| Author |
 Topic  |
|
Doc
Keeper of the Scrolls
2010 Posts
|
|
 Posted -
28/05/2004
:
16:29
|
LANCASHIRE TEXTILE PROJECT
TAPE 78/AI/06 (Side two)
THIS TAPE HAS BEEN RECORDED ON APRIL 27TH 1979 AT 13 AVON DRIVE BARNOLDSWICK. THE INFORMANT IS STANLEY GRAHAM WHO WAS THE ENGINEER AT BANCROFT MILL AND WHO HAS BEEN THE INTERVIEWER ON MOST OF THE TAPES..
Picture number 10. Negative number 777235.
This is a close-up view of the low pressure cylinder front piston rod gland. The gland is the hole in the cover of the cylinder through which the piston rod passes into the bore of the cylinder. A little thought will show us that the joint between the piston rod and the front cover of the cylinder has got to be steam tight otherwise the steam which is admitted to force the piston back down the cylinder will escape round the piston rod by virtue of the fact that the rod has to be free to move. This results in a loss in efficiency. Before I start talking about this, realise that the front and back of the low pressure cylinder are exactly the same and the front and back of the high pressure cylinder are exactly the same as the low pressure. In other words there
(50)
are four of these glands on the engine, one on each end of each cylinder.
In older engines the gland which was used, or the arrangement for preventing steam leakage past the piston rod, was exactly the same as that used on a household tap. In other words there was a recess on the cylinder cover which was packed with cotton waste or cotton rope heavily impregnated with wax, or grease, and an arrangement whereby you could screw down a housing on top of that forcing the packing into the gap between the walls of the gland housing and the piston rod. So that the piston rod was rubbing on a compressed surface of cotton impregnated with wax or grease which gave you the seal. Now this was all right as long as it was very well maintained. I say this because it's all too easy to stop a leak by screwing a gland down more tightly, This compresses the packing and forces it against the rod thus stopping the leak. We have all done it, I have done it myself. And with something that only turns intermittently, such as a valve stem, or the stem of a household tap this isn't so bad because the rod spends very little time rubbing on it. But if you consider a piston rod which is moving backwards and forwards 136 times a minute you very soon get into the stage where, no matter how well the packing is constructed, no matter how soft the cotton is or how well it's greased it starts to wear the rod. This gets worse if the packing is allowed to dry out and get hard. The classic error is not to clean all the old packing out occasionally and start from fresh with new, soft packing. As the grease in the packing carbonises it can get mildly abrasive. In that case we get the condition known as 'Necking of the rod.’ In other words the packing wears the surface away until it's a smaller diameter than the rest of the rod. And the only way that you can keep it steam tight, is to keep tightening the gland up, keep tightening the packing up; and every time you tighten it you wear the rod a little bit more. And that’s why on very many steam locomotives and a lot of old engines you'll find that as the engine's running there is steam blowing out of the joint between the cover of the cylinder and the piston rod. One of the things that people used to comment on when they came into the engine house at Bancroft was the fact that they couldn’t see the steam. They were used to seeing pictures of steam locomotives with steam flying out of every joint and every packing on them. So they used to think it was very surprising when they came into the engine house at Bancroft and there wasn't a wisp of steam to be seen anywhere. This was because we had efficient glands and efficient packings and we recognised that any loss of steam through places like that, romantic as it may have looked, was a waste of coal, and so we didn't tolerate leaks.
Now one of the engineer's greatest friends in doing this is the Universal Metallic Packing. This is what you are looking at on this picture, the large round housing on the front of the low pressure cylinder surrounding the piston rod where it comes through the cover is a Universal Metallic Packing. I'll attempt to briefly explain what one of these is, if anybody listening to this is at all interested I've no doubt that if they look back through the old technical literature they'll find all the drawings which will show them exactly how they were constructed. They were made originally by an American company which set up a branch in Bradford called the Universal Metallic Packing Company. Now I have an idea that what happened was that somebody left their employ in Bradford, re-designed the packing slightly and set up in business on their own, and I think they called it Bradford Metallic Packings Ltd. Eventually the Universal company took the rivals over and they are still in business.
