Sailing under ballast conditions
It was found that these ships experienced trouble while sailing under ballast conditions.
The main circulating pump's inlet drew in air due to rolling in heavy seas, with consequent
loss of vacuum which caused the exhaust turbine to disengage. Racing of the circulating pump under these conditions was also a problem.
The two - 20 ton - fuel oil settling tanks on the starboard side of the engine room gave the vessels a natural list to starboard under ballast conditions, thus accentuating the problem. Because of the above, the "River" ships were usually loaded with at least 1000 tons of cargo.
Fuel consumption and type
Steaming at around 10.5 knots and covering approximately 250 miles/day, the "River Class" ships burnt about 27 tons of fuel oil.