Water Line Insulation

[ivanlocke]

I have a 6" or 12" ductile line going in that will need to come up over an obstruction. The line will only be feeding a single service, so I'm worried about freezing and want to insulate it. The line will be about 2' deep - frost line is at 42" - for maybe an 18ft length. I do not know if the line is in an area where traffic will be going over it - this will probably make a lot of difference in what I can use. Is there any kind of insulation that would be able to take a load, or am I looking at building a box and filling it with foam or something?

Thanks for any ideas.
Ivan

 

[KRSServices]

There are plenty of insulation options, but that is only one of your concerns. You need to:

1) Determine the minimum and maximum flow demand of the service line.

2) Determine the minimum, maximum and average velocity of the water in the pipe.

3) Determine the soil types the pipe will be constructed in and their susceptibility to movement due to uneven freeze/thaw (considering the moisture content, soil type and swelling)

4) Determine the maximum ambient tempurature of the soil in the pipe zone (assuming a worst case winter, cold degree days, traffic versus non loading, little or no snow).

5) Determine the "R" value of the soils and perform a detailed thermal analysis of the water in the pipe to determine the freezing characteristics. Also perform a time to complete freeze.

Once the above is completed, you will be able to develop a few options to ascertain the best solution for your problem. One word of caution, with the 12" or 6" pipes, there will be a few unique issues to deal with and the solution may involve a combination of proper sizing, insulation and earthworks. If you wish, you can email me for more information or advice.



KRS Services

http://www.krs-services.com

 

[CarlB]

Or you can go with time-proven, extruded polystyrene subgrade insulation board. Its thermal equivalence is at least 2 feet of earth per inch of insulation. So a 4 foot wide board, 2 inches thick should be plenty to prevent the line from freezing. Place it about 6" over the pipe so it has 1.5' cover. You can get it in different strengths, may want to go to 60 psi rating for this fairly shallow application.

See

http://www.dow.com/styrofoam/

for product info & applications.

 

[KRSServices]

CarlB,

The board insulation does indeed work well, but only when the abient tempurature of the ground is within the rate of heat loss of the ground. Since the pipe is very shallow and may be within the traffic (loading) zone, it may not be very effective. As I pointed out, insulating the pipe will likely be part of the solution, but without reviewing the thermal characteristics of the fluid, the soils and the pipe and their corresponding behaviours to freezing, I would caution against a "one stop solution" so quickly.

KRS Services

http://www.krs-services.com

 

[kenvlach]

I suggest
1) Do your homework as per KRS' first post.
2) Consider placing your pipe concentrically inside a larger pipe (4 or 6" larger diameter), then filling the interstitial space with polyurethane foam.
Much less work than building a box!

 

[TVE]

As an option to sheets of insulation, you may want to consider a pre-insulated pipe. Sheets are wonderful in theory, but there really isn't any guarantee that the insulation won't be "lost" the first time someone excavates across or near the watermain.

I know that one company that has pre-insulated pipe is Urecon (

http://www.urecon.com).

They supply a product that has 50mm (2&quot of insulation as an outer covering on the pipe. They also have the heat-loss rates for their product so you can do your calculations to determine it if will be enough.

David Dietrich
Thames Valley Engineering

 

[KRSServices]

There are many options. Urecon does indeed make a preinsulated pipe. But in this case it is going to be quite shallow and that difference alone is going to require special consideration.

It is apparent that some of you folks have never used this type of insulation before. It is tedious, tenacious and very difficult to work with, particularly in conjunction appertenances. It is also expensive. It may very well be a solution and then again, it may not be. As I noted earlier, do the math first, then select the appropriate options. I have extensive experience in cold climate utility (water and sewer) installations and can only offer advice based upon what options I know will work and what will not.

KRS Services

http://www.krs-services.com

 

[ivanlocke]

Thanks for the suggestions. I'll make sure I consider everything.

 

[BobPE]

do a search on eng-tips, there are several very good discussions on this subject.

BobPE

 

[nackra]

I've used Pittsburgh Corning products with aluminum jacket

http://www.foamglasinsulation.com/product_info.html

selection depends on several constraints - check with tech support for product to confirm