Feedwater Fill‑Up process in Boilers: Procedure, Importance, and Safety Guidelines
Steam is generated from water in a boiler, making feedwater management one of the most critical aspects of boiler operation. Before lighting up a boiler, the system must be properly filled with feedwater to ensure safe startup and efficient performance. Improper filling can lead to air entrapment, thermal shock, or uneven heating, which may damage boiler pressure parts.
🔹 Importance of Feedwater Fill‑Up
- Ensures safe boiler startup.
- Prevents air pockets that reduce heat transfer efficiency.
- Protects tubes and drums from thermal shock.
- Maintains proper water circulation in economisers, water walls, and evaporators.
- Provides the correct drum level for stable operation.
🔹 Feedwater Flow Path
1. Deaerator to Economiser – Feedwater is pumped from the deaerator storage tank to the economiser using a boiler feed pump.
2. Economiser to Drum – Once the economiser is filled, water enters the steam drum.
3. Drum to Downcomers and Water Walls – From the drum, water flows down through downcomer tubes and gradually fills the evaporators/water walls.
4. Drum Level Rise – After all tubes are filled, the water level in the drum begins to rise.
-- Air trapped in economisers and water walls must be vented through air vents provided at the economiser and steam drum.
🔹 Step‑by‑Step Procedure for Initial Feedwater Fill‑Up
-- Always follow the boiler manufacturer’s operation and maintenance manual for specific instructions.
- Fill the deaerator storage tank with sufficient feedwater.
- Ensure all isolating valves of the feedwater line are open.
- Check gland cooling and bearing cooling water availability for the boiler feed pump.
- Keep economiser air vent and steam drum vent open.
- Start the boiler feed pump with the discharge valve closed. Observe pump vibration, temperature, sound, and current.
- Slowly open the pump discharge valve and monitor changes in vibration, current, suction pressure, etc.
- Begin filling the economiser by opening the feedwater control valve gradually.
- If feedwater is hot, introduce it slowly to avoid thermal shock.
- Once water flows out of the economiser vent under pressure, close the vent valve.
- Allow water to enter the steam drum. From there, it flows into downcomers and water walls.
- As tubes fill, the drum level rises.
- Keep drum level below normal working level to account for swelling (increase in water volume when heated). Adjust drum level after firing.
🔹 Feedwater Fill‑Up for Hydro Test
For hydrostatic testing, all boiler pressure parts must be filled with feedwater:
- Fill the steam drum until water comes out of the drum air vent under pressure, then close the vent.
- Water then enters the superheater.
- Keep the superheater vent valve open and drain valve closed during filling.
- Once water flows out of the superheater vent, close the vent valve.
- Close the feed control valve to prevent pressure buildup in pressure parts.
📌 Key Takeaways
- Proper feedwater fill‑up ensures safe boiler startup and prevents damage.
- Air venting is essential to avoid air pockets that reduce heat transfer.
- Drum level must be carefully managed to account for swelling during heating.
- Hydro test requires filling all pressure parts, including the superheater circuit.
