alizafari1
Petroleum
- Mar 17, 2011
- 9
Hi; How we can find allowable distance between two crossing or beside pipelines.
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allowable distance between two adjacent pipelines
- Thread starter alizafari1
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Crossing or paralleling another pipeline is a very common activity, and as far as I've been able to find there are no regulatory or industry guidelines. Many companies have policies that mostly apply to how close they'll "let" someone come. Often these policies require unreasonably great distances, but they are not enforceable. I had a company tell me once that I "Had" to go 3 m under their pipeline. I laughed at them and they told me they were serious. Their pipeline was 2 m underground and sitting on a rock ledge. My pipeline was pretty much 1.2 m deep and I told them that my guidelines (which didn't exist) allowed me to approach within 0.5 m and I was going over top of them. Their field guy tried to stop me by bluster and yelling. I didn't yell back, I just crossed him with the sounds of his threats of lawsuits ringing in my ears. We finished the job and the lawsuit never materialized.
At 0.5 m either over or under you pretty much avoid cathodic interference. People that require more distance than that are generally just making numbers up.
For lines that parallel each other, I like to be as far as the right of way will allow. I've seen cathodic interference on lines that were 5 m apart running in parallel for more than a few hundred meters.
David
At 0.5 m either over or under you pretty much avoid cathodic interference. People that require more distance than that are generally just making numbers up.
For lines that parallel each other, I like to be as far as the right of way will allow. I've seen cathodic interference on lines that were 5 m apart running in parallel for more than a few hundred meters.
David
It depends more on how you will plan to do any excavation, lifting, replacement and lowering of any one of those pipelines. Each one of those may depend on the diameter and weight of the pipe. It would not be unusual to require 60 feet width (perhaps 40 on one side and 20 on the other) for 12" pipelines. Possibly smaller for lesser diameters and definitely wider for 36-48" diameter lines.
Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus
Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus
BigInch,
In gathering systems (a LOT smaller pipe than you usually work with), the norm in the states has become to excavate around lines with hydrovac equipment. I don't always agree with the trend, but the risks are lower.
With the requirements to hydrovac, I'm a lot more concerned about my line becoming a sacrificial anode than getting hit. At 12" the cathodic interference (for parallel lines running together any distance) is almost guaranteed. At 10 ft interference is pretty common if the pipes run together more than a few dozen yards.
For over/under, I use the 12" as well.
David
In gathering systems (a LOT smaller pipe than you usually work with), the norm in the states has become to excavate around lines with hydrovac equipment. I don't always agree with the trend, but the risks are lower.
With the requirements to hydrovac, I'm a lot more concerned about my line becoming a sacrificial anode than getting hit. At 12" the cathodic interference (for parallel lines running together any distance) is almost guaranteed. At 10 ft interference is pretty common if the pipes run together more than a few dozen yards.
For over/under, I use the 12" as well.
David
Oh ya. He didn't say what kind of pipeline, so I was just out to include the big diameter longer runs. In gathering systems, usually not covered by DOT regs, you can get away with a lot of things you can't with a DOT line.
I think we would tend to bond the CP of parallel lines together as well, whereas you may actually be talking about different company's pipelines running parallel, we could bond together two parallel company lines. CP interference between different systems can happen over several hundred meters or more as well, and with overhead electrical lines and railroad electric power etc., something you probably don't often see in a US gathering system line.
Vertical separation I use a 18" minimum of sand-cement bags with rock shield, since gravity tends to get closer in a vertical environment anyway.
Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus
I think we would tend to bond the CP of parallel lines together as well, whereas you may actually be talking about different company's pipelines running parallel, we could bond together two parallel company lines. CP interference between different systems can happen over several hundred meters or more as well, and with overhead electrical lines and railroad electric power etc., something you probably don't often see in a US gathering system line.
Vertical separation I use a 18" minimum of sand-cement bags with rock shield, since gravity tends to get closer in a vertical environment anyway.
Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus
I remember one 60 ft ROW that I got into for a quarter mile that had 9 lines from 7 companies. Five were protected and 4 weren't (including mine, let's not go into why not but the reasons made sense at the time). WHAT A PAIN. I ended up putting in block valves before and after the mess with isolation kits. I operated it for 3 years and it hadn't failed yet. I'll be surprised if it lasts 10 years.
