There are generally no requirements for selling items to a scrap yard as scrap dealers are regulated, not their customers. However, scrap dealers may not be able to accept certain appliances if they aren't delivered properly or are potentially dangerous.
Large appliances are often regulated to prevent environmental harm and injury. Refrigerators, in particular, must be handled correctly before they're left at a scrap yard. Most refrigerators use Freon gas, which is potentially damaging to the atmosphere if it leaks. As a result, federal law requires that certified experts drain Freon from refrigerators before they're disposed. Scrap yards might not be willing to take a refrigerator that's not been drained or that's been drained incorrectly.
People delivering items to scrap yards might also want to check if the dealers are willing to take their items. This applies for both new and old appliances. Older large appliances in particular often contain a significant amount of potentially valuable metals. However, their age means that individual components might be difficult to sell.
It is easier to find customers for newer appliances, but they often use smaller amounts of cheaper metals due to their superior efficiency. Before loading an appliance to drop off at a scrap yard, it's worth taking a few minutes to call and make sure the lot has room and the items are acceptable.