Steam heat coaches - How does it work?

[colchesterken]

How do steam heat systems work? Not as stupid as it sounds!


I know there two pipes brake and steam heat and that it runs through the coaches on the way via radiators under the seats. Where does the steam go? I spend hours watching the Bluebell cam and there is no steam exhaust from the last coach as there is no return pipe the steam must go somewhere?

Also are the coaches nearest the loco hotter as the steam cools on its way to the back?

 

[peteb]

Not sure about the technicalities but in the front carriage it always seems warmer than the last, and I am in the front carriage of an SVR train at present!!! (Warmer than the last carriage of the previous train I rode on).

 

[Ken H]

How do steam heat systems work? Not as stupid as it sounds!


I know there two pipes brake and steam heat and that it runs through the coaches on the way via radiators under the seats. Where does the steam go? I spend hours watching the Bluebell cam and there is no steam exhaust from the last coach as there is no return pipe the steam must go somewhere?

Also are the coaches nearest the loco hotter as the steam cools on its way to the back?

Surely the latent heat is given up converting the steam into water. So there must be a way of dumping that water somehow.

 

[LowLevel]

The steam pipe runs under the train from the locomotive under pressure with a constant supply of steam. There are condensate valves under the coaches at the lowest point in the pipe where the pressure of the steam blows condensate out using a spirax valve. You increase the pressure with increasing train length.

 

[Gloster]

A quick look at Keith Parkin’s HMRS book gives the following, if I have understood correctly. A one-and-a-half inch diameter pipe (possibly later two inch) distributed the steam through the train: there were traps at the end of each vehicle to allow water to escape and also drain cocks. The heaters in the toilets were fed directly off the main pipe, but the rest of the vehicle had a smaller subsidiary pipe. The problem of the front vehicles being stiflingly hot and the rear ones chilly lessened as trains generally became shorter.

 

[Western 52]

Some people still think the front of a modern train is warmer! Recently my parents, who are nearly 90, wanted to sit at the front of a class 158 for that reason!

 

[John Webb]

Most coaches will vent a small amount of steam and water most of the time, so the steam moves down the train. The venting is very noticeable on North Yorkshire Moor Railway trains - see https://www.nymr.co.uk/goathland-webcam but only a couple of more times today (31st Oct) as it's the last day of running for a while!

 

[Vespa]

I remember riding Irish Rail carriages in the 90s round the island, they were using steam heating, I presume they were using cascaded rolling stock from British Rail and regauged to Irish gauge.

If I recall they weren't that warm as I had expected when compared to modern British Rail stock at that time which used electric heating, from what I gathered they used latent heat from the steam heating unit to warm up the carriages which then condensed into water as it cooled down and drained off, I didn't think it was particularly effective.

 

[hexagon789]

I remember riding Irish Rail carriages in the 90s round the island, they were using steam heating, I presume they were using cascaded rolling stock from British Rail and regauged to Irish gauge.

No, they would have been either the Park Royals built from kits (withdrawn 1994) or the Cravens, 10 delivered built, the rest supplied as kits (withdrawn 2006). Neither were BR designs (though the Cravens are Mk1-esque in some respects) neither were built by BR but both types were steam heat and vacuum braked.

They had the heating supplied from a boiler van they always ran with. Some of these heating vans were converted from BR Mk1s sent over in 1973 but none of the passenger coaches were. Other heating vans were of Dutch (Werkspoor) origin.

The only stock cascaded from BR to IR/IÉ were some Mk2z/a/b/c stock swapped with Vic Berry for some withdrawn C Class diesels and one ex-BR HST Mk3 TRUK converted to a push-pull Café-Bar car and the aforementioned ex-BR Mk1 steam heat vans.

All other stock was either built new, sent over as kits or built from scratch in Ireland for Irish Rail.

 

[edwin_m]

Most coaches will vent a small amount of steam and water most of the time, so the steam moves down the train. The venting is very noticeable on North Yorkshire Moor Railway trains - see https://www.nymr.co.uk/goathland-webcam but only a couple of more times today (31st Oct) as it's the last day of running for a while!

