Will 31vdc burn up a 24vdc coil?

 

ASCO certainly does not recommend it; their limit is 10% over nominal "for short periods"
https://s2.postimg.org/woa6vwgop/Coil_Voltage_operating_ranges-hi.jpg

But it's a big world, lots of manufacturers. There might well be another vendor who says that 30% over nominal voltage is acceptable.