Now, what the metallic packing is is a series of brass blocks lined with white metal, shaped to fit on the rod, they are split so that there are four pieces surrounding the rod at each and held together by coil springs round the periphery. The individual blocks float and adjust themselves to the shape of the rod. There are two sets of these, one behind the other, with the joints opposed so that no joint is directly facing another one. Behind them is a white metal wedge shaped cone which is also split which rides on the shaft as well and that's held together with springs. And the whole thing is confined in this housing which we see here. The effect of this arrangement is to form a cross between a sliding packing, similar to the gland packing we were talking about made of cotton waste, and a labyrinth packing which is a packing whereby there is actually a passage through for the steam but it is made so labyrinthine, in other words the steam has such a long way to travel to get through, that it starts to condense and the condensate forms the seal.
These packings were tremendously successful as long as they were fitted properly in the first place. Once fitted, they gently polish the shaft and keep it in a very high state of gloss and in fact the shaft used to get glazed, the surface used to get work hardened by the constant friction and it almost got to be as hard as glass. And, as long as they weren't disturbed, and that was the important thing, not to disturb them, they were efficient. There is one more requirement to keep the metallic packings efficient, this is lubrication.
There are two ways of lubricating them. The most efficient way is by entraining the oil in the steam so that the leaking steam is carrying oil into the packing and keeps it lubricated. That’s the theory but in practice found that it was always a good thing to use the thistle lubricators which are these rod oilers on the top of the housing shaped like a thistle. This is simply a housing that you fill with cylinder oil and it has a needle valve in it that you can adjust to put one drip on to the rod say every 10 or 15 strokes. This means that the rod is always covered with a thin smear of oil and in effect the packing in riding in oil all the time. I found that if you did that you had no trouble at all with these packings, they just about run for ever.
Notice that the piston rod is stained and not brightly polished. This is the low pressure side, it runs fairly cool and there is a lot of condensate flying about when it is running. What happens every night when you stop, there is always moisture about and it condenses on the coldest part of the cylinder which is the piston rod because part of it is exposed to the relatively cold air outside the cylinder. This starts mild corrosion on the rod which causes the staining you can see in this picture. I used to put some oil into the low pressure lubricator about half an hour before stopping time in an attempt to get a coating of oil on the cylinder and piston to protect it during the night. Bear in mind that I was the last custodian of the engine, the staining was a product of almost 60 years running and some of the engineers hadn’t been too careful about this.
In point of fact they wouldn't have been so bad on this cylinder had it not been for the fact that these metallic packings were getting to the stage where they were just about shot. I have been singing the praises of metallic packings and then saying that these were just about shot but bear in mind that this cylinder had run from 1922 to 1978 and had never been touched. Now when I say that, I have reason to believe that the metallic packings had been renewed or repaired once, but the cylinder had never been opened since the engine had been first bedded down and settled down as new. It had never been re-bored, valves replaced, anything, never been touched. It was as it was built. Because this was the low pressure cylinder the packings were never really under steam because we weren't heavily loaded, we never ran that engine at full load because there weren't the number of looms on. Andy any leakage there was just a slight leakage on the vacuum. In other words those packings weren’t letting steam out, they were letting air in, they were sucking rather than blowing. If it had been on the high pressure cylinder, it would have been a different story altogether, and we would have done them straight away. But all it amounted to was that we were losing a little bit of vacuum by reason of the fact that the metallic packings were getting worn. Because they were getting worn they weren't just seating on the piston rod as they should have done and that’s the reason why these corrosion spots are so visible; otherwise each morning the friction, what friction there is in a metallic packing, would have cleaned the rod up each morning.
The valve that you can see underneath the packing was kept closed during the day and a certain amount of condensate and oil collected in the housing as the engine ran. This ran out of the packing when it reached the level of the bottom of the orifice the rod runs through and was collected in the bucket. On finishing at night the valve was opened and the housing drained. This condensate didn’t do any harm while the engine was running but it would have been a mistake to leave it in overnight. This would amount to about a quart a day and when the bucket was about half full I would take it and throw the mixture on the coal. The water helped to slake the dust and the oil clung to the coal and was burned in the furnaces.
