The Importance Of Pipeline Coatings
When you go to the car wash and put quarters in the vacuum cleaner, air flows in a mighty stream from the nozzle back to the vacuum machine. Everyone who has been through this process has noticed the static electricity buildup on the hose because it makes arm hair stand up. A gas pipeline behaves in exactly the same way. Flowing gas in an underground pipeline causes static buildup on the pipe. Being electricity, it will try to go somewhere following every conducting path. If it can, the gas will arc from the pipe to the ground in an electrical spark just like when you touch a doorknob after crossing carpet. This discharge will vaporize a tiny pit in the pipe wall and corrosion of the steel gas pipeline will begin there. Left undetected, the pit will grow with continued arcing. Uncorrected, the pit will grow to be serious corrosion, thinning the wall too far and endangering the pipe’s ability to contain high-pressure gas. To prevent this corrosion, we coat the pipe with an insulator so that it performs electrically just as if you buried a piece of insulated wire. Because serious corrosion can emanate from a pinpoint arcing location, the insulation coating must be perfect.
Imagine the pipe
Cross-country lines carrying lots of gas are typically buried three to five feet below the surface. These lines might be a thousand miles long and cost a thousand dollars per foot. Because pipelines are very expensive, they are well maintained and receive the constant scrutiny and attention of highly-trained and talented specialists. Maintenance activities include corrosion prevention, damage prevention, inspection, lifetime and wall thickness analysis.
Just picture that. You have this very expensive facility buried in the ground and the consequences of it failing include fire, explosion, disruption of critical service, and loss of product. This facility is buried in soil having moisture content and chemistry. Its economic value is tremendous because there is no other way to transport the volume of product. The only thing between the steel and this soil is an insulating layer of pipe coating. This coating protects the pipeline from corrosion resulting from soil chemistry reaction and static discharge arcing damage. For these reasons, pipeline operators pay a lot of attention to coating integrity and when required, coating repairs.
Many types of pipeline coatings
Coating technology has evolved over decades. One old coating was asbestos paper laid in hot tar and then mopped over with the same tar. Another was the same mopped tar with burlap or other fabric as the matrix holding the tar in place. Other types include a thick layer of wax mopped onto the pipe with rags providing the insulating coating and thick adhesive vinyl tape (like electrician’s tape) candy-cane wrapped onto the pipe and adhered with a primer coat. Beeswax is used as a coating as well, particularly on fittings, valves, and where the pipe emerges from the soil to above-ground.
Today, for the most part, new pipe comes ready to put in the ditch with a factory applied coating of epoxy fused to the new steel exterior surface. In the field on the bank of the ditch, adjacent joints of pipe are welded together. After inspection, the welds are abrasive blasted and coated with a two-part epoxy. After cure, the coating is inspected and tested with a “jeep”, a high voltage method for locating pinholes or holidays in the coating.
Contact Serco, Inc. with your questions and for more pipeline coating maintenance tips. Call us at (806) 273-7614 or contact us via email for more information on the services we provide. You can also stop by our office located at 1430 North Main Street in Borger, Texas.
Imagine the pipe
Cross-country lines carrying lots of gas are typically buried three to five feet below the surface. These lines might be a thousand miles long and cost a thousand dollars per foot. Because pipelines are very expensive, they are well maintained and receive the constant scrutiny and attention of highly-trained and talented specialists. Maintenance activities include corrosion prevention, damage prevention, inspection, lifetime and wall thickness analysis.
Just picture that. You have this very expensive facility buried in the ground and the consequences of it failing include fire, explosion, disruption of critical service, and loss of product. This facility is buried in soil having moisture content and chemistry. Its economic value is tremendous because there is no other way to transport the volume of product. The only thing between the steel and this soil is an insulating layer of pipe coating. This coating protects the pipeline from corrosion resulting from soil chemistry reaction and static discharge arcing damage. For these reasons, pipeline operators pay a lot of attention to coating integrity and when required, coating repairs.
Many types of pipeline coatings
Coating technology has evolved over decades. One old coating was asbestos paper laid in hot tar and then mopped over with the same tar. Another was the same mopped tar with burlap or other fabric as the matrix holding the tar in place. Other types include a thick layer of wax mopped onto the pipe with rags providing the insulating coating and thick adhesive vinyl tape (like electrician’s tape) candy-cane wrapped onto the pipe and adhered with a primer coat. Beeswax is used as a coating as well, particularly on fittings, valves, and where the pipe emerges from the soil to above-ground.
Today, for the most part, new pipe comes ready to put in the ditch with a factory applied coating of epoxy fused to the new steel exterior surface. In the field on the bank of the ditch, adjacent joints of pipe are welded together. After inspection, the welds are abrasive blasted and coated with a two-part epoxy. After cure, the coating is inspected and tested with a “jeep”, a high voltage method for locating pinholes or holidays in the coating.
Contact Serco, Inc. with your questions and for more pipeline coating maintenance tips. Call us at (806) 273-7614 or contact us via email for more information on the services we provide. You can also stop by our office located at 1430 North Main Street in Borger, Texas.