River Bore Pipeline Coating
In the pipeline world it is a fairly common occurrence that a pipeline be bored underneath a river; just like it is common for pipelines to in a directional bore under a road, a directional bore under a railroad, a directional bore under a lake, a directional bore under a bay or sometimes even a directional bore under land that could not be torn up due to right of way or environmentalist reasons.
Isn't that a beautiful sight? Boring a pipeline underneath a river like this is going to raise ALL KINDS of questions. Some very fair. Some not fair. It will politics as usual, that you can be certain of. One of the concerns with a directional drilling project is that once the pipeline goes down into the wet, black hole....no one is EVER going to see it again! No one is going to be able to inspect the pipeline to be certain the pipeline coating you've selected is still in place and functioning properly. In some cases it will even be difficult to be certain that your cathodic protection system is going to be able to properly protect your pipeline if there was any damage during the pull through.
Beyond that, if there is some kind of pipeline catastrophe, where will all of the product from the pipeline go? There will certainly be no way to repair a pipeline -- replacing the line will be the only option and that is incredibly expensive. In light of all of that, obviously, the external pipeline coating selection for this section of the pipeline is incredibly important.
For the main line coating, here in the USA it is generally accepted that the best coating option is going to be either a dual layer FBE (with the outer layer having more ARO qualities) or an FBE with a Powercrete type ARO (abrasion resistant overcoat) installed over the outside of it. For the field joint coating, there are more schools of thought.
Believe it or not, I live in The Woodlands, TX. A wonderful community just north of Houston, TX. It is a booming part of the state with people moving in by the droves. Many large corporations are also in the middle of moving their bases of operations to this area. Given all of that, you would think we might be on the cutting edge of technologies when it comes to the pipelines that are constructed in our neighborhoods. You would be wrong!
Just two years ago, I saw a bore underneath one of our largest creeks. Right next to this creek where the bore took place sat a bridge that sees heavy traffic just about all day long. Whoever owned/worked on that pipeline chose to put a cold applied tape on the field joints of the road bore section of the pipeline! (Are you wondering what happens to cold applied tape during a road bore? Read and find out). This was a unique situation for us as we had a good contact with that very tape manufacturer. He was horrified that his product was used on a road bore in a heavily populated area underneath a bridge and a creek. Horrified. So horrified in fact that he went in with us to visit with a couple of engineers and tell them that they had made (and had been making) a terrible mistake by using his product for that purpose. Amazingly, they either didn't care -- or were uninterested in getting involved. I drive over that bridge twice a day (once with my children in the car with me) and I am absolutely certain that those field joints are now bare. I sure hope the CP system is working because that is all they've got.
Likewise, near my neighborhood there is a section of pipe that has been welded and coated and lying in the dirt next to the golf course for weeks! It might even be months. Just driving by there I can see that the cold applied tape is bubbling up in some spots; peeling back in some spots and getting disfigured already from the weight of the pipe. I can see it going by at 40 miles per hour! Why has the pipe been sitting so long? Well it looks like they are waiting for the boring equipment to come out so they can pull it underneath a different creek!
There is always the option of bringing out flocking equipment and applying dual layer FBE in the field, but given the cost of the equipment that often doesn't make a lot of sense (since bores tend to be somewhat short in length). Another option is to apply a two part epoxy like Powercrete or Protal. Those are good options and they have been quite successful as long as the surface preparation is done properly, the crews are experienced and the job allows for a longer cure time.
In my world though, the absolute best solution for any critical service field joint (like underneath a river) is to use the DIRAX shrink sleeve system. It has been proven again and again and again. Cure times are down under thirty minutes. Install times are down under 6 minutes (depending on pipe size). Heck, it has even been used to hold bumpers in place during a bundled directional drill. If this product can prevent pipes in a bundle from banging against each other while passing through a bore - and it doesn't move - and it doesn't disappear - and it isn't damaged - just imagine how much less taxing simply coating a field joint is! Read about a recent BBS success here.