Other things you can see clearly in this picture are the low pressure lubricator in the top left hand corner, the cover nuts and the blued steel held on by screws which covered the middle of the cover. This had insulation behind it. The cover itself has a large boss on the inside of it which fits inside the cylinder, it's a lot thicker than the outside edge where it actually fastens on to the cylinder. I never had one of those covers off, I always said that I would do but I never got round to it. I should think
that that cover's probably 6 to 9 inches thick in the middle.
Picture number 11. Negative number 777812A.
This again is a picture of the back end of the low pressure cylinder but this time in motion. As I’ve already said, I like to have pictures of the engine that actually show it running. One advantage about a long exposure is that the moving parts eliminate themselves and you can see the whole of the slide, not normally possible because the bell crank is always in the way. You can see the grooves in the oil left by the slide as it travels. The funny thing about these slides is that the oil always ends up at the end nearest the cylinder. Don’t ask me why.
Picture number 12. Negative number 776205. Picture 13. Negative number 777232.
We’ll take these two pictures together as they contain a lot of information about the low pressure tails slide. Notice the massive construction of the tail slide itself, bolted down solid on to the flour on two pillars. These in turn are bolted down on to the cast iron frame which is let into the floor of the engine house and connected to the bed of the cylinder and also locked into the end wall of the engine house. This is to make sure that everything is absolutely solid. Again, polished steel rails on cast iron stanchions round it. The rails are very highly polished and woe betide anybody who puts their fingers on them when they come in because they'll go rusty very quickly. There is something very satisfying about keeping something as clean as that, it looked well and really looked efficient. Again notice the nameplate, the brass nameplate Mary Jane and a better view this time of the valve gear on the inside of the low pressure cylinder. Both steam bonnets and both exhaust bonnets are visible on 12. The steam valves are at the top of the cylinder and the exhaust valves at the bottom. A very good arrangement because it means that any condensate which collects in the cylinder can drain out through the exhaust valves in the bottom. When we were talking about relief valves on the cylinders I mentioned slugs of water. A slug of water is any quantity of water which collects or enters a cylinder in one mass or body. This is very dangerous because water is virtually incompressible. There is a certain clearance in the end of the cylinder when the piston is at the end of its stroke but if the volume of the water is greater than the volume of this clearance it means that the piston is trying to compress the water, and water being incompressible, if there is no way of it escaping, either by relief valve or by wear allowing it to get past the side of the piston or through the valve or through the gland in the end of the cylinder, it means that that cylinder will certainly, and I stress that, will certainly suffer damage. Now it's a very dangerous thing. This is the thing that has caused more trouble in steam engines than anything else. Slugs of water in cylinders lead to cracked covers, cracked pistons, cracked cylinders and all sorts of other damage. We used to dread it. The most usual cause was priming in the boiler. In other words if the water in the boiler was dirty and started frothing up, usually on a sudden demand for steam, when the steam pressure started to drop and the water in the boiler started to flash off steam the froth could rise up so far that you were actually getting that froth coming into the pipe and down to the engine. It was carrying muck into the engine and carrying water. In most cases the cylinder will get rid of the water but boiler composition and dirt going through the cylinders does them no good at all. One of the first things a fitter will do when he strips a cylinder down to repair a smash is to look for what looks like dirty whitewash inside the steam spaces. This is a sure sign that the boiler has primed.
We avoided priming at Bancroft by careful attention to boiler water treatment, water levels and good maintenance but there were certain installations that were plagued with it. A lot of good engines have been ruined by these things.
