INFORMATION SHEET

 

                                  BOILER LIGHT-OFF/BURNERFRONT OPERATION

                                                   Information Sheet Number 62P-201

 

 

INTRODUCTION

 

            Since a boiler light-off is one of the most potentially dangerous evolutions in a steamship, the importance of the safety associated with it cannot be over-emphasized. This evolution requires strict compliance with precise procedures to preclude damage to equipment and injury to personnel.  Such precision is required that the light-off must be closely supervised and the Type Commanders have mandated that a safety observer be present for light-off.  This safety observer must be a qualified Engineering Officer of the Watch (EOOW) or someone designated in writing by the Commanding Officer (the Burnerman ECCTT, for example).

 

            It is clear that the safety observer must supervise the actual light-off of boiler fires.  As you read through these procedures, the precision and safety required obviously requires a great deal of supervisory involvement.  By virtue of that, they seem to dictate the involvement of the safety observer earlier than the light-off procedures themselves.  Since it is unclear which steps the safety observer must observe beyond the actual lighting of fires, each ship must establish their own guidelines.  It is recommended that the safety observer be present to observe all steps from the BTOW inspecting the atomizer before it is inserted and the firebox inspected until a stable flame pattern and clear stack have been established.

 

            The following summary of the boiler light-off and the burnerfront procedures provides a broad overview. The subsequent actions to bring the boiler on the line are discussed in the Dynamic Plant Operations lesson.

 

 

REFERENCES

 

            (a)  600 psi Main Propulsion Boilers NAVSEA S9221-A3-MMO-010

            (b)  Boilers NSTM Chapter 221

            (c)  Engineering Operational Sequencing System

 

INFORMATION

 

A.        PREPARATIONS FOR LIGHT-OFF.  Prior to commencing the light-off, various pre- conditions must be checked and established.  Each step is included in the EOSS and must    be followed precisely to preclude problems or delays.  Many steps can be accomplished          simultaneously, but several others must follow sequentially.  Before starting the light-off,       all MLOC checks must have been completed.  This ensures that the space is safe and free         from potential fire hazards while establishing a consistent and standard starting point.

 

1.  ESTABLISH BOILER WATER LIGHT-OFF LEVEL.  To progress logically through the procedures, it is helpful to state the starting point assumptions.  Before the actual steps to light fires start, the boiler must be filled with water and the light-off level established.  This ensures that the boiler has enough water for light-off, the economizer is full of water which will absorb the heat of the exhaust gases and prevent it from overheating, and that the feedwater system is properly aligned.

 

2.  PRELIMINARY FIREBOX INSPECTION.  A preliminary inspection of the firebox is conducted by the BTOW with a boiler inspection device (BID) to see if there is any fuel on the furnace floor or damage to the refractory.  This helps preclude any unnecessary delay in light-off but still needs to be accomplished again later in the sequence after the fuel oil has been aligned and the atomizer inserted into the boiler.

 

3.  TEST THE BOILER CONSOLE AND THE ABC SYSTEM COMPONENTS.  The automatic boiler controls are tested and the console aligned for operation.  This procedure verifies that the final control elements should operate in remote manual control since each component is actually manipulated from the console.  There is no means prior to light-off to verify that the system will operate properly in automatic.  An indication of proper automatic operation can be achieved by testing the minimum signal selector prior to light-off.  This helps verify that the system should respond in the desired series/parallel manner, allowing air to precede the fuel on an increase (series) demand signal and both to come down together on a decrease (parallel).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4.  TEST FUEL OIL TANKS, ALIGN FUEL OIL SYSTEM AND TEST THE QUICK CLOSING VALVE.  Fuel oil service tanks are sampled and tested for bottom sediment and water (BS&W) before being placed on suction. This includes aligning the system for light-off, also. Since the fuel oil service pumps are positive displacement pumps and need to provide a constant flow or the system will over-pressurize, the fuel oil service system is aligned to recirculate the fuel back to the tank on suction. The system is aligned in accordance with Equipment Operating Procedures (EOP) for the fuel oil service system and a fuel oil service pump placed in operation with the "recirc" valve cracked open to provide a flow.  This EOP for the fuel oil system requires that the firesafe fuel oil strainers be pressurized and tested and the operation of the fuel oil quick closing valve (FOQCV) be tested from each location.  This test ensures that the valve does not leak by, allowing fires to continue to burn because the flow of fuel cannot be stopped.  The test of the FOQCV must be done while the system is pressurized, usually at the maximum fuel oil header pressure.  Testing the FOQCV while under pressure helps protect the seat and disk from accelerated wear.  The test requires that the FOQCV be tripped and the header pressure gage board be observed to ensure that the pressure reaches zero PSI.  When pressure is zero, the "recirc" valve is shut and the pump is operated against the dead head of the FOQCV to verify no leak-by.  Do not operate the pump on a no flow condition for very long.  Fuel oil quick closing valves will deteriorate over time and will need work to provide no leak-by.

 

5.  INSPECT AND INSERT ATOMIZER.  With the fuel oil system re-aligned after testing the FOQCV, an atomizer is assembled and then inserted into the firebox.  ALL atomizers shall be inspected by the BTOW before being inserted into the burner assembly. This external inspection ensures that the atomizer is assembled correctly.  In the past, improperly assembled atomizers have been inserted into the burner assembly and have caused serious casualties.

 

6.  ALIGN ATOMIZATION SYSTEM.  Since the high quality steam needed for steam atomization is often not available for the initial light-off, low pressure compressed air is used for atomization for light-off.  The air pressure must be at least 85 PSIG.  To be of sufficient quality for light-off, the temperature of the steam must be above 370oF. The air is aligned to the burner through a detachable flexible hose which is connected when being used and disconnected when not being used.

