Laying Pipes Underwater


 Pipes aren’t just underground – there’s a number of reasons pipes would need to be installed in or across bodies of water. However, paying pipes underwater poses several challenges for companies to install. There are different ways to install pipes underwater to ensure they are successful, don’t leak and will last for a long time.

Tow-In Pipelines

These pipelines are suspended in water via buoy and a tugboat, or two, will drag them into place. Once they are in the proper location the buoys will be flooded with water, or otherwise released, and the pipe will then sink to the floor of the body of water. This kind of installation can happen when the pipeline is above the water (surface tow), submerged in the water (mid-depth tow), already close to the bottom of the water (off-bottom tow) or it could be dragged along the floor of the body of water (bottom tow). The first three will work for all varieties of water, however a bottom tow is usually only used when the water is shallow and the floor is soft and flat so that no damage will be done to the pipe during installation.

S-Lay Pipelines

For this kind of installation, the pipe is slowly pushed off the back of a ship or boat while it moved forward in the water. The pipe will naturally curve downward through the water as the boat deploys more and more of it, and this will be done until the pipe reaches a pre-determined touchdown point which is usually the destination, or the floor of the body of water.

With this kind of installation it’s very important to ensure proper tension is used. If there’s too much tension on the pipe it could buckle or be damaged during installation, causing leaks or even breaking while still in use. An S-Lay installation can be used in water that is up to 6,500 feet deep, and can be installed at a rate of 4 miles per day.

 J-Lay Pipelines

While recognizing some of the major disadvantages to using a S-Lay Pipeline, the J-Lay is very appealing. This kind of pipeline puts less stress on the pipe by inserting the line into the water in an almost completely vertical position. The pipe will be lifted – usually via tall tower – off the back of a boat or ship and then inserted into the water. This pipe will only curve once – at the bottom of the water – unlike an S-Lay which has a double curvature and thus more chances for pressure, tension or breakage. Once it has hit the bottom of the water, it will take on the shape of the letter J which is what it was named for.

Since there is less tension and stress on this kind of pipeline it works in waters much deeper than an S-Lay would allow for, and it can withstand strong underwater motion or currents.

 Installing underwater pipelines is much different than ones underground because can create various pressure points, pipes weigh different amounts in water vs. on land and bodies of water can generally unpredictable. However, if the right kind of underwater pipeline is selected then it should last for many years and will be able to fulfill what is required of it. Regular maintenance, or even replacing sections of pipe, may be needed if the pipe is going to be use for a long period of time but as long as the installation is done accurately and maintenance is performed there won’t be any leaks or sections breaking prematurely.

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