Pipe Risers Height 1

[birken]

Hi All,
At our gas plant, I have seen some pipes connected to the underground drain with flange connections just inches aboveground (3-5"). Is this a good practice for installing pipe risers?

 

[ZDR1985]

It is common because most of the time, buried pipe flange connection is not a good practice. The flange being a restrained joint wont give much flexibility from earth movement, thus will cause stress to the pipeline.

 

[birken]

So there is no issue in having flanges so close to the ground? Water accumulation, soil interface causing corrosion?

 

[PaperEngr]

I have always seen face of flange set at least 12" above top of grade. That's for process or cooling water lines. Drain lines probably aren't as critical.

 

[BigInch]

Exterior, underground compatible, pipe coating should extend up at least 12" above grade. Been a standard forever. The transition zone between water/air, or earth/air is the most critical attack point for corrosion.

 

[birken]

These lines under discussion contain process drain.
Where this reference of 12" can be found in order to implement this recommendation?

 

[BigInch]

On every pipe elevation drawing.

 

[birken]

In this case, piping isometrics mentioning elevation for first flanges of risers are matching the field installation.

 

[MickMc]

Birken,

I don't think you will find this under any code but is often referenced in various Client & Contractor Specification and additional to previous replies there has to be sufficient envelope to insert and remove bolting.

Regards.

Mick.