Functionality and design of crane air conditioning units

Safety refrigerants for a safe refrigerant cycle

Crane air conditioning units use the phenomenon of evaporation heat for the cooling effect: When liquid evaporates, it extracts heat energy from its surroundings. The evaporating liquid is a safety refrigerant. They are non-toxic, non-flammable, non-explosive and differ in terms of their working pressures. Depending on the supplier, environmentally friendly refrigerants can also be used.

The refrigerant circulates in a closed circuit between two heat-transferring devices: In the evaporator, heat is absorbed, i.e. extracted from the environment - in the condenser, heat is released back into the environment. These heat exchangers are often designed as copper tube bundles with copper fins. This is because copper has a high thermal conductivity.

The actual work in the refrigerator unit is performed by the compressor. It compresses the refrigerant so that it subsequently condenses in the liquefier. The liquefier unit in which the compressor is housed is therefore also called the machine part. In crane air conditioning units, semi-hermetic or open compressors are used, which are designed for heavy-duty operation. From this "high pressure side" of the refrigerator unit, the refrigerant passes through an expansion valve into the air conditioning unit, where it becomes gaseous due to the lower pressure in the evaporator. It is then transported back to the compressor. Maximum or minimum pressure switches check whether the refrigerant pressures are within the permissible range, and switch off the refrigerator unit if necessary.

Cooling, heating, dehumidifying, and filtering with one device

The machine part of the air conditioning unit contains the compressor, the liquefier and various fittings. If necessary, the refrigerant collector is also located here. The housing is designed so that the heat released at the liquefier can be completely drawn off with the surrounding air.

In addition to the evaporator and the expansion valve, the air-conditioning section contains the electric heater, the circulating air fan and the thermostat that controls the chiller and the heater. The recirculating air fan sucks in the room air through the evaporator and heater so that it is cooled or heated. The heating is electrically interlocked with the circulating air fan and can only be operated when the fan is operating. The thermostat sensor in front of the evaporator measures the return air temperature; alternatively, a room thermostat can be installed in the crane cabin.

The filters are also housed in the air-conditioning section. The fresh air filter consists of a dust filter with a downstream activated charcoal filter that adsorbs gases and odorous substances from the air. Separate filter devices can also be combined with the crane air conditioning unit. Depending on the application, crane air conditioning units are equipped with special gas filters, chemical filters and special filters so that the air for the crane cabin, switch room and switch container can be reliably cleaned of gases and other pollutants. The amount of fresh air supplied is regulated by a speed-controlled fan as well as a protective slide.

Compact devices offer flexible arrangement and easy mounting on cranes

Crane air conditioning units are divided into compact units and split units according to their structure. With a compact device, all climate-relevant parts are in one device. It can be set up or mounted directly on the room to be air-conditioned; air is exchanged with the room via air ducts. The condensing unit and the air conditioning unit can be set up vertically or horizontally. A horizontal arrangement of the air conditioner ensures a low center of gravity, which prevents it from tipping over in the event of sudden crane movements. Standing on top of each other, the crane air-conditioning unit requires less space in terms of width. The compact device can be combined with a filter system. This prepares the outside air before it is fed into the crane cabin or the crane switch container. Compact devices can usually be installed and put into operation by the customer himself in the crane cabin, crane control room or crane switch container.

Split units for crane air conditioning allow individual adjustments

In the case of split units, the machine part and air-conditioning part are housed in two separate units and connected to one another via the refrigerant lines. Because the air in the room to be air-conditioned does not come into contact with the outside air, the air conditioning prevents dust from entering. The machine part is set up outside the room, i.e. the crane cabin or the crane control room, and reduces the space required for the air conditioning inside the room. An air duct system as in some compact crane air conditioning units is not required. The combination of different machine and air conditioning parts enables the crane air conditioning unit to be optimally adapted to individual performance requirements. If a split device is used, outside air can be prepared via a separate filter system and fed into the crane cabin or the crane switch container. This creates an overpressure that keeps dust away from the crane cabin or container, even if the construction is leaky.