 

 

 

 

 

 

 

 

7.  INSPECT THE FIREBOX.  After the atomizer is inserted, another firebox inspection is conducted using the BID.  This additional inspection is required to ensure that the atomizer and burner assembly do not leak allowing fuel into the firebox.  Fuel oil header pressure is regulated to the light-off pressure for this inspection. There is no specific guidance for what header pressure should be, however it is universally accepted to be light-off pressure.  The firebox is inspected in accordance with CP NO. BID.  If no unburned fuel is found on deck, light-off may proceed. For a hot boiler with fuel on deck, follow the procedures in EOCC for Loss of Boiler Fires. For a cold boiler with fuel on deck, follow the procedures in the EOP.

 

8.  PURGE THE BOILER.  After achieving a satisfactory firebox inspection, the boiler is purged to provide good, fresh air and avoid a potentially explosive atmosphere in the boiler.  All boiler light-offs are conducted using the electric forced draft blower to preclude creating a potentially explosive condition from excess air called a white smoke condition.  Excess air causes fuel to become an aerosol without burning.  This fuel goes up the stack and may condense and pool on the cooler upper portions of the stack creating a serious explosive hazard.  The electric blower is designed to be too small to supply enough air to create this white smoke condition.  Other material problems may cause white smoke to occur, despite this design precaution.  Purging the boiler in accordance with the purge table, which is mounted on the burner front, gives five volumetric change outs of air in the firebox and the uptakes.  When purging, all air registers are opened and left so for the time directed in the purge table.  The time required for the purge is based upon the actual windbox or draft pressure.

 

9.  VERIFY POSITIVE WINDBOX PRESSURE.  When the purge is completed, all air registers are shut except for number one burner.  This is the burner used for light-off and the air register is left open to verify positive windbox pressure for light-off.  Positive windbox pressure guarantees that there will be enough air for combustion.  The watch team has five minutes to light fires after the purge is completed or another purge must be conducted.  This five minutes starts when all air registers are shut, excluding number one air register.

 

 

 

 

 

 

 

 

 

 

 

B.         BURNERFRONT LIGHT-OFF PROCEDURES. 

 

1.  When the required tests and checks have been completed, the burnerfront is considered ready for light-off.  The light-off is accomplished under the direction of the BTOW and the supervision of a safety observer.  The burnerman is assisted by another person, usually the fireroom lower levelman.  The minimum protective clothing for these two watchstanders is long-sleeve fire retardant coveralls.  The burnerman or torchman must wear a face shield and gloves.  There is no requirement for manning damage control gear since a 27 pound PKP fire extinguisher should be mounted on or near the burnerfront.  Many ships actually dismount the 27 Lb. PKP fire extinguisher and man it in case it is needed.  This is not required but many ships find it a useful practice.

 

2.  Close all air registers except number one.

 

3.  Adjust the combustion air and fuel oil pressure for lighting fires.

 

4.  Close the number one air register.

           

5.   LIGHT THE TORCH.  The torch is lighted using a metal encased lighter.  Using a plastic butane lighter is prohibited because of the danger of explosion.  Once lighted, the torch is inserted into the firebox and verified to be lighted.  When being inserted into the firebox through the torch port, the torch is sometimes blown out by the difference in air pressure between the firebox and the space.

 

6.  LIGHT FIRES.  When directed to light fires, the burnerman opens the safety shut off device and the root valve operator opens the root valve one half turn.  Ignition must occur within three seconds or the evolution must be terminated.

 

7.  IGNITION OCCURS.  When ignition occurs, the root valve is opened fully, the torch removed, and the recirc valve is shut.  On certain burner assemblies, the air register is fanned (rapidly opened, closed and opened again) to bring the flame in to the tip of the burner.

 

8.  STABILIZE FIRES.  The console operator reduces the fuel oil header pressure to minimum pressure to allow the boiler to heat up slowly.  The stack is monitored continuously through the periscope and by a topside smoke watch to ensure good, clean combustion.  The smoke watch must be in constant communications with the fireroom.  This watch remains on station until the boiler controls are placed in automatic .

 

 

 

 

9.  RAISE PRESSURE.  Raise steam pressure slowly to allow the boiler to warm-up evenly and expand smoothly. As steam pressure increases, a variety of steps are followed to prevent damage to the plant or complications to the light-off process.  It should take one and a half hours to bring a boiler online from a steam blanket and about two hours for a cold boiler.  LHA and LHD class ships generally take longer to come on line.

 

C.        FAILURE TO LIGHT FIRES.  If ignition does not occur within three seconds, secure the         root valve and safety shut-off device and follow the procedures in the EOP.  Inspect the           firebox for accumulations of fuel and inspect the atomizer for proper assembly.  If the            cause is determined and corrected, the boiler is re-inspected, re-purged and the light-off       reattempted.  If there is evidence of unburned fuel oil on the furnace floor, the boiler shall           be tagged out and opened to wipe up the oil.

 

D.        SHIFTING ATOMIZATION.  In ships using steam atomization where the light-off was            done with air atomization, a shift to steam atomization is conducted when steam          temperature and quality are satisfactory (greater than 370oF).  This is done by lighting off       a burner in number 2 burner assembly with steam atomization and then securing the             atomizer in number I burner assembly.  When number I burner assembly is ready for steam        atomization, it is re-lighted and number 2 burner assembly is secured.  Additional     atomizers are assembled, inspected, inserted and lighted-off as needed while raising steam    pressure.