If you look at the right hand end of the tail slide, the forward end of the tail slide down on the floor you'll see a row of four little lubricators with pipes going down through the cast iron chequer plate in the floor. There are a set of these at each side of the low pressure slide and they are the lubricators which were quietly feeding oil down to the joints in the bell crank which drives the air pump in the cellar. The air pump of course is really a big water pump which draws water out of the dam through the condenser into which the exhaust steam was passed from the cylinder exhaust. Steam plus cold water equals instant vacuum, and that gave a vacuum on the back end of the engine which increased its efficiency. You'll notice in picture 12 that the bell crank has almost disappeared. The picture was taken while the engine was running. If you look at picture 13 you can see the linkage which connects the bell crank to the slipper on the end of the low pressure tail rod, the tail rod is the name we give to the piston rod which comes through the back cover. Notice that there are no lubricators on it. When I first took this engine over there were four lubricators exactly the some as the ones which are feeding the bell crank in the cellar and the air pump linkage. I found that these threw oil all over the place as it was running during the day and decided that the linkage didn't need anywhere near that amount of lubrication so I took them off. I just used to give them each a squirt of cylinder oil before we started and the same at dinner time and that did them for the rest of the day. The links are only oscillating, they just need a smear of oil.
Notice the wall of the engine house, for the first 5ft up, the wall is faced with cream glazed bricks. These are very easy to keep clean, a wipe over with a damp cloth keeps the place tidy.
Behind the tail slide is the nerve centre of the engine house, the easy chair and the desk. The insurance requirement is that a competent engineer should be in charge of the engine while it is running. This was based on experience, the best way to ensure trouble free running is constant supervision. Funnily enough there was never any statutory requirement for formal qualification for running land based boilers and engines. A move was made c.1910 to impose the same standards on land based engineers as marine but the bill ran out of time and was never ratified.
The sandwich box on the desk is an indication of constant attention. I used to eat my lunch while the engine was running because there were routine tasks to be done while the engine was stopped at mealtimes. I was paid from when I started to finishing time at night. It was recognised by the management that I couldn’t take set meals.
The small tin wedge shaped object on the back end of the tail slide in the picture number 12 is simply a splash guard. There is one at each end of both the high and low pressure slides. It is there to catch any oil thrown up by the slide when it stops at the end of its stroke.
The dashpot on the back low pressure steam valve linkage can be clearly seen in both pictures. Notice the adjusting screw in the base of the dashpot for the relief valve which adjusts the cushion of air under the piston when the spring slams it down as the valve catch is released. The temptation with these is to always maintain a good cushion as this makes the engine run quieter. In fact, if taken to excess this can destroy the effect of the Corliss gear. The whole point about Corliss valve motions is that they give a clean, sharp cut off. Too much cushion slows down this effect and you might as well have an old-fashioned slide valve. The ideal setting was one which gave a clean cut-off in the valve but mitigated the worst effects of the piston slamming down.
Notice also on picture 13 the steam valve bonnet in the top right hand corner. The bonnet is the name for the casting bolted on the cylinder casting. This carries two bearings which support the valve spindle and keep it in the correct position in the valve housing bore. It also provides a housing for a spherical seal where the spindle emerges from the cylinder, this stops leakage between the valve and the outside atmosphere. The whole provides a solid base for the valve spindle against which the forces of the valve operating rods act. The small lubricator on top of the bonnet drops oil into this seal, it is constructed so that it can be isolated from the pressure (or vacuum) in the valve whilst the body is filled with cylinder oil. Once filled, the top orifice is closed and the bottom one opened and oil can find its way into the seal. The spindle is not part of the valve itself, it is simply the means of transmitting the motion of the vale operating rods to the valve. It has a flat end on it rather like a large parallel screwdriver blade which is a close fit in a mating slot in the end of the valve. By this means the valve is allowed to float in its housing but can be operated by the linkage. The valve has to float because it is not an exact fit in the housing, steam pressure or vacuum forces it onto the valve face and gives the seal.
The end of each of the valve spindles has a square machined on it. This is useful during maintenance for moving the valve but has another very useful function. We have to go back to basics here and understand that steam engines do not have any gear box or clutch, they are permanently connected to the drive. This is possible because the steam engine develops its maximum torque, or turning power, on the first stroke. This is because the full pressure of the steam is admitted behind the piston. However, remembering what I said earlier about the four impulses per revolution, the engine has to be in the right position for this start to take place. Usually this is taken to be with the high pressure drive train at the point where the valve is ready to admit steam to the back of the piston, ready to drive it forwards.
