Minimum depth of piping

[BFZHA]

Hi,
I am working on gas facility and I want to know if there is any restriction on a minimum depth to respect for piping elements?

Thanks.

 

[pennpiper]

BFZHA,
Your question is too vague. Please give us more information defining the situation.

 

[SNORGY]

Depends on what risk you are trying to mitigate.

A good rule of thumb for me is that minimum depth should be at or just below frost line. Up here, that's usually deep enough that it addresses traffic loads, overburden issues, and other things as well.

Regards,

SNORGY.

 

[BigInch]

Inside a protected facility where pipe locations are well known and marked, almost any clear depth cover would do, but something like 0.2 m would be typical if vehicle traffic is restricted from crossing.

Outside a facility for a pipeline, 1 meter clear cover is usually acceptable in cross country areas, or 0.5 m if the pipe is placed on a sand bed in a cut rock trench with 2 wraps of rock shield.

You might use something like 1.25 m at desert trail crossings where nothing more than a light truck would go and maybe 2 meters under more heavily traveled roads.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[SNORGY]

BigInch:

So, you folks actually have facilities where underground pipe locations are well-known and marked?

We don't...our clients don't see the value in accurate as-builts for such lines.

It keeps the hydro-vac companies in business, Failing that, we find them rather reliably with pile driving equipment.

Uh-oh...must be time for another coffee...

Regards,

SNORGY.

 

[zdas04]

"Pile driving equipment"? Not a bad technique. I always use a track hoe or rock saw, but then I do my best to stay out of plants.

David

 

[BigInch]

I said nothing about as-builts. Even if we had them, I wouldn't believe them. Well-known locations mostly means, "go ask the old-timer. He knows everything about this place".

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[zdas04]

Yeah, but the oldtimers are getting pretty scarce. I retired 6 years ago and still get 8-10 calls a year that start with "remember when we ..." because even surveyed as builts get lost.

David

 

[SNORGY]

In any event, irrespective, magnetic line location and hydrovac + (and / or) manual hand (shovel) exposure are mandatory excavation practices any time you can't "see" a line, no matter how well its location is marked.

The good old "bend a couple of welding rods at 90 degrees and hold them out like this" technique actually does work, by the way. I wouldn't have believed it until I tried it.

Regards,

SNORGY.

 

[BigInch]

Snorgy,

A lotta' help you were last week.
thread164-255850


**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[SNORGY]

Sorry I missed it, BigInch.

Perhaps I should try a couple of bent paper clips to look for the right threads to read on my computer screen.

In future I'll try not to let you down.

And...I hope *you know* I am kidding and in no way mean any disrespect towards a fellow colleague who happens to be pretty smart and earned my respect many posts ago...

Regards,

SNORGY.

 

[zdas04]

Line locating is fun. The best one I saw was a ditch with a steel line and a fiberglass (FRP) line, the marker-tape for the steel line was CAREFULLY wrapped around the STEEL line, the track hoe didn't even slow down when it went through the glass line.

We have a few thousand miles of FRP pipelines around here and we've tried everything from ground penetrating radar to witching sticks and a cost vs. reliability analysis always shows that a couple of bent wires come out way on top. The Ground Penetrating Radar thing looked like a lawn mower and was just about as effective in finding FRP lines in sandy soil. It worked slightly better in damp soil, but the results were anything but repeatable. The other devices that look like something you should take to a beach to look for lost change were no more repeatable. I trusted the bent wire every time (i.e., if the %10,000 detector disagreed with the bent wire I believed the bent wire and dug there, by hand).

David

 

[BigInch]

Down in south Texas, we just waited for the pipe to explode (thin pipe and no corrosion control) and then it was easy just following the big blue flies to the gas leak.

We did have some guys back then that knew where everything was, in the 800 well system, but they were going to get vested in the pension plan in a few months, so Stanley fired them. I tried to start what must have been the first attempt at an oilfield GIS system right after that on a MacII PC, but then one Friday I had enough money for a full tank, so I got in the truck and headed back to Houston.

Snorgy, be cool.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[rconner]

As some pipelines may be exposed or must transition in and out of the ground etc. at least at some locations, “minimum depth” of piping is kind of an oxymoron. I guess what is meant is that where lengths of piping are intended to be buried in e.g. horizontal reaches, how deep should the pipes normally be buried, or as depth often controls construction cost what is the minimum standard depth to be controlled by the contractor or inspectors etc. in those specific areas of a project? I think there can be a lot of factors to consider and many references to consult in this regard (perhaps not the least of which in some cases is experience!), and regulatory entities such as DOT’s, railroads, and DNR’s et al have thrown their opinions or requirements into the fray on projects within their scope.
ASCE’s publication, “Pressure Pipeline Design for Water and Wastewater” (rev. 1992) says in at least partial explanation in this regard, “Depth of bury of pipelines is a function of the probability of line protection from construction damage, surface live loads, freezing and rupture, scour depth at river crossings and occasionally, pipeline grades” (and in another area talking about truck/vehicle loads and impacts, “Depth of cover over a pipe will influence the amount of truckload transmitted to it. Extra consideration should be given to loads that are transmitted to the pipe by heavy construction equipment or pipe with very little earth cover.”)
While some references speak of about 2-1/2 feet (or 0.75 m) or a pipe diameter or more in the case of larger pipes (and depth of cover can also be related to thrust and other "restraint"), ASCE’s MOP N0. 89, “Pipeline Crossings” (rev. 1996) makes many statements that can be related to requirements in some special cases for up to four or five feet or more of minimum cover depth for some crossings. It also briefly discusses depth as it relates to some seismic issues/applications, and it furthermore also says with regard to yet another (it appears sort of Archimedean) issue, “Simply put, pipelines will float or become buoyant when the mass of the pipe material, commodity, and backfill is less than the mass of the fluid displaced by the pipeline.”
The “Recommended Standards for Water Works” (“Ten States Standards”) curtly says, “Water mains shall be covered with sufficient earth or other insulation to prevent freezing.”
In summary, I guess it could be argued meaningful depth of cover may some “insulate” the pipeline from many more effects and impacts than just thermal, and the vulnerability of a pipeline in many respects is perhaps at least some reduced with some degree of increasing cover depth (in perhaps now even more respects than before!)