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Boiler Talk

ANNUAL COMBUSTION TUNINGS

Many organizations perform their annual boiler maintenance and inspections (“Annuals”) during the summer months. Most states and/or boiler insurance companies require an internal inspection to maintain proper operating certification for the vessel. As with any equipment, a good routine boiler inspection and maintenance program will result in an efficient, reliable, and safe operating unit. Below we will provide a guideline for boiler preparation, inspection and maintenance.

The purpose of the pre-outage inspection is to detect conditions requiring repair or attention during the schedule outage. Some conditions can possibly be corrected prior to the outage. Others, however, will require parts to be ordered and repair schedules to organize. The inspection is performed while the boiler and auxiliary equipment are in operation. As a guide, the following items should be addressed:
  • Check for gas and/or oil leaks around burner piping,
  • Check burner flame for proper combustion, pattern, and impingement,
  • Listen and note unusual noises that may indicate a steam or water leak,
  • Look for any traces of water on the floor or leaks from the boiler casing, settings, and supports,
  • Look for any unusual conditions such as discoloration or “hot spots” on the boiler casing, doors, or other access panels,
  • Check the boiler blower(s) and pump(s) (feed water and fuel) for unusual noise or vibration, overheating bearings, and discolored lubricating fluids and lubricate levels,
  • Check boiler valving for packing leaks,
  • Check the boiler level control mechanism and the low water fuel cut-out mechanisms for proper operation,
  • Check boiler gauges (temperature and pressure) for integrity and accuracy,
  • Inspect the boiler safety valve(s) for signs of leakage and water deposits. Also make sure the safety valve(s) are set at the proper pressure and have adequate capacity,
  • Inspect the boiler casing and insulation for signs of deterioration,
  • Soot blowers, if equipped, must be blown before the boiler is removed from service,
  • Schedule outage inspection with the Jurisdictional or Boiler Insurance Inspector,
  • Schedule with Al Hill Boiler any necessary repairs or parts required during the outage.

 

After removing from service, isolate the boiler from the steam header and allow to cool and de-pressure. If possible, operate the draft fan (forced or induced) to expedite cooling the boiler refractory. Also, operate the bottom blowdown valves; alternately, front and rear, to remove any loose sediment from the water-sides and allow fresh water to fill and cool the boiler (NEVER ALLOW WATER LEVEL TO LEAVE THE GAUGE GLASS). Continue operating the draft fan and filling and blowing down boiler until the stack temperature reaches 120-140oF and water temperature reaches 150-180oF. The boiler can then be drained.

After the boiler is drained, isolate the unit per your organizations Lock & Tag Out Procedures or OSHA CFR1910 requirements.

 

Once the boiler is cool and drained, open the access doors and panels to the boiler firesides. Secure Confined Space Entry Permits as required by your organization or OSHA CFR1910 procedures, if necessary.

Firetube Boilers

  • Clean soot and other deposits from tubes, tube sheet, and furnace,
  • Inspect tubes for signs of leakage, cracks, deformation, or distress. Repair or replace any suspect tube(s),
  • Inspect tube ligaments for signs of cracking or distress. Repair as necessary,
  • Inspect and sound stay bolts or rods for tightness and integrity. Repair or replace as necessary,
  • Inspect the integrity of the fusible plugs in the tube sheet. Replace as necessary (HRT boilers),
  • Inspect rear door refractory and baffle tile, bridges or crowns. Repair, replace or seal any broken areas or cracks,
  • Inspect furnace for signs of leakage, bulging, blistering, flame impingement, or other signs of distress. Repair as necessary,
  • Inspect burner diffuser, gas spuds or oil nozzles, and pilot assembly for cleanliness, signs of distortion, and alignment. Clean and repair or replace as necessary,
  • Inspect the burner throat and liner tile and refractory. Repair, replace, or seal any broken areas or cracks,
  • Inspect front door refractory/insulation and baffles tile or plates. Repair, replace, or seal any broken areas or cracks,
  • Clean all gasket bearing or sealing surfaces on doors, baffles and burner mounting and install new gaskets.

