The weight being handled is not a factor at all. The stress on the attachment of the bicep tendon is what matters. You could tear a bicep with 100lbs if you jerk/seizure it up hard enough.
Just make sure your technique is dialed in. Keep your tricpes flexed hard when you set up and when you pull. This will keep your elbows locked and will make it so your biceps will barely fire at all. The triceps are an antagonist muscle to your biceps. In other words, flex them hard as shit and you get to a point where you can't flex your biceps.
Keep your arms, forearms, and grip as strong as you can. I know guys who have torn biceps while pulling and the common denominator is not training one of those three things and having bad technique. Most of the biggest pullers on earth use a mixed grip and havent had bicep problems.