I've been fixing leaking faucets in a bathroom. There are total six faucets in a bathroom,
Two made into a bathroom basin, two made into the wall in the shower tube
And the last two are on the wall on top of the mop sink.

I have fixed the leaks with basin's faucets but was unable to do it with other four faucets because
Have failed to remove the faucet covers (see on the photos).

http://img860.imageshack.us/img860/7886/18042011231.th.jpg (http://img860.imageshack.us/i/18042011231.jpg/)
http://img14.imageshack.us/img14/4299/18042011233.th.jpg (http://img14.imageshack.us/i/18042011233.jpg/)

They seems to be stuck. To get a better grip I wrapped some duct tape around the chrome covers and then used
The spanner - but to no avail. Tried the strap wrench - no luck too.

I thought it could be the silifon sealant that glued the covers to the wall - but after I have removed most of the sealant
(used the sealant remover to soften the sealant and then putty knife) it has not changed the situation at all
As the cover is still stubornly refuses to unscrew.

Any ideas how can I get these covers off? Can you recommend some special tools, I was thinking about
A type of a pipe wrench for cone shaped pipe (as the cover is shaped as a cone)?

Would really appreciate any help!
Thank you for your time.

Great shot from above in picture #2, any chance you can do that same shot from below? That's where we may see a set screw. Most of these escutcheons are threaded so I would have started just as you did. You may ned to buy, rent a strap wrench Google Image Result for http://www.plumbingsupply.com/images/reed-strap-wrench-sw12a.jpg (http://www.google.com/imgres?imgurl=http://www.plumbingsupply.com/images/reed-strap-wrench-sw12a.jpg&imgrefurl=http://www.plumbingsupply.com/reedtools.html&usg=___e5nmgF6BdA7JmGAgw0DiJgN8KU=&h=338&w=600&sz=24&hl=en&start=31&zoom=1&tbnid=YYkMzYw9zdktoM:&tbnh=106&tbnw=189&ei=i2OsTar-KYzpgQfRzrTzBQ&prev=/search%3Fq%3Dplumbing%2Bwrenches%26hl%3Den%26sa%3D X%26biw%3D1658%26bih%3D824%26tbm%3Disch0%2C742&itbs=1&iact=hc&vpx=1333&vpy=545&dur=577&hovh=168&hovw=299&tx=123&ty=131&oei=XmOsTaasKuL20gHsj6H5CA&page=2&ndsp=32&ved=1t:429,r:31,s:31&biw=1658&bih=824)

Try wrapping with double sided carpet tape and then using a strap wrench. The sticky surface of the carpet tape will help the strap grip.