cooling water underground piping system

[lganga]

Dear friends
Construction company, has designed all the CWS and CWR as an underground system.
It is a high flow system with CWS in 60" and CWR in 68" and flow, about 30,000 cubic meters per hour.
None pipe supports has been considered . The above ground CWS pumps laid on a concrete slab, connect to a floating underground system. The same happens for any other equipment placed around the plant, where the UnderGround pipe systems connects to AboveGround, like pipe racks, heat exchangers ,vessels,power plant condenser etc.
I have already told the vendor to do stress analysis, considering the flow dynamics in elbows, branches, and the relative displacement due to soil resistance variation because of the ground water levels, along the weather seasons, with weight and dynamic loads acting .
On concrete blocks or any other support, but the soil friction (lime type and clay).
The only standard I have read about, is B31.8 .Does AWWA has some information.
I will appreciate your opinion
Regards
Luis

 

[LittleInch]

I would have thought B 31.1 was a more suitable design code to use.

Are these steel pipes?

My motto: Learn something new every day

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

 

[lganga]

Yes it is carbon steel.
The design code is B31.3 but there is no underground piping on this code
Does code 31.1 has it?.
I am quite sure that another's companies have considered the supporting for this service.

 

[weldstan]

Under ground and above ground pipe are covered by B31.3 as well as B31.1.

 

[BigInch]

And B31.4 and .8 are pipelines, but speciality pipelines typically oil and gas related, and chilled water system is not technically falling within either of thosse codes scopes. ASME ORG says, "ASME B31.4 covers piping transporting liquids between production facilities, tank farms, natural gas processing plants, refineries, pump stations, ammonia plants, terminals (marine, rail, and truck), and other delivery and receiving points. Key changes to this revision include new requirements for CO2 piping (presumably for CO2 dense phase transport) and the incorporation of requirements of ASME B31.11 (slurries) into ASME B31.4.

B31.8 is similar, but reserved for gases.

Chilled water is not power piping B31.1, nor is there any process, so process piping B31.3 is not applicable.

I would have thought you want B31.5 and other ASHRE standards, see here

http://www.baltimoreaircoil.com/english/resource-library/file/1482

you must get smarter than the software you're using.

 

[bimr]

You can use AWWA A100 pipe standard.

 

[lganga]

bimr
Is not easy to find an standard that follow this type of this underground design.Forces induced by elbow reduction and branches, added to the type of soil and ground water.
May some stress analysis considerring thos forces can help to solve this. This is floating underground system conneectin to fixed system above ground
Regards

Luis

 

[BigInch]

Adapt the principles you need from the underground pipe design discussions in the B31.1 appendicies. Check the resulting stresses against the design code of choice.

you must get smarter than the software you're using.

 

[bimr]

Have you investigate the handbook?

 

[bimr]

Have you investigate the handbook?

 

[bimr]

Here is a link to the Steel Piping Handbook:

http://www.steeltank.com/Portals/0/pubs/Welded Steel Pipe 10.10.07.pdf

 

[LittleInch]

You keep referring to this system as "floating underground". What do you mean?

Any set of steel pipes full of water will not "float". If you have waterlogged ground you might have an uplift force, but use soil, concrete or anchors to keep it down in the occasional circumstances when the pipe is empty.

If the ground swells or contracts a lot compared to the above ground slab then the design will need to allow for this and be quite flexible.

If the vendor does stress analysis then you need to ask him what code he is analysing this to.

Not many details here so not many detailed answers..

My motto: Learn something new every day

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

 

[lganga]

Littleinch
All the pipes has been buried without any consideration about, ground water, settling of the pipe after loading it, no concrete blocks or no support blocks on the discharge cooling water pumps manifold. I am very sure that this system will move, that is the reason the why I was saying a floating system. Because above ground, is almost fixed on concrete slabs or in pipe racks.
Regards
Luis

 

[LittleInch]

Where is this plant so I can avoid being anywhere near it when it breaks...

My motto: Learn something new every day

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

 

[weldstan]

Was there no civil engineering review with underground design, based on the Geotech Report? If not, I'm with LittleInch - don't want to drown when it ruptures.

 

[rconner]

Not a whole lot of detail has been given; e.g., the means of support for the ("fixed"?) foundations/structures, as well as the comparative bedding and soil borings wherein the buried pipelines are "floating". Also, what kind of joining has been used for the piping, is the piping insulated, and/or how etc (your inquiry, however, sounds a little like the whole piping system may be welded or rigid, and you are concerned about relative or attempted movement of the soil mass/buried pipe to the structures?) Thermal effects must definitely be considered, and perhaps particularly in purposefully thermal pipes.
While there is probably precedent for some fully rigid pipeline systems basically working with at least quite sturdy soils and with the strength and some perhaps non-obvious flexibility in steel piping, if there is relative movement expected beyond these capabilities I guess it might be possible to insert a couple flexible, e.g. bolted couplings (i.e. "rocker pipes") in the transition areas it sounds like you are apparently worried about to provide for some movement. If so, you must still provide any restraint where needed, e.g. for any thrust foci influencing the piping, in the areas, as needed.

 

[BigInch]

Buried in ground is usually a far cry from "floating", unless your soil liquifies. Unless pipe is of considerable length, over 300 m or so, it is possible that it will move slightly, or settle, if the pipe is placed in uncompacted fill, but those movements will normally be minor given adequate construction techniques, unless it is for hot water.

you must get smarter than the software you're using.

 

[BigInch]

This being cold, places pipe in axial tension, normally less of a problem than compression. I tend to think you will not get cold enough to cause too much trouble. That said, the pipe is large diameter and heavy when full of water, so if you don't compact the trench bedding well, it will more likely than not compact it for you and some additional settlement induced stresses will be developed.

you must get smarter than the software you're using.

 

[racookpe1978]

So now I'm wondering what will happen when the pipe flow is stopped - but not drained - and parts of the pipe freeze. Above, below ground, or both.

How the bleedin' d*mn h*ll do "engineers" get away with this kind of cr*p? What are people being taught overseas?

 

[BigInch]

No worries. It doesn't freeze there. OP hasn't mentioned any possibility of freezing.

you must get smarter than the software you're using.