Application of the hottest all position automatic

2022-08-06
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Application of all position automatic tube sheet welding system in condenser manufacturing of power construction

Abstract: combined with the manufacturing characteristics of condenser in power construction industry, this paper systematically introduces the application of all position automatic tube sheet welding in its manufacturing

key words: power construction; Condenser; Full position; Tube sheet welding

introduction

in recent years, in order to meet the demand of power consumption for the rapid development of industry, all parts of the country have stepped up the construction of new power plants and power plant capacity increase projects, among which the manufacturing of large condensers is particularly important. The original condenser was manufactured by the copper tube expansion process. After long-term service of the equipment, the problems of copper green and leakage at the copper tube expansion will occur, which will seriously affect the heat exchange efficiency and service life, and the later maintenance cost is high. Therefore, at present, in order to prevent cl- corrosion, the condenser heat exchange tube is changed to Ti alloy in the coastal area and austenitic corrosion-resistant stainless steel in the inland area. The strength expansion and densification sealing process is adopted to completely solve the leakage problem. There are 40000 to 80000 welded junctions on the entire condenser tube sheet, which is a heavy workload, difficult manual operation, tight construction period, and high weld quality requirements. Many factors determine that it is imperative to use all position automatic tube sheet welding equipment to weld NCM materials in the power construction industry, generally including ncm111, ncm424, ncm442, ncm523, ncm622, ncm811 and other condensers. This paper mainly introduces the characteristics and application of all position automatic tube sheet welding

1. Generally speaking, the condenser structure is in the form of

tubesheet thickness mm. The material is 304 stainless steel or composite plate, which has become an important new material industry base in China (the base is 16Mn and the cladding is 5mmti alloy). The material of the heat exchange tube is the same as that of the tube sheet, which is 304 stainless steel or Ti alloy, and the specