Natural Gas Industry: Keeping the Transfer Pipes Safe
With natural gas posing more problems than other hydrocarbon products, safety is the lynch-pin of all operations within the industry.
It is only in recent years that natural gas has become a viable energy form due to advances. These advances have been made in overcoming the difficulties in transporting gas from the well to refineries, and then on to the end user. In this article, we take a look at the role of transfer pipes in the natural gas industry and what we need to do to protect them.
Are Transfer Pipes the Answer?
There are various methods of transporting natural gas from source to end-user, but pipes are by far the most common method used within the industry.
The gas can be liquefied, but this presents its own set of risks and furthermore, converting gas into an LNG is an incredibly costly process, which fiscally restricts its use to long-distance transportation only.
They are also considerably less dangerous than rail for example, but a major problem is due to the additional volume that gas takes up, which can be in excess of 600 times that of petroleum for a similar energy value. Large diameter pipes are often used to transport gas at high pressure (200 – 1,500 psi) to reduce gaseous volume and therefore these pipelines must conform to the pressure and strength standards before they can be installed into a system. This will ensure that they’re suitable for their purpose.
As such, the most common method of moving natural gas is via a piping network, which is both cheaper and safer, with the network fundamentally being comprised of three distinct sections:
- The gathering system
- Long-distance connections
- Distribution to the end-user
Protection From the Elements
The long-distance transfer pipes provide the backbone of this network across America as they carry large quantities of gas for hundreds of miles. Due to its inherent characteristics, natural gas can escape from the smallest of fissures, especially when it’s being transported at high pressure. To safeguard the pipes from leakage, a process of pipeline protection and corrosion control needs to be implemented.
This is entirely dependent upon where the pipeline is situated and the environmental conditions that it will be faced with. From piping gas across the land at high climates or in hot and arid conditions, subsea structures, or even through areas that suffer a high risk of seismic activity such as in California and along the countries west coast, provisions need to be made to ensure the pipelines remain fully functional.
In addition to pipe coatings and suitable connection fittings that can be applied to the pipe along the network, cathodic protection is an effective defense against galvanic corrosion. Underground pipelines can almost benefit from a permanent lifespan using this method.
One of the threats posed to the continued integrity of the piping networks comes directly from the natural gas itself, and as such actions are needed to protect the pipelines from this vulnerability.
One such frequent problem to come from inside the pipe is through water being carried within the fluid stream. Drying the gas will help prevent hydrates being formed within the network that build-up and cause multiple problems, however, this is not the biggest danger within the gathering system.
It’s important to know exactly what the fluid stream contains, as many deposits contain increased amounts of Hydrogen Sulphides, known as sour gas. This is especially important due to the toxic nature of sour gas. It is incredibly harmful to both humans and the environment and so requires the utmost care in containing it. The increased corrosiveness of these Sulphides is also a major concern, as they can cause pitting corrosion and Sulphide stress cracking which are both harder to detect than the regular, uniform corrosion.
To prevent and minimize this risk, a regulatory body was set up, called The National Association of Corrosion Engineers (NACE). They publish a comprehensive set of industry standards for the use of materials and coatings. They cover all aspects of oil and gas retrieval and this is an invaluable resource for ensuring your equipment is suitable to the task at hand.
Live Monitoring of the Network
With America’s interstate and intrastate gas pipeline networking currently in excess of 300,000 miles in length, it’s impossible to physically monitor all aspects of the system that runs continuously at all times of the day, week and year. This is where the use of technology comes to the rescue.
By setting up a series of monitoring equipment along the network including sensors that can detect fluctuations in temperature, pressure, and gas flow rates, this operation can be automated and detect any activity which falls outside of the normal parameters. This is used in conjunction with dividing the pipelines into sections that then allows engineers to not only locate any problems that occur, but also isolate them from the system at large and prevent the problem escalating.
The use of monitoring and automatic shut-down systems can, therefore, help circumvent a wide-range of problems such as those created by construction defect, deterioration over time, and external interferences.
Forewarned is Forearmed
Whilst the monitoring system adds a huge element of control over the transfer pipes, it’s also important to closely check both the accuracy of the equipment and secondary systems. To increase reliability and add as a further early-warning system to prevent problems developing.
Smart-pigs offer one such solution after robotics advanced to a level that has allowed a cleaning tool to now be used as a piece of inspection equipment. It offers unparalleled amounts of information on the condition of the actual pipes. This apparatus is only suitable for larger diameter pipes, though, and for all of those un-piggable sections in the network, there are other solutions available.
In-line inspection can be carried out with ultrasonic equipment to evaluate the condition of the pipes from the outside using non-destructive testing. Using a piezoelectric device can provide field data. This data offers an in-depth analysis of structural integrity and similar to this, magnetic flux leakage equipment is also widely used throughout the industry.
This equipment is often hand-held and operated manually by engineers and although it doesn’t clean the pipes like the intelligent pigging technique, it is a cheaper alternative that can quickly be used at any given location, rather than being slowly fed through a pipe to reach the target area.
What keeps the transfer pipes safest of all though, is the trained engineers who combine these modern techniques with a pro-active mentality. This ensures that standards are maintained to the highest possible degree, allowing the gas to flow securely from source.
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