Anyone know what this component is?

The photo shows 75020 on the scrap line at Carnforth, now my question is does anyone know what the rail located on the upper bulkhead of the tender is for? Just a bit of it can be seen on the right above the coal hopper, from other pictures the rail extends the whole width and appears to be an angled fabrication with a tube located below the angle overhang. I wondered if this was a mechanical slacking tube plumbed in to spray water over dry coal to keep dust down, I want to incorporate this on my model build since this part is not included in the original Jim Harris etches. All help will be gratefully received, thanks chaps.