Скачать или смотреть Boiler Safety Valve

Safety valve is used to guard the boiler against the excessive high pressure of steam inside the drum. If the pressure of steam in the boiler drum exceeds the working pressure then the safety valve allows blow-off the excess quantity of steam to atmosphere. Thus the pressure of steam in the drum falls. The escape of steam makes a audio noise to warm the boiler attendant.

Working Principle:
In the normal condition, the downward force due to spring is higher than upward force applied by steam. The valve is closed due to spring force. When steam pressure exceeds the normal limit, upward force due to steam pressure is become higher than downward force due to spring.Thus the valves are lifted from their seats opening the passages for steam to release out of boiler.