Nitrogen can be used for a range of similar applications such as line or tank purging, drying, line clearing, pigging or pressure transferring to eliminates the presence of oxygen and moisture and prevents oxidation from occurring, below are some examples of application.
Nitrogen purging is an industrial standard technique or process where unwanted gases, hazardous, undesirable atmosphere or other impurities are eliminated from a manufacturing system environment using nitrogen gas. Due to its inert properties, nitrogen can be used to effectively displace oxygen and other pro-oxidative gases from industrial processes without reacting chemically with the substrates.
The benefits of nitrogen purging are numerous, but the most crucial reasons for nitrogen gas purging are to prevent chemical alteration of products and to prevent moisture-related equipment damage or even combustion. A lot of industrial manufacturing processes could be adversely affected when conducted in the presence of moisture or oxygen-rich air. The oxidative damage caused by these unwanted impurities will diminish the quality of the final products with costly implications for profitability. Oxygen-sensitive operations integrate nitrogen purging equipment to prevent unfavorable manufacturing conditions.
Nitrogen inerting is a simple yet effective process that enables hot work to be carried out on hydrocarbon handling systems in complete safety. The nitrogen is injected into a process system at a low point and allowed to completely fill the vessel and pipework, rendering the internal atmosphere inert. On completion of hot work operations, the nitrogen foam degenerates into small amounts of water, surfactant and gaseous nitrogen. Typical inerting applications include vessel and pipework modification and/or replacement, hot cutting and system decommissioning.
Pipelines are designed to operate at a certain maximum allowable operating pressure (MAOP). Pipelines must be pressure tested to ensure that it is structurally sound and can withstand the internal pressure before being put into service.
Although a lot of industrial components require pressure testing before installation, not all testing methods are ideal for all components. For example, hydrostatic testing uses water to conduct fluid pressure testing which is not feasible in moisture-sensitive systems. Corrosive damage to test components from water channeled through them will significantly diminish their useful life spans. While pneumatic testing provides an alternative to hydrostatic testing, this too can expose test materials to harmful moisture.
Pressure test with nitrogen is used to determine and verify pipeline integrity.
Using a nitrogen pressure test procedure allows operators to circumvent the challenges associated with other forms of testing. Due to its inert characteristics, many industrial processes use nitrogen gas at several stages of their inspection and manufacturing. Gaseous nitrogen can be safely used to assess pipework, check the integrity of pipeline networks, and test vessels for leaks.
Nitrogen gas possesses unique physical and chemical properties that make it effectively inert, this makes it perfect for pressure testing. As a result of its low reactivity, gaseous nitrogen will displace oxygen and moisture from the internal environment of the test components while simultaneously assessing for any potential leaks.
Using nitrogen offers a number of advantages for drying operations, making it very effective for drying out any pipeline or process system. Nitrogen is clean, inert, extremely dry gas (low dew point as low as -40oF/C) makes it an ideal choice for pipeline drying. As a value-added feature, nitrogen is totally inert; it displaces oxygen, retards oxidation, and prevents explosions.
Filling nitrogen into pipelines or process systems that may go unused for long periods of time - months, even years. By maintaining a positive nitrogen atmosphere inside a pipeline or process system, ongoing corrosion can be reduced and even eliminated, provided the system is dry and there are no leaks present. This service is particularly effective for drying of chemically sensitive systems such as oxygen and hydrogen.
Why Is Pipeline Drying Important?
Moisture is not a friend to pipelines. Not only does water need to be cleared from pipelines as part of the commissioning process, removing moisture helps to inhibit corrosion once the pipeline is in service. Unwanted moisture can accumulate for several reasons. Water and other contaminants can collect in the pipeline during the construction process. Pipeline drying after a hydrotest is particularly challenging since there will be additional water to remove before the pipeline is ready for commissioning.
There are specific problems that can be created by pipeline moisture. For medium-pressure gas pipelines, water can make pressure regulators susceptible to freezing in the winter, and high-pressure gas pipelines can be clogged by hydrates that can form within the pipeline. Finally, in addition to moisture-speeding normal corrosion, the presence of water can make gas pipelines subject to internal stress corrosion cracking (SCC) which can cause damage inside pipelines in as little as a few years.
