Original Post
Interesting, I hadn't heard of this before ... Explanation from YouTube site:
Published on Dec 9, 2012
DB Schenker / EWS 66017 & 66019 Grumble through Northolt Park with the autumn rail head treatment train (RHTT) from Willesden to Willesden via the Chiltern Circuit (London Marylebone - Alyesbury via both High Wycombe and Amersham).
Here seen grumbling through Northolt Park on the Chiltern Mainline heading North towards Ruislip and High Wycombe.
The Rail Head Treatment Trains (RHTT) are employed across Britain's railway network every Autumn/Fall to spray a mixture of sand and water (Sandite) onto the running rails to clear away the grime and gunk left by decomposing leaves from trees. Most RHTT services are provided by one of two of the major freight train operators such as EWS or DRS, but on occasions Network Rail operate a few and the services tend to run from the middle of October to the first of week of December.
The loco hauled canisters send water jetting down onto the rails is at an incredibly powerful pressure -- at over 20,000psi, it is able to easily clear the railhead of any grime or leaf mulch. The jetting can take place at speeds of up to 60mph, but cannot be done when the train is stationary, as the highly-pressurised water would cause serious damage to the rails themselves! Laying sandite paste, however, can only be done at a maximum of 40mph.
