Date£º2021-11-22 hits£º574
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 plumb work, check
the integrity of pipeline networks, and test vessels for leaks.
Learn how nitrogen gas leak testing
works in an industrial setting.
Leak testing is a method of analyzing
industrial storage and transport equipment (vessels, tubing, and pipelines) for
defects. Leak testing is done to ensure that newly installed systems can
withstand the temperatures and pressures associated with normal operations.
This type of testing forms an integral part of safety protocols in different
industrial settings.
For example, nitrogen gas testing done
before pipeline commissioning allows oil and gas operators to safely prepare
their systems for first use.
Nitrogen Pressure Testing ¨C Why Nitrogen?
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.
Using a nitrogen pressure test procedure
allows operators to circumvent the challenges associated with other forms of
testing. Nitrogen gas possesses unique physical and chemical properties that
make it effectively inert. This makes it perfect for leak 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.
A nitrogen leak test procedure is quite
straightforward and is done in an orderly sequence to guarantee maximal safety
during all aspects of testing. While the specific steps will vary depending on
the nature of the component being tested, some general guidelines are
universally applicable.
Before the commencement of a nitrogen
gas leak detector test, the test component must be isolated from the rest of
the system. This can be achieved by closing connecting pressure valves and
other connection ports that link the test vessel/pipeline with other system
equipment.
Once the test area has been isolated,
gaseous nitrogen supplied from a nitrogen cylinder or synthesized by an on-site
generator is directed into the component via an inlet valve left open.
Contaminants within the test vessel will be purged under low pressure. This
type of nitrogen purging is typically no higher than 25% of
the component¡¯s
pressure rating during routine operation. This phase of pressure testing with
nitrogen gas is sustained for a reasonable duration to ensure the test
component can handle it without leaking.
Following successful low-pressure
testing, the applied pressure is gradually but continuously increased to see
how well the test component can maintain its integrity. Although testing will
continue till the standard pressure rating of the test vessel is achieved, the
upper limit for the test will be determined by varying industrial regulations
concerning leak testing.
Visual inspection for nitrogen leaks is done
by applying a soapy solution to the surface of the component being tested.
Leaks present in the material will cause gas bubbles to form at defective spots
therefore guiding post-test repairs. Keep in mind, other nitrogen leak
detection methods are available.
Nitrogen gas required for leak testing
can be sourced either from pressurized gas cylinders or an on-site nitrogen generator. Although using nitrogen gas cylinders
appears to be the cheaper option, it is significantly more costly in the long
term when compared to the one-time payment for a nitrogen generator.
Once installed, a PSA or membrane nitrogen generator will only require few scheduled
maintenance checks yearly whereas the purchase of gas cylinders will remain a
constant part of the operational budget.
Other benefits of using an onsite
nitrogen generator for leak testing include:
There are multiple ways to detect a
nitrogen gas leak in an industrial setting however, the accuracy varies between
methods. The two most common test methods are outlined below:
