Application of lap joint flange in aerospace pulverized coal gasification plant

This paper introduces the application of lap joint flange on equipment, special pipe fittings and metal hose in aerospace pulverized coal gasification plant, and determines that butt welding ring loose flange should be selected in the above situations according to relevant specifications. It has a certain reference significance for the selection of loose flange in similar occasions.

What is a lap joint flange?

Lap joint flange is to use flanging nipple or steel ring to cover the flange on the pipe end. The flange can rotate freely on the pipe end. See fig.1 for details. At present, loose flange is widely used in non-metallic lined pipeline. The use of loose flange can make the construction and installation more convenient and the subsequent pipeline replacement more convenient, and save time for the successful completion of the project.

Fig.1 schematic diagram of loose flange

In the process of aerospace pulverized coal gasification, inert gas is used to transport coal, pure oxygen and steam are used as gasifiers, pulverized coal is gasified at pressure of 4.ompag and temperature of 1200-1700 ℃, and crude syngas is produced by quenching process. The space pulverized coal gasification unit mainly includes coal grinding and drying unit, coal pressurization and coal feeding unit, gasification and syngas washing unit and slag and ash water treatment unit.
In the aerospace pulverized coal gasification plant, considering the convenience of construction or maintenance, loose flange will also be used. The following is a summary of its application.

Application of loose flange in equipment

Fig.2 application of loose flange in equipment
In the gasification and syngas washing unit of aerospace pulverized coal gasification plant, the start-up ejector and ejector separation tank are directly connected through the flange nozzle, as shown in Fig. 2. In order to facilitate the installation of two sets of equipment, and considering that the ejector separation tank is designed in the equipment room, while the start-up ejector is purchased, the manufacturer is required to design butt welded flange for the nozzle of the ejector separator, and the corresponding nozzle of the ejector separator tank is designed as a loose sleeve flange. According to the above design, the problem of bolt hole misalignment caused by installation error in the process of equipment connection is avoided, and the equipment installation efficiency is improved.

Application of loose flange in pipe fittings

Fig.3 application of loose flange in pipe fittings
The application of loose flange in pipe fittings is shown in Fig.3. In slag and ash water treatment unit, one nozzle of special tee pipe fittings is directly connected with high-pressure flash tank, and the other is directly connected with angle valve. If there is error in the processing of special tee pipe fittings or errors in the construction process, it is very easy to cause the bolt holes of special tee pipe fitting flange to be out of alignment. The angle valve in Figure 3 is a standard part, and the flange is generally welding neck flange. The above problem can be solved by designing the pipe fittings connected with the special tee pipe fittings as loose flange. In addition, in order to resist the erosion of black water, the special tee needs to be replaced after a certain period of service. The looper flange is set on the special tee pipe fittings, which will be very convenient in the subsequent repair and maintenance process.

Application of loose flange in metal hose

Flange type metal hose is set up in the coal pressurization and coal feeding unit and gasification and syngas washing unit. In the conventional design, one end of the metal hose is designed as a butt welding flange, and the other end is designed as a loose flange. The metal hose is considered as a vulnerable part and needs to be replaced after a certain period of time. Through the above design, it will be easy to align the bolt hole when replacing.

Fig.4 application of loose flange on metal hose

Selection of loose flange

Table.1 shows the sealing surface form and application scope of loose flange. It can be seen from table 1 that loose flange is generally used in medium and low pressure situations, and the maximum allowable nominal pressure of slip on ring flange is PN16, and the nominal pressure of loose sleeve flange in the first three examples is PN20. It can be seen that the pressure requirement of slip on ring loose flange can not meet the pressure requirements. The maximum allowable nominal pressure of loose flange with welding ring in domestic standard can reach PN100 (Class 600). The maximum allowable nominal pressure of domestic standard butt welding ring loose flange is up to Class 2500, it can be seen that the butt welding ring loose flange meets the pressure requirements. Therefore, in the above three examples, the butt welding ring loose flange is selected.

Table.1 types of sealing surface of loose flange and its application scope

Conclusion

• (1) Loose flange is set on the direct connection equipment, pipe fittings and metal hose, which is convenient for construction and installation, as well as convenient for subsequent pipe replacement and maintenance;
• (2) Due to its poor stress strength, loose flange is recommended to be used in medium and low pressure situations and should not be used on pipes with large bending or torsion stress.

Source: China Lap Joint Flange Manufacturer – Yaang Pipe Industry (www.epowermetals.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

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