• Titanium Alloy Hard-sealed Ball Valves for PTA

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Titanium Alloy Hard-sealed Ball Valves for PTA

  • Oct 08, 2022
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PTA is ethylene terephthalate, which is mainly used in the production of polyester. Polyester is the most important variety of synthetic fibers, accounting for nearly 80% of the world's total output of synthetic fibers. In China, polyester fibers produced from polyester have already accounted for more than 80% of the total output of synthetic fibers. Therefore, the demand for PTA products is good, and the various types of machinery and equipment required in the PTA industry also have good market prospects.
 
The whole process of manufacturing PTA is accompanied by high temperatures. The refining reaction temperature is higher than 280°C, and the oxidation reaction temperature is higher than 180°C; the tail gas’s catalytic incineration temperature is higher than 300°C, and the steam temperature is higher than 350°C. In addition, high pressure is also a challenge for PTA production plants. In the manufacturing process of PTA, the refining reaction requires a pressure higher than 8MPa. The steam pressure used for material preheating is as high as 9.5MPa, and the hydrogen pressure is also higher than 9.0MPa. In the manufacturing process of PTA, the main media are acetic acid and hydrobromic acid with various concentrations, accompanied by PTA solid materials. These media are highly corrosive and easy to deposit and block. It can be seen from the above analysis that the PTA’s production environment is extremely harsh.
 
As a key component of a production device of PTA, the operational reliability of the valve is directly related to the safety of the entire device and the surrounding environment. It is widely used in production devices of PTA due to the heat resistance and corrosion resistance of titanium alloys. Valves made from Titanium alloy are widely used in equipment used for manufacturing PTA. The main types of titanium alloy valves are titanium alloy ball valves and check valves. At present, most of the metal-sealed valves that meet the production conditions of PTA devices in China rely on imports. With the large-scale construction and production of PTA devices in China, the design and development of titanium alloy hard-sealed valves have become a development trend. Titanium alloy hard-sealed ball valves have attracted much attention as the key device for the development of PTA devices.
 
The status of PTA titanium alloy hard-sealed ball valves
In the early stage of China's introduction of PTA production lines from abroad, most of the titanium pipelines, equipment and valves used in PTA production plants were imported. Among them, titanium valves are mainly imported from Japan or Germany. In the early stage of the introduction of PTA devices, there is a big gap between domestic and foreign titanium valves in terms of design, quality of titanium, surface hardening of titanium parts, packing for sealing, and precision machining of key titanium parts.
 
In recent years, the technical level of materials and equipment manufacturing in China’s titanium industry has advanced rapidly, and the titanium pipelines and containers used in manufacturing PTA have been made in China. Although the manufacturing technology of the domestic valve industry has also improved rapidly in recent years, at present, titanium valves used in domestic PTA production devices, especially large-diameter titanium alloy hard-sealed ball valves, still rely on imports. Domestic titanium valves are mainly used for the maintenance and replacement of PTA production equipment, or non-critical parts with small diameters, medium and low pressure. The titanium valve manufacturing technology of some domestic valve factories has approached the international level, which greatly promoted the domestic application of titanium valves for PTA production equipment.
 
The design standard of 3PTA titanium alloy valves
The relevant international standards for titanium and titanium alloy valves are still incomplete. The design, manufacture and testing of domestic PTA titanium alloy valves are mostly based on American standards, and only some standard parts adopt the Chinese standard. The current design standards mainly adopted are API 6D Pipeline Valves, API 608 Flanged, Threaded and Welded Metal Ball Valves, MSS SP-72 Flanged or Butt Welded Universal Ball Valves, API 594 Flanged, Lug, Wafer and Butt Welded Check Valves, API 602 Steel Gate Valves, Globe Valves and Check Valves With Nominal Size Less Than or Equal to DNl00 for the Oil and Gas Industry, API 609 Double Flange, Lug and Wafer Type Butterfly Valves, API 599 Flanged, Threaded and Welded Metal Plug Valves, API 600 Bolted Bonnet Steel Gate Valves for the Oil and Gas Industry, API 603 Flanged and Butt Welded Corrosion Resistant Bolted Bonnet Gate Valves. The main test standards are API 598 Inspection and Testing of Valve, API 6FA Specifications for Fire Tests for Valves and ISO 15848 Microleakage, Tests and Identification Procedures for Industrial Valves.