Watertube Boilers

  • Clean soot and other deposits from tubes,
  • Inspect tubes (radiant and convective) for signs of leakage, cracks, bulges, flame impingement or distress. Pay particular attention to the tubes in the transition area as they are more susceptible to erosion. Repair or replace any suspect tube(s),
    Inspect radiant tube membranes for signs of distress. Also check tube-to-tube spacing are within tolerances. Repair or replace as necessary,
  • Inspect superheater tubes, if equipped, for signs of leakage, cracks, bulges or distress. Repair or replace as necessary,
  • Inspect refractory and tile at the back wall. Repair, replace or seal any broken areas or cracks,
  • Inspect furnace floor refractory tile. Repair, replace, or seal any broken areas or cracks,
  • Inspect burner diffuser, gas spuds or oil nozzles, and pilot assembly for cleanliness, signs of distortion, and alignment. Clean and repair or replace as necessary,
  • Inspect the burner throat and liner tile and refractory. Repair, replace, or seal any broken areas or cracks,
  • Inspect refractory/insulation along the mud and steam drums for integrity. Repair, replace, or seal any broken areas or cracks,
  • Clean all gasket bearing or sealing surfaces on access panels and doors and install new gaskets.

Cast Iron Boilers

  • Remove burner tray from furnace, if atmospheric, or pull power burner,
  • Clean soot and other deposits from furnace and extended surfaces on sections,
  • Inspect cast iron sections for signs of leakage, cracks, or distress. Replace any suspect section(s),
  • If equipped with a power burner, inspect burner diffuser, gas spuds or oil nozzles, and pilot assembly for cleanliness, signs of distortion, and alignment. Clean and repair or replace as necessary,
  • If equipped with a atmospheric burners, inspect burner plates, orifices, and pilot assembly. Clean and repair or replace, as necessary,
  • Clean all gasket bearing or sealing surfaces on doors, baffles and burner mounting and install new gaskets.

 

Once the boiler is cool and drained, remove all manhole and handhole plates, or inspection/washout openings. Dismantle the level control and low water fuel out mechanisms. Remove all plugs and caps from the water column equalizing lines, pressure control header, and feed water and blow down lines, if equipped. Secure Confined Space Entry Permits as required by your organization or OSHA CFR1910 procedures, if necessary.

Firetube Boilers

  • Clean loose scale and sludge from the tube surfaces, furnace and shell of boiler,
    Inspect boiler tubes for pits, water solid deposition, and general corrosion. Clean, repair or replace as necessary,
  • Clean the steam outlet dry pan. Also inspect for security and integrity. Repair or replace as required,
  • Clean feed water line and distributor or deflector plate. Inspect for security and integrity. Repair or replace as necessary,
  • Clean bottom blowdown and surface blowdown lines, strainers and valves. Inspect operation and integrity of valves. Repair or replace as necessary,
  • Inspect all nozzle openings in boiler for signs of weld distress and/or corrosion. Repair or replace as necessary,
  • Inspect pressure control header for cleanliness, corrosion, and integrity. Clean, repair, or replace as necessary,
  • Inspect the pump control and low water fuel cut-out mechanisms for cleanliness, corrosion and integrity.

Float Type Control

  • Inspect float ball for signs of corrosion, distortion, pinholes, etc. Replace as required.
  • Inspect mechanical linkage of float to insure free movement. Replace as necessary.
  • Inspect bellows assembly for corrosion, distortion, pinholes, etc. Replace as necessary.

