Developments in high-pressure water-tube boilers for marine use placed more demands on safety valves. Valves of greater capacity were required, to vent safely the high steam-generating capacity of these large boilers. As the force on their valves increased, the issue of the spring's increasing stiffness as its load increased (like the Naylor valve) became more critical. The need to reduced valve feathering became even more important with high-pressure boilers, as this represented both a loss of distilled feedwater and also a scouring of the valve seats, leading to wear.