Protective Carbon Steel Sleeve on Underground Piping - Road Crossing Piping

[leont]

Hi everyone,
Is there any opportunity in this forum I am provide with technical information about the trend nowadays in the use of corrosion protective wraps on underground piping instead of typical design of corrosion protective wrap on pipe and carbon steel casing.
There are countless underground piping installed with wrap on carried piping and metallic sleeve with corrosion protective sleeve, but with no cathodic protection.
However, experience appears to point out sleeves become a problem over time once they failed due to soil corrosion.
Is it feasible the installation of corrosion protective wrap + cathodic protection as an option in terms of cost effective, easy inspection as long as I ensure the mechanical integrity of the pipe in the road crossing section?
What is the trend on design for underground piping that may help me out?

Best regards. I hope to hearing from you guys soon
leont

 

[1503-44]

3 ply fusion bonded epoxy FBE coating is used almost exclusively for both pipeline and casings.

Protective wraps may be wrapped over the FBE for installation purposes.

Casings often interfere with cathodic protection of the pipe, so they have been out of favor for years, but if required by the crossing permit authority, casings should be isolated from pipeline with rubber end seals and interior spacers placed around the pipeline. Often a paraffin or other insulating material is injected into the annular space to prevent the accumulation of condensed water. Casings are normally vented at both ends and sloped down to a drain at the bottom of the casing at one end (drain rising to above the surface) to allow for pressured blow cleaning, or pump out if necessary.

 

[leont]

Thank you 1503-44 !!
All my concern and my focus is on the fact GW testing completed on some of the underground piping revealed moderate metal loss.
Since this is gasoline -clean service- I am not expecting internal corrosion. Conversely, given the very old piping with over 30 years in service I am expecting external corrosion. Chances are the sleeve failed and piping is exposed.

I am evaluating the feasibility of removing the sleeve and install a full corrosion protective wrap. Soil corrosion damage mechanism is mitigated and an integrity assessment will support the continued service of the pipe.
Hence my question regarding using only corrosion protective wrap and done.
Any thought ?

Thanks
Tito

 

[1503-44]

Internal casing metal to pipe contact often short circuits the protective measures. Can you check for shorts? Is there a test box installed with pipe and casing contacts?

Clean the pipe to be wrapped very, very well. All paints and mastics require a clean dry, oil free surface to bond well. Do not use a cheap wrapper. No dust or condensation on the surface. Double wrap. Follow all mfgr instructions to the letter.

The last secret to a good wrap is quality control of the workmanship and testing of the finished job.

Just be sure that the crossing permit issuer will approve the uncased pipeline crossing and that the casing is not structurally required to protect the pipe from excessive load.

 

[BenMacier]

On new pipe crossings I used either pipe-in-pipe or bore-through design solutions.

First one uses the casing option and if metallic, it requires suitable connectivity between the inner pipe and the outer pipe (casing). The connectivity solution has to be selected based on the crossing environment. In some instances, complete isolation was required (zero connectivity), in others full continuity (zero resistance between both pipes).
With a mineral casing, the corrosion protection strategy is different. Some people even refer to it as micro-tunelling solution.

Second one uses heavy duty external coating to protect the main pipe. There is no casing.

* Finding a solution is great * Knowing how to implement it is fantastic * Believing it is the only one and best is naive ?

 

[LittleInch]

For a long time there was a bit of a divide in the pipeline world as to how to do crossings.

ASME B 31.8 for sure used to specify cased crossings for a long time and hence lots of other country codes based on 31.8 did the same.

Gradually the mood changed and people realised that they were getting a lot of corrosion failures in those cased crossings, either because there was water getting in, no CP because it was shielded and /or flattening of the CP system as the casing touched the carrier pipe and was either bare pipe or the coating was damaged.

Hence why B31.8 relented possibly 20 years ago and moved to non cased crossings.

Additionally the general design moved to using the main pipe only or where carrier pipes were used they were then filled with grout or something else to prevent water intrusion.

Casing pipes are often protected with sacrificial CP systems to prevent them collapsing, but if grout filled sometimes not.

Use of PE tubes or concrete sleeves can prevent this.

The trend though is to use only the main carrier pipe if you can. A lot depends on your crossing method.

LI



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

B31s never required use of casings, unless needed for load protection. It was the railroads that habitually required casings of all pipeline crossings, regardless of depth. They may still.

Texaa law requires casings when needed for protection from the E80 rail loading specification.

https://www.bnsf.com/about-bnsf/pdf/utility.pdf

http://www.csx.com/index.cfm/librar.../pipeline-design-construction-specifications/

 

[LittleInch]

I'm talking over 20 years ago and I can't find a copy of a pre 2000 31.8, but it definitely pointed you in that direction or needed a lower design factor if it wasn't cased, whereas now that difference in DF is much lower.

This section or wording was added at some point

861.1.6 Isolation From Casings. The use of metallic
casings [highlight #FCE94F]should be avoided as much as as possible from
a corrosion control standpoint[/highlight].



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

B31.8 first edition was 1968 and CFRs were enacted in 1970. I can go back to 1980 in my head. At Northern Natural Gas, we only used them when the railroad companies made us put them in, which they did, at every RR X-ing.

Right. That section was added to discourage the RRs to require casings, but it didn't work to eliminate them.

The design factor was reduced from 0.72 to 0.6 in public road x-ings. That was still less hassle than installing casings, test boxes, vents, cad welds, spacers, end boots and maintaining the things. We were happy doing 0.6 without casings.

 

[LittleInch]

B 31.4 added this section also - 2006 edition

434.13.4
[highlight #FCE94F](b) Installation of uncased carrier pipe is preferred[/highlight]
Installation of carrier pipe, or casing if used, shall be
in accordance with API RP 1102. As specified in para.
461.1.2(f), if casing is used, coated carrier pipe shall be
independently supported outside each end of the casing
and insulated from the casing throughout the cased section, and casing ends shall be sealed using a durable,
electrically nonconductive material.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[leont]

Thank you very much all of you!!
Your feedback on this regard has been really good. Could not be better.
In parallel I will held a meeting with a company. They have been doing this kind of jobs for a while.
In a preliminary chat it was pointed out the issue created in terms of repair, execution time, risk and so forth when the sleep fails -mostly on those very old underground piping- and they confirm that trend points out to avoid the sleeve -cased piping- as much as possible. In somehow, it is pretty much the same you guys highlighted here.

I will go deeper in all your comments and will be great to share my experience and results as added value.

It is great to be part of this Forum.
I wish you have a great day
leont