Probe Type Control

  • Inspect probes for signs of corrosion, solids deposition, distortion, and security to probe holder. Clean or replace as necessary,
  • Inspect probe holder for signs of corrosion, distortion and leakage. Clean or replace as necessary.
  • Inspect the water level gauge glass, water gauge valves, and tricocks, if equipped. Clean or replace the level gauge glass. Repair or replace valve and tricocks as necessary,
  • Clean all gasket bearing or sealing surfaces on handhole, manhole and level control/low water cut-out and install new gaskets.
  • Fill boiler with water (60-100oF) and hydrostatically test at 110% of operating pressure or maximum allowable working (gag or remove relief valves), whichever is less. Inspect boiler tubes, piping connections, handhole and manhole plates, etc. for leaks. Repair or replace as necessary.
Watertube Boiler
  • Clean loose scale and sludge from the tube surfaces and boiler drums,
    Inspect boiler tubes for pits, water solid deposition, and general corrosion. Clean, repair or replace as necessary,
  • Inspect the baffle plates in the steam drum for signs of distortion and integrity. Repair or replace as necessary.
  • Clean the steam outlet dry pan or other separation equipment. Also inspect for security and integrity. Repair or replace as required,
  • Clean feed water line and internal distributor header. Inspect for security and integrity. Repair or replace as necessary,
  • Clean surface blowdown lines, strainers and valves. Inspect for security and integrity of internal piping and operation and integrity of valves and strainer. Repair or replace as necessary,
  • Clean bottom blowdown line and valves. Inspect for security and integrity of internal piping or trough and operation and integrity of valves. Repair or replace as necessary,
  • Inspect all nozzle openings in boiler for signs of weld distress and/or corrosion. Repair or replace as necessary,
  • Inspect pressure control header for cleanliness, corrosion, and integrity. Clean, repair, or replace as necessary,
  • Inspect the pump control and low water fuel cut-out mechanisms for cleanliness, corrosion and integrity.

Cast Iron Boiler

  • Clean loose scale and sludge from the sectional surfaces,
    Clean feed water line and strainer. Inspect for security and integrity. Repair or replace as necessary,
  • Clean bottom blowdown line and valves. Inspect for security and integrity of piping and valves. Repair or replace as necessary,
  • Inspect all nozzle openings in boiler for signs of distress and/or corrosion. Repair or replace as necessary,
  • Inspect pressure control header for cleanliness, corrosion, and integrity. Clean, repair, or replace as necessary,
  • Inspect the pump control and low water fuel cut-out mechanisms for cleanliness, corrosion and integrity

 

While all phases of a boiler maintenance and inspection program are important, the most crucial part is the maintenance, testing and inspection of the boiler operating and safety controls and interlocks. In fact, the vast majority of boiler failures or outages are related to control and instrumentation failure or problems. These failures result in low water conditions, over-pressure, over-firing, furnace explosions, etc.

All Boilers

  • Inspect all boiler operating gauges or instruments (pressure and temperature). Recalibrate or replace as necessary.
  • Test and inspect the boiler main fuel valve(s) and actuator for tightness (leak thru), closing time, opening time, stroke and staging sequence. Also inspect electrical connections and terminals for cleanliness and tightness. Repair or replace as necessary,
  • Test and inspect the fuel vent valve and actuator, if equipped, for tightness, closing time, opening time and sequence. Also inspect electrical connections and terminals for cleanliness and tightness. Repair or replace as necessary,
  • Test and inspect the pilot fuel valve and actuator for tightness, closing time, opening time, stroke, and sequence. Also inspect electrical connections and terminals for cleanliness and tightness. Repair or replace as necessary,
  • Test and inspect fuel pressure regulator for stroke, fuel delivery, and pressure requirements. If the pressure regulator is a diaphragm type, inspect exhaust port to insure clean and open. Repair and replace as necessary,
  • Stroke and inspect fuel metering valve and linkage to insure free movement. Clean and lubricate ball joints and linkage . Repair or replace as necessary,
  • Test and inspect the high fuel pressure interlock for proper setting and functionality. Also inspect electrical connections and terminals for cleanliness and tightness. If the switch is the mercury bulb type, inspect mercury for oxidation. Repair or replace as necessary,
  • Test and inspect the low fuel pressure interlock for proper setting and functionality. Also inspect electrical connections and terminals for cleanliness and tightness. If the switch is the mercury bulb type, inspect mercury for oxidation. Repair or replace as necessary,
  • Test and inspect the high steam pressure and the hi-high steam pressure switch for proper setting and functionality. Also inspect electrical connections and terminals for cleanliness and tightness. If the switch is the mercury bulb type, inspect mercury for oxidation. Repair or replace as necessary,
  • Test and inspect the steam pressure modulating controller. Inspect bellows or Bourdon tube for signs of corrosion, pinholes, or fatigue. Inspect signal output generator (potentiometer, etc.) for cleanliness, burn spots, etc. Also inspect electrical connections and terminals for cleanliness and tightness. Repair or replace as necessary,
  • Test and inspect the water level controller and low water fuel cut-out switches for proper setting and functionality. Also inspect electrical connections and terminals for cleanliness and tightness. If the switch is the mercury bulb type, inspect mercury for oxidation. Repair or replace as necessary,
  • Inspect the draft fan (forced and/or induced) blower for damaged or loose blades or vanes, cleanliness, bearing (radial and thrust) condition and lubrication, and coupling assembly to driver (motor or turbine). Additionally, inspect the blower cage or housing for signs of corrosion, distortion or other distress.
  • Stroke and inspect air dampers or louvers and linkage to insure free movement. Clean and lubricate ball joints and linkages. Clean and inspect air intake filter or “bird screen”. Repair or replace any necessary parts.
  • Test and inspect the flame scanner or rod for broken lens or ceramic and adequate flame signal strength. Also inspect sighting port for alignment and cleanliness. Clean flame scanner or rod and correct any adverse conditions,
  • Test and inspect flame safeguard control (chassis, amplifier, program module) for proper operation, sequence, control, and interlock capabilities. Replace any necessary or suspect parts. Also, clean, tighten, and inspect wiring terminals and connections on the controller sub-base,
  • Inspect the draft fan(s) and feed water pump(s) motor starters for loose or corroded connections, terminals, or weak coils. Repair or replace as necessary,
    Perform combustion tuning and efficiency optimization on burner for all ranges of firing rate (low, medium and high).