There are basically three ways in which this can be achieved, if you are very lucky or very skilful you can stop the engine in the right position for it to start. Failing this you can engage the barring engine and bar the engine round until it is in the correct position. The name ‘barring engine’ comes from the fact that in the earliest engine the turning of the flywheel was effected by inserting a heavy bar in a slot in the flywheel and by means of a fulcrum point, physically bar the flywheel round one slot. By repeating this operation the engine could be positioned properly. As engines increased in size this became too hard and steam barring engines were fitted. The third and easiest way is to decide which end of one of the cylinders was about to come on to the power stroke and manually open the steam valve using a large spanner thus forcing the engine over it’s first stroke. Once this had happened the valve gear took over and your engine was away and running.
Now there is no problem with this in respect of the high pressure cylinder because once the stop valve on the main steam line is opened, steam at boiler pressure fills the steam chest on top of the cylinder and is available to drive the piston as soon as the steam valve is manually opened to initiate the first stroke. However, if the piston even necessary to start the engine is on the low pressure side you have a problem because the steam chest on the low pressure cylinder is fed by the exhaust from the high pressure. If the high pressure cylinder is not functioning there is no exhaust and therefore no steam to power the low pressure piston over its first stroke.
In order to understand how we get over this problem you have to realise that when the high pressure cylinder exhausts steam it does not go straight into the low pressure cylinder. It charges a receiver up underneath the floor which is permanently connected to the low pressure cylinder steam chest. During normal running this receiver performs the same function as the steam pipe from the boiler, it supplies the steam for the low pressure. If we consider the situation when the next power stroke is on the low pressure piston we can see that after opening the steam valve, steam is available at the high pressure cylinder but cannot deliver its energy because both the high pressure steam valves are closed. What is needed is steam in the receiver.
There is a small by pass pipe from the main steam main to the receiver and the procedure is to open this valve and pressurise the receiver to about 30psi. As soon as this pressure is reached the appropriate low pressure steam valve is opened with the valve key on the square end of the valve spindle. 30psi of steam is admitted into the low pressure cylinder and this drives the engine over its first stroke, half way down this stroke the valve mechanism automatically opens the appropriate valve on the high pressure cylinder and your engine is running normally. At this point you close the valve on the by-pass line to the receiver and run as normal.
Picture number 14. Negative number 777231.
This is an overall view of the low pressure cylinder, low pressure crank, flywheel and the gauges from the back of the high pressure cylinder. You are beginning to get a better picture now of the valve gear on the low pressure cylinder. One thing to notice about this valve gear is that unlike the high pressure cylinder, it isn't controlled by the governor. The reason for this is because this cylinder works on steamy that has been exhausted from the high pressure side. Any action the governor has on the valves on the high pressure side automatically adjusts the amount of steam which is going to the low pressure side because it has adjusted the amount of steam delivered to the high pressure cylinder.
Notice the eccentric rods coming from the bell cranks mounted on the low pressure bed and driven initially from the eccentrics on the flywheel shaft. The top rod controls the steam valves and the bottom operates the exhaust valves. It is important to realise that the timing of the valve events is controlled solely by the position of the eccentrics on the flywheel shaft. Any other adjustment in the steam valve gear is simply one of duration of the event, not of position in relation to the flywheel. The exhaust valves have no adjustment beyond those necessary to balance the action of both valves against each other.
