For safe operation and dependable service to be maintained as a boiler system is brought online or offline, certain steps need to be followed. These steps vary depending on whether the system is hot or cold.
Startup, Hot System
The following steps apply to a boiler in a hot system coming back online:
- Power the burner switch, and prove the pilot and main flames.
- Ensure the boiler vent and the drain between the main stop valve(s) and the non-return valve are open. This bleeds any air from the system.
- If one is installed, open the equalizing valve around the main steam stop valves.
- Open the main steam stop valve(s).
- When the pressure reaches 10 to 15 psig, close the boiler vents.
- Test the low-water cutoff by securing the boiler feed, and let the boiler steam off naturally. If the switch does not cut power to the burner at the proper low level, break power to the burner immediately, and take corrective action. If it does cut power, reopen the boiler feed valve, and allow the low-water cutoff to automatically recycle, restarting the boiler.
- When the steam pressure reaches 75 to 85 percent of the system line pressure, open the non-return valve.
- Manually test the safety valve for proper operation and reseating.
- During low fire, increase boiler pressure slowly, allowing the non-return valve to automatically cut the boiler into the live system.
- Close the equalizing line valve (if installed) and the drain between the main stop valve(s) and the non-return valve.
- Verify all automatic controls are operating properly.
Startup, Cold System
A cold boiler system is one in which the piping and boiler are cold or at ambient temperature. The system is in a contracted state and expands as it heats up. The following steps detail how to bring a cold boiler system online:
- Check for evidence of leaking, such as dripping or calcium deposits on piping, joints, and fittings.
- Inspect the expansion joints’ ability to expand properly when the system “grows” with heat.
- Check the fuel supply. For heavy oil, ensure the preheating equipment (electric and/or steam) is functional. For light or heavy oil, confirm the tank is full and void of water near the bottom. If firing gas, ensure proper pressure at the main regulator.
- Ensure inspection openings in the boiler are gasketed properly and closed. Make sure any covers on the vent stack and manual dampers in the breeching or stack are open.
- Open the boiler vents and the manual boiler feed valve. Ensure the blowdown valves and any bypass valves are closed. Open the manual gas valves, and check for any leaking of the automatic valves in both the main and pilot. Check the safety valves for proper piping and safe discharge through the roof.
- Fill the boiler with water to the level indicated by the boiler’s sight glass.
- Check the boiler feed system, including the pumps, for proper alignment and packing, if required. Check the automatic feedwater valve for signs of leaking or damage. Allow the feed system to fill to its proper level, and apply power to check the operation of the pumps, including their discharge pressure.
- Check the condensate transfer pumps for proper condition and operation.
- Engage the burner switch, bringing power to the boiler’s control circuit. Visually inspect the pilot and main flame ignition. Test the flame scanner for proper operation.
- Begin warming the boiler slowly, allowing for gradual expansion. Open the (automatic) non-return and main steam stop valves. Open all drain valves to allow condensate to exit the piping before steam fills the system.
- Watch the gauge glass on the boiler’s low-water cutoff to ensure the proper water level is maintained.
- After the pressure reaches approximately 15 psig, begin closing the boiler air vents and drains.
- Blow down the low-water cutoff and its gauge glass.
- Ensure the operating systems are working properly.
- Check the water-softener and/or dealkalizer electrical power, operation, and brine-tank filling.
- Switch the boiler to automatic operation, and monitor to ensure safety and reliability.
Shutdown
To shut down a boiler:
- Power off the burner.
- Shut off the fuel to the burner.
- Open the superheater outlet drain valve (if equipped).
- Close the main steam stop valve(s), and open all drains.
- Shut down the boiler feed system.
In addition to following procedures for proper boiler startup and shutdown, scheduling routine maintenance is important for safe and reliable operation.
Steve Connor is an expert on steam and hot-water generation with more than 50 years of experience. He retired as director of technical and marketing services for Cleaver-Brooks. He can be contacted at [email protected].