Boiler Start-Up

Read the boiler manufacturer's manual.

to avoid extinguish of istabished flame also to proper convexsation u must have to maintain -20mmwc draft.

tmp

Hi,

Starting with the furnace draft, it will be maintained between -5 MMWC to -20 MMWC, it depends on the boiler manufacturer and the operator who starts the boiler. It is maintained so, inorder to avoid fire / ash coming out of the furnace , if positive draft is maintained and also to help combustion.

Secondly, this 30% of air flow is enough to maintain the combustion rate at low / starting loads.More air will also reduce the efficiency of combustion by reducing the temperature of the furnace... you can find some more reasons if u go thru the manufacturers manual.

Regards

Karthick

I'm assuming that you did read the manual and that's where you got your numbers. I am also assuming that you are talking a cold start after some down time.

Not knowing the size of your furnace, the things that come mostly to mind are that until your firebox is heated up (refractory bricks etc.,) you don't want to thermally stress all the furnace structure as it heats up and they want you to bring it up to temperature slowly giving the unit time to expand without cracking up things.

It is also very hard to properly fire a furnace or boiler without a hot refractory chamber. Any fuel that does not properly combust coming out of the nozzle will generally burn up as it comes into contact with hot refractory. When you have cold refractory some of the fuel can be deposited onto the refractory and this is not good.

Like the man said, pushing a lot of cold air into a furnace and causing a positive pressure in the firebox is a good way to cause leaks, distortion and wreck your refractory. I would imagine that the operating manual also gives you parameters as to when to increase your fan speeds if this is not an automatic combustion control system.