Eductor for sampling sustem 1

[Shaman2]

I need help diagnosing the failure of an eductor sampling system for a gas stream. We have 5 nearly identical systems, two of them have Karked it. the other three continue to work fine. I have prodded, probed, cleaned, washed and prayed and nothing seems to improve the function of the 2 that are malfunctioning. I now have the opportunity to remove and post mortem one of the "baddies" to see why after three years of good service they suddenly went bad. I am wanting to make sure I check for any possibilities.
The design is pretty simple two legs attached to a gas stream connected by a down leg. Detector in the upper leg, after a moisture trap, eductor using compressed gas in the lower leg. no moving parts so nothing should go wrong except blockages which I have ruled out by the above mentioned prodding, cleaning etc.
Thanks for any help or suggestions.

 

[MikeHalloran]

Section one of the bad eductors along its axis and compare it with catalog drawings of eductors for similar service. Feel free to link photos so we can all see it.

My guess is that something inside (there are no _moving_ parts, but there _are_ parts) has eroded/ corroded/ come adrift, and the propulsive stream is not being accelerated properly.



Mike Halloran
Pembroke Pines, FL, USA

 

[kenvlach]

A low tech test: switch a good one & a 'bad' one. Something in your system may have changed, e.g., corroded as suggested by Mike.

 

[Shaman2]

Kenvlach

Thanks,
but unfortunately The "nearly" in my "nearly identical" description prevents that. There are problems with left/right handedness and distance between connections.
I am currently having a new system made up for the worst performer and doing the paperwork for switching them out.
After I get the bad boy out I will take great pleasure in a totally destructive autopsy!

 

[EdStainless]

Before you cut it up run it on a bench with shop air. Check pressures and flows against the rating. Run at different pressure/flow points to check against the curve. At least then you will know what 'bad' really is'

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[Shaman2]

Update.

Finally was able to remove examine and clean the worst offending system.
Found (as per one of my suspisions)that ther was excessive build-up exterior to the sampling spears inside the process. However despite the previous rodding out , both spears were also blocked. Some build-up was found throughout the system.
Completely revamped and reinstalled the system, and it works fine.
So the answer to my personal "which of these problems is the cause" seems to be, "All of the above". Everything I had considered as a possibility was in process of occuring, just the spear blockages got there first.
Have scheduled the refurbishment of the other malfunctioning system for this week.