Does flue need to be reinforced before insulation

[justmaybe]

I'm getting my cavity walls insulated and I've just been told that I need to get an additional pipe put all around the chimney/flue of my oil boiler from the outside in so that the beading thats being pumped in won't go near the exsisting pipe or it will overheat and go on fire. Looked on line but nobody seems to have ever mentioned this problem so I'm wondering if it's necessary

 

[DGOBS]

Yes, would depend on fire rating, but regulations do give a minimum distance of 25mm from the flue to any combustable material unless the flue is twinwall type, then the 25mm can be measured from the inner flue, wich is usually spaced at 25mm anyway providing the spacing required