Stream Trap Selection Criteria

[Iomcube]

@

https://www.tlv.com/global/TI/steam-theory/trap-steam-mains.html

From the above article I cannot understand the bold criteria for selection
When installing a steam trap on a steam main, TLV typically recommends the use of traps that discharge condensate continuously, such as the Free Float® type. Other trap types such as disc, bucket, or balanced pressure thermostatic can be used provided that the collecting leg is adequately sized to prevent back-up into the steam main. Bimetal traps are not recommended for use on steam mains due to the possibility of large back-up distances which could pool condensate in the steam main itself. This is an especially worrisome situation when the trap is located close to the steam main.

What he means by collecting leg? What if I am sending condensates to open atmosphere?
Secondly large backup distances?

 

[mk3223]

The collecting leg is the steam condensate discharged typically from the multiple steam traps. And, the collecting pipe is routed to the condensate collecting tank.
As the steam trap is discharged to the grade (open atmosphere) without recovering the condensate, there is no condensate collecting pipe.

 

[Latexman]

Instead, properly sized, wider piping called a drip leg ([highlight #EDD400]collecting leg[/highlight], or drain pocket) is typically installed to help enable the efficient and effective removal of condensate.

Good luck,
Latexman

Engineers helping Engineers

 

[Iomcube]

Thanks for replying. Can you please also elaborate why we cannot use Bimetal traps; I cannot comprehend TLV's reasoning may be because English isn't my mother language!

 

[Compositepro]

The goal is to remove liquid condensate from the steam main at all times. Bimetalic steam traps often operate as on off valves. They close when heated by steam and will open only after they cool down sufficiently by heat loss to the ambient environment. By the time the valve opens again, condensate will have collected in the pipe to the trap, and when this pipe is full there will no longer be any removal of condensate. Then condensate will move on down the steam main. So you must provide enough storage volume for condensate between the steam main and the trap, that condensate does not back-up to the steam main.