Thermostatic Steam Trap
Thermostatic trap, also known as the temperature trap uses expansion of a bimetallic strip, an oil filled element or a flexible below to activate a valve.
In an oil filled element type steam trap ( as shown in the figure), the element A expands as the temperature of the condensate rises. The expansion of element A leads to the closing of valve D. The temperature at which the valve needs to be actuated is to be set with the help of an adjustment screw E. The pressure of the system in which this type of valves are fitted, keeps on varying and thus there are chances of waterlogging or escaping of the steam.
The bi-metallic strip type steam traps are more efficient than the oil filled steam traps. The bi metallic strip expands and deflects as the temperature of the condensate increases. The deflection of the strip thus closes the valve. This type of steam trap can work on a wide range of pressure without readjustments. It can also work under superheat conditions without water hammering or vibrations.
In the flexible bellow type, the bellows is filled witha mixture that boils at a temperature lower than that at which the steam does. The trap holds back some of the condensate till it fully cools down in order the valve to open, thus self-compensating for operating pressure. This trap cannot resist any kind of water hammer or vibrations and would immediately damage if subjected to super heated steam.
In the next article we will discuss the thermodynamic type of steam trap and also learn how the maintenance of steam trap is done?