heating canned veggies
I am catering for the Noon Lion's Club; just 'pinch hitting' for unspecified time frame because a friend's wife is losing her battle with cancer. People are eager to help, but sometimes I drown in questions and/or advice. (The day rolls on to become a 'community dinner', so it's a 7 am to 7 pm gig).

The fellow who I am subbing for has always heated his very Large cans of vegetables by peeling off the label and placing the can, unopened, into a pot of water, bringing it to a boil and then simmering (in the last hour of prep). He then opens the can slightly to drain part of the liquid off, pouring the remainder into a serving dish, which is covered with plastic to keep it Hot in case the Number One lion talks too long before sending people through the buffet.
A friend (whose daughter has Cordon Bleu training) insists that this is a dangerous way to heat canned vegetables. I can go either way with this, as I am not tall and muscular for dealing with the darn cans in the first place...but I am curious about the Food Safety issue.

The food safety issue is that boiled unopened cans can literally blow up.
Either puncture the cans, or heat in an open pan, which can be covered.