Re: STEAM ENGINES AND WATERWHEELS
Posted: 18 Jan 2018, 04:57
The second time we ran was less eventful of course because we had no dramas on starting or stopping. We ran it for about half and hour this time and almost put a polish on the rods. There was however, one thing different. When we came to light the boiler the day before, the chimney wouldn’t draw. In other words, there wasn’t enough natural draught on the flue to get hot gas drawn into the chimney and gain artificial draught due to the difference in temperature between the flue gasses in the chimney and the exterior air. Actually this isn’t quite accurate. The draught on a flue is the product of the difference in weight of the column of gas in the stack and the air outside. This difference in weight because the flue gas is hot reduces the atmospheric pressure in the furnace below the ambient pressure and it is this difference that drives air in to the furnace and supports combustion. The flue is under a disadvantage when you first start up with coal because the black smoke, loaded with carbon particles because of incomplete combustion, is heavier than clean air and so as it fills the stack you have to have quite a differential to get it lifted to the top. It worsens as the smoke cools in the cold stack. Even the forced draught fans won’t lift it and so extraordinary measures have to be taken. In Newton’s words, “You have to larn the chimbley to smook!”
To do this we opened a door in the main flue at the back of where the old economisers used to be and built a wood fire in there to further raise the temperature of the gas. After a few minutes you could feel the air being drawn into the chimney and the wood started to roar as it burned. At this point we shut the door, and shovelled some more coal in, we were away. Another point to mention is that at this time we didn’t have any automatic stokers, we had to fire by hand direct into the furnaces.
A couple of days after we had steamed the second time I was up on the chimney and there was a strong smell of sulphur. I asked Peter about it and he said he had noticed it since the second firing. We went down and opened the flue door and had a peep in, the whole of the flue was on fire, we had set fire to the flue dust which was actually partially burned coal. We shut the door and left it to it. There was nothing we could do, it wouldn’t do any harm and in the event it did a good job because it burned for three months and kept the flue dry all winter. It also reduced the level of dust in the flue to about a foot of proper flue dust on the floor. This was the industrial equivalent of mother sweeling the flue at Norris Avenue in my childhood!
While we are talking about flues I’d like to recount one incident that happened much later when I was running the engine each weekend for the public. We started doing this as soon as we had a viable engine, properly insured and this was before I had trained the volunteers so I ran the engine every weekend by myself for 18 months. I got it to a fine art and knew that if I got to Ellenroad at about four o’clock in the morning I could fire up, warm the engine and be ready to run at ten o’clock. It may sound strange but I often used to think as I drove over to Ellenroad first thing in the morning that it was nice to unique. I was the only man in the whole world setting off to run a 3,000 hp engine on my own. There must be thousands of people who would have given their eye teeth to be doing this.
On the particular morning this incident I want to describe happened it was very cold and foggy. I lit the fires as usual but had no draught and the products of combustion were blown back by the fans on the stokers into the boiler house. I knew I had to shut the stokers off and open the flue door at the bottom of the chimney in order to light a fire at the chimney base to get the column of air moving in the stack. There was no wind and when I opened the flue door the smoke fell out of the chimney and gathered in the yard like a big black pool! I’ve seen smoke fall from the top of the chimney down to the ground in similar conditions but I’d never seen it as bad as this. It intrigued me and I tried an experiment. I lit a piece of oil soaked rag and threw it into the smoke just to see what happened. There was no danger of explosion because it wasn’t confined. The rag was extinguished immediately it hit the smoke, there was no oxygen at all in the mixture.
Curiosity satisfied I waited until the smoke had run away along the ground and the chimney base was clear and then I hung an old raincoat soaked in diesel in the flue entrance, lit it and waited for a minute. It soon started to pull and was roaring away. I went into the boiler house, turned the stokers on and then went outside and shut the flue door. That did the trick and the draught soon built up to normal as the hot flue gases warmed the flue. The point about this story is that it shouldn’t have happened because a flue doesn’t normally lose it’s draught in a week, it takes much longer than that. In this case, I reckon it was my fault because I’d started a green fire on coal too soon, I should have burned wood or very small quantities of coal to keep the smoke down on starting. However, I was in a hurry and careless and what I’d done was try to get the chimney to lift heavy smoke, heavy enough to overcome the draught and literally choke the flue. I’d never seen this before and it just goes to show that we can always learn from our mistakes.
To do this we opened a door in the main flue at the back of where the old economisers used to be and built a wood fire in there to further raise the temperature of the gas. After a few minutes you could feel the air being drawn into the chimney and the wood started to roar as it burned. At this point we shut the door, and shovelled some more coal in, we were away. Another point to mention is that at this time we didn’t have any automatic stokers, we had to fire by hand direct into the furnaces.
A couple of days after we had steamed the second time I was up on the chimney and there was a strong smell of sulphur. I asked Peter about it and he said he had noticed it since the second firing. We went down and opened the flue door and had a peep in, the whole of the flue was on fire, we had set fire to the flue dust which was actually partially burned coal. We shut the door and left it to it. There was nothing we could do, it wouldn’t do any harm and in the event it did a good job because it burned for three months and kept the flue dry all winter. It also reduced the level of dust in the flue to about a foot of proper flue dust on the floor. This was the industrial equivalent of mother sweeling the flue at Norris Avenue in my childhood!
While we are talking about flues I’d like to recount one incident that happened much later when I was running the engine each weekend for the public. We started doing this as soon as we had a viable engine, properly insured and this was before I had trained the volunteers so I ran the engine every weekend by myself for 18 months. I got it to a fine art and knew that if I got to Ellenroad at about four o’clock in the morning I could fire up, warm the engine and be ready to run at ten o’clock. It may sound strange but I often used to think as I drove over to Ellenroad first thing in the morning that it was nice to unique. I was the only man in the whole world setting off to run a 3,000 hp engine on my own. There must be thousands of people who would have given their eye teeth to be doing this.
On the particular morning this incident I want to describe happened it was very cold and foggy. I lit the fires as usual but had no draught and the products of combustion were blown back by the fans on the stokers into the boiler house. I knew I had to shut the stokers off and open the flue door at the bottom of the chimney in order to light a fire at the chimney base to get the column of air moving in the stack. There was no wind and when I opened the flue door the smoke fell out of the chimney and gathered in the yard like a big black pool! I’ve seen smoke fall from the top of the chimney down to the ground in similar conditions but I’d never seen it as bad as this. It intrigued me and I tried an experiment. I lit a piece of oil soaked rag and threw it into the smoke just to see what happened. There was no danger of explosion because it wasn’t confined. The rag was extinguished immediately it hit the smoke, there was no oxygen at all in the mixture.
Curiosity satisfied I waited until the smoke had run away along the ground and the chimney base was clear and then I hung an old raincoat soaked in diesel in the flue entrance, lit it and waited for a minute. It soon started to pull and was roaring away. I went into the boiler house, turned the stokers on and then went outside and shut the flue door. That did the trick and the draught soon built up to normal as the hot flue gases warmed the flue. The point about this story is that it shouldn’t have happened because a flue doesn’t normally lose it’s draught in a week, it takes much longer than that. In this case, I reckon it was my fault because I’d started a green fire on coal too soon, I should have burned wood or very small quantities of coal to keep the smoke down on starting. However, I was in a hurry and careless and what I’d done was try to get the chimney to lift heavy smoke, heavy enough to overcome the draught and literally choke the flue. I’d never seen this before and it just goes to show that we can always learn from our mistakes.