Industry standard on pipeline crossing 4

[engr2GW]

Hi all,

what API or other documents (or other resources) can I consult to find industry standards on pipeline crossings. I'm more interested in finding useful information about pipeline crossing for buried (and may be above ground) pipelines.

There was an incident where a still pipeline was installed below an already existing fiber glass salt water line and the filling in between them was not compact enough, afte a few months, the soil inbetween them gave way and the fiber glass line deflected (sagged) to the point where it failed and caused a release. We are currently using sand bags inbtween the top and bottom lines, does any one have any recommendation or experience with that/

Thanks for your help.

As much as possible, do it right the first time...

 

[zdas04]

Every answer to this question has a lot of hair on it. There is limited guidance in the DOT, but beyond that it is pretty much up to the owners of the line. In fact, it is usually up to the owner of the new line because the owner of the old line too often doesn't show up to a crossing.

If I'm crossing fiberglass, I try to preferentially go over it, but that isn't always possible. A stack of sandbags between the new pipe and the old pipe is a terrible answer because the bags tend to flow under compressive forces over time. I found that out in a situation similar to the one you described, except instead of a "leak" I ended up with a guillotine fracture that got really exciting. If you've going to use sandbags, use a LOT of them. Start building up on the bottom of the new ditch and stack them to the ditch walls all the way to the fiberglass (maximize the containment so they can't flow).

I've thought about cutting about 20 ft of the next size HDPE in half laterally and using it as a saddle, but that requires an increase in the disturbed soil under the fiberglass and probably hurts more than it helps.

David

 

[LSThill]

engr2GW (Petroleum)

LOOK FOR SAUDI ARAMCO STANDARD PIPELINE ROAD CROSSING & NACE

BEEN THEIR DID THAT 1977

L S THILL

 

[BigInch]

The standard you are looking for is API-1102, "Recommended practice for liquid petroleum pipelines crossing railroads and highways"

1.) Sand bags is a common method. Sand-cement bags, even better.
2.) Use a half-casing, or full casing, Precast Concrete Pipe, installed as an arch above the sandbags around your pipe, sand bag over that and continue up and around the crossed pipe.
In lieu of PCP, just a concrete load-bearing slab.
3.) If it's a very large pipeline you're going under, dig a deeper pit farther away on both sides and thrust bore with pleanty of clearance (1.5 to 2 m) underneath.



From "BigInch's Extremely simple theory of everything."

 

[zdas04]

Road and railway crossings are a different issue. I believe that the OP is asking about pipelines crossing pipelines. I assumed he was talking about gas, but that might just be my bias (I've never used fiberglass for liquids).

David

 

[engr2GW]

Thanks for all your posts, and yes, I was talking about pipeline crossing pipeline, especially where the second pipeline will be underneath the first one.

Thanks.

As much as possible, do it right the first time...

 

[BigInch]

Pipeline crossing, or crossing pipeline??
Doesn't matter much. You need to support what's above with what's below without breaking either one of them.

From "BigInch's Extremely simple theory of everything."

 

[BigInch]

The industry standard is remove any lose and unsuitable materials in the work area, stack sand-cement bags (brick laying fashion) then place well compacted granular fill. If you do it properly, 999/1000 you will never have to touch it again.

zdas, You never can go over, because the first pipeline didn't know you were coming and they took the minimum trench depth. You should have reserved your space in advance. I have a reservation system for pipeline over crossings already in place. Anywhere you want in the world, held in reserve until you decide to use it, $100.00 ... Only.

From "BigInch's Extremely simple theory of everything."

 

[cvg]

you can nearly always go over gravity lines (sewers) which are often very deep. sometimes over waterlines and rarely over gas lines which seem to be installed in the worst possible locations...

never heard of the sandbag method, that must be only for the petroleum pipeline industry.

 

[MiketheEngineer]

If the "above" pipe is existing and well anchored (or supported) then why would you have a problem??

 

[engr2GW]

Thanks everyone,
@ Biginch;
if youre going to backfill with compacted granular, my question is, if it going to be easy to re-excavate incase of a repair, or any other reason why one would need to go back there?
thanks.

As much as possible, do it right the first time...

 

[cvg]

mike

when going under an existing pipe, you generally must remove the supporting soil from under it and you may have limited information on it's design or construction. you probably are not going to do a pipe stress analysis of the existing pipe. so to protect it you must support it as recommended by the owner of the pipe or in a better manner so that you may rest easy at night that it is well supported should the new trench backfill you placed beneath it begin to settle or should the new pipe below it leak and saturate the soil or create a void.

a common way is to place permanent supports under the existing pipe to hold it. These are often reinforced concrete.

If it appears weak, Possibly replace part of the top pipe with new, stronger pipe.

