"FIRE PULL" handle query

[mp01]

Probably a daft question, but what does this handle do - does it set off an alarm, or an extinguisher, or something else? The image is from a class 40, but similar appears on class 37. Thanks.

 

[pdeaves]

Extinguisher, I think.

 

[John Webb]

Confirm this releases gas from cylinders (probably CO2) to extinguish an engine compartment fire. Brief details can be found in the BR handbook "Diesel Traction Manual for Enginemen" (1962 and later dates, by The British Transport Commission).
Early DMUs generally used a plastic tube around the underfloor engine which on melting released the extinguishing agent close to the fire. At one time this was BCF (Bromo-Chloro-diFluromethane) but due to this being not good for the Ozone layer it has been replaced by other compounds. I'm not up to date on the equipment fitted to current multiple units.

 

[TheEdge]

I'm not up to date on the equipment fitted to current multiple units.

Most modern units are just a foam. Gases I think tend to be Inergen.

 

[mp01]

Thanks all.

 

[Llama]

AFFF these days on most diesel units.

195s have a reservoir of AFFF and a little one of N2 to assist with deploying the AFFF - the N2 is the small red cylinder on its side half way down the unit.

 

[John Webb]

Thanks to The Edge and Llama for the updates. Using AFFF (Aqueous Film-Forming Foam) makes a great deal of sense as a modern agent - not so readily dispersed as a gaseous agent so will continue to give some protection after discharge. Also, if used in a diesel loco engine compartment, doesn't require special precautions regarding reduced oxygen levels, other the normal precautions needed when entering a compartment where there is or has been a fire. (Sorry if getting technical, but I've now been involved in fire safety matters for 50 years this year!)