Pipelines need to be pigged to maintain their integrity and operational efficiency. For this reason, regular pipeline cleaning pig programs are recommended to clean debris from the pipeline. But what do you do if a regular cleaning program hasn’t been maintained or your pipeline has never been pigged? You get progressive.
As manufacturer of the original ‘Polly-Pig’, Girard Industries has been producing high-quality pipeline cleaning pigs and accessories for over 55 years. For more than 25 years, Girard has partnered with Tremco Pipeline Equipment to distribute its pigs and equipment in the Oceania region.
Since the start of their partnership, Girard Industries and Tremco Pipeline Equipment have provided technical advice and equipment to a large range of pipeline projects, including some lines with significant build up. Here, the partners share their tips on how to restore a pipeline’s full capacity using ‘progressive pigging’.
What is progressive pigging?
Progressive pigging is a method used to clean pipelines with reduced internal diameters, gradually removing deposits until the line’s full capacity is restored.
It’s typically used when the line has significant buildup, and once completed, routine pigging can prevent the need for such extensive cleaning in the future.
Lines with significant buildup have a reduced internal diameter due to the accumulation of deposits, such as mineral scale or other debris. Standard pigs can’t accommodate extreme diameter reductions, so a gradual approach using pigs of various diameters is required to avoid blockages.
In the case of concentric buildup, the process begins by determining the internal diameter of the pipeline, often using a light-density swab for accurate measurement.
How to use the progressive pig approach
Girard recommends the below general progressive pigging guidelines for badly scaled pipelines. The pigs may be propelled using water, air, nitrogen, or sometimes the product in the line.
- Determine the internal diameter of the pipeline:
Begin by measuring the internal diameter of the pipeline by using a light-density swab to sweep out loose material and verify the line size. It’s recommended to use a line-size swab as deposits can vary in thickness along the pipeline. Hard scale will wear away the soft foam and the diameter or true opening may be more closely determined. Often, it’s recommended to run another swab through the section to remove additional loose scale.
- Start with an initial run:
Once the internal diameter is determined, Girard recommends running a criss-cross pig just slightly larger than the true opening of the line. It may be necessary to run a full size swab behind the criss-cross pig to improve the seal and allow the criss-cross pig to continue its travel. Continue this process until a pig is discharged from the line in reusable condition.
On unlined ductile iron, cast iron, or carbon steel pipes, run a criss-cross wire brush pig of the same size as the previous pigs. Again a full size swab may be required to obtain a better seal. Use only criss-cross pigs on lined pipe, PE or PVC pipe.
- Increase pig size gradually:
After the initial runs, progressively increase the size of the pigs in small increments. These increments can range from ¼-½ inch depending on the line’s length, build-up, and other factors. Throughout this process, the ideal pigging speed is between 200 and 300 feet per minute. Continue to run swabs behind the pigs as necessary.
- Repeat steps as necessary:
For each pig run, the procedure may need to be repeated. Larger pigs are used in subsequent runs to continue removing buildup. Swabs are also run after each pig to assist with movement through the line and to remove any loose debris. The goal is to gradually move through the pipeline until you reach the full internal diameter.
- Complete a final sweep with line-size pig:
Once the full internal diameter of the pipeline has been attained, run a line-size criss-cross or wire brush pig to perform a final sweep of the entire pipeline. Run a full size swab to sweep out loose debris and compare its condition to the first swab which was run.
- Establish a routine pigging program:
Once the progressive pigging process is complete, implement a routine pigging schedule to maintain the cleanliness of the line. Regular pigging can help prevent the need for future progressive pigging.
About Girard
The original polly-pig manufacturer, Girard Industries is at the forefront of innovation in pipeline cleaning, batching and gauging pigs, developing new products to meet the demands of a changing industry.
The team at Girard makes and provides technical assistance on pigs to clean even the most difficult natural gas, hydrocarbon, water and special application pipelines, with all equipment manufactured at its plant in Houston, Texas.
Its product catalogue includes polly-pigs (or foam pigs), steel mandrels, solid cast polyurethane, polyurethane spheres and pig tracking equipment for both pipeline and meter proving applications, as well as replacement cups, discs and other urethane wear parts to fit most pigs on the market.
For more information about progressive pigging or the right cleaning, batching or gauging pig to meet your needs, contact Brett Trembath at brett@tremcopipeline.com.au
Subscribe to The Australian Pipeliner for the latest project and industry news.