Where can I rent a sand blaster?

Wear a respirator, p-100 cartridges.

If you have access to a compressor, you can get a sandblaster at harbor freight pretty damn cheap

Have you ever used one before? You'll want to set up a booth and be extremely careful. You can easily mess yourself, someone else or unintended property up with a quickness.

Try to get a wet blasting setup. If not, use a forced air respirator. Silicosis is bad stuff.

Don't listen to these boys. I walk in and out of yards every day and see guys doing it in short sleeves with no gloves. Just don't be a idiot and release the hose while it still has pressure in it.

Whether you buy or rent a blaster you will probably wind up being surprised at the final cost. After you rent the compressor and hoses you have to buy the blasting media at about $9 per 80#. Then you have to clean it all up. Find the painters who work for the pipeline companies keeping the valves painted and get a price. You won't regret it.

If you are going to paint it quickly or not worried about water you can buy a sandblasting attachment for a pressure washer for a couple hundred bucks.