Roto Pumps Ltd. Is the manufacture of Relief Valves. Roto Pumps Ltd. Is an ISO 9001-2000 certified company. The Relief Valves are used for relieving excess pressure from closed-top vessels or piping systems. The relief valve is versatile and widely utilized. The features of Relief Valves are compact size, ease of setting, readjustment and repeatability. The pressure setting in the relief valve is done manually.