Pipeline Drying Campaign
Comprehensive drying campaign for lifetime expansion of gas pipeline
In a Nutshell:
Safely operating a pipeline requires keeping track of many different factors, including maintenance and repairs. Regulations offer guidance on what elements must be considered; one of the key factors for gas pipelines is humidity. The standard in Mexico, NOM-001-SECRE-2010, requires humidity in gas pipelines to be below 110 mg/m3. This case study details the drying of a 42" natural gas pipeline in Mexico, specifically the last 230-km section of the line, which had exceeded acceptable humidity levels.
In the case of this Mexican asset, the mountainous terrain surrounding this specific pipeline causes water to collect in areas of low elevation, which increases humidity and poses a threat to asset integrity. In-line drying activities are also effected. Increased water and humidity levels can render simple pig runs ineffective for two primary reasons: 1) Displacing liquid upwards is complicated. 2) Due to the elevation changes along the pipe route, cleaning tools would seal less effectively and much of the liquid would bypass the pig.
What is the solution?
This is a classic example of why a full cleaning program is more effective than just one run. In this case, the plan devised by ROSEN experts included a dewatering configuration to push as much liquid as possible out of the pipe, followed by a series of bare foam pigs to absorb remaining liquid like a sponge. So, in short: dewatering first, then drying.
The program began with a dewatering train consisting of two ultimate cleaning pigs with multiple sealing discs and brushes, five low-density foam pigs, and three high-density foam pigs. This initial dewatering train, propelled by the gas flowing through the pipeline, would push not only liquid out of the line but also dust and debris. The sludge subsequently created could not be sent downstream into the next pipe sections. Therefore, a separation and filtration system was installed at the receiver end. This system first separates the sludge from the gas and then filters smaller particles from the medium. These products can then continue to move downstream without causing damage to the rest of the pipeline system.