FRACKING APPLICATIONS
Pumps that thrive under pressure The evolution of hydraulic transmission technology in the pressure pumping market By Dean Bratel
Hydraulic transmission technology is evolving to keep up with the performance requirements for hydraulic fracturing applications like these SINOPEC rigs in China. In the U.S., the race to extract natural gas from the Marcellus shale has led to the development of more powerful fracking transmissions as production shifts away from shallow vertical wells. Images courtesy: Twin Disc
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racking technology is driving transformation of North American energy production capabilities. Since 2005, most of the increase in domestic natural gas production resulted from ongoing development of horizontal drilling and hydraulic fracturing technology. Producers developed more efficient ways to extract gas and crude oil from deposits of shale, sandstone, carbonate, and other geologic formations. The hydraulic transmission technology that fracking applications rely on has evolved to meet demanding and increasing performance and reliability requirements. The 30K-foot view All hydraulic transmissions operate on the same basic principles. Clutch operation is activated via hydraulic pressure. To shift, there is a sequence of activity in which a control system tells a solenoid to turn on or off, directing pressurized hydraulic fluid to various clutches within the transmission. In most cases, power is transmitted from the engine to the transmission through a torque converter, which is a hydrodynamic device that multiplies torque. These components help engines operate in the most efficient speed range, producing rated horsepower regardless of load demand.
For example, in a car, as soon as the accelerator is pressed, the torque converter is engaged in order to provide adequate power until the input shaft of the transmission reaches a certain speed. Once that happens, a clutch inside the torque converter is engaged, bypassing the hydraulic circuit and directly connecting the engine to the transmission. Hydraulic transmissions for fracking applications must be able to transmit tremendously high horsepower to the pumps. They must also be efficient, preventing the loss of power output as waste heat. Fracking applications must operate at top capacity in dirty, dusty and often hot environments. The transmissions must be designed to protect them from foreign materials. To reduce downtime, the transmissions must be designed to minimize the frequency of oil changes required. Hydraulic fracturing rigs are vulnerable to excessive vibration. Torsional vibrations and shock loads can cause harmful torque spikes, reducing the service life of the equipment. Fracking transmissions must be capable of withstanding these vibrations. Transmissions must also have long life and durability. Fracking sites now run longer stages for longer hours. In past years, frack pumps on a wellsite might only run for six hours at time. Now, they need to run 24 to 36 hours at a time. Case study: Universal Well When companies began extracting natural gas from the vast reserves found in the Marcellus Shale in the Appalachian Basin, it required equipment with higher-power pumps and engines than required for shallow vertical wells. This put greater performance demands on the transmissions involved. While upgrading its fracking fleet, Universal Well Services Inc., a provider of hydraulic fracturing services, needed a replacement transmission for its pressure pumping applications that would provide greater reliability and improved service OIL&GAS ENGINEERING DECEMBER 2019 • 11