 

[engr2GW]

@cvg;

that's new to me "placing a permanent support under the existing pipe to hold it". Do you think that in the event of revisiting the bell hole for a repair, etc, that the permanent structure will be a problem since it'll be directly connected to the buried pipe.

and by re-inforced concrete, do yo mean like a pillar like structure from the base of the ditch to the base of the pipe as a support between the pipe and the void?
Thank you.

As much as possible, do it right the first time...

 

[cvg]

see attached details for some standard methods of pipe supports plus link below to Los Angeles standard detail of a concrete "blanket" which is useful for crossing over an existing pipe

bond breaker such as plastic can be used so that it is not "directly connected", but yes, any type of concrete placed into the trench might cause issues for long term O&M of both pipes. Thats why it's best not to cross anything...

http://eng.lacity.org/techdocs/stdplans/s-200/s255-1.pdf

 

[engr2GW]

Thanks everyone!

As much as possible, do it right the first time...

 

[BigInch]

Not cross anything. There's an idea.

Actually petroleum & gas pipeline operating companies do require someone that crosses their pipelines to apply for their permission, for which if granted, after a stress analysis for temporary loss of support etc., they will send out a supervisor to view the work in progress and make sure it is done in accordance with the approved permit drawing. On occasion I have done a lowering the line analysis, not for a pipeline crossing over, but usually for a road that was going through which of course had to go over the top.

Offshore it is impractical to go under an existing pipeline, so over crossings are the only way. A pyramid structure of sand-cement bags is stacked on top of the existing mudline and the new pipeline is encased in the sand-cement bags, and/or an inflatable bag (for cement to be pumped down into the bag as filler) is then mattressed over the top as well.

From "BigInch's Extremely simple theory of everything."

 

[zdas04]

Require??? I don't know of a single state where you can get exclusive ROW from the Feds or State (ROW negotiations on private land is whatever you can negotiate). I've had pipeline companies tell me that I "couldn't" cross them. My response is always "I'm going to cross, you can participate in the analysis or not". Or they would say that I "have" to go under them by at least 4 ft. My response to that is "I don't really 'have' to do much of anything, I'll go under or over depending on where your pipe is and where my pipe is at that point. I'll try to get as much clearance as makes sense, but I'm not going to blast". I hate it when companies think that their policy automatically applies to the industry.

The pipeline owner really cannot prevent someone from crossing them. Any that try always fail, and then find themselves eventually coming hat in hand to someone that they tried to bully to ask their "permission" to cross them. The companies that have tried to jack me around always get the response "no, you can't cross me". Then I watch them squirm and stir around and finally find out that I didn't have any authority over where their pipe went.

David

 

[cvg]

that being said, standard of care is to work with the other pipeline owner and try to equal or exceed their requirements if possible. keeps the lawyers at bay...

 

[zdas04]

I will always work with someone who says "let's see how we can do this best". I don't ever work with people who say "[my way] is the only way that will be considered".

When I was operating a gathering system I had zero fear of lawyers--my company got sued by someone somewhere in the world every workday of the year. We had a pre-printed response the "I'm going to sue you", it was the address of our attorney so the paperwork could be served properly.

David

 

[rconner]

While there are certainly other responsible organizations and references etc. as mentioned in earlier responses, the ASCE “Pipeline Crossings Technical Committee” was one of the charter committees of the Pipeline Division when it was formed in 1956. I believe there have also been a great many papers presented in many ASCE venues, e.g. beginning in the “Transportation Journal” with regards to many sorts of pipeline crossings in the many years since. While not saying same will answer your specific questions, in 1996 this committee also presented in Burlington, Vt a new ASCE MOP No. 89, “Pipeline Crossings”, that I believe addresses to at least some extent many different aspects of various types of crossings with many rather detailed generic considerations, and includes also at least a brief section dealing further specifically with “Protection of Adjacent Pipelines and Structures”. I guess some provisions for such have been discussed on or referenced in this thread already, and some have not

While I don't guess I know enough more about this subject to get any further up on any soapbox (that surely I would not want to do -- gee I liked zdas’s characterization!), I will only say it appears present designers and constructors may be sort of victimized in many cases by what has come before, e.g. in prior choice of weak pipe materials etc. After all, who “would have thunk” it may ever be necessary to cross pipelines in the future, and what the value of a strong and/or also flexibly joined existing system that can tolerate some subsequent movement or settlement without over-stressing might be when that is necessary??
If, indeed “when” (in much of the real world (as has already been intimated) it is necessary to cross existing pipelines, it can be argued it may be virtually impossible in many practical circumstances to cross an existing pipeline or structure underground without at least some effect on the support of, and concomitant three-dimensional effects, on one or the other.