boiler lagging

When a boiler is lagged on a modern restoration, are more efficient forms of lagging used or are the same materials used as per the 60s?

With the greater chance of locos having the fire dropped between steamings would this help conserve the boiler by retarding the rate of it cooling down?

 

Wot, you mean asbestos? Nah, tends to kill people.

In the past fibreglass wool has been used, although now ceramic fibre is more the clothing of choice. I believe the ceramic stuff is slightly better, it is certainly easier to use. I am unaware of any major improvement over asbestos however. On the other hand the modern engines built in Switzerland have very effecient insulation, however I understand this is partly down to the thickness of the material, making it difficult to implement on traditional British designs. Would be interesting if anyone has any more info on this.

The asbestos/manganese solution used in Swindon was actually very good; part of the problem with the legislation against this material is finding something that can adequately replace it.

 

They are more modern laggings, weather they are better or not is open to question.
On a lot of railways, during the summer, a loco may not actually have any time out f steam, to go cold, between wash outs!

 

There is some kind of cermaic stuff similar to that used on the tiles of the Space shuttle apparantly, 92212 had this used and you could actually lean on the backplate whilst it was in steam.
Would love to know the details of it though to use in fututre.

 

I believe the King also has a layer of aluminum foil - leading to various "oven-ready" jokes towards the end of the last overhaul.

Maybe one of the KE1 regulars can expand, and tell us if it makes any apreciable difference?

Neil.

 

From my understanding the foil is primarily there to stop any damp lagging coming into contact with the boiler. This can be a problem these days, as infrequent use means that any moisture in the lagging can take ages to dry out. I imagine that it probably does help with heat retention as well.

Would be interesting to know exactly what type of foil they used, as this is something of a issue at Didcot, with the number of static engines that can get left outside.

 

The purpose of the aluminium foil is two fold;

One to keep the fibrglass together as a blanket., and two, to reflect the heat back to the boiler.

 

I think you may be thinking of a different type of lagging there Ian - the fibreglass stuff you mention is indeed held together by the foil, however I believe the King uses ceramic Kaowool, which stays together a lot better. Although I haven't used the foil-fibreglass type before, I imagine it beats slapping a blanket on, and then spending the next few hours trying to wrap chicken wire around it...

 

My experience with fibre lagging has convinced me not to use it... Rutland's Avonside "Dora" failed with a very badly corroded front boiler barrel, however when the lagging was removed it was FULL of water and the corrosion was from the outside IN not the other way round. (and the lagging used was espacially designed NOT to hold water... it didn;t work!!!)

With locos that are in steam a lot, the water should be evapourated off regularly and not be a problem, but for locos that are steamed occasionally, this to me seems like a big problem.

I know it's not practical for the main line locos, but for the smaller locos, I think timber lagging is as good as anything.

 

I belive Trevithick actually recomended Clay as boiler lagging. Not a serious suggestion on my part, but just something for you to all think on.

 

Interesting suggestion! Surely the clay would over time crack because of the movement of the loco.

Alex

 

Indeed Alex, but of course, he was used to stationary engines, so it was what he knew.

 

Pitchford Hall's boiler is covered in foil and was done so before 6024's.

 

The Swiss rack tanks do have very thick insulation which is really done to reduce standby looses to next to nothing. You can shut the firing off and come back the next morning with enough steam on the clock to get going immediately. This sort of "exaggerated" insulation is the standard approach in the world of modern steam. In addition all boiler fitting valves are of modern types not prone to leakage which is also very important. Similar things have been done on FCAF in Argentina. It has the effect of making the small boilers look fairly big! It certainly saves lots of fuel.

On 6024 the main reason for using foil next to the barrel was to prevent damp/wet insulation being in contact with the barrel and firebox to reduce the amount of external corrosion. With irregular use locos on decent water treatment you are more likely to get the boiler failing from external corrosion than internal.

I guess we'll find out how successful the foil has been when we come to the next overhaul and remove the insulation. In terms of heat retention the foil, 2 layers of Kaowool topped off with another layer of the heavy duty foil does seem to have made an appreciable difference but no figures are available to prove it. That said out on FCAF comparisons between Kaowool and fibreglass have been made. This gives a bit of detail: http://www.martynbane.co.uk/modernsteam ... 3-cyls.htm

 

Wot, you mean asbestos? Nah, tends to kill people.


quote]

It's a great shame that the asbestos legislation ended up going completely over the top. The original problems, and they were severe and usually fatal, were with the fibres found in blue and brown asbestos, crocidolite and amosite, which were acid-resistant and resulted in later life in a very nasty and fatal disease called mesothelioma. Chrysotile, or white asbestos, is not acid-resistant and will dissolve in a few days, in the slightly acidic environmet of the lungs. White asbestos, other than in large or repeated concentrations, is not a killer. It just got tarred with the same brush as the other two, which most definitely were. Because of this, a huge industry was crippled and, as has been noted, nothing as good has been found to replace it.

 

The material concerned is blown ceramic fibre to 127 Kg density. It has been used by Tyseley Loco works on all loco's overhauled there since 1996 ( some 8 years before 6024 was done), and has subsequently been used by many of TLW's contacts. The aluminium foil was used in an attempt to keep damp lagging from directly contacting the boiler shell, as many engines which are parked outside regularly can absorb considerable quantities of water into the lagging. Similarly the outside of the lagging is wrapped in foil to keep moisture at bay from the cleating, as well as helping to prevent water ingress from cleating joints. As a point of interest, many of the earlier Stanier LMS engines were lagged solely with a material called "Alfol" which was basically crumpled aluminium foil. It was eventually discarded in favour of the much more efficient asbestos, and we all know what happened then. One problem with Great Western engines, is that the palstic magnesite which was used for lagging the boiler formed a solid base for the cleating, and consequently did not require the use of crinoline hoops as in LM practice. Usually with a bit of adjustment to the lagginghere and there to accomodate the extra thickness of butt strips etc, 50mm thick ceramic fibre will compress sufficiently to provide a solid base for the cleating plates whilst maintaining the correct external shape, so that crinoline hoops are not required. Having said that they are really no more difficult than any other engines to lag. It is important to note that all insulation material, including the 200mm in your loft can produce dust which can be a hazard to health, so take great care with it.

 

Modern lagging, like Micafill is much more efficient than household fibreglass. And will not fall apart after a couple of years, hold moisture. But it is much more expensive!

 

Has anyone ever considered applying a modern foam insulation similar to that used on an airing cupboard domestic hot water cylinder? I do appreaciate a boiler at circa 225 psi is a lot hotter than domestic hot water hence the word similar. (Those households with a combi boiler need not reply).

 

We've used that on 5322, on the tricky parts of the cylinders. I'm not sure how easy it would be apply to a boiler - where we used it, we had the benefit of having the cladding already in place.