Weight Limit

I just bought an existing tanning salon in Dec. and I have 5 old two piece Wolf tanning beds,SCA Wolf series 2. and a few newer ones. How do I find out what the weight limit is on those beds? Better yet, what do you do when you think someone is to over weight for the beds. I really need help on this. I don't have a manual to the beds and don't know how to get it. I called the acrylic manufacture and he was no help.
Thanks,