At boiler’s start-up, one should take care of water swirling at boiler’s Drum, especially when you start at Cold Start Mode.
Swirling at cold start, makes water level fluctuates very much at the Drum. Therefore it can trip the boiler with Drum level Hi Hi protection (MFT).
Imagine you have some of water in a kettle, and you start boiling the water, the mixture will be water and bubbles. That is what happened at drum but with so many fluctuations.
Water swirling takes time until water level stabilize, when a build up pressure at Drum equal to 1 barg. You can notice this from the Drum level indicator.
So, how can we eliminate such this problem?
1- Open start up blow off valves ( 2 valves )
2- Open continuous blow down valve ( 1 valve )
3- Reduce warm up fuel flow mass ( rate of fuel )