Removing termostat from radiator

[Andymk2010]

Hi all,
I have a radiator thats not working very well. A long time ago I saw a plumber remove the cover from the termostat, and freed up the pin inside, allowed the water to flow again.

But I can figure out how to remove the cover.
Its a Reliance Water Controls valve.
Tried pulling, twisting, no luck

Here's a picture
http://i146.photobucket.com/albums/r278/lucasite/DSC_0018.jpg

Cant find anything on the internet.
Can anyone help?

Regards

Andy

 

[cross thread]

large knurled nut below white plasic head,unscrew anti clockwise

 

[Andymk2010]

large knurled nut below white plasic head,unscrew anti clockwise

Brilliant. Found and fixed. thanks alot.