Drain and rinse the beans. In a large enameled cast-iron casserole, combine the beans with the water, ham hocks, onion, bell pepper, garlic, vinegar, black pepper, thyme, bay leaf and cayenne. Bring to a simmer over moderate heat. Cover partially, reduce the heat to moderately low and cook, stirring occasionally, until the beans are tender, about 1 1/2 hours. Add the ham, andouille and scallions and cook over moderate heat until the beans are just beginning to fall apart and the sauce is reduced to a thick gravy, about 30 minutes.