Weight of ice in insulation 2

[MalcolmA]

We have a line on our Demethanizer that has several breeches in the insulation jacket. Ice is visible at the breeches.

My worry is that a large amount of ice has accumulated inside the insulation underneath the jacket and is not visible. Since the line is sch 10S, there is not any extra wall thickness to support the extra weight of ice.

Does anyone have any experience with ice accumulation inside the insulation of lines in cryogentic service? I would like to get a feel for how much ice there could potentially be underneath the insulation jacket.

The line operates at -132F and the plant is located in a humid coastal environment.

 

[pmover]

MalcolmA,

first and foremost, think about how the ice formed in the first place. obviously, the vapor barrier failed (not installed, small opening(s), etc.) which allowed the moisture to migrate towards the cold, thus freeze. nobody writing in this forum can tell you how much ice has formed below the insulation jacket.
i suggest using a small drill bit or some other device (like those used in obtaining ice samples on ice sheets) and determine the locations ice formation. that will provide you ample data as to where to replace the fouled insulation.
as far as 10s pipe, well, the pipe can only support so much before failure. acting now on the problem will certainly demonstrate a prudent decision in maintaining the overall integrity (i.e. reliability and availability) of the plant/system.

good luck!
-pmover

 

[unclesyd]

You have the wrong insulation material for the service along with apparently poor installation.

I would look at using Foamglas or any other insulation material that has low permeability to moisture. Whatever you use it needs to have the proper lagging/covering applied.

http://www.foamglasinsulation.com/default.asp

 

[25362]

Besides the heat gain and ice formation from air humidity, a coastal zone means the uninsulated pipe sections may be exposed to airborne corrosive salts.

 

[Montemayor]

MalcolmA:

The real secret (& probably the main one) to successful cryogenic or cold insulation is the effectiveness of the surface (& crevice) sealer material & techniques that you employ - and constantly inspect/maintain. The insulation material underneath the sealer is of secondary importance. Even FoamGlas (my personal preference for this type of service) will fail - and fail miserably - if you don't install and maintain an efficent sealer.

It is imperative that you keep invasive atmospheric humidity out of the insulation. Once the outside air moisture makes a successful invasion of your insulation, it accumulates to the point of ruining the insulation and causing other damaging effects - besides intolerable heat losses. Installing a successful and effective sealer + insulation material is the strength of an experienced and diligent insulation contractor. Nothing should be spared in selecting the best, experienced craftsman in the business. Notice that I said "craftsman" - this is an application where professional know-how and experience should be at the forefront. You will never regret using those qualities as your guidelines in selecting the person(s) that can give you a successful application.

I'm offering this advice from many years of experience in specific cold and cryogenic applications - as a process/project engineer and on through as a project manager.

 

[25362]

Montemayor is 100% right. As tutorials you may find these links useful:

http://www.energymanagertraining.com/Documents/Sethuraman-2-EE07.pdf

http://www.timsa.org.uk/Tgn02.pdf

 

[TheMalstrom]

I am wondering what type of insulation is used on your pipes? Because of the high delta T and moisture it is important to design these systems properly. It is difficult to see what caused the failure based on your information. It can range from poor design, to poor material performance, to poor application.

There are several insulation systems on the market. i.e. bonded PU foam with PE outer jacket, or high efficiency insulation such as an aerogel. I know that testing is being performed for both insulation systems on cryogenic lines due to the strong growth in the LNG construction market. The PU foam systems have the problem that they get a very high tensile strength in conditions of less than -20 degC. This means less flexibility, however there are systems with PU foam developed to accommodate for this. Some companies supplying these technologies:

http://www.brederoshaw.com/

http://www.permapipe.com/

http://www.bayouflow.com/

http://www.logstor.com/

There are other insulations such as aerogels, which are hydrophobic in nature and will not absorb water vapor. These are normally supplied in blankets and can easily be wrapped around the pipe. I think adhesives can be used. I would think they would be perfect for retrofit situations, of course with proper engineering in advance. The U-value achieved for this is much better than any other insulation system (k < 0.012 W/mK).

http://www.aerogel.com/

http://w1.cabot-corp.com/controller.jsp?entry=product&N=23+4294967102+1000+4294967086

Not to sound boring but there is yet another class of insulations that I can think of used in LNG facilities. This a phenolic based material, an organic polymer with high strength characteristics and fire retardant. It is applied as a pack in place material, much like play dough and sticks onto the structure over an adhesive/corrosion protection layer. The outside surface is wrapped with phenolic GRFP and acts as a moisture barrier.

http://www.alderleygroup.com/

I have mostly been working with the design of subsea insulation systems, but same materials are used onshore.

Best of luck