Crosti boilered 9F's

Ten of the BR Standard Class 9F locomotives, Nos 92020-9, were built with Franco–Crosti boilers in 1955. Like the German 50.40 these were 2–10–0 tender locomotives with a single feedwater heater under the main boiler.[2]
The standard funnel was retained, but was only used for lighting-up and was blanked when running. The final chimney was located on the right-hand (fireman's) side, just forward of the firebox. The Crosti preheaters provided less improvement than had been expected, and were a problem for maintenance, owing to acidic fluegases condensing in the feedwater heater and causing corrosion. All were converted back to a more standard form within a few years, the preheaters remaining in place, but blanked off, as seen in the accompanying photographs

92022 still working in original configuration

https://railway-photography.smugmug.com/BRStandardSteam/BR-Standard-9F-2-10-0-92/9202092029-FrancoCrosti-Built-/9202092029/i-fQssmtk

92020-92029 - Railway-Photography


92028 in original configuration


https://railway-photography.smugmug.com/BRStandardSteam/BR-Standard-9F-2-10-0-92/9202092029-FrancoCrosti-Built-/9202092029/i-MGJWrgg

92020-92029 - Railway-Photography
railway-photography.smugmug.com

92020

https://railway-photography.smugmug.com/BRStandardSteam/BR-Standard-9F-2-10-0-92/9202092029-FrancoCrosti-Built-/9202092029/i-kdGc4ND

92020-92029 - Railway-Photography
railway-photography.smugmug.com

92026

https://railway-photography.smugmug.com/BRStandardSteam/BR-Standard-9F-2-10-0-92/9202092029-FrancoCrosti-Built-/9202092029/i-3PMD5P7

92020-92029 - Railway-Photography
railway-photography.smugmug.com

92028
https://railway-photography.smugmug.com/BRStandardSteam/BR-Standard-9F-2-10-0-92/9202092029-FrancoCrosti-Built-/9202092029/i-z5HMHKs

92020-92029 - Railway-Photography
railway-photography.smugmug.com

92029

https://railway-photography.smugmug.com/BRStandardSteam/BR-Standard-9F-2-10-0-92/9202092029-FrancoCrosti-Built-/9202092029/i-gkddWRn

92020-92029 - Railway-Photography
railway-photography.smugmug.com


Neil

 

I've always liked the look of a Crosti 9f . Just a shame one of them didn't make it in to perservation.

 

If I remember rightly, the Crosti 9s were down rated to 8f. Once the Crosti preheater was blanked off, as they weren't as powerful as the "standard" as built machines....

 

https://railway-photography.smugmug...2029-FrancoCrosti-Built-/9202092029/i-MGJWrgg
Nielsons Sidings Wellingborough shunting train

 

The Crostis were a bigger failure than the Clans. At least the latter could have been put right with a bit of development work to improve the steaming. The "conversion" of the Crostis was half-hearted; the entire boiler, firebox and pre-heater should have been thrown away and a conventional boiler fitted. The cost of that would have been too embarrassing for those in charge who were still too close to the original authorisation.

 

On the other hand if there was enough work to be found for locos with reduced boiler power then what would have been the point in spending the money on new boilers?

 

Correct ,its a late Ken Fairey photo' a mate of mine .Hope the copy write has not been broken. The first photo, 92022 ,is at the entrance to Wellingboro' shed, well away from the foreman's office.
Another friend of mine a passed cleaner went on loan to Wellingboro' he was firing on a Toton to Brent coal train and return with a Crosti all week .A inspector was on the footplate checking coal consumption. On arrival back at Wellingboro' coal consumption was no different to a normal 9F. Impossible he said ,should have been a lot less.
After conversion when the Toton- Brent coal trains were dieselised 6 or 7 were based at Kettering ,they were always known as number 9s.
Any one interested in more photo' of Crosties please go to my FLICKR photo site http://www.flickr.com/photos/5611hongkong ,they are in a album called 9Fs and Garretts .

 

I wondered whether, once the Crosti experiment had finished, the redundant barrel could have been used as an air pre-heater, with air passing through the tubes and exhaust steam been fed into the barrel. One problem might have been that excessive grate temperature might lead to clinkering. Any condensate could be returned to the tender and reused.

 

If I've done my sums correctly, heating the air from 15 deg C to 100 deg C would reduce the density by 23%. Presumably you could return the air mass flow to normal by adjusting the draughting.

 

I think the original Crosti draughting arrangement would have been pretty challenging. You are correct though in that there would only be the ashpan vacuum to pull air through the pre-heater drum.
An alternative would be to have a pipework arrangement to let the preheated air act as secondary air (i.e. above the fire) and use fresh air as primary air (under the grate) in the conventional manner. This would reduce the clinkering problem. There is a risk that a forced draught fan might lead to a positive pressure in the firebox, which could be hazardous on the footplate.

 

Air pre-heater? Perhaps they could have modified it to look like this?

 

With the current NR height limitation?

 

The Italian class 741 was rather more elegant and lasted in service until the '70s. One of them is preserved.

Why did it go so wrong on the 9F I wonder? Was it an attempt to shoehorn something onto the existing design which was never really going to fit or some other design error? I'm sure E.S. Cox said something about it in his book about the BR Standards but I seem to have lost my copy.

 

I remember reading somewhere that the 9F already had an exhaust steam injector, which already provided a lot of feed heat, so the Crosti pre-heater wasn't such an advantage.

 

There's a couple of 741s preserved, one in working order, plus an earlier 743 which has a pair of preheaters either side of the boiler. I believe preheater increased the efficiency of a 740 by about 12%. As 9F is going to be far more efficient than a loco from pre-WW1, I doubt it was really worth the effort.

 

Thanks for the responses. How did the Italians deal with the corrosion issue in the pre-heater, which was presumably the reason why it had to be blanked off in the 9f?

 

I always had a soft spot for the Crosti 9Fs, even though they had been converted by the time I spotted them. They lasted almost to the end, so they can't have been that bad.

I seem to remember reading that the boiler was slightly smaller than a standard 9F, presumably to allow room for the pre-heater.

 

I guess the reduced power output would help them last well.