David
David
Check your local code for guidance (if any). The code where I am states a minimum of 30 cm for a crossing, though generally speaking the farther apart the better. No guidance is given for paralleling pipelines, though as mentioned above, if it is someone else in the ROW, the farther the better to avoid interference. If it is your own pipeline there to begin with, you might consider putting it closer and using the same cathodic protection system. Even if it is your own, the minimum distance guideline we would use for example is 15 ft, this is to aid in construction and any future maintenenace on the lines (regarding workspace, spill piles, etc.). I will assume you are in the open and not in a facility yard.
While very good points are mentioned above, I'd like to add that for parallel large diameter pipelines, concern should be given to pipe-trench interaction and trench requirements.
When buried pipes are installed in parallel, principles of analysis for single pipes still apply, however soil cover must be greater than minimum. In other word, the design of parallel buried pipes requires an additional analysis for heavy surface loads (given that a common trench is used). In fact for buried parallel pipes soil slip between the pipes becomes the bottleneck for the distance calculation. Talking about 1 m or more separation then the concern becomes faded but it all depends on your pipelines diameters and soil density.
If the pipelines are in separate trenches, then embedment stability becomes a concern when a trench is excavated parallel to an existing buried flexible pipe. You should address what would happen to a buried flexible pipe when some or all the side support is removed in a parallel excavation. Ans also the existing trench stability itself is an issue to concern. At less than minimum side cover, X, side support is lost and the soil on the pipe must be supported by the pipe. If ring stiffness is inadequate, the pipe collapses.
For a detailed discussion, please refer to "Buried Pipe Design" by A. P. Moser, Steven Folkman chapter 3.
When buried pipes are installed in parallel, principles of analysis for single pipes still apply, however soil cover must be greater than minimum. In other word, the design of parallel buried pipes requires an additional analysis for heavy surface loads (given that a common trench is used). In fact for buried parallel pipes soil slip between the pipes becomes the bottleneck for the distance calculation. Talking about 1 m or more separation then the concern becomes faded but it all depends on your pipelines diameters and soil density.
If the pipelines are in separate trenches, then embedment stability becomes a concern when a trench is excavated parallel to an existing buried flexible pipe. You should address what would happen to a buried flexible pipe when some or all the side support is removed in a parallel excavation. Ans also the existing trench stability itself is an issue to concern. At less than minimum side cover, X, side support is lost and the soil on the pipe must be supported by the pipe. If ring stiffness is inadequate, the pipe collapses.
For a detailed discussion, please refer to "Buried Pipe Design" by A. P. Moser, Steven Folkman chapter 3.
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- #10
alizafari1
Petroleum
- Mar 17, 2011
- 9
Hi;
In piping support design specs & codes we see tables of pipe spans, as distance between two supports in a straight line cannot exceed this amount.Now the question is if the line is not straight and there is a change in the direction of line (for instance by elbows), what amount shall be used for pipe span.
In piping support design specs & codes we see tables of pipe spans, as distance between two supports in a straight line cannot exceed this amount.Now the question is if the line is not straight and there is a change in the direction of line (for instance by elbows), what amount shall be used for pipe span.
With regard to the original inquiry, you have gotten many answers. If ever an inquiry screamed out for an answer “It depends…”, maybe this is one of them. There are numerous codes, specifications, standards, regulations and at least a few technical papers in the field available talking about proximity of various pipelines to one another, either crossing and/or pretty much parallel. I think a good search on these forums and with other good search engines with a few key words will reveal many of them. Some reasons for maintaining variously stated clearances may be obvious, and perhaps some less so.
ASCE MOP #89, “Pipeline Crossings” (1996) contains the somewhat generic statements, “The commodity being carried by a pipeline will be of importance to the Owner of the facility being crossed….” , “The type of facility being crossed is of paramount concern in designing the pipeline crossing….” , and of course, “Of greatest concern will be combustable fluids (hydrocarbons) under pressure, which may require special protective design features…” (its spelling). This MOP also talks about situations when different entities might be involved in ownership of the pipelines etc. involved, and even if they don’t have “primacy” all might at least deserve a “say”!
