The function of installing steam traps is to obtain fast heating of product and equipment by removal of condensate , air and non condensable gasses from the steam line , without discharging the steam.
The function of installing steam traps is to obtain fast heating of product and equipment by removal of condensate , air and non condensable gasses from the steam line , without discharging the steam.
Mechanical traps :- These are actuated by the level of condensate.These steam traps include ‘ ball and float types’ and inverted bucket type.
Thermostatic traps :- These are actuated by fluid dynamics.
Thermodynamic traps:- These are actuated by temperature of condensate.These steam traps rely partly on formation of flash steam from condensate.Eg- thermodynamic , disc , labyrinth, steam traps.These are most common steam traps in power plants.Other two types of steam traps are used where process heating and temperature is more important.
Energy audit of steam traps:-
Instruments used in energy audit of steam traps:
- Mechanic stethoscopes , screwdrivers, metal rod etc.
- Pyrometers , thermal imagers etc.
Performance assessment of steam traps:
Performance assessment of steam traps gives the answer to the following points.
- Is the trap working correctly?
- If not then
- If failed in open condition:- loss of steam and condensate.
- If failed in closed condition:- Condensate carried and steam quality deteriorates.
- If making a rapid cycle (frequent opening closing) partial loss of steam and condensate.
- Is the trap selected right :Thermodynamic traps are used in steam line for maintaining main steam temperature and pressure and quick condensateremoval , other traps are used for process plants for process heating application where temperature of steam is more important.
Sight method:
Sight method is based on the visual observation of steam downstream the trap.This is possible if the drain line is open to atmosphere ( no condensate recovery).However one has to distinguish that the steam coming out is live steam or flash steam generated.If flash steam is coming out the steam trap is ok and if live steam is coming out the steam trap is faulty.Live steam will have high velocity steam and may not be easily visible as it exits the trap. Flash steam is low velocity steam.
Sound method combined with temperature method
Practically thermodynamic steam traps can be identified by listening to the sound of the valve.They are either fully closed , fully open or opening closing rapidly (rapid cycle).if there is no sound observed in the mechanic stethoscopes trap is either fully open or fully closed .this is to be further cross examined with temperature .If temperature at outlet of trap is less than 100 deg then it is condensate and trap is ok.If temperature of steam is more than 100 deg it is live steam.The temperature at inlet to steam trap should be greater than 100 deg because it is live steam.Thermostatic and mechanical steam traps are to be identified more based on the temperature same in similar way .the temperature at inlet has to be more than 100 deg and temperature at outlet has to be less than 100 deg for the trap to be ok.