If you examine the steam valve rod carefully you will see that it terminates at the cylinder end in a large block of metal to which all the other linkage is attached. This is the Dobson Block, so named after its inventor and it slides backwards and forward with the motion of the eccentric rod in a lubricated cast iron slide bolted to the front of the cylinder. It is the motion of this block which operates the valves. In order to understand how this mechanism works you must first realise that there is no permanent connection between the rods running from the steam valve spindles to the block. The motion connecting the block to the valve spindle is only operative when a catch is dropped by the mechanism on top of the block which allows the hardened steel wedge on the end of the valve spindle to be caught by a corresponding wedge on the block. The length of time that these wedges are engaged is controlled by the angle of the levers in the top mechanism and this angle is adjusted by the threaded rod running through the wheel on this top mechanism. By this means, the cut-off point on the steam valves can be adjusted if necessary.
This is a very complicated explanation and the only way to fully understand what is happening is to read and understand this and then watch the valve motion doing its job. The bottom line is that the combination of mechanisms I have described ensures that the valve events on the low pressure cylinder occur at the correct time and for the required duration.
You'll notice there is a tray on the floor in front of the cylinder filled with cotton waste. This was there to collect any drips of oil and keep things tidy. When it became soaked with oil and water we stored it in empty drums in the boiler house and used it for fire lighting. It was also a good place to store oilcans and spanners which were needed during the day. It also served as useful sound insulation.
If you look carefully you will see that at each end of the tray is a small rod with a polished handle. These are far more important than they might appear. Once more, I have to go back to basics in order to explain what they are used for. I have already talked about the dangers of water in cylinders. The most common source for water in cylinders is when steam comes into contact with relatively cold surfaces and condenses into water. For this reason the engine was never allowed to cool down except during the holidays. As long as there was steam on the boiler a small amount was bled off the main steam line and injected into the high pressure cylinder when the engine was stopped. From here it permeated through the engine and kept it warm during the night. This is why it was known as the ‘warmer’.
This strategy kept the engine warm but not hot enough to completely alleviate condensation. The only circumstance that achieved this was when the engine was actually running. You will see that we have a problem here because when we start the engine we are going to produce dangerous amounts of condensate until the engine has fully warmed up. The small handles that you can see are our defence against this. They are connected to drain pipes connected into the bottom of the cylinder and these are left open until the engine is thoroughly warmed up. They allow the condensate to escape and it is important that they are not restricted in any way so they exhaust to atmosphere in a drain outside the engine house. Another safety feature is that the handles are connected to cocks and not valves. These are a simple plug valve with a hole drilled through the plug. A quarter turn opens or closes the valve and the position of the handle indicates clearly whether the valve is open or closed. If they are facing into the house they are open, if they point to each other they are closed. There are similar cocks on the high pressure cylinder and if you look carefully at the chequer plate in front of the cylinder you will see that on this side there is a small mark on the floor. This is the top end of a rod connected to the drain cock on the receiver under the floor and in the tray in front of the low pressure cylinder you will see a ‘T’ key which is used to open and close this cock. The procedure was that the engine was started with all these cocks open and the drains blowing to atmosphere. This dumped any condensate in the cylinders and avoided it building up into a slug, a body of water large enough to exceed the available compression space at the end of the cylinder. This is a potentially dangerous situation and has been the downfall of many an engineer. Incidentally you may ask why, because you know that there are relief valves fitted specifically to guard against this. The short answer is Brasso. Nearly all relief valves were stuck down with Brasso that had got on the seat while the engineer was polishing the brass housing. All relief valves should be checked frequently to make sure they are free.
Again you can see the low pressure cylinder lubricator at the front of the cylinder. Notice the pipes conveying the oil to the valve seatings and the flat rod connected to the steam valve eccentric rod which drives the lubricator pump by means of a ratchet and pawl. As I have mentioned before, this is a very bad way of lubricating valves and cylinders. It is particularly bad on a Roberts engine such as this because they tended to make their valves with a thick rib in the centre. The oil dripped onto this rib and from there fell straight through on to the exhaust valve so most of the oil you fed in did no good at all. I used to feed oil in very fast for the last 15 minutes each day and half an hour on Friday afternoon to make sure there was a reasonable coating of oil in the cylinder while it was stopped.
When I took this engine over the lubrication of the high pressure side was exactly the same but I very soon did away with that and the engine ran a lot sweeter - but more about that when we come to describe the high pressure cylinder.