Even without venting, the steam contracting and condensing as it cools will create a partial vacuum to draw more steam down from the locomotive.

 

[1955LR]

I was on the Servern Valley railway last week and one could see water vapour venting from the heaters on each coach along the train.

 

[Vespa]

No, they would have been either the Park Royals built from kits (withdrawn 1994) or the Cravens, 10 delivered built, the rest supplied as kits (withdrawn 2006). Neither were BR designs (though the Cravens are Mk1-esque in some respects) neither were built by BR but both types were steam heat and vacuum braked.

They had the heating supplied from a boiler van they always ran with. Some of these heating vans were converted from BR Mk1s sent over in 1973 but none of the passenger coaches were. Other heating vans were of Dutch (Werkspoor) origin.

The only stock cascaded from BR to IR/IÉ were some Mk2z/a/b/c stock swapped with Vic Berry for some withdrawn C Class diesels and one ex-BR HST Mk3 TRUK converted to a push-pull Café-Bar car and the aforementioned ex-BR Mk1 steam heat vans.

All other stock was either built new, sent over as kits or built from scratch in Ireland for Irish Rail.

It did look like MK1, that's where I got my assumption from, that said it didn't feel that warm to me.

 

[kjsway]

If a steam locomotive boiler operated at 200+ psi, would there be a pressure reduction valve onboard to lower the pressure in the carriage supply pipe?

 

[AndrewE]

If a steam locomotive boiler operated at 200+ psi, would there be a pressure reduction valve onboard to lower the pressure in the carriage supply pipe?

from what is said in post #4, the driver or fireman can vary the pressure depending on train length, so there is definitely a variable pressure valve. Whether it has an upper "cut-off" / ceiling or limit I wouldn't know.

 

[paul1609]

If a steam locomotive boiler operated at 200+ psi, would there be a pressure reduction valve onboard to lower the pressure in the carriage supply pipe?

Yes it varies from Loco to loco on our tank locos on the K &ESR we generally maintain the steam heating pressure at around 25 to 35 psi.

 

[hexagon789]

It did look like MK1, that's where I got my assumption from, that said it didn't feel that warm to me.

Very typical I understand, neither Park Royals nor Cravens had particularly effective heating by all accounts.

No wonder the Mk2D stock offered such a step-change in comfort when launched in December 1972.

 

[Ken H]

of course all this was subject to freezing so all water had to be removed from the systems in very cold weather when the coaches were parked up, or there would have been bursts.

 

[Rescars]

Recollections of travelling on Anglo-Scottish sleepers in the early 1980s. Each compartment had its own heating controls - and the default settings were to have these full on. So if you didn't want to be roasted in your berth then it was sensible to turn down the electric heating when getting aboard at the London end. But it was also important to turn off the steam heating valve as well or else you got the full sauna effect after the loco was changed for a steam heater at IIRC Carlisle or Edinburgh!

 

[D6975]

The only stock cascaded from BR to IR/IÉ were some Mk2z/a/b/c stock swapped with Vic Berry for some withdrawn C Class diesels and one ex-BR HST Mk3 TRUK converted to a push-pull Café-Bar car and the aforementioned ex-BR Mk1 steam heat vans.

All other stock was either built new, sent over as kits or built from scratch in Ireland for Irish Rail.

Not quite. There were also the 'International' coaches which were almost exclusively used on the Galway line.

 

[hexagon789]

Not quite. There were also the 'International' coaches which were almost exclusively used on the Galway line.

They were privately built by BREL as a sort of showcase train, rather than specifically as BR stock though.

 

[torten]

One trick often used to get the heat to the back of the train quicker is to keep the steam cocks at the back of the train open for a few minutes, which blasts any condensate out.

 

[rower40]

Some people still think the front of a modern train is warmer! Recently my parents, who are nearly 90, wanted to sit at the front of a class 158 for that reason!

Does this tell us something about how warm the driver keeps the cab, relative to the passenger accommodation?