For applications that cannot tolerate the threat of ignition from electric power, or where the operator cab is far removed from the engine compartment, hydraulically powered climate control is a practical alternative. Large mobile cranes, like the one shown, often use Kenway Engineeringâs 9067 HVAC for climate control in the equipmentâs cab for safety and maximum operator productivity.
The system can be used in series, in parallel, or with a dedicated circuit. (In series and dedicated circuits are the most common.) The system’s hydraulic circuits are designed to protect pump, valves, and seals from damage caused by fluid breakdown as well as any pressure and flow fluctuations. Hydraulic power is only used to heat the cab, so the system has no thermal impact on the main fluid reservoir.
The compact 9067 Series components can be installed as a split system or as a self-contained unit about the size of a small window air-conditioner. The split system consists of a hydraulic drive unit (usually mounted on the superstructure behind the cab) and a blower unit inside the cab. The components are mounted, plumbed, and then charged with refrigerant and hydraulic fluid. The self-contained unit requires a rectangular opening in the cab wall, three hose connections (hydraulic supply, hydraulic return, and case drain), and a single electrical hookup for power and ground. The system has no tanks of propane or diesel fuel and there is no hydraulic reservoir or filter (other than the machine’s) to maintain. This eliminates regularly scheduled service steps for the heater. The AC portion of the system is a standard automotive thermo-expansion valve system (vapor-compression cycle); therefore, a specially trained HVAC technician is not needed to work on it.
Because the Kenway 9067 Series does not rely on engine heat to run an antifreeze/coolant-based HVAC system, the unit works just as well with the cooler-running EPA Tier 4 engines as it does with pre-compliancy engines. The 9067 system can output up to 27,000 BTU per hour at idle. The hydraulic fluid temperature is limited to 205° F.
Older crane HVAC systems suffer from thermodynamic inefficiencies. The compressor might be hidden deep in the engine compartment, while the evaporator and heater core are in the cab. The distance between them calls for multiple hoses, connections, and a hydraulic swivel to transfer the engine coolant and refrigerant from the chassis to the cab. This results in pressure, flow, and temperature changes, which are detrimental to system performance and durability. The Kenway system eliminates these concerns: each component is within a few feet of the others.
Flexible control
The 9067 Series system can be controlled with a PLC. With that arrangement, a keypad allows the operator to select fan speed, mode, and comfort temperature. The PLC will automatically control the temperature in the cab, as well as minimize the effects of the system on other machine functions. The PLC uses inputs from speed, temperature, and pressure sensors and other switches. These inputs tell the PLC how the machine and the system are operating. The control takes the inputs and, through an in-house developed program, determines how to control the outputs. The outputs include signals to the AC and heat clutches, relief valve, and fan-speed control. The program is designed to optimize operator comfort without adversely affecting machine function.
