-94 F dew point dry air - issue with condensation

[Boiler1]

Greetings,

I have got an Oil Free Air system with desiccant dryers set to -70 degC / -94 F dew point. The system pressure is maintained at 7bar / 100 PSI.
The system dew point is monitored at several locations downstream form the central plant and its maintained within the spec (-70 degC / -94 F ) with no issues.
Lately, however, a noticeable condensation started occurring at one of the peripheral laterals with water droplets being very visibly ejected out of compressed air outlets. The whole cluster of laterals is on a sort of a dead leg and one of these laterals started condensing.
The condensing lateral isn’t the first in that cluster nor is it the last. The upstream or downstream laterals are not showing visible signs of condensation.
I have placed a hygrometer on one of the good laterals in that cluster and its showing a dew point temperature at around 0 degC / 32 F which is way above the spec. That said, it takes the hygrometer hours to stabilise and get the correct reading – trend so far isn’t promising.
What could have caused such an increase in the dew point temperature at the field end of the distribution pipework?


Regards

 

[georgeverghese]

If you have oil lubricated air compressors, the dessicant driers are probably poisoned with carry over lube oil vapors.
If you are serious about air dewpoint, there is no choice but to use oil free compressors.

 

[pierreick]

Hi,
When did you replace the desiccant for the last time? When did you perform an overall of the unit?
You may want to contact your vendor ?
My 2 cents
Pierre

 

[goutam_freelance]

If the cooling water pressure is higher than the air pressure(7 bar) then there is a chance that water may leak to compressed air.

Also, as indicated in earlier posts, the operation of the air dryer may be in jeopardy.

Engineers, think what we have done to the environment !

https://www.linkedin.com/in/goutam-das-59743b30/

 

[LittleInch]

V difficult to fault find remotely.

How long has this line been subject to no flow?
Could compressed air have leaked in at any point?
Has the system been taken off line?
Maybe there was an upset on the dryers not noticed by the monitoring and has just gathered in this deadspot
What does this distribution system look like?
Did the deadleg get blown down but left open to ambient air?

See why this is so difficult to do without any data or not having a vague clue about your operating history or layout or anything really?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Compositepro]

I don't think that I have ever seen a compressed air distribution system that stayed dry consistently, including instrument air systems. Flow surges are almost impossible to prevent, and driers cannot deal with them. Most humidity sensors are very slow to respond and will not detect transients. Once liquid water gets into pipes it is almost impossible to get them dry again without significant and careful efforts. The whole piping system must carefully designed and installed so there are no low spots and always sloped to drains. There should be a reciever tank between the compressor and drier to allow the air to cool and water to separate. Then there should be a receiver tank after the drier to store dry air and prevent flow surges through the drier. If dry air is truly important, it should be dried just prior to the point of use. Pipes going from outside in the sun or freezing weather, to inside where the air is condition is a problem.

 

[MacMcMacmac]

A chilled mirror dewpoint monitor is a much faster reacting device for dewpoint measurement.