‘Isotubs’ should be installed on thermodynamic traps to reduce distribution loss and increase the life of the steam trap.

Atmospheric conditions are one of the several factors that influence the performance of the thermodynamic steam trap. To underst

The thermodynamic steam trap consists of free-floating disc and an annular groove which forms the seat face (see fig). The cold condensate arrives at the underside of the disk and pushes this disk upwards, thereby opening the annular path to the outlet. When hot condensate arrives at the steam trap, some part of the condensate gets converted to flash steam, moves along the edges of the disk and accumulates on top of the disk in an area called the ‘control area’. The flash steam exerts pressure on the disk pushing it downwards to close the steam trap outlet. This flash steam loses its heat to condense thereby reducing the downward pressure on the disc and thus the steam trap opens again to release the condensate collected.

Now when the thermodynamic steam trap is placed in harsh atmospheric environments such as winters or heavy rains, the rate of condensing of flash steam in the control area will increase and the steam trap will open more frequently. This condition is called ‘rapid cycling’ of the steam trap. This rapid cycling has two effects on the steam trap

• The rapid upward and downward movement of the disc damages it, reducing the life of the steam trap.
• During rapid opening and closing of the steam trap, live steam may also escape along with the condensate, leading to higher distribution losses.
• To avoid such conditions, it is recommended to install a protective cap on the top of the thermodynamic steam trap to isolate it from the surrounding environmental conditions.
• This cap is called as an ‘Isotub’. In areas with long spells of rain or high winters installing isotubs on the thermodynamic steam trap will be especially rewarding.