Best practices for drying an stainless steel (austenitic) pressure vessel without use of heat

[Magdonel13]

I have this challenge because off a client specification said as mandatory to dry this type off vessels without using any heating source (hot air). Does anyone have an standard or procedure to achieve this? I read about vacuum drying and nitrogen purging but this methods are useful just for remove moisture and due to the internal configuration of the equipment (baffles) it still retains water from the hydrostatic test.

The vessel material is SA-213 TP304/304L; Design 405°C @ 63 kg/cm2; Operation 316°C @ 50 kg/cm2; MAWP 340°C @ 65 kg/cm2.

Kindly regards.

 

[Compositepro]

A high vacuum can be used to complete dry any vessel that can structurally tolerate a high vacuum. This is done with freeze-dried foods. Technically, heat is still required to vaporize water, but it is not high temperature. The heat comes from the ambient temperature. The vacuum just has to be sufficient that the absolute pressure is lower than the vapor pressure of water at ambient temperature.

https://www.youtube.com/watch?v=y4BGV7-1lhs

 

Concur, but understanding that not all PVs can withstand vacuum.

Nitrogen is useful in evaporating water because bottled N2 contains virtually zero moisture.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[refined sweat]

Nitrogen is what I would consider first.

 

[chicopee]

Since the external pressure of pressure vessels is ROUGHLY half the maximum allowable pressures calculated from formulae of the NB/ASME codes, the maximum internal pressures of 63, 50 and 65 kg/cm^2 as described in your OP can be taken roughly as half if your tanks were exposed to vacuum. It is my opinion that exposing your tanks to full vacuum should not be a problem but double check anyway. Freeze drying and then placing items under partial or full vacuum is a practice used when water damaged documents are to be salvaged.

 

[SnTMan]

Vessels may be tilted and rolled to assist draining.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[LittleInch]

Operation is 300C but the owner doesn't want hot dry air at 60 to 70C??

Is that a generic specification?

Ask for a deviation?


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

 

[georgeverghese]

The spec forbidding the use of hot air for drying probably is to avoid chloride induced SCC in SS304L at temps greater than 60degC or so due to trace amounts of salt in the drying air. If you want the client to approve the use of hot air / hot N2 as the heating medium, you may have to prove that the air or dry N2 is treated such that it is completely free of airborne salt (especially so if air is from some place near the sea), in addition to be of low water dewpoint.
Be wary of inert gas generator produced inert gas if oil lubricated screw compressors are the source of compressed air to the inert gas generation unit.