Squeezing Value continued
NGTL expects to make an initial filing by the second quarter and construction is expected to begin in 2019. The latest expansion is in addition to existing projects to expand NGTL capacity associated with an investment of some C$7.2 billion ($5.62 billion). For example, in September 2016, the NEB granted approval for the Towerbirch Expansion Project, including the construction of approximately 87 km of new natural gas pipeline and associated facilities in northwest Alberta and northeast British Columbia. The new sections came online in October 2017 and November 2017, respectively.
The NGTL system initially began commercial operations in 1957 and today includes some 24,500 km of pipeline and various auxiliary infrastructure. In 2016, NGTL delivered more than 4 tcf (trillion cubic feet) of gas.
Figure 3. Integrated package. The SGT-A35 is integrated into a compact, lightweight and easily maintainable package designed for oil and gas applications.
The latest Nova project
The latest order for a gas turbine-driven compressor train associated with this NGTL capacity expansion is destined for the Winchell Lake Compressor Station in Alberta. As a critical element of
pipeline expansion to transport natural gas to new export markets, commercial operation of the turbo-compressor train is expected to begin in the fourth quarter of 2019.
Used to re-pressurize natural gas along NGTL’s Western Alberta System Mainline, this line – via the Gas Transmission Northwest (GTN) System that begins at the Kingsgate compressor station on the British Columbia-Idaho border – exports natural gas into the states of Washington, Oregon, California, and Nevada.
The scope of supply for the compressor train includes a Siemens RFBB36 pipeline compressor driven by a Siemens aeroderivative SGT-A35 gas turbine and associated auxiliary systems.
For gas compressor applications a key requirement is reliability. Matthew Rickert, the Texas-based Director of Business Development for Gas Turbines at Siemens Energy explained: “The most important thing is always reliability, when you have a pipeline delivering gas primarily feeding a power plant to generate electricity or it’s providing a heating source for homes.”
Based on the industrial RB211 developed by Rolls-Royce, for the SGT-A35 its reliability credentials are second to none.
Figure 4. SGT-A35 cutaway. The two-spool architecture allows maximum operational flexibility and a high tolerance to transient excursions and challenging cycles.
Rickert said: “The SGT-A35 is a well proven engine. We’ve demonstrated reliability over 99%. Recognized as having a reliability advantage over the competition, that’s one of the main reasons it’s often selected for both pipeline applications and for offshore applications. For those two applications reliability is king, you have to have proven reliability in order to compete in that market.”
Siemens acquired Rolls-Royce’s Energy Division in 2014, also acquiring the RB211 designs and those of its successor the Trent engine. Since rebranded as the SGT-A35, the RB211 began life powering aircraft such as the Lockheed TriStar. It also subsequently found itself in the airframes of the McDonnell- Douglas DC-10 and Boeing 747.
Designed as one of a family of high bypass turbofan engines that entered service in 1972, the RB211 was the first production three-spool engine with a triple-shaft architecture. In this arrangement three groups of turbine rings rotate separate concentric shafts powering three sections of the compressor. The separate compressor sections can then run at different speeds, allowing each stage of the compressor to run at optimal efficiency.
Designed for aircraft, the engine has been adapted for industrial usage and in 1974 the industrial RB211 was launched. The main changes are based on the principal that while aircraft engines are optimised for thrust, industrial engines used to drive compressors are optimised for torque.
The large diameter turbofan blade from the front of the engine is removed and the first few stages of the compressor section are adapted to such industrial applications but the Rolls-Royce proprietary technology remains inside the aeroderivative core. In the SGT-A35 configuration the design is a two-spool engine. As Rickert says: “We’ve made minimal changes to the core engine.”
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