Boiler Operation Procedures Chapter 8
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A simplified do' & dont's for low pressure boiler start-up in industries.
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Boiler Operation Procedures Chapter 8
- 1. PowerPoint® Presentation Chapter 8 Boiler Operation Procedures Taking Over a Shift • First-Time Boiler Start-up Procedures • Routine Boiler Start-up Procedures • Boiler Maintenance Procedures • Boiler Shutdown Procedures • Boiler Inspection • Hydrostatic Test • Boiler Troubleshooting
- 2. Chapter 8 — Boiler Operation Procedures Boiler operation information is communicated to the boiler operator starting the shift to specify any special procedures required.
- 3. Chapter 8 — Boiler Operation Procedures When blowing down the gauge glass, water should enter the gauge glass quickly when the gauge glass blowdown valve is closed.
- 4. Chapter 8 — Boiler Operation Procedures During a bottom blowdown, the boiler should be under light load and the water level should be at the NOWL.
- 5. Chapter 8 — Boiler Operation Procedures The blowdown valve is opened to evacuate the low water fuel cutoff chamber with the burner firing during blowdown.
- 6. Chapter 8 — Boiler Operation Procedures When testing the flame scanner, the flame scanner sensor is covered to simulate a flame failure.
- 7. Chapter 8 — Boiler Operation Procedures Before starting the boiler for the first time, the boiler should have a minimum water level of approximately 2″ above the bottom of the gauge glass.
- 8. Chapter 8 — Boiler Operation Procedures The burner is started in low fire according to procedures specified by the manufacturer.
- 9. Chapter 8 — Boiler Operation Procedures The boiler vent is closed when pressure in the boiler reaches 10 psi to 15 psi.
- 10. Chapter 8 — Boiler Operation Procedures The main steam stop valve is opened slowly to allow the pressure to equalize when the boiler is a few pounds below the header pressure.
- 11. Chapter 8 — Boiler Operation Procedures A broken or discolored gauge glass is replaced using standard procedures for maximum safety.
- 12. Chapter 8 — Boiler Operation Procedures The low water fuel cutoff controls must be installed vertically for proper performance.
- 13. Chapter 8 — Boiler Operation Procedures The burner is maintained and tested to ensure proper operation and maximum efficiency.
- 14. Chapter 8 — Boiler Operation Procedures Feedwater pumps should be checked periodically to ensure proper bearing temperatures and checked for any unusual vibration.
- 15. Chapter 8 — Boiler Operation Procedures Safety valves are routinely tested to ensure proper operation and must be serviced by an authorized manufacturer representative.
- 16. Chapter 8 — Boiler Operation Procedures Steam traps are checked for proper operation when determining the cause of a steambound feedwater pump.
- 17. Chapter 8 — Boiler Operation Procedures When inspecting a boiler, inspect tube sheets, tubes, and other internal parts for corrosion, overheating, and/or other damage.
- 18. Chapter 8 — Boiler Operation Procedures Handhole covers are removed to provide access to boiler parts during a boiler inspection.
- 19. Chapter 8 — Boiler Operation Procedures All internal surfaces are exposed and cleaned prior to the boiler inspection.
- 20. Chapter 8 — Boiler Operation Procedures Troubleshooting steps from the manufacturer provide a guide to correcting a boiler operation problem.
- 21. Chapter 8 — Boiler Operation Procedures The boiler room log lists boiler operation data that can be used to increase boiler efficiency and identify a potential malfunction.
Editor's Notes
- After performing initial safety checks, the boiler operator should have a duty checklist listing routine duties. A duty checklist helps to ensure quality and consistency in performing various tasks. The duty check-list is devel-oped in conjunction with the boiler room log to ensure that critical duties such as safety valve testing are performed. When taking over a shift, any extraordinary concerns are communicated by the boiler operator ending the shift to the boiler operator starting the shift. This alerts the boiler operator of special procedures that may be required during the shift. See Figure 8-1. Procedures commonly completed during a shift include water column and gauge glass blowdown, bottom blowdown, low water fuel cutoff testing, and flame scanner testing.
