Boiler Warmup 1

[longbow7]

I have worked many years on drum watertube boilers with superheaters.We always started a boiler with the superheater drains and vents open.The drum vent was initially open and then closed at about 25psig.I now work with a boiler that does not have a superheater..We start it with the drum vent open and with the main steam outlet open to the blowdown tank but closed to the steam header.
Do we need to open the valve to the blowdown tank or can we just warm up the boiler with vent open until 25 psig.
Full pressure is 750 psig.Warm rate is 100 f/hr.

 

[davefitz]

It is difficult to know the correct answer without more data for your specific case, but in general:

a) the greater the steam flow path area avalable, the better, in order to limit the rate of increase in drum pressure ( and the coresponding increase in drum metal temperature). This becomes of greater importance as the drum wall tickness increases over 4" thk, and also is important if you do not have a low turndown burner.

b) During initial fires in a cold furnace , the water in the waterwall is subcooled ( ie the temp is below saturation temp for the current drum pressure). Natural circulation of water will not initiate until the water is warmed up to saturation temp. This process of initiating nat circulation is handicapped if you build up drum pressure too fast. So having a lot of open area for the steam to flow is also important from this standpoint.

If the noise is too much for you, you can either put a muffler on the blowdown tank vent, or buy a startup ignitor gthat has much better turndown ( to about 10% MCR heat input), then maybe you can thrttle down the line to the blowdown tank. Some minimum steam flow is needed to pre-warn the main steam line and stop valves prior to lifting the nonreturn valve off its seat.

 

[longbow7]

I agree with what you say .I would prefer to leave the lines open and bring the boiler up at a drum metal rate of 100 f /hour.This is what I have always done in the past.
Some of the people at my new position say they never did this and instead just turned off the gas when pressure climbed too fast.
The turndown of the burner is very good and noise is not a great issue since we are far out in the bush.
Thank you for your reply