 

Safe, reliable, and efficient operation of steam boilers is always the goal of the Boiler Operator. Below are listed some proven maintenance tips for your boiler.

Maintenance: Daily

1. Blowdown boiler at least twice every 8 hour period in use. On high pressure boilers, it is recommended the boiler be blown-down at 15 - 25 PSIG if possible. Blow down as follows:

  • Open the first valve from the boiler.
  • Open the second valve from the boiler.
  • Allow boiler to blow down until the pump turns on and the burner cuts off.
  • Close the second valve from the boiler.
  • Wait for the pump to turn off, then repeat steps 2, 3, and 4 at least three times.
  • Close the valve from boiler.


2. Blowdown water gauge glass to keep free of scale obstructions. See item 5 weekly below.

3. Blowdown the water column and level control, and check that the pump starts and the low water cut-off operates in the proper sequence, at least twice every 8 hour period.

Maintenance: Weekly

1. Check flame safety system for proper operation.
2. Check ignition wires and replace if brittle or cracked.
3. Clean scanner tube with a soft cloth and detergent. Wipe completely dry.
4. Visually check burner condition and flame appearance.
5. On 80 HP and larger, guage glass valves should be closed and reopened to maintain freedom of the ball check mechanism. The ball check mechanism is to prevent steam and water from spraying from the water column in case of guage glass blow-out.

Maintenance: 90 Day

1. Avoid excessive "popping" of the safety/relief valve as even one opening can provide a means for leakage. Safety/relief valves should be operated only often enough to assure that they are in good working order.
2. Blow-out steam guage and pressure switch line slowly at 15 to 20 psig.
3. Remove all handhole and man hole plates for internal inspection of scale and corrosion conditions, scrape clean internal seating surface and plate surface. Wash the boiler thoroughly, especially the rear tube sheet and top of furnace. Install only new gaskets. Replace leaking gaskets immediately to prevent wire drawing of the seating surface.
4. Remove plugs on feed line and water column connections and clean out fittings into boiler shell.
5. Inspect tubes for cleanliness and leaks.
6. Repack leaky valve stems.
7. Replace water guage glass as necessary for good visibility of water level.
8. Clean pump suction strainer.
9. Clean lint and dust from blower wheel blades.
10. Check and clean airway to pilot. This may be done easily by pushing a hacksaw blade or similar piece of material through the opening several times. Low pressure air may be used.

Maintenance: Yearly

1. Call inspector for annual inspection.
2. Remove water level control float and clean float bowl.
3. Remove secondary low water cut-off prove and check for corrosion.
4. Clean Steam Dry Pan on Vertical Tubeless Boiler. Clean Boiler Feed Fitting, be sure to install "Top" as stamped on nipple.
5. Tune burner combustion parameters.