PREHEATING, OR ACCUMULATING PREHEATED, FEED-WATER FOR STEAM GENERATION; FEED-WATER SUPPLY FOR STEAM GENERATION; CONTROLLING WATER LEVEL FOR STEAM GENERATION; AUXILIARY DEVICES FOR PROMOTING WATER CIRCULATION WITHIN STEAM BOILERS

Description

F22D covers the preheating, supply, and control systems for feed-water in steam generation plants, along with devices that enhance water circulation within boilers. This includes economizers and feed-water heaters that raise inlet water temperature before entry into the boiler, feed-water supply equipment and regulation systems, water-level control mechanisms, and internal circulation-promoting devices such as baffles or circulation tubes. The class encompasses both the thermodynamic efficiency improvements from preheating and the operational safety and stability features related to water management in steam boiler systems. Related auxiliary equipment for steam generation itself is classified elsewhere under F22B-F22C.

Filing statistics

CPC subclass F22D recorded 5,699 patent applications worldwide between 2013 and 2023. Annual filings grew from 227 in 2013 to 702 in 2023 (+209%), peaking at 774 applications in 2020. The most active applicants in class F22 are XIAN THERMAL POWER RESEARCH INSTITUTE COMPANY (544 applications), SIEMENS (306 applications) and PHILIP MORRIS PRODUCTS (258 applications).

Source: EPO PATSTAT, worldwide filings