Having 30 different icons for such thing is A VERY BAD IDEA. My suggestion is to use algo described here: http://www.gamedev.net/topic/621035-how-would-a-filling-clock-drawing-algorythm-work/?view=findpost&p=4917427
Or you can use shader based approach described here: http://www.gamedev.net/topic/603658-circular-health-bars/?view=findpost&p=4820385
Hope this helps