point, before tubes or sheets are exposed to flame. It must be tested on a set schedule.

A vertical sight glass connected to the boiler drum that shows the water level. It has top and bottom shutoffs and a drain valve so it can be blown clear and checked.

A spring-loaded valve that opens at its set pressure and closes after relieving steam, protecting the boiler from overpressure. It is not a control valve and must never be blocked.

A switch that shuts off the burner at a pressure above the normal operating range, backing up the operating control and the safety valve.

The periodic inspection of a boiler by a state inspector or authorized commissioned inspector, required by law before the unit may be operated and at set intervals afterward.

The document issued after a boiler passes its required state inspection. It shows the allowed pressure and the date by which the next inspection is due.

The National Board Inspection Code, used by inspectors and repair organizations for repairing, altering, and inspecting boilers already in service; repairs often need a certified R stamp.