「\"Major Equipment in the Field of Chemical Engineering Equipment\" 567-2021: Dalian Yizhong Manufacturing’s PTA reactor for the Dongying Weilian PTA project

The PTA reactor and crystallizer equipment manufactured for Dongying Weilian this time meet extremely strict quality and technical standards. The inner wall of the PTA reactor needs to be cladded with a 33 alloy that possesses strong corrosion resistance. To ensure product quality, Dalian Nuclear Power Petrochemical adopted an innovative approach by installing 4 TIG welding torches on one operating machine to carry out welding simultaneously, thereby achieving automatic TIG welding and reducing the welding cycle by nearly half. At the same time, the steel plate used for the cylinder sections of the crystallizer is of a very special type; its minimum required thickness is 194 millimeters, which represents the limit of manufacturing capability for domestic steel producers. Additionally, this steel plate must have a 3-millimeter thick stainless steel layer added on top of it. This results in a long production cycle and high manufacturing complexity, which causes the steel plates to arrive at the factory late, leaving relatively little time for processing within the factory. Faced with numerous difficulties and challenges, Dalian Nuclear Power Petrochemical, with a strong sense of responsibility toward its customers, actively organized production managers to identify the difficulties in product manufacturing and the key control points one by one, continuously improved the manufacturing processes, and made every effort to ensure deliveries on schedule. On this basis, the roles of Party members and cadres, model workers and craftsmen, as well as technical experts were fully utilized to overcome the impact of the pandemic on production. Various measures were taken and tasks were carried out in parallel; production of the products was organized in upper and lower sections. Strategies such as carrying out 33 alloy surfacing work and internal component installation simultaneously, coordinating two machine tools to process the bolt holes at the same time, and conducting the final heat treatment of the upper section alongside the welding of the skirt attachments were employed, enabling the products to be delivered on schedule.

Alloy33 alloy (UNS R20033) I. Introduction: Alloy33 is a relatively new chromium-based austenitic alloy that was introduced in 1995; it exhibits excellent resistance to highly oxidizing media. The corrosion resistance of the alloy is further improved by adding molybdenum and copper. The alloy contains nitrogen, which results in a small grain size in its solid solution state, thereby increasing the yield strength and toughness of the alloy. II. Performance: High high-temperature strength, excellent oxidation and corrosion resistance; it exhibits outstanding resistance to both general and localized corrosion in applications involving hot acids and chlorides. Its corrosion resistance in corrosive environments such as acids and alkalis is excellent, particularly in terms of resistance to stress cracking. It also has good weldability. III. Applications: Typical applications of Alloy33 include sulfuric acid plants and systems for the recovery and distribution of sulfuric acid, pickling plants, seawater systems, the evaporation of salts and alkalis, chemical pulp bleaching plants, as well as various components in plate or tube heat exchangers used on offshore platforms that utilize seawater or brackish water as a cooling medium, including heat exchangers, containers, piping fittings, and other equipment. IV. Similar grades: Alloy33, R20033, 1.4591, NS1405, Nicrofer 3033. V. Chemical composition (%): C≤0.015, Si≤0.50, Mn≤2.00, S≤0.010, P≤0.020, Ni=30~33, N=0.35~0.60, Cr=31~35, Mo=0.5~2.0, Fe=balance, Cu=0.3~1.2. VI. Relevant technical standard: ASTM B625