A cargo tank is designed for vacuum loading and has a full-opening rear head. How frequently must this tank receive an external visual inspection under 49 CFR 180.407?

49 CFR 180.407(c)

Vacuum-loaded, full-opening-rear-head tanks see more wear from the loading process, so DOT requires external checks twice as often as standard tanks. A driver operating this tank type should expect inspection markings dated more recently than on an ordinary cargo tank.