Caterpillar Derives Power From The Cold
By DJ Slater21 March 2017
This article was originally published in the January-February issue of COMPRESSORtech2. Subscribe for free to receive every issue in your mailbox or your inbox.
To an engine, cold weather can be a best friend. Cold air offers more power — if the proper adjustments are made to maintain performance while boosting the engine’s power capability. That’s why Caterpillar developed an optional feature to instinctively take advantage of cold-weather situations — ambient based rating (ABR).
ABR, available on G3600 A4 engines, allows the engine’s sensors to detect the temperature change and automatically adjust to benefit from cooler, denser air. This process occurs without the need for stopping or resetting the engine, said Ed Porras, marketing, Caterpillar Oil & Gas.“With previous engines, you shut down the engine and retune it when it’s cold to get more horsepower,” Porras said. “(ABR) allows the engine to adjust up and down to provide more power when it’s cooler. The engine signals compressor controls, letting the system load the com- pressor package to the engine’s full power for the actual temperature in real time.
“ABR operates by tracking charge air temperature and detecting when ambient temperatures drop. Lower charge air temperatures mean wider detonation margin and denser air. With more air density, there is more oxygen available for combustion. More detonation margin and more oxygen means more power is available to move gas.”
ABR is capable of giving a G3600 A4 engine up to a 7% power boost. While 7% doesn’t appear to be a substantial increase, Porras said that amount has significant quantifiable value in a gas compression package.
In a gas compression package, an engine accounts for 33% of the package cost, Porras said, adding that installed horsepower has double the value of the entire package. Once delivered and installed at the station, the system is valued at more than six times the cost of the engine, he said. Making a change — even 7% — can bring about recognized perks in operational effectiveness.
For example, the G3606 A4 engine is rated at 1875 hp (1398 kW). Adding 7% boosts that amount by 135 hp (101 kW), Porras said. If the value of horsepower is equal to US$2000/hp, then the ABR provides US$270,000 in capital value, he said. Extrapolating that number across a six-engine operation brings the benefit to US$1.6 million.
“This is a dynamic control system that can send a signal to the compressor system to say it can handle more load,” Porras said. “(ABR) really does present more value in the capital sense and in ongoing production revenues.”
The Cat G3600 first came about in 1990 for natural gas applications. More than two decades later, the engine series includes the G3606, G3608, G3612 and G3616. The en- gines have power ratings ranging from 1875 bhp (1398 bkW) at 1000 rpm to 5350 bhp (3990 bkW) at 1000 rpm.
The updated version of the 3600 series debuted in 2015, offering expanded fuel flexibility and temperature capabili- ties, as well as 5.6% power increase (see January-February 2015 COMPRESSORtech2, p. 28).
Even without the ABR, Porras said the engines are de- signed to deliver a consistently high bhp rating in hot conditions and high altitudes. With ABR, however, the engine can do even more to move gas whenever temperatures fall below summer highs, day or night.
“I don’t know what we could have done to make this a better engine, technically speaking,” he said. “We’ve exceeded our targets in every critical metric.”
While some locations, such as Houston, Texas, don’t see the same cold temperatures as frigid locations, Porras said the ABR still has merit, providing substantial value as com- pared to associated costs. Caterpillar is able to evaluate the estimated ABR value for any location, estimating annual average horsepower gains on a site-by-site basis.
“It’s very satisfying that we created something that’s going to contribute this dramatically to the industry,” Porras said. “It’s more than we hoped for.”