Shouldn't be a problem. I think My pipe on my hyfire is about the same. The pipe itself won't get that hot on the outside. maybe 200 degrees. You need a lot more than that to ignite coal. It's more making sure you have enough clearance for loading and servicing it.
You need to get the coal burning back on the grates and have low draft to get a hopper fire, and normally it just smolders, IF you even have one. Don't get alarmed, it is NOT a real common thing, but does happen.