nitrogen purging procedure

What Is Nitrogen Purging? | Procedure and Equipment Used

There are many uses of nitrogen which vary from industry to industry (see more about argon vs. nitrogen). After discovering the inert properties of nitrogen, it became a highly sought after as a blanketing gas. Although nitrogen blanketing is one of the more popular uses of nitrogen, it also serves another crucial purpose — its ability to purge lines and tanks.

If you are wondering why nitrogen is used for purging, here’s what you need to know.

What Is Nitrogen Purging?

Before we dive into specific purging systems, it’s important to discuss this process as a whole. Put simply, nitrogen purging is an air-cleansing method used to ensure that no trace of harmful contaminants or gases is left in the atmosphere. The ultimate goal here is to re-stabilize the environment to prevent an explosion. The production of nitrogen gas is also very affordable when an on-site nitrogen generator is used.

That is why the industrial use of nitrogen in the oil and gas industry is so common. When aiming to purge pipelines, for instance, dry nitrogen gas can be run through the lines to eliminate any remaining water. In addition, the nitrogen prepares pipelines or vessels that will later be exposed to flammable or explosive gases.

nitrogen purging system

Some of the other applications of nitrogen purging include but are not limited to:

  • Headspace purging when brewing beer. This helps extend the shelf life.
  • Purging toxic gases from varying process chambers, such as sputtering tools.
  • Purging volatile organics within the chemical and petrochemical industry.
  • Purging pipelines to bring oxygen levels to within a safe limit. Learn more about NiGen’s pipeline maintenance services.
  • Optimizes efficacy in pharmaceutical labs (preserves pH, eliminates microbial growth, minimizes corrosion, etc.)
  • Metal fabrication, more specifically while welding materials such as stainless steel, titanium and nickel (removes water vapor, oxygen and other gases that may compromise a welding joint).

4 Nitrogen Purging Systems

To better understand your options when it comes to determining the right nitrogen purging procedure for you, the following four methods are available. Not only do they differ in terms of their application, but also in regard to the nitrogen purging equipment that will be required.

1. Nitrogen Purging Procedure and Drying

As nitrogen is continuously introduced to a vessel, contents are mixed and exhausted through an exit point. That is why the location of the entry and exit points are so important when opting for this method. In comparison, although similar in terms of the overall process, drying will allow you to expel residual materials. Pipeline drying and dewatering frequently use nitrogen gas to purge chemicals and moisture after testing.

2. Nitrogen Displacement Purging and Pigging

Commonly used for pipelines, the introduction of a “pig” can help clear lines when combined with nitrogen. As the nitrogen gas pushes this small bullet-shaped object through the line, contents can be purged with ease. Nitrogen gas is typically a dry gas – making it perfect for pipeline pigging.

3. Pressure-Hold Vacuum Method

When a “sweeping action” of nitrogen is not possible within a vessel, the vessel is repeatedly pressurized. By mixing the contents with nitrogen, they are diluted and then vented. This procedure (which is ideal for vessels with one opening only) is repeated until the vessel has been successfully purged.

4. Pressure Liquid Transfer

If you would like to transfer liquids without using a pump, nitrogen can help you pressurize a vessel’s headspace. In turn, you will significantly reduce oxidation risk. This method is particularly useful when there are space constraints that make it challenging to pump. It can also be used when materials, including those that are corrosive, may hinder pump efficacy.

Still unsure which option is best for you and your current needs? Please contact NiGen today to discover the full spectrum of nitrogen purging capabilities.