The are some more specific guidelines with regard to some aspects and services in the “Ten States Standards” for water and wastewater, and I am also aware e.g. another fairly well-vetted standard ANSI/AWWA C600-05, Installation of Ductile- Iron Water Mains and Their Appurtenances contains the guidance,
“4.3.1.3 Clearance. When crossing existing pipelines or other structures, alignment and grade shall be adjusted as necessary, in accordance with the contract documents, to provide clearance as required by federal, state, or provincial, and local regulations or as deemed necessary to prevent future damage or contamination of either structure.”
All that being said, there are for whatever reasons many situations that have reportedly occurred in the field that have brought about at least discomfort and sometimes worse with some close-together pipes. I suspect a search using the term “cross-bore” will yield multiple perhaps rather extreme examples. Another ongoing, highly visible current event that has recently caused at least some consternation is that it was reported months ago that a “pipe bursting” operation, with 10" hdpe upsizing from existing 6" clay, was routed in 2008 just a few inches away from the disaster involving the 30” San Bruno high-pressure gas pipeline installed decades earlier (I noticed while a newspaper report of this alleged association entitled, “Link between sewer job and San Bruno explosion grows stronger” has been removed from its original location at , the ensuing blog discussion of same still remains.)
While I understand that occasionally, due to right-of-way restrictions, common utilidors, other strong desires/necessity of the Owner etc., some pipelines inevitably will be placed rather closely together at some point (and huge numbers of quite close clearances or crossings likely remain problem-free.) It is however clear that there needs to be reasonably good Engineering and construction judgment, as well as investigation or knowledge of all applicable issues, codes and regulations, etc. employed. [And at least at some point, maybe the (red) lights need to start flashing and the call go out, ?)
One thing is for sure, with inreasing population and congestion underground and elsewhere, problem will not go away!
ASCE MOP #89, “Pipeline Crossings” (1996) contains the somewhat generic statements, “The commodity being carried by a pipeline will be of importance to the Owner of the facility being crossed….” , “The type of facility being crossed is of paramount concern in designing the pipeline crossing….” , and of course, “Of greatest concern will be combustable fluids (hydrocarbons) under pressure, which may require special protective design features…” (its spelling). This MOP also talks about situations when different entities might be involved in ownership of the pipelines etc. involved, and even if they don’t have “primacy” all might at least deserve a “say”!
The are some more specific guidelines with regard to some aspects and services in the “Ten States Standards” for water and wastewater, and I am also aware e.g. another fairly well-vetted standard ANSI/AWWA C600-05, Installation of Ductile- Iron Water Mains and Their Appurtenances contains the guidance,
“4.3.1.3 Clearance. When crossing existing pipelines or other structures, alignment and grade shall be adjusted as necessary, in accordance with the contract documents, to provide clearance as required by federal, state, or provincial, and local regulations or as deemed necessary to prevent future damage or contamination of either structure.”
All that being said, there are for whatever reasons many situations that have reportedly occurred in the field that have brought about at least discomfort and sometimes worse with some close-together pipes. I suspect a search using the term “cross-bore” will yield multiple perhaps rather extreme examples. Another ongoing, highly visible current event that has recently caused at least some consternation is that it was reported months ago that a “pipe bursting” operation, with 10" hdpe upsizing from existing 6" clay, was routed in 2008 just a few inches away from the disaster involving the 30” San Bruno high-pressure gas pipeline installed decades earlier (I noticed while a newspaper report of this alleged association entitled, “Link between sewer job and San Bruno explosion grows stronger” has been removed from its original location at , the ensuing blog discussion of same still remains.)
While I understand that occasionally, due to right-of-way restrictions, common utilidors, other strong desires/necessity of the Owner etc., some pipelines inevitably will be placed rather closely together at some point (and huge numbers of quite close clearances or crossings likely remain problem-free.) It is however clear that there needs to be reasonably good Engineering and construction judgment, as well as investigation or knowledge of all applicable issues, codes and regulations, etc. employed. [And at least at some point, maybe the (red) lights need to start flashing and the call go out, ?)
One thing is for sure, with inreasing population and congestion underground and elsewhere, problem will not go away!
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