A submarine pipeline is any pipe system or part thereof which is submerged in water. The term generally refers to any type of pipeline including crude oil, natural gas, industrial byproducts, or treated sewerage routed under a body of water. It is, however, most commonly used to describe oil and gas pipe systems which are submerged in the sea. Submarine pipeline systems include many different designs and construction specifications depending on the materials transported. These include traditional steel lines, composite pipes, and even collapsible plastic pipelines, with each having its own benefits and installation methods.
Submarine pipelines are fairly commonplace and are responsible for transporting hundreds of millions of tons of often hazardous materials safely across the oceans every year. These materials include a wide range of fluid or gaseous mediums ranging from crude oil to gas, treated sewage, and fresh water. Although the range of transported materials is diverse, the most common large submarine pipeline systems transport natural gas. These pipelines typically carry or vent their products across or into expanses of ocean although submerged pipe systems in inland waters are also fairly common.
The most common type of submarine pipeline is the traditional steel variant which is usually used to transport hazardous materials such as gas, hydrocarbons, and oil. Steel pipelines are generally installed from specially equipped ships in one of two ways. The first is a system of completed lengths of pipe held on large rolls on the deck of the ship which are laid out behind the moving vessel in much the same way as a submarine cable. The second method involves fabricating the pipe on board prior to laying it on the sea bed. Depending on prevailing conditions, the pipeline may either be laid out on the surface of the sea bed or buried.
Another common submarine pipeline type is the composite variety which is generally used in applications where the pipes are laid in shallow, inshore waters. These pipelines are generally a lot smaller than steel types and are used to transport non-toxic or non-corrosive materials such as fresh water. A fairly new development in the area of submersible pipeline technology is the collapsible plastic pipe system. These pipes are made of a flexible, bellows type plastic material anchored on the sea bed. One of the great benefits of this type of pipeline is the ability to cut off the flow of material and allow the pipe to deflate, thereby minimizing the risk of damage in stormy seas.
As diverse as these piping systems may be, they all share one common characteristic: the amount of care and attention given to their planning, installation, and maintenance. Submarine pipeline failures can have a catastrophic effect on the surrounding ecosystem and pose huge health and safety risks to people living in close proximity. For this reason, the submersible pipeline industry is heavily legislated and the integrity of the systems subject to continuous, stringent scrutiny.