- When blowing down the water column and gauge glass, the operator should carefully monitor the action of the water in the gauge glass. See Figure 8-2. Water should enter the gauge glass quickly when the gauge glass blowdown valve is closed, indicating that the lines are free of sludge, sediment, or scale buildup. If the water returns sluggishly to its normal level, there may be an obstruction partially blocking the flow of water. If the apparent obstruction cannot be removed by blowing down, then the boiler should be shut down and allowed to cool. If the gauge glass is integrated with the low water fuel cutoff, the float (or probe) chamber should be opened and inspected. Mud, scale, or sediment deposits should be removed completely. Linkage should also be examined to ensure proper working order. All connecting piping should be inspected for any obstructions.
- The quick-opening valve is opened first when a quick-opening and slow-opening valve are used. See Figure 8-3. The slow-opening valve is opened slowly to the full open position. The slow-opening valve takes the wear and tear of blowdown.
- The low water fuel cutoff is tested by blowing down the low water fuel cutoff or by an evaporation test. The low water fuel cutoff is blown down with the burner firing. The blowdown valve is opened on the low water fuel cutoff. See Figure 8-4. Water and steam leaving the chamber helps to clean out any sludge and allows the float to fall. This shuts off the fuel valve as if there were a low water condition in the boiler. The low water fuel cutoff should be blown down every shift or daily, depending on plant operations.
- The flame scanner is tested with the burner firing to simulate a flame failure. See Figure 8-5. A flame failure can result in a furnace explosion from the ignition of accumulated fuel in the burner. The flame scanner is removed and the scanner sensor is covered. After a short delay, the main fuel valve must close and the flame failure alarm sounds. The flame scanner is cleaned as required and replaced. The programmer is reset by pressing the reset button and the burner is monitored through a complete firing cycle.
- First-time boiler start-up procedures should be followed as specified by the boiler manufacturer. Check the condition of all accessory equipment and interlocks used to start and operate the boiler, such as pressure controls, fuel train, and feedwater supply pumps. Standard procedures include the following: 1.When the boiler is closed, check and close the blow-down valves, water column and gauge glass drains, and try cocks mounted on the water column. 2.Open the boiler vent valves and gauge glass valves. 3.Fill the boiler with water above 69°F to a minimum level of approximately 2″ above the bottom of the gauge glass or enough to close the low water cutoff contact in the burner control circuit. See Figure 8-6. Fill slowly and vent properly to prevent any pressure buildup from flashing of warm water. See complete procedural list on pages 208-210.
- …Continued from page 210. 6.Start the burner in low fire according to procedures specified by the manufacturer. See Figure 8-7. 7.The boiler should be warmed up and boiler metal temperature allowed to equalize. As the boiler begins to warm up, it should be closely monitored for leaks and signs of expansion. See complete procedural list on pages 208-210.
- …Continued from page 210. 8.When pressure in the boiler reaches 10 psi to 15 psi, close the boiler vent. See Figure 8-8. Open drains in the steam headers to warm as required. 9.Test safety valve(s), check all combustion controls, and blow down the boiler. See complete procedural list on pages 208-210.
- …Continued from page 211. 6.When the steam pressure gauge records pressure on the boiler, blow down the gauge glass, water column, and low water fuel cutoff. Close the boiler vent when the pressure in the boiler reaches about 10 psi to 15 psi. 7.Test the flame scanner. 8.In a battery of boilers, when the boiler is a few pounds below the header pressure, slowly open the main steam stop valve and allow the pressure to equalize. The main steam stop valve is opened slowly until it is wide open. See Figure 8-9. See complete procedural list on page 211.
- Checking the gauge glass is the quickest way to determine water level in the boiler. The gauge glass must provide an accurate indication of boiler water level. A broken or discolored gauge glass must be replaced immediately. For maximum safety, the boiler should be OFF and cool when the gauge glass is replaced. A broken gauge glass on a boiler under pressure is replaced using standard procedures. See Figure 8-10.
- The internal mechanism of the low water fuel cutoff should be removed from the bowl at the recommended intervals to check and clean the float ball, the internal moving parts, and the bowl or water column of the boiler. Never polish the float ball to a shine. Polishing removes material and will eventually cause a leak. At the same time, the pipe plugs from the boiler tees or crosses should be removed to ensure that the cross connecting piping is clean and free of obstructions. Low water fuel cutoff controls must be vertically aligned for proper performance throughout the life of the equipment. See Figure 8-11.
