need some ideas on how a 18" cooling water underground pipe leak

[hmui]

Two holes, 3/4" and 1" within 10' of piping. The water is treated. There is no brace or any other metal near where the holes were. What could cause these holes to form? Any ideas?

 

[Ripz]

External Corrosion.

 

[cvg]

with no further information on either water quality, installation or pipe material and coatings it could also be internal corrosion or defective pipe or damage to the pipe during installation...

 

[LittleInch]

Any photos? Any details such as age of pipe, material of pipe, wall thicknesses of pipe, type of coating, any CP, any overhead power lines, any railway line?

Give us a few clues and we might guess the answer.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[Ripz]

Give us anything to work with.

I'm going to answer by making assumptions.

The fluid is water, so carbon steel piping was used. Since it was buried, it would have been externally coated and/or wrapped.

Since the corrosion was isolated in the form of holes and not generalised, I would assume the external coating/wrap got damaged at some point, likely at installation, resulting in minuscule holidays, exposing the susceptible Carbon Steel to the highly corrosive soil, eventually resulting in holes.

...

But these are just assumptions.

 

[hmui]

Piping is 18" C.S. STD, wrapped in ArmorFlex, burried 5' in the ground (top of pipe.) Installed in 2005. Water is treated with sulfuric acid and some other chemicals. On the surface, there are a lot of transfer pumps that discharge fluid to the ground. The fluid is water + product. The product is around 5 pH.

 

[hmui]

Link

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Sorry for using the link function. The image function doesn't show on Preview for some reasons.

 

[cvg]

well, that's a start
water quality is - aggressive/corrosive; temperature?
corrosion protection - non-existent?
no exterior coating?
installation - armor-flex? what about backfill type, quality and compaction and loadings?
interior lined or coated? with this corrosive water, why not?
is sulfuric acid dripping on the ground?

 

[btrueblood]

Is this for a heap leach copper mine? It looks like the supply pipe was buried beneath a membrane/liner - was the supply piping set in a clay layer?

Was the membrane punctured/damaged near the leaks, to cause the pipe to be wetted by the acid solution?

Like cvg asks, is there some reason you didn't use pvc for the acid solution?

 

[LittleInch]

Can you expand a bit on this coating. I looked it up and came up with a substance used for water proofing pavements!

http://www.apoc.com/linedetails.aspx?id=252

Also it is clear that the line was laid and then someone decided to instal a set of foundations directly over it. The risk of damage to the coating is very high when this occurs, especially if your coating is not a pipe coating able to resist the rather hazardous liquid you are apparently leaching into the ground.

However the contents of the pipe look corrosive to carbon steel to me. Normally "treated" means water which is suitable for disposal, not with unknown amounts of acid and "other chemicals". Carbon steel is not normally used for these substances as it corrodes.

If you can provide some more details of the water we might be able to see if carbon steel is suitable or not. I suspect not and your pipe may just start to sprout lots more holes in the next few years.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[Ripz]

One of two things. Either coating was damaged and you had external corrosion. Or the pH 5 solution being transported is corroding the internals. Both are likely. You'll need to show us pics of the actual failures and perform some visual and thickness inspections.

 

[hmui]

cvg (Civil/Environmental)

well, that's a start
water quality is - aggressive/corrosive; temperature? getting this info
corrosion protection - non-existent?correct, nothin
no exterior coating? nope
installation - armor-flex? what about backfill type, quality and compaction and loadings? backfill type?
interior lined or coated? with this corrosive water, why not? no interior lining. From what I found so far, people at the plant assume the cooling is neutral.
is sulfuric acid dripping on the ground? no, only added to the cooling water to "treat"

 

[hmui]

btrueblood (Mechanical)

Is this for a heap leach copper mine? It looks like the supply pipe was buried beneath a membrane/liner - was the supply piping set in a clay layer?

No, not around copper mine. Yes, we have a membrane above the line. Yes, the soil property of our area resembles clay.

Was the membrane punctured/damaged near the leaks, to cause the pipe to be wetted by the acid solution? Is is a possibility.

Like cvg asks, is there some reason you didn't use pvc for the acid solution? no idea what the rasonale for the choice for this install. another good question for the project guys

 

[hmui]

LittleInch (Petroleum)

Can you expand a bit on this coating. I looked it up and came up with a substance used for water proofing pavements!

http://www.apoc.com/linedetails.aspx?id=252

Also it is clear that the line was laid and then someone decided to instal a set of foundations directly over it. The risk of damage to the coating is very high when this occurs, especially if your coating is not a pipe coating able to resist the rather hazardous liquid you are apparently leaching into the ground.

However the contents of the pipe look corrosive to carbon steel to me. Normally "treated" means water which is suitable for disposal, not with unknown amounts of acid and "other chemicals". Carbon steel is not normally used for these substances as it corrodes.

If you can provide some more details of the water we might be able to see if carbon steel is suitable or not. I suspect not and your pipe may just start to sprout lots more holes in the next few years.
I think so too. I was surprised to find that sulfuric was in the composition. I am looking into what other chemical is there. This might take a bit, I'm actually on vacation and folks that might know this are also.

 

[hmui]

Ripz (Mechanical)

One of two things. Either coating was damaged and you had external corrosion. Or the pH 5 solution being transported is corroding the internals. Both are likely. You'll need to show us pics of the actual failures and perform some visual and thickness inspections.

Unfortunately no picture. This happened when I was away. I did manage to get UT done. Waitting on the results now.

 

[chicopee]

I would not be surprised if you had significant wall thickness reduction when you receive your UT results. Make sure UT's cover elbows and "T's" fittings.

 

[cvg]

backfill type and conditions / armorflex

http://www.conteches.com/Products/Erosion-Control/Hard-Armor/ArmorFlex.aspx

well, I suspect water quality may be the issue but there are other possibilities.
bedding and backfill was native soil? any large rocks in the backfill which could damage the pipe?
what is the corrosion potential of the soil and groundwater?
any electrical lines running nearby causing stray current?

 

[NegativeZero]

if your pipe continues to have leaks than you may have water issues or overall coating issues. But this looks like a isolated hole. Someone hit it with a shovel or bad back fill exposed the raw pipe....and you got corrosion.