46 CFR 35.35-55: -55 Transfer of other cargo or stores on tank vessels—TB/ALL.

(a) No packaged goods, freight, or ship's stores may be loaded or unloaded during the loading or unloading of cargo of Grade A, B, or C except by permission of the Person in Charge of the transfer of liquid cargo in bulk. No explosives may be loaded, unloaded, or carried as cargo on any tank vessel containing cargo of Grade A, B, or C.

(b) Where package and general cargo is carried directly over bulk cargo tanks, it shall be properly dunnaged to prevent chafing of metal parts and securely lashed or stowed.