Flexible metal hose for low pressure gas pipeline and standards?

[tinphattech2010]

Hi Brothers!
I am doing maintenance work for low pressure gas pipeline.
Now one pipeline is sunk because the soil is unsound.
The situation is:
The pipeline is buried at the depth of 1.5 meter underground before coming up above ground connecting to gas distributing station. At the beginning of the station it has a isolating flanged ball valve. When the soil sank, the pipeline went down. It cause the ball bolting stretched so there is leakage there.
Now we are going to cut the above ground pipe and replace by flexible metal hose.
The condition is:
Pipe diameter is 6 inches; Operating pressure is 25 bar; The flow rate is 1000 scmd/h (standard cubic meter per hour).
I am looking flexible metal hose which has specification adopted: the length is more than 80 mm, the operating pressure is more than 25 bar, diameter is 6 inches.
And are there any standard that guide us use flexible hose for gas pipeline.
Please give me an advise!
Thank you very much.
Best regards.

 

[BigInch]

Here's what I'd do.

Stay with the hard piping. Excavate the crap soil and replace it with good compacted fill, but this time also make and install a proper concrete pad (with rock shield layers between) for your riser support. One large enough that it will prevent the underground pipeline from sinking any further.

Worth a try, no?

 

[tinphattech2010]

Hello BigInch!
Thank you very much for your soon reply.
Your solution we have ever tried but the pipeline still sank.
The pipeline have length of 2.5km. And the enough compacted soil is 30m below.
We are also driving two 32m length concrete pile two side the pipeline for support. But it is rather expensive (we think we have to use 6 concrete pile total).
Would you please give me another advice!
Best regards!

 

[BigInch]

Add some buoyancy tanks.

Add some soil dewatering points and a few pumps to drain the water from the soil.

Hopefully your facilities are on a barge.

 

[tinphattech2010]

Thank you very much BigInch!
My manager agreed with the Using concrete pile solution.

 

[BigInch]

Permanent stability is best. Hopefully your piles will hold.