If you lock at the back of the low pressure cylinder below the cover, you'll see a tin there. That’s serving exactly the same purposes as the bucket at the front end, it's there to collect the water and oil that drips out of the metallic packing housing. Notice the very high polish on the lagging of the cylinder, you can see the reflections of the dashpots. The polished pipes that you can see coming down from the top of the cylinder to the bottom where they join into another pipe, are the drains from the bonnets of the low pressure cylinder. These drains were there to catch any condensation that collected in them, very similar to the drains on the metallic packings. They drained into the exhaust bonnets and because they were always under vacuum the oil and condensate was drawn into the seal and lubricated it. From there the oil and water was blown away by the exhaust into the jet condenser in the cellar.
Anybody who is fairly knowledgeable about boilers and condensers will realise that this means that we were in effect injecting oil into the condenser water all day in small quantities. This water was being used for feeding the boiler. Now in theory the worse thing you can have with a Lancashire boiler is oil going in with the water because what happens is that it collects in the hottest part of the boiler, on the crown of the firetube. There it bakes on with the scale and the theory is that it can eventually insulate the firebox crown, allow it to get red hot and this weakens it and causes a collapse. This is all perfectly true in theory and in fact as well, but circumstances alter cases. Bancroft boiler ran off water from the moor, out of the lodge and the feed water was of such high quality that it was possible for us to run that boiler for 12 months without draining it. When I say without draining it, we used to test the water regularly each day for alkalinity and also once a week for total dissolved solids. A Lancashire boiler is accepted as being perfectly safe up to 75,000 parts per million of dissolved solids in the water. This is the figure which governs the amount of scale that forms in your boiler. In practice Bancroft boiler never got above 6,500 parts per million all the time I was testing it. Due to the fact that we used to return all condensate from the engine and heating system to the boiler, and it was very good feed watery anyway. This meant that we used to get very little scale in the boiler and in consequence there was very little danger of oil causing any trouble in the boiler and so we never bothered about it. In fact, the fact that oil was going into the boiler was in many ways a good thing because it used to get out in mysterious ways into the pipework in the mill and every piece of pipework that you took down in the mill you'd find that the inside of the pipe was clean, dry and slightly oiled. Nowadays there are systems that you can buy for injecting oil and different chemicals into the pipelines to be carried forward by the steam to protect the inside of the pipes. It appears that we might have been running on a sort of a hit and miss type of steam pipe protection since 1922 by virtue of the fact that we were using oily water in the boiler.
Another thing about the fact that there wasn't so much scale in the boiler, was that we only needed to scale the boiler once every year. And when we scaled it we’d be lucky if we got half a barrow load of scale out of it. Some boilers have to be scaled once a fortnight, once every three or four weeks, it can be a terrible problem. ‘Experts’ will always try and tell you that you don’t want any scale at all in a boiler because you want to get the maximum heat transmission from your beating surfaces through to the water. In theory this is true but in practice 1/16 " of scale is a good thing. In the old days if the railway company were putting a new locomotive into service which was going to run in a soft water region, in other words in a region where it wouldn't be making any scale, they used to send that locomotive to work in a hard water region for a month or so beforehand before it went into the soft water region. This was to give the boiler the protection of a thin layer of hard scale which is the best protection against corrosion. In the old days this used to be done by giving them a coat of concrete grout, a rendering on the inside of concrete. I never bothered a lot about scale, there didn't seem any point. I did once read in a text book that the loss in heat converted in the boiler due to a thin layer of scale meant nothing as long as the boiler was running with economisers. Because the fact was that that meant that their gas temperature was slightly higher which meant that there was less problem with the dew point in the economise and greater heat transfer. In other words what you lost on the roundabout you gained on the swings. So don't bother about 1/16” of scale, because it's not doing any harm.
I shall go on to the next tape now because there's still a lot in these two pictures which needs describing.
SCG/09 September 2003
6,790 words.
Back to Stanley Graham's Page
|
|
|
|
Stanley Graham (Engineer & Researcher) Tape 09
