The PED (Pressure Equipment Directive, 2014/68/EU) is a mandatory safety directive for pressure equipment in the European Union and constitutes a mandatory CE compliance requirement for industrial equipment exported to EU markets. In principle, the PED governs all pressurized industrial equipment. Its core judgment criterion is clear: any equipment with a maximum design gauge pressure exceeding 0.5 bar is classified as pressure equipment and must comply with PED requirements and obtain relevant certification before being sold and operated within the European Union. This regulation aims to control safety risks associated with pressure vessels, pressurized pipelines, heat exchangers and other components, preventing potential hazards such as leakage and rupture. All pressurized industrial equipment entering the EU market must be assessed in accordance with these standards.

Libr absorption chillers are widely applied in industrial and commercial central air-conditioning systems. Operating on a completely different principle from conventional compression chillers, they do not rely on compressors for pressurized refrigeration. Instead, they use Libr solution as the absorbent and water as the refrigerant, and operate entirely under vacuum negative pressure conditions to complete the refrigeration cycle. The core refrigeration components, including evaporators, condensers and absorbers, operate under vacuum with internal pressure far below atmospheric pressure, making the whole system a negative-pressure device. This is the primary reason why many practitioners assume that Libr absorption chillers are exempt from PED certification. According to heat source types, Libr absorption chillers are categorized into steam-fired, direct-fired, hot water-fired and waste heat-fired models, and structural pressure differences among these types determine whether PED certification is required.

A common misconception in the industry is that Libr absorption units, due to their vacuum operating condition, are fully exempt from PED certification. Nevertheless, the PED judgment mechanism only focuses on the presence of pressurized structures within equipment, regardless of vacuum components. Libr absorption chillers adopt a dual-circuit structure. The refrigeration circuit operates under negative pressure and requires no certification, while the auxiliary heat exchange circuit may work under positive pressure, which is the fundamental reason why certain models require PED certification.

Steam-fired and double-effect steam Libr absorption chillers are the most typical models requiring PED certification. These units adopt high-pressure steam as the heat source to drive the refrigeration process. The operating pressure on the steam side of the high-pressure generator generally ranges from 2 bar to 8 bar, which significantly exceeds the 0.5 bar PED threshold. The steam heat exchange cavities, tube bundles and connecting pipelines are defined as standard pressure equipment, making PED certification mandatory for such models exported to the EU.

Only chillers with low-pressure heat sources are exempt from PED certification, including standard low-pressure hot water-fired and industrial waste heat-fired Libr absorption chillers. Equipped with low-pressure hot water or low-temperature waste heat as the heat source, such units operate below 0.5 bar with no high-pressure structures, and therefore do not meet the definition of regulated pressure equipment and are exempt from PED certification for EU export.

In summary, the vacuum refrigeration circuit of Libr absorption chillers is permanently exempt from PED requirements. The necessity of PED certification depends entirely on the heat source system. Units equipped with heat exchange structures operating above 0.5 bar must comply with the EU Pressure Equipment Directive and obtain valid certification. In contrast, units operating solely with low-pressure heat sources without any pressurized components are eligible for PED exemption.