Analysts predict the global demand for natural gas will triple over the next 20 years. Anticipation of such an increase has spurred new exploration of gas fields previously left untouched due to their remote locations. These regions challenge pipeline development teams – and pipeline materials– with exposure to harsh and demanding conditions.
In Peru lies a field with the potential to move the country toward a substantial leadership position in Latin America’s growing natural gas industry. The bounty from the site, however, can be tapped only by running a pipeline 408 kilometers (254 miles) from the Andes Mountains to the Pacific Ocean coast. Determining the fruitful results of such a project outweighed the challenges, the PERU LNG project was born.
In October 2007, PERU LNG awarded the contract for the pipeline to international engineering and construction firm Techint. The firm quickly found itself faced with a number of construction challenges, including work zones in high altitudes of more than 4,000 meters (14,000 feet), high winds, low temperatures, heavy rains and steep slopes. The pipeline’s remote location also made it hard to transport materials and manpower to the jobsite.
Due to the region’s extreme conditions, welding quickly became one of the most difficult aspects of the job. As with any pipeline project, every joint of the PERU LNG pipeline is welded. This, combined with the Andes’ harsh environmental factors, requires equipment and consumables that can effectively perform under demanding outdoor conditions and high altitudes. The extreme heights of the PERU LNG project presented a particular challenge for the welding wire originally specified. During the consumable testing, it was discovered that welds being performed over 3,000 meters (9,800 feet) above sea level were exhibiting symptoms of porosity, which can directly impact the overall quality of the weld. Techint turned to its long-time partner, global welding leader Lincoln Electric, to help solve this challenge.
Reanalyzing the Welding Wire
In many areas of the world, stick welding (SMAW or MMAW) remains a popular method for cross-country pipeline construction. Techint, however, has found a competitive advantage with the self-shielded, flux-cored arc welding (FCAW-S) process, which yields faster travel speeds and requires less grinding and cleaning than SMAW – all factors that contribute to faster project completion. This process uses a welding wire electrode that includes shielding, denitriding and deoxidizing materials built right into its inner core, eliminating the need for external gas bottles. This creates a slag that helps protect the weld puddle from the surrounding atmosphere.
For more than 20 years, Techint has used Lincoln Electric’s Innershield® line of self-shielded, flux-cored (FCAW-S) welding wire. For this project, Techint crews started using another Lincoln Electric wire – the Pipeliner® NR-208XP wire – on the PERU LNG project, which is being constructed using API 5L X70 steel with a 863 mm (34”) pipe diameter and wall thicknesses of 17.5 mm (0.688”), 19 mm (0.750”), 22 mm (0.875”) and 28.6 mm (1.125”) thicknesses.
However, as the project climbed higher into the Andes and the atmospheric pressure and oxygen levels decreased, Techint’s initial testing revealed welds completed at higher elevations were more susceptible to porosity and slag entrapment within the welds. Both of these factors can cause unacceptable defects.
Lincoln Electric team members – including local technical support and representatives from the company’s U.S.-based headquarters in Cleveland, Ohio – spent time on the Techint jobsite testing other welding consumables. Back at the manufacturer’s United States headquarters, the Consumable Research & Development and Applications Engineering teams developed a unique barometric pressure chamber to simulate the mountainous environment. For comparison, engineers set the chamber to test welds in the vertical down position at sea level. Next, they pumped air out of the chamber to recreate the higher elevations and then repeated the previous test.
The ability to replicate conditions at the appropriate altitude enabled Techint and Lincoln Electric engineers to develop a welding solution, using Lincoln Electric’s Innershield® NR-207+, that could provide the benefits experienced with NR-208XP, while eliminating the issues of porosity and trapped slag at higher elevations. This required both fine tuning the wire electrode, as well as procedure welding development and control to ensure weld quality and performance.
Jobsite testing using automated ultrasonic (AUT) girth weld inspections, which is performed on every joint, confirmed the NR-207+ performed well on every position around the pipe. As with the NR-208XP used at lower elevations, the NR-207+ also worked well at higher elevations.
In addition to the Innershield® welding wire, Techint is using Lincoln Electric’s IdealArc® DC-400 power sources, K345-10 Innershield® guns and LN-23P wire feeders on the PERU LNG project to construct the heavy steel wall pipeline, which requires both single and compound bevel groove welds to reduce welding time.
Two Techint welding teams work simultaneously on the PERU LNG project. Each crew includes approximately 130 people, composed of 50 welders plus supervisors, grinders, pipe fitters, assistants, heavy-duty operators and technicians.
When the project is completed in late 2009, these crews, who live and work on site, will have welded more than 33,000 joints. Production targets vary according to the terrain and weather conditions, but in some of the coastal sections, weld teams were able to complete up to 90 joints – of the 130 joints present for each mile of pipeline – in one day.
This large number of total girth welded joints raised the issues of weld consistency and repeatability. Senior Welding Technologist Bob Dissauer, who worked on the testing at Lincoln Electric’s headquarters, spent time on site in Peru helping Techint qualify welding procedures, which provided the guidelines necessary to ensure ongoing consistency between different welders and across the life of the project.
According to Techint, this, combined with the unique job conditions, made properly skilled welders on the job all the more important. As with many industries, though, finding skilled workers was a challenge for Techint. While many of the welders are from Peru, the company also recruited from nearby countries, including Colombia, Argentina, Brazil, Chile and Bolivia.
A comprehensive training program was employed for all of the welders and support team members. For example, before beginning work, all welders were trained and qualified using the same materials, position and equipment used in the field.
Additionally, the type of welding performed, coupled with the extreme outdoor conditions, makes jobsite safety paramount for the PERU LNG project. Techint created a formal safety plan for each area of the project. For the welding portion, this included personal safety equipment, specific induction courses and daily safety talks.
Alpacas and Flora
Much of the construction work on the PERU LNG pipeline occurs in environmentally sensitive areas. Many of the areas adjacent to the pipeline contain rare varieties of plants and a multitude of wildlife, including wild alpacas and vicuñas. From its inception, all members of the PERU LNG project have aimed to minimize the footprint of the pipeline and construction zone to maintain the integrity of these critical areas. Signs posted at strategic distances remind workers to be aware of the borders of the construction area footprint and to respect the natural environment surrounding them at all times.
With the varying elevations, erosion is another environmental challenge. To combat this, the company has developed controlled erosion works before clearing and grading activities are started at key points of construction. These include permanent rock gabions – large rectangular, heavily galvanized wire mesh baskets filled with rock that connect to form the base of a bank to create a structural sidewall. These gabions help control erosion and serve as a catch basin to store cut material removed during construction. In addition, silt fences and wooden fences are being used for the same purpose.
The PERU LNG pipeline also crosses a number of rivers and wetland areas. Techint designed special construction procedures for the crossings at these environmentally sensitive areas in order to protect native plants and animals.
With overall demand for natural gas continuing to rise around the globe, an increasing number of pipeline projects have moved into previously untapped remote regions to extract gas for processing and use in the global market. Some of these projects cross a variety of terrains and altitudes, and face environmental barriers, creating a wide array of challenges for construction and welding teams.
The PERU LNG project, which also includes a processing facility and robust marine facility at the coast, is one of the newest and most prominent examples of how these crews surmount various technical and environmental roadblocks facing countries and construction companies building pipelines in undeveloped areas.
For Techint, mountainous elevations and the effects of high altitude on the welding wire posed the greatest test for construction crews on the PERU LNG project. But by working closely with partner Lincoln Electric, the company has been able to stay on schedule with the PERU LNG pipeline and expects to meets its construction deadline at the end of 2009 by matching the right consumable chemistry to the job at hand.