Absorption Column - Wet Insulation
Absorption Column - Wet Insulation
(OP)
Hey guys, I thought I may pick your brains on this sticky issue.
Background: 19 m tall, 2 m ID, insulated trayed column. Operates at a steady -70 degC with rare trips to -10 degC. A couple of months ago ice started forming around several locations of the column and associated piping. This has created a hazard, as we're having chunks of ice falling, plus a slightly increased susceptibility to CUI. Documentation is not too great, and we're not a 100% sure of the insulation material, we believe it to be Polyurethane foam. Everyone pretty much agrees that the insulation got wet somehow, and the ice pattern does suggest that hypothesis (spreading like water would do from the top of the column), although the insulation cladding seems undamaged at the top.
Site is keen on stripping the whole thing and replace all the lagging. For process reasons this requires a plant shutdown, and this would be a very long and costly one.
What I'm suggesting instead is the following:
1) Strip lagging at selected location (accessible from existing platforms) to check for CUI.
2) Remove insulation from the top of the column and
3?) Dry the insulation somehow? Could we pump hot N2 in there and dry it? Does any of you have experience with such a thing? Feasibility?
4) Re-lag, re-seal top of the column.
5) Are there any extra barriers we could install to prevent future water ingress?
Your opinions are greatly appreciated.
-Francisco
Background: 19 m tall, 2 m ID, insulated trayed column. Operates at a steady -70 degC with rare trips to -10 degC. A couple of months ago ice started forming around several locations of the column and associated piping. This has created a hazard, as we're having chunks of ice falling, plus a slightly increased susceptibility to CUI. Documentation is not too great, and we're not a 100% sure of the insulation material, we believe it to be Polyurethane foam. Everyone pretty much agrees that the insulation got wet somehow, and the ice pattern does suggest that hypothesis (spreading like water would do from the top of the column), although the insulation cladding seems undamaged at the top.
Site is keen on stripping the whole thing and replace all the lagging. For process reasons this requires a plant shutdown, and this would be a very long and costly one.
What I'm suggesting instead is the following:
1) Strip lagging at selected location (accessible from existing platforms) to check for CUI.
2) Remove insulation from the top of the column and
3?) Dry the insulation somehow? Could we pump hot N2 in there and dry it? Does any of you have experience with such a thing? Feasibility?
4) Re-lag, re-seal top of the column.
5) Are there any extra barriers we could install to prevent future water ingress?
Your opinions are greatly appreciated.
-Francisco





RE: Absorption Column - Wet Insulation
There is no way one can push Nitrogen through polyurethane foam. What you described is commonly applied for full containment tanks and cold boxes in cryogenic service, where continuous Nitrogen purge is employed through Perlite insulation for the same reason. But the expanded Perlite is designed to allow for purging (flakes).
I'm not an expert on insulation but Polyurethane foam doesn't sound like the best solution for cryogenic equipment and piping operating at -70C. I see on some manufacturer's websites that it is not recommended below -22F (-30C), although some others quote working temperatures down to -150C. See http://www.wbdg.org/design/midg_materials.php#ppgi... and http://www.insulation.org/articles/article.cfm?id=... and http://www.aaamsa.co.za/images/Technical%20Publica...
You should definitely try to locate damaged sections of the insulation and replace/repair them, to prevent further escalation. On the long run, consult with insulation specialist to see if it is better to use different type of insulation.
Dejan IVANOVIC
Process Engineer, MSChE
RE: Absorption Column - Wet Insulation
Regards
StoneCold
RE: Absorption Column - Wet Insulation
RE: Absorption Column - Wet Insulation
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: Absorption Column - Wet Insulation
Dejan IVANOVIC
Process Engineer, MSChE
RE: Absorption Column - Wet Insulation
* Okay, so it seems that drying the insulation is a long shot - and yes, you've made a good point, even if dried, the insulation would still be damaged, at least where the ice is.
* I'm not too worried about CUI, still have to do my due diligence and inspect it.
* A leak is highly unlikely, this column handles a C1-C2 mix at 4 MPa, if that was the case the ice would 'radiate' from a single point and would creep up. We do have leak sniffing campaigns, I don't know how effective they actually are though.
RE: Absorption Column - Wet Insulation