250mm Water main

[eski1]

Hi
We are looking to install a new 250mm Pipe run for Mains Water into our factory .Most of which will be underground.
The parts which are above ground we were going to spec 254 x 2mm 316 stainless steel pipe and below ground use the same pipe but wrap with Petroleum tape (denso Tape).
The other alternative would be to use plastic underground and only when it exits above ground into factory use stainless . If so what plastic would be acceptable and would it need to be Glass Lined as someone else mentioned it might need to be ?
Are there any inherent problems with using stainless steel underground ? . We would make sure there is minimum cover above pipe of 900mm & pipe bed on pea gravel or similar .The entire system will need to be pressure tested to 4 bar and chlorinated before use .

Thanks in advance for any help
Bit new to this game but want to make sure the contractors install the correct system.

 

[LittleInch]

Are there any inherent problems - not really providing you're not in a very salty environment, but I would love to work for your company as it seems you're willing to spend lots of money for no reason. A standard Poly Ethylene (PE) line of PE80, SDR 17.6 should be entirely feasible and I would image cost about half or less than a Stl stl line - for which 2mm is very thin - I can only image the fun (and expense) the contractor would have handling and welding stuff this thin.

Searching PE water mains or PE pipe design will give you more information that I ever could, but glass lined PE I've never heard of and who ever is telling you this is not correct for potable water.

Why do you want to use Stl Stl??, even Above ground. Other than fire protection, PE is a suitable above ground as it is below ground at these pressures.

My motto: Learn something new every day

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

 

[eski1]

Hi LittleInch

There is some inherent problems but in my mind not actually caused by the pipe used before .
problems are :-
Pipe bed was too angular, flint type material & coupled with this the pipe was over pressured to 9 bar for an unknown time until they realised.
So would have imagined the plastic pipe they used when the original install was done vibrated & abraded on the bed causing several leaks all over the place .
Months of repairs resulted until they have finally decided to replace the whole 150 meters of it . So think the Stainless is a bolt & braces measure !!.

 

[cvg]

you have numerous options for underground water pipe but stainless steel is not even on my list.

ductile iron
steel, coated and lined, possibly with cathodic protection
Polyethylene
FRP / GRP
PVC

pea gravel is not typically used for pipe bedding. depending on the soils, you could use native material or if not suitable I would recommend sand instead. soil conditions really need to be investigated, they are a critical factor in underground piping.


.

 

[LittleInch]

What type of "plastic" was it? I can only imagine it was a "hard" plastic such as PVC which could abrade - not PE which is remarkably forgiving.

Stl Stl is very unusual for this application. I echo cvg - sand is better than pea gravel, but beware GRE underground - it can abrade as well and is not the easist of pipes to install below ground.

for 150m, why don't you just internally line it with PE??

My motto: Learn something new every day

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

 

[zdas04]

I would use something like SDR 13.6 HDPE (the SDR 17.6 mentioned above wouldn't take your 9 barg transient). For the above ground portions, you'd be money ahead to use 10 inch Sched 20 grade B carbon steel with a PE liner. The cost would be about 1/3 of SS with far better performance.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

 

[eski1]

Thankyou all for your responses.

As the existing main is still being used although on last legs , we haven't got the option to internally line it with PE unfortunately .
I agree St/st does seem like a crazy choice for this but the factory managers seem to want to go this way , although I will pass on all your comments .
I suppose what I need to now do is find try to find out if there any inherent problems with using stainless steel underground ?
is the 254 x 2mm st/st Pipe strong enough underground ? I believe above ground in food factory's this is quite commonly used .
Will the Denso Tape wrap be enough protection underground.?

 

[LittleInch]

Inherent problems –no

254 x 2mm –yes. One it doesn't exist. 10" pipe is actually 10.75" od and the smallest standard pipe is sched 5s, which is rarely stocked, is 3.4mm. Sched 10S is 4.19mm and much more like it.

Stl stl is corrosion resistant so an external wrap is ok.

My motto: Learn something new every day

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

 

[zdas04]

While SS doesn't tend to rust, it is still subject several "cracking" corrosion modalities. Some classes of SS are more prone to this than others. I'm always really nervous when people talk about burying SS because once it is wrapped and in the ground you can't inspect it for Chloride Stress Cracking, Hydrogen Embrittlment, etc. I wouldn't do it on a bet. Especially since there are much better alternatives that cost a whole lot less.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"