On 07/08/2016 21:50, Roger Mills wrote:
On 07/08/2016 12:45, Maurice wrote:


I've never seen a chamber with such a projecting flange.


I've never seen one without a flange. The flange is *under* the lid and
supports it. You can't see it when the lid is in place.

What do you suppose stops the lid falling into the chamber?

I have a similar lid in my drive - which is clad with imprinted concrete
rather than crazy paving. Mine doesn't screw down though, but it *does*
have a couple of holes into which cranked T-bars can be inserted to lift
it. My holes look like what I imagine your 4 holes would look like if
you removed(!) the screws. I'll try to post some pictures tomorrow in
case they help.

Lids are only normally screwed down when they're inside a building and
need to be completely sealed against odors and surcharging. These
invariably have a rubber gasket underneath. I have a spare (cast iron -
not paved) lid and frame of that sort, and will post some pictures of
that, too, if I've got time tomorrow.


Its a double sealed inspection cover.
There are loads of different ones here...

https://www.drainagesuperstore.co.uk...le-covers.html

The double sealed ones have four screws just like the OP has and they
hold the cover down.

The others have holes for keys to remove the lid.

The double seal ones you can use a "J" key that hooks into the hole
between the top and the threaded hole in the frame.

They are something like
http://www.screwfix.com/p/monument-o...ing-keys/6650k
but you need to check the size of the hole under the screw.