Steam banging?

[deerefanatic]

Hello all,

When I fired up my prototype gasifier last time, I had some issues with what I think was steam formation. I was running the unit, and it was just starting to fire up. Pre-Heat exchanger temps were about 850F. The water was at 50F when I started (the whole system was cold) and it didn't warm up very fast. My temperature controllers hold the stove circulator off until the water in the stove reaches 180F. At 150F, I stepped outside and could here the stove "kettling" or gurgling. Pre-Heat exchanger temps were now around 925F. I decided I might want to start manually cycling the circulator to gradually introduce the cool water to not shock the boiler. I switched on the circ pump and a tremendous bang insued. I immediately shut the pump off. I tried again and it banged again. Water temp was starting to cllimb toward 180F by this point. I finally just switched on the pump. The pipes banged 3 or 4 times before things settled out.

All the piping to & from the boiler is black iron, the primary loop is black iron, and all the piping to/from my storage tank is black iron. The pumps are all on the primary loop pumping toward the various devices. I was running open topped expansion tanks at the time that were elevated about 4 ft above the boiler, with about 2 ft of water in them. I'm planning on going to a low-pressure pressurized system. (about 5-6 psi working pressure)

What do you all think was happening? I'm pretty sure I was boiling the water right around the firetubes while the rest of the water was still well below the boiling point. If it means anything, I'm using a 0010 on this boiler.

 

[steam man]

I'm thinking you had some flashing when the cold water hit the hot piping. There's nothing gradual about the flow rate on an 0010. What do you think the flow rate is through the boiler? I'm curious. Just to experiment you could put a bypass around the pump or preferably the boiler to slowly bring the flow rate up.

Mike

 

[Nofossil]

I have a bypass loop that allows recirculation through the boiler. I start the circulator as soon as I light the fire, and recirculate until it reaches temp. The EKO controller starts circulation at about 150. I would think waiting for 180 is too long - you'll have hot spots that could be much higher.

 

[deerefanatic]

OK.

I figure the flow rate through the boiler is probably close to the no-head flow of the pump. I only have about 30 feet of 1.5" pipe going to/from the boiler (about 18 to the inlet, and 12 from the outlet) with 9 elbows. The heat exchanger jacket is very open inside, so not much restriction there.

Ok, I'll lower the temperature for start-up down around 150F and see if that's different. I wonder if running some pressure will help keep kettling down. I know that even with the circulators running, after the stove starts burning hard (around 1250F exhaust temps) the fans start cycling unless the house is drawing heat. Even then, with the circs running water through and the water temp at ~190, I can hear the gurgling in the stove.

What I'll do is allow the primary loop to run continuously and then have the stove circ run continuously whenever the stove fan controller is energized. Then if the stove is operating too low, I'll have the override relay shut down all the loads... That way the water in the stove can circulate continuously, but I'll still have boiler protection from under-temp.

Question, the capacity of the stove heat exchanger, stove pipes, and primary loop is about 70 gallons. Is that too much to have for the stove during warm up or is it ok? Once the system is fully operational, that water shouldn't get below 100F ever.

Thanks for the help.

 

[Willman]

Are you "pumping away" ?
Will

 

[deerefanatic]

Oh yes, definitely. Pumping away from the primary loop.

 

[Willman]

How about from PONPC ? Very important for noise issues. Just asking.
Will

 

[deerefanatic]

Yes, on a primary/secondary system, the entire primary loop is considered the PONPC.......... Of course, It was just a psi or so due to just being down pressure from the overhead expansion tanks......