UG piping within Frost depth
UG piping within Frost depth
(OP)
Hi,
Regarding underground piping, one gentleman came up with a new idea. The frost depth at site is 3.9 m and he tries to put u/g piping at 2.0 m below surface with 100 mm Styrofoam layer 150mm above the pipes. The Styrofoam should be working as an insulator.
But, I have two concerns.
1)Does it work as insulator to prevent piping from freezing within the frost depth area? In my opinion, the Styrofoam just delays heat transfer between cold surface and piping and at equilibrium state, the service in pipe might be reaching to freezing temperature.
2)Is it durable for life time 20 years? The Styrofoam seems not strong enough to sustain the weight of soil and is going to be squeezed and to lose its insulation effects as time goes.
Could you advise me about this approach, please?
Many thanks,
Regarding underground piping, one gentleman came up with a new idea. The frost depth at site is 3.9 m and he tries to put u/g piping at 2.0 m below surface with 100 mm Styrofoam layer 150mm above the pipes. The Styrofoam should be working as an insulator.
But, I have two concerns.
1)Does it work as insulator to prevent piping from freezing within the frost depth area? In my opinion, the Styrofoam just delays heat transfer between cold surface and piping and at equilibrium state, the service in pipe might be reaching to freezing temperature.
2)Is it durable for life time 20 years? The Styrofoam seems not strong enough to sustain the weight of soil and is going to be squeezed and to lose its insulation effects as time goes.
Could you advise me about this approach, please?
Many thanks,





RE: UG piping within Frost depth
With an insulating layer above a pipe, you must somehow prevent water from entering the soil from around the edges of the insulation sheeting, which is very difficult to guarantee will never happen. http://www.schundler.com/pipe.htm
These guys say to wrap the entire installation with PVC. I don't think that will reliably maintain dryness and other measures will probably also be needed. By the time you do that, it may be better just to bury below the frost depth, no matter how deep that may be.
In any case don't use styrofoam. As you already know, strength is not sufficient. Normally a casing pipe with a pressure filled polyurathane is used if product and pipe temperatures are not too high.
http://virtualpipeline.spaces.msn.com
"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain
RE: UG piping within Frost depth
RE: UG piping within Frost depth
http://virtualpipeline.spaces.msn.com
"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain
RE: UG piping within Frost depth
How about wood? the powdered wood may be split moulded to form a casing around pipe and this may be made rot proof over 20 years or so??
Just a idea.
regards
Siddharth
Siddharth
These are my personal views/opinions and not of my employer's.
RE: UG piping within Frost depth
The particulars of the thickness & width of the insulation required depends on design surface temperature (or annular variation), soil characteristics, pipe size, temperature & flowrate of product, etc.
See this link for one study:
h
RE: UG piping within Frost depth
ALL USCOE materials are available for
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SR97-1 here,
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maybe you'll want to add this one too.
SR97-29,
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http://virtualpipeline.spaces.msn.com
"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain
RE: UG piping within Frost depth
I believe unless underground (or for that matter any) insulation is shielded with an impermeable vapor barrier, it will in addition to undergoing some level of mechanical stressing also be exposed to moisture/vapor in a great many underground environments. I have also seen more in depth discussions that even closed cell foams can be subject to some forms of aging and there will be over time some degree of diffusion of the blowing agent out of the foams, and diffusion/permeation of substances (e.g. water vapor?) into even the cells of the foam. I have also heard that water in insulations can/will? decrease the initial "R-value" (an maybe even bring up other questions if it freezes etc.?) While all of this may of course be immaterial if the foam is sufficiently durable and also appropriately conservative (considering all effects) long-term insulation values are chosen for design, I didn't happen to see these specific issues discussed specifically in the CRREL report. Do you know of any good studies or references that address the long-term issues specifically with regard to buried insulations? Since the idea of buried insulation is being sort of legitimized in this thread and by these references, we should probably also mention the caveat in the CRREL report that under some conditions insulation can actually cause a narrow sheet of ice to exclusively form on roadways (I guess immediately over the protected pipe?).
RE: UG piping within Frost depth
I certainly wouldn't put uncased insulation material of any kind under a road or other high load areas, especially in a pipeline environment and I'd be pretty damned careful wherever I tried using it, to the point of being suspicious of compression by soil loads above or by pipe movement. So far, for uncased buried pipelines, earth and appropriate burial depth is all I have ever needed to keep product temperatures sufficiently high for my purposes.
http://virtualpipeline.spaces.msn.com
"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain
RE: UG piping within Frost depth
In a few minute search, this document seems to address the longevity question pretty well-
www.xpsa.
RE: UG piping within Frost depth
http://virtualpipeline.spaces.msn.com
"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain
RE: UG piping within Frost depth
Here's a data sheet for styrofoamm pipe insulation.
htt
It was used on smaller diameter pipes at this brewery, sounds like it was cut to shape and strapped on.
http://
RE: UG piping within Frost depth
Its summertime now. I'll have a look in Jan.
"If everything seems under control, you're just not moving fast enough."
- Mario Andretti- When asked about transient hydraulics
http://virtualpipeline.spaces.msn.com
RE: UG piping within Frost depth
RE: UG piping within Frost depth
RE: UG piping within Frost depth
-what kind of pipe and product
-temperature & flow variations
-where located/climate
-soils conditions
-depth of bury
..etc..