I need help in metriod prime 3

Ok, im at the homeworld Seed and I am fighting Omega Ridley, but I cant seem to open up his metal plate with the grapple beam. Every time I latch onto him, i just get health. I grapple onto his heart plate, but it just gives me health and he always gets away. I CANT HURT HIM!!

please help.

first scan him

then shoot him when hes got a flame coming out of his mouth it will stun him then move closer and rip the plate off with the grapple.

also if you goto www.gamefaqs.com they have walkthroughs for every game