Starting In Safety
What Should You Do Before Starting Boilers After A Summer Layoff?Editor's Note: Reprinted with permission of The National Board of Boiler and Pressure Vessel Inspectors (www.nationalboard.org), National Board BULLETIN, [October 1989 and Spring 1995, respectively).
With the heating season upon us, it is a good time to reconsider steps that need to be taken prior to starting boilers after a layoff. While this list is not all-inclusive, it can serve as a guide for those responsible for boiler operation.
Before a boiler is placed in operation, boiler operators and other responsible personnel and/or supervisors, must check over the entire system and carefully review operating procedures.
Operating ManualsAll manufacturers of boilers and fuel-burning systems supply operating manuals with their equipment. Unfortunately, many boiler rooms do not have manuals and operating instructions available because they have either been lost or misplaced. It is the responsibility of the supervisor in-charge to obtain these publications and see that they are read, understood, followed, and available in the boiler room.
Maintenance During SummerThe summer shutdown period is a good time to accomplish necessary boiler and fuel-burning system preventive maintenance. A suggested checklist of such maintenance follows:
- Drain and flush the boiler, open all handholes and manholes, clean and remove soot and scale from the firesides. Examine the boiler for damage and corrosion.
- Have the boiler inspected by an authorized inspector, as required.
- Install new gaskets, replace all handhole and manhole covers, refill boiler, and perform a hydrostatic test, if required.
- Institute a suitable boiler water treatment program to reduce scale buildup and corrosion.
- Have the fuel-burning equipment cleaned and adjusted by a competent service technician. Verify operation of all operating and limit controls, interlocks, and gauges. Have the technician disassemble the low water cutoff and water feeding devices, clean, recondition, and reassemble them. Have the technician leak test all fuel safety shutoff valves.
- Lubricate all mechanical equipment such as fans and pumps, and verify motor rotation.
- Check all boiler piping for leaks and missing insulation.
- Make sure provision is made for establishing and keeping a boiler log.
Start-up ChecksImmediately prior to boiler start-up perform the following:
- Check that all ventilation and combustion air openings and louvers are clean and free of debris.
- Verify boiler water level.
- Check that all stack dampers are open.
- Examine the boiler furnace for foreign material.
- Check the furnace and flue passes for fuel accumulation.
- Make sure the manual fuel valves are open.
Normal Start-upAfter completing the start-up checks, close the operating switch and commence the normal starting sequence. The following list suggests a typical starting sequence:
- Close operating controls;
- Close interlocks (safety controls);
- Start fans and purge the boiler;
- Meet purge requirements;
- Energize igniter;
- Prove ignition flame within 10 sec;
- Energize main fuel valve(s);
- Establish and monitor main flame;
- De-energize ignition, prove main flame; and
- Release firing rate (combustion) control to demand normal operation.
This starting sequence should be carefully observed to make sure that all steps are normal. Readings on flame signal strength meters (if fitted) should be observed and recorded in the boiler log.
A normal shutdown should be initiated by opening the manual burner switch. After the post purge has been completed, check the furnace for flame cutoff and make sure there is no residual flame in the furnace. Have fuel safety shutoff valves repaired or replaced if required.
Additional guidance can be found in the boiler operating manuals and in ASME CSD-1, "Controls and Safety Devices for Automatically Fired Boilers," or in the National Fire Protection Association's NFPA 8500 standards on prevention of boiler furnace explosions.ES
The Forgotten Boiler That Suddenly Isn'tBy Lee Doran
The old elementary school in which the subject boiler was installed had been closed down for several years, and the boiler had been removed from the active inspection list by the jurisdiction.
But recently the rundown school building had been reactivated for other uses, and the neglected watertube boiler was started up and placed in service. This was done without inspecting or servicing the boiler to ensure that all controls and safety devices required by the jurisdiction were installed and tested for proper operation.
This forgotten boiler became the center of attention, however, when firefighters were summoned to the school to find the boiler "glowing cherry red" and smoke throughout the building. The boiler system was shut down, thus limiting damage to the boiler itself.
Reviewing this incident, the following was found:
- The boiler was equipped with only one low-water fuel shutoff (combination low-water fuel shutoff and water feeder).
- The piping to the low-water fuel shutoff was plugged.
- Both safety shutoff valves in the main fuel gas train had failed in the open position. These are normally closed valves that must be energized to open, and when examined, all power had been shut off.
- One of the safety shutoff gas valves was an obsolete diaphragm, weight-loaded valve, actuated by an electrical solenoid.
The boiler had been seriously overheated, causing the steam drum to grow lengthwise about 8 in., parting the insulation. This caused the "cherry red glow," a fireman reported.
The boiler experienced a runaway firing condition due to stuck safety shutoff gas valves, and the boiler was dry due to a malfunctioning low-water fuel shutoff and plugged piping. The resulting intense heat melted all the tubes in the boiler.
This incident was preventable, had the boiler been properly serviced and inspected before being placed in service.
Had the boiler been inspected first, the inspector would have recommended that all controls and safety devices required by regulation be installed, and the plugged low-water fuel shutoff piping would have been replaced. The fuel train would have been upgraded to meet current requirements.
It is true that the work required to bring this boiler into compliance with safety standards would have been quite expensive, estimated between $2,500 and $3,000. However, compared to the repairs or more likely replacement, which will cost approximately $45,000 to $50,000, such preventive maintenance would have been a bargain - not to mention preventing hazards to people and property.
This incident again shows the need for thorough inspections by qualified inspectors. Had the jurisdiction been notified prior to placing the boiler in service, this forgotten boiler would not have been remembered so suddenly, dangerously, and expensively.
Safety Tips for Reactivating Idle Boilers
- Exterior shell and/or insulation: Look for indications of overheating.
- Leaks: Look for water on the floor. Check for water or steam escaping from any part of a pressurized system including the boiler, valves, or piping.
- Flue gas leaks: Look for black dust (soot) around sheet metal joints. Check any part of boiler enclosure and breaching, especially in the connection to the stack, and check the boiler exhaust system integrity.
- Controls: Look for open panels, covers, and signs of rewiring on floor or bottom of panels. Check for jumper wires and locked shutoffs.
- Safety Devices: Test all operating controls and safety devices for proper operation. Observe at least three cycles of automatic operation before independent operation.
- Electrical: Ensure that covers are installed on overlimit switches, temperature sensors, and controls.
- Safety valves: Ensure that a safety valve is installed with full-sized discharge piping properly supported and directed to a point of safe discharge. Safety valve set pressure must be equal to or less than boiler maximum allowable working pressure. Safety valve relieving capacity must be equal to or greater than boiler output.
- Fuel sources: Check for the ability to shut off the fuel source to the vessel.
- Gauges: Make sure temperature and pressure gauges are operational and are located for proper monitoring.
- Hazards: Remove all fire hazards from the boiler room and do not use the boiler room for storage.
- Air openings: Check combustion air openings for obstructions.
- Proper piping: Check for proper supports and allowance for expansion and contraction.
- Operating certificate: Observe certificate, noting last date of inspection and expiration date, as well as when next inspection is required.