A railway tank car including a protective structure for the top of its cargo tank and surrounding a valve group mounting nozzle and a pressure relief safety valve nozzle, to protect the associated valves against damage resulting from the car being overturned, particularly while the railcar is moving along a railway. The protective structure includes an upstanding wall of metal plate that surrounds and is located at a radial distance outwardly apart from the tank top valve group mounting nozzle. A reinforcing band is attached to an upper portion of the upstanding wall to enhance its strength. Also disclosed is a method of protecting fittings mounted on a nozzle on the tank top of a railway tank car by providing and mounting such a protective structure to surround the tank top nozzle and associated fittings.