- Maintenance of the burner and controls is crucial to maintain boiler efficiency. See Figure 8-12. Spare burner parts should be kept clean and ready to be changed as necessary. Check burner linkage, jack-shafts, drive units, cams, etc. Make sure all linkages, linkage arms, and connections are tight. Lubricate or grease as required. If the burner and control parts cannot be repaired when the boiler is in operation, it should be noted in the boiler room log so repairs can be made when the boiler is taken out of service.
- Feedwater pumps require little maintenance during normal operation. Periodic checks should be made to ensure proper bearing temperatures and check for any unusual vibration. See Figure 8-13. Lubrication should follow manufacturer recommendations. Feedwater pump service should coincide with other scheduled main-tenance to minimize effects on plant operations. During service, the bearings should be checked for wear and lubricant replaced or added. Flexible couplings should be opened and checked for wear and alignment. The coupling should be washed thoroughly and reassembled with new lubricant. The pump seals should also be inspected and, if necessary, replaced. If boiler room log entries indicate feedwater pump performance has sig-nificantly decreased, an overhaul of the pump may be required according to manu-facturer specifications.
- There is no routine maintenance on a safety valve. However, safety valves are routinely tested to ensure proper operation. Safety valves are commonly tested by lifting the safety valve try lever. See Figure 8-14. With the boiler pressure at a minimum of 5 psi, the safety valve try lever is lifted to wide open position. Steam is discharged for 5 sec to 10 sec. The try lever is released, and the disk should snap to the closed position against the valve seat. Malfunctioning safety valves must be replaced as soon as possible. Replacement safety valves must comply with the ASME Boiler and Pressure Vessel Code and all design specifications of the boiler. Any adjustments or repairs to a safety valve must be performed by the manufacturer or an authorized manu-facturer representative.
- Feedwater pumps are designed to pump liquids, not steam. Water vaporizes when the temperature becomes too high or the pressure becomes too low. A steambound feedwater pump is a pump where the entering feedwater turns to steam and causes the pump to quit pumping. To correct a steambound feedwater pump, water fed to the feedwater pump must be cooled. Water that is drawn from a condensate return tank may be cooled by adding water from the makeup system. Cool water can be carefully poured directly on the feedwater pump without spilling water on the motor if the problem persists. Steam traps on the condensate return line should also be tested for proper operation. See Figure 8-15.
- A boiler inspection is performed as a part of plant procedures and/or requirements by the inspection agency. The boiler inspector thoroughly examines the boiler and related equipment for corrosion, overheating, and/or other possible damage. See Figure 8-16. De-pending on boiler inspection requirements, a written report is filed and a new boiler certificate is issued after boiler inspection requirements are met. An inspection date appointment is made to minimize plant downtime. The boiler operator must be present during the boiler inspection. Before inspection, the boiler must be taken off-line. Close, lock out, and tag out the main steam stop valve. Open the boiler vent or try cock to prevent vacuum buildup in the boiler. Close, lock out, and tag out the feedwater line valve to the boiler. If applicable, the makeup water valve is also closed.
- As soon as the boiler has been dumped, open the handholes, remove the manhole cover, and thoroughly flush and wash out the water side. See Figure 8-17. Do not dump a boiler unless it can be flushed immediately. If a boiler is dumped and not flushed right away, the sludge and sediment air-dry on the heating surfaces, making it extremely difficult to clean.
- Frequently, the boiler inspector requires all of the plugs removed at the water column and the low water fuel cutoff controls opened so the inside float chamber can be inspected. Fusible plugs must be replaced. After both the fire side and water side of the boiler have been cleaned, notify the inspector that the boiler is ready for inspection. See Figure 8-18.
- Boiler troubleshooting must identify the problem and restore steam to all loads as soon as possible. Standard troubleshooting steps provided by the manufacturer are followed to isolate and remedy the problem. See Figure 8-19.
- A boiler room log is used to record information regarding operation of the boiler during a given period of time. See Figure 8-20. The number and frequency of the checks to be performed depend on the plant. Some plants maintain a log for every 8-hour period. Other plants maintain a log for a 24-hour period. Maintaining a boiler room log allows the operator to evaluate the past performance of the boiler. In addition, boiler room log information can be useful in determining the cause of a malfunction and/or predicting a possible problem.