The short answer is YES nylon ratchet straps are approved for tie downs. You get 1000 lbs of tie down power for each inch of strap width.
The problem with straps are.....
You can not have knots so the strap end must have a approved hook.
Any cut (no matter the size) will weaken the strap so it is render no good.
Any corner the strap goes around must have corner protectors to prevent abrasion. A strap must lay flat (in width) the whole way so it needs to pull on a straight plane for the most part.
Straps are great for what they were made for. Holding pallets of bagged material on a trailer.
For heavy iron and pulling around corners get you some chain.