Steam Quality Question - Is it Condensate Carry Over

I am working with flash steam from a steam separator. The flash line is trapped in three locations before it takes a 90 degree turn upward to travel to a higher floor. It is trapped a fourth time just prior to the 90 degree upward turn. The is no acitivty at any of the first three traps -- no cylcing -- and the flash line is roughly horizontal. The fourth trap, however, cycles 8-9 times a minute -- it is an Armstrong 813 IB -- which translates to about 4 GAL per minute exiting the trap. If the trap vents are blown, the steam appears very dry at each of the first 3 traps, and very wet at the fourth.

The flash steam feeds a header that is also fed by a main steam line. The main line steam carries 30-40 degrees of superheat. The flash and main line steam are not mixing in the header. It appears that the flash is feeding only part of the application. The application requires dry steam. The application is responding in a fashion that suggests the steam is not dry and carrying a fair amount of condensate.

It has been suggested that the problem is condensate carry-over from the separator that fails to drop in the first three drip legs, but does so at the 90 degree up turn. Is this conceivable given the fact that the steam is dry at each of the first 3 traps ? Are there other possiblities ? Means of verifying ? It is very important to diagnose this correctly -- there is a plan to replace the separator -- can the problem lie downstream ?

Is there a book that can be suggested to use to calculate steam quality, line losses, separator size, anyhting that could help solve this problem ?

Many thanks in advance.

 

[DeltaCascade]

If the steam is dry then there is no condensate. The steam tables will tell you if the stream is dry and a calorimeter can be used to determine quality if it is not. I presume you are well aware of that.

It is tricky determining if steam is dry by looking at it leaving an opened valve.

Can you open a valve to see if the first 3 steam traps aren't really flooded and malfunctioning? Are they the same type of steam trap?

Perhaps lack of insulation is causing excessive condensation in the flash line, particulalry at the vertical spot? Perhaps the flash steam line needs to be sloped back to the separator, and perhaps also a larger diameter is needed to avoid plug flow of carry-over or freshly condensed steam.

How could the flash and superheated steam not be mixing?

Are you sure the superheated line is superheated? Perhaps insulation problems there? Measruements accurate?

It will be good to see what others post...

 

[TBP]

4 GPM of condensate translates into about 2,000#/hr. That sounds like a lot.

The only time you want superheat is for a turbine, or steam engine. If you have a superheated steam steam supply to a heat exchanger, the sensible heat that is superheat must be dealt with before you get to the latent heat, which is where all of the action is. A heat exchanger being fed superheated steam will behave as if it is airbound.

When dealing with saturated steam systems operating at the pressures encountered in general industry (usually under 300 PSIG) you actually don't get much superheat even after PRV stations. The steam quality isn't normally 100% in these operations, so the end result is usually just nice, dry steam after the PRV.

It's always hard to tell without seeing the installation, but my first impression is that you've got superheated steam at your application, rather than dry saturated.

 

[ChasBean1]

Being that the last trap before the vertical is showing excessive condensation while those closer to the steam source are not, I would suspect the condensate source to be from some point on the vertical. If anything's not insulated, improperly pitched, or throttling the steam downstream of this trap (specifically on or near the riser), that may be the cause. I would focus on the downstream equipment first. Good luck.