pipeline drying 2

[pipeliner3000]

how long does a dry pipeline stay dry?

We are planning on drying with super dry air. The drying specs calls for -20degC dew point and to be left at +ve pressure 0.5 to 1.0 barg. If this is proven by soak testing how long can it be expected to stay at -20degC dew point? as long as temperature does not drop below -20degC does the dryness last, weeks, months...? Can this drying be considered as preservation that would preserve the pipeline for upto 9mths or would we need to monitor and re mob equipment to dry again within the preservation period?

Thanks

 

[zdas04]

It is not magic, it is thermodynamics. You are physically removing H2O molecules in your drying process. With a dew point that low, any liquid water in the line will evaporate pretty quickly (raising the dew point of the air). If you keep circulating air until the exhaust dew point meets your spec then the water will be gone. Now you seal the line with the -20C air in it. There is no source of new water since you have dried up all the liquid. The pipe will stay dry as long as a positive pressure of dry air is maintained.

David Simpson, PE
MuleShoe Engineering

Law is the common force organized to act as an obstacle of injustice Frédéric Bastiat

 

[LittleInch]

A star for the response.

A dry pipeline will stay dry unless you introduce water into it, either a liquid or more humid air.

This should preserve your pipeline unless you have temperatures below -20c and keep it at positive pressure.

Using a super dry low pressure nitrogen fill is seen for long term preservation so that even if some water appears for whatever reason, there is no oxygen to get any corrosion.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way