Cat 336E H Hydraulic Hybrid Excavator Designed for Fuel Efficiency

Hydraulic hybrid technology captures and reuses energy.

April 17, 2013
CDR Staff
Equipment & Products
Caterpillar, Peoria, Ill., has begun shipping orders for its Cat 336E H excavator. The new excavator centers on a fuel-saving hydraulic hybrid system that captures and reuses energy. The hybrid model offers greater fuel efficiency than its nonhybrid predecessors, according to the company—as much as 50 percent greater than the 336D.
Caterpillar says the benefits include lower fuel costs, reduced exhaust emissions and a smaller carbon footprint—all without any compromise in production, reliability, durability or operability.
According to Ken Gray, global product manager for large hydraulic excavators for Caterpillar’s Excavation Division, customers have shown tremendous enthusiasm for the 336E H. “Customer interest has been off the charts,” Gray says. “They’re not only reaching out to Cat dealers to learn more about the 336E H, they are placing orders. In fact, we received our first signed orders Oct. 17, 2012, the day after the reveal.”
Gray also says customers want to know about Caterpillar’s plans for expanding hybrid technology to additional excavators. “We’re getting a lot of questions about what other models will be available as a hybrid and when,” says Gray. “While I will not divulge our full hybrid strategy, I will say we will have two additional hydraulic hybrid models, the 336F H and 336D H, on the way.” 
Both the 336F H and 336D H models will have the same hybrid Cat electronic standardized programmable (ESP) pump as the 336E H. The 336F H will feature a Cat C9.3 ACERT engine that meets Tier 4 Final/Stage IV emissions standards; the 336D H will feature a Cat C9 ACERT engine designed to meet the needs of customers in those countries with emissions standards different than Tier 4 Final/Stage IV. 
“We have active development programs for the machines which will follow those two,” Gray says. “And we will continue to add appropriate hybrid technology to models where it adds value for customers—where it lowers owning and operating costs to help their businesses succeed. Our objective is to ensure our customers make more money with Cat products than they can with others.”
According to Gray, no other commercially available technology has higher power density than hydraulics, and that’s why Caterpillar selected a hydraulic solution to help its customers achieve substantial fuel savings. “We leveraged our standard Cat hydraulic components to take advantage of economies of scale across our product line, which in turn significantly reduces the cost for our customers to own the 336E H. Plus they sacrifice nothing in terms of reliability, performance, power, force, speed or production,” says Gray. “And it is surprisingly quiet.”
To achieve fuel savings, the design of the 336E H is relatively straightforward, Cat says, using three building block technologies: 
  1. Conserving fuel with engine power management via the Cat ESP pump; 
  2. Optimizing performance using restriction management via the patented Cat Adaptive Control System (ACS) valve; and
  3. Reusing energy via the hydraulic hybrid swing, which captures the excavator’s upper structure swing brake energy in accumulators and then releases the energy during swing acceleration. 
Caterpillar’s patented ACS manages the restrictions and flows in the system. As the “brain” of the hydraulic hybrid system, ACS comprises an extensive set of algorithms that are designed to control implement motion with no loss of power. Because of ACS and the system integration with the ESP pump and hybrid system, operators experience no difference in control, hydraulic power or lift capacity, according to the company. 
The independent metering valves of ACS are designed to independently manage inflow and outflow restrictions to and from each circuit of the machine to maximize performance. This restriction management system means no extra valves are needed for in-cylinder flow regeneration of boom, stick and bucket and it eliminates the fine swing control valve but maintains this functionality. Because it’s integrated with the hybrid swing system, it allows transparent, smooth operation for higher productivity from operators, Cat says. In addition, the ACS warm-up control automatically warms the hydraulic oil and valve system in cold weather for improved performance and longer component life, which also helps reduce customers’ owning and operating costs.
Customers can expect the 336E H to use up to 25 percent less fuel compared with the standard 336E model and up to a 50 percent improvement in fuel efficiency compared with a 336D model in a wide variety of operating conditions, according to Cat. When customers can expect to recoup their initial investment in a 336E H depends on fuel prices, a customer’s specific application and the number of hours the machine operates in a year. Assuming today’s fuel prices and a production application for a 336E H, Caterpillar estimates a customer can realistically expect to see a return on the investment in a hybrid excavator model in as little as one year, with 18 months as typical. 
The 336E H uses the Cat C9.3 ACERT engine, which is designed to operate efficiently on ultra-low-sulfur diesel fuel or a B20 bio fuel blend. Generous hydraulic flow in the implement circuits and a high main relief pressure generate high hydraulic horsepower. This means the 336E H can handle buckets as large as 3.33 cubic yards, as well as a variety of work tools from shears and multi-processors to hydraulic breakers and rippers.
The heavy-duty extended-length undercarriage of the 336E H and its 5.4-ton counterweight combine to form a strong work platform for digging, lifting and attachment use, Cat says. And the heavy-duty reach boom can be paired with either a 10.5-foot stick or a 12.8-foot stick.
The 336E H is designed for ease of serviceability, with features like ground-level access to major maintenance points, electric fuel system priming pump, remote fuel tank drain to evacuate water and sediment and a fuel level indicator to help avoid overfilling. Among its many safety features, the 336E H includes a cab-integrated roll-over-protection structure (ROPS), anti-skid surfaces, programmable halogen lights, upper and lower windows that store easily, a large skylight and rearview camera system, according to Cat. 
Click here to watch how the Caterpillar 336 E hybrid excavator allowed crews to save fuel during a light rail extension project in Northern California.