Steam traps hold the steam and drain out the condensate. When in service, a steam trap has to perform against many odd conditions. There are different types of steam traps which are suitable for different applications.
Process steam traps are used on different process equipment for the efficient removal of condensate. This ensures efficient product heating. In general, a good trap essentially has some features and characteristics which separate it from ‘not so good’ traps. Selecting a good trap is crucial to ensure product quality, production rates and long life of process equipment. Wrongly selected process steam trap can drastically raise the number of rejections and batch timings.
Essential characteristics of a good steam trap
1. Should not leak live steam
A good steam trap drains out the condensate without venting out live steam. In order to achieve this, the trap should respond fast when steam starts going out through it. A good trap closes quickly when it senses the steam and hence wastes minimum amount of steam.
2. Quick and complete removal of condensate
A good trap should remove the condensate completely as soon as it is formed. There are some applications (tracing) where it is allowed to hold condensate for some while before discharging it out. In most of the process heating applications, condensate needs to be removed as soon as it is formed. If a process steam trap fails to remove condensate quickly, it may result in water clogging inside the heating equipment which in turn hampers the product quality and production time.
3. Should sustain heavy start-up loads.
Condensate formation rates are higher during the system start-up compared to the running loads. This is because of the fact the surfaces of the distribution pipe network and the equipment are cold at the startup. In case of process steam traps, start-up loads are higher because surfaces of process equipment are cold. After some time, the surface temperature goes up and amount of condensate reduces down to a steady amount. The trap selected should be able to sustain both the loads- at the startup and the running loads.
4. Good air venting capacity
Air and other non condensable gases have detrimental effects on the steam system. When the steam is shut off, these gases will occupy the space previously occupied by steam. If these gases are not removed from the steam system, they will form air pockets affecting the process. Presence of such gases might also result in corrosion. Hence, at the time of startup, this air should be removed from the system. This makes air venting capacity an essential quality of process steam traps.
5. Should operate against the back pressure
Discharge characteristics of a steam trap steam trap depend on the differential pressure across the trap. Back pressure can affect the discharge capacity of a steam trap. A good process steam trap should work satisfactorily against the back pressure.