One of the advantages of being old and having had varied experiences means that you can often bring a different point of view to something that is going on by reaching back into the past.
As I write this on Monday, 10 March 2008, we are sitting under the deepest low pressure system I think I have ever seen. My barometer is fairly accurate and is showing 940mb and still falling. The Met Office are forecasting very strong winds for later in the morning and the whole of the SW and S Coast is on flood watch because the wind will coincide with a high tide and some coastal flooding is expected. There are reports this morning of very high speeds in the Jet Stream which circles the globe at about 40,000 feet and this tail wind is cutting an hour off trans-Atlantic flights. I had experience of this in the 1980s when I was on a flight from Los Angeles to London which cut two hours off the flight time and had an average over-the-ground speed of over 700mph so nothing new there.
Plenty to grab people’s attention there and the news programmes are full of forecasts of doom, gloom and disaster, it won’t be long before someone couples these reports to climate change……
My mind went back to something entirely different: The problems that conditions like this posed for the fire-beaters in hundreds of mills all over Lancashire.
Let’s step back a little. One of the major characteristics of the Lancashire cotton industry from 1800 until 1914 was continuous expansion. This led to many new mills being built but it also had another effect which isn’t quite as obvious. Existing mills were expanded by building extensions and installing more capacity. This required more power and put more load on boilers and engines. In some cases the plant was replaced to get more power but in most mills the demand was met by modifying existing engines and plant. The result was that by 1900 many mills in Lancashire were running with heavily overloaded engines and boilers and the effects began to show in an increase in cracked flyshafts, loose flywheels and replacement of other parts of the engines. In many cases, the boilers were simply fired harder.
This meant that firebeaters had to be on top of their job and a bad load of coal or a minor breakdown in the stoking arrangements could lead to loss of steam-raising capacity and possible stoppages in the mill. At the very least, in winter, the steam heat would be turned off and all capacity diverted to the engine.
There was another circumstance that led to problems with the boilers; very low atmospheric pressure. This is where experience comes in, if you haven’t done the job you won’t realise what a difference small things can make to the ability of the boiler to keep up with the load. For instance, heavily loaded boilers were always a problem at the start of the week when the brick settings were relatively cold. By Wednesday they had heated up and the job was a lot easier. All these boilers relied for their draught on the difference in pressure between the column of hot gases in the chimney and atmospheric pressure in the stokehold. Contrary to general belief, the chimney didn’t suck on the furnaces, atmospheric pressure forced the air in.
I think you will be able to see where I am going here….. The lower the atmospheric pressure the less air was forced into the furnace. Conversely, the higher the pressure the more air you got. The best conditions of all for a boiler working on natural draught are a combination of a sharp frost and high pressure. The worst is what we have today, high humidity and low pressure.
So, 100 years ago there would be men all over Lancashire anxiously watching their pressure gauges and doing all they could to keep steam pressure up. They had plenty of problems already on a heavily loaded boiler but low pressure like this could be the straw that broke the camel’s back. It really did make a difference to performance. There was another factor that came into play here, in a badly fired boiler there will be occasions where too much coal is added at one time and there will be a burst of black smoke, a sure sign of bad combustion and waste. This smoke is heavier and cooler than the normal flue gas and took more lifting up the stack. It wasn’t unusual to see smoke emerging from the stack and literally falling down into the mill yard.
So, lower atmospheric pressure used to have more consequences than simple bad weather. One further thing strikes me…… You will all have seen pictures of millscapes in Northern towns where every chimney is belching smoke and in view of what I have said about waste, you might wonder why they were working like this. It is often said that efficient fuel combustion wasn’t understood until the late 1930s and the publication by the Ministry of Power in 1944 of ‘The Efficient Use of Fuel’. Whilst there may be a lot of truth in this, smokeless burning and the consequent savings in fuel costs was understood long before this. The book codified all this knowledge and no doubt made a difference but there was a lot of inertia to overcome because it was a common belief amongst engineers that ‘you couldn’t make steam without smoke’. This was corrupted into a belief that the more smoke you made, the more steam and so engineers and boiler men didn’t immediately associate smoke with waste but with heavy loading and production. The mill-owners didn’t help because they had the same belief, it was a badge of good order books and prosperity to have a smoking chimney, in those days a chimney without smoke meant a stopped mill and loss of face. It wasn’t unusual for a mill to burn rubbish in bad times when the mill was stopped in order to look busy. The Clean Air Acts of 1956 and 1968 eventually killed the belief and probably did more for fuel efficiency that any other measure as well as cleaning up our towns.
So, next time you see very low pressure, remember all those old firebeaters fighting for steam in the bad old days! By the way, if you’re wondering about the title of this piece…. We had a mirror mounted on the engine house porch at Bancroft so that the firebeater could see the top of the chimney from the firing floor.
SCG/10 March 2008
The engine house porch at Bancroft had a mirror mounted on it so that the firebeater could see the chimney top and so would know what his smoke condition was.