Keeping Your Compressor Stations Maintained: What Needs To Be Done?
The last problem you want are leakages from your compressor stations, which could then lead to methane emission. Here’s a guide on what needs to be done to keep them maintained.
Compressor stations have been identified as one of the major sources of methane emissions along the U.S. natural gas transmission network.
These emissions are often from leaking compressors, valves, connections, and other components in the compressor station.
The leakage can also be attributed to the mechanical and thermal stresses mounted on these components. Specifically, research has revealed that as much as 95% of methane emissions are from 20% of leaking components situated at these stations.
Accordingly, there is a need to know how to maintain your compressor station properly to minimize these emissions.
We’ve outlined easy steps on how to maintain your compressor station to reduce these leakages. And at the same time, reduce methane emissions that could impact on human life and the environment.
What Are Compressor Stations?
Compressor stations are regions located along natural gas transmission pipelines.
These stations are used to store and maintain specialized compression equipment that will help ensure that the natural gas in the pipeline has the proper pressure gradient.
On the other hand, the compressor unit is the main component of the compressor station.
This unit helps in compressing natural gas to give the required PSI level for the pipeline. The PSI can be between 200 PSI to 1,500 PSI.
And the wide disparity in operating specs can be tied to the pipeline’s diameter as well as its elevation amongst other operational factors.
The types of compressor units often found in these stations are:
- Turbines featuring centrifugal compressors
- Electric motors featuring centrifugal compressors
- Reciprocating engine with a reciprocating compressor
Aside from the compressor unit, other components of the compressor station are:
- Gas cooling systems
- Meter and regulators
- Filters and scrubbers
- Launchers and receivers
- Separation and dehydration facilities
- Compressor skid modularizations and housing
How to Maintain a Compressor Station
Here are some ways you can maintain your compressor station:
Setup a Directed Inspection and Maintenance (DI&M) Program
A Directed Inspection and Maintenance (DI&M) Program allows you to use a cost-friendly way to find, detect, and fix the leakage of components at the compressor station.
The program centers on a baseline survey of identifying and quantifying leaks.
First off, repairs are carried out to fix the leaking components. But the fixes are carried out on components that are profitable to repair, hence, they offer cost-effective benefits.
In the same vein, these are components with the highest potential to leak.
After this survey, other surveys can be carried out with reliance on the data obtained from previous surveys. These surveys help operators to focus on components that could potentially leak in the future and maybe more profitable to fix.
Leakage Screening Techniques and Measurement of Leakage
Part of the DI&M program includes the use of leak screening techniques as well as leak measurement techniques.
Here’s a detailed breakdown of either of these:
Leak Screening Techniques
Leak screening techniques are carried out on components that are most likely to leak significantly.
The leak screening techniques that can be employed include:
1. Soap Bubble Screening
This is an inexpensive and fast leak screening technique where soap is used to find loose fittings and connections. The loose fittings can be tightened immediately to stop leakage.
However, the process begins with spraying a solution of soap on small components including threaded connections. This technique helps in fixing leaks and confirming the tightness of a repair.
On the other hand, the soaping technique could take operators an hour to check 100 components.
2. Electronic Screening Technique
This technique involves the use of small hand-held gas detectors to check for gas leaks.
Sniffing devices can also be used in the process.
On the other hand, the gas detectors used in the process feature thermal conductivity and catalytic oxidation sensors. These sensors detect when certain gases are present. This method is also more preferable for larger openings that cannot be screened using the soaping technique.
However, 50 components per hour may be checked by the electronic screening technique, which makes the soaping technique faster.
3. Organic Vapor Analyzers (OVAs) and Toxic Vapor Analyzers (TVAs)
Hydrocarbon detectors such as Organic Vapor Analyzers (OVAs) and Toxic Vapor Analyzers (TVAs) are useful devices in detecting leaks.
For starters, OVAs are flame ionization detectors (FID) that measure the concentration of organic vapors between a range of 9 to 10,000 parts per million (ppm).
TVAs, on the other hand, combine photoionization detector (PID) with FID to aid in the measurement of organic vapors and at concentrations that are above 10,000 ppm.
4. Infrared Cameras
Infrared cameras can also detect when there is gas emission in components at the compressor station. These cameras operate by converting scanned regions into a moving image in real-time.
To that effect, it makes gas plumes visible as these gases absorb infrared light.
IR cameras help in the fast screening of components, hence, hundreds can be screened in an hour.
Also, components located in confined or elevated spaces can be screened remotely from a location that is accessible that is within a viewing distance.
Leak Measurement Techniques
Aside from detecting leakage in components of the compressor station, it is also important to measure the volume of leakages from these components.
The ability to measure these leaks will ensure that resources and manpower are targeted towards significant leaks that will be most profitable to repair.
Some leak measurement techniques you can rely on are:
1. Toxic Vapor Analyzers (TVAs)
Toxic Vapor Analyzers (TVAs) serve to predict the mass leak rate.
The measurement of concentration in ppm is then changed to mass emissions rate with the help of the correlation equation.
There is, however a downside to this measurement since the correlation equations are not tailored to a particular site.
2. Bagging Techniques
These techniques help in the measurement of mass emissions as a result of equipment leakage.
Here, a bag is used to cover the leaking component or its opening, before nitrogen or any other inert carrier gas is passed through the bag using a known flow rate.
As the carrier gas reaches equilibrium, the gas sample is taken from the bag and its methane concentration is measured. The methane concentration of the sample found on the bag as well as the carrier gas flow rate are used for the mass emission rate calculation.
It is possible to keep your compressor stations maintained by ensuring there are no leakages in components, which could lead to methane emission.
And given that the compressor station helps the natural gas pipeline to operate at the right pressure, it is important to keep these components working well.
This maintenance can be carried out by following the leakage detection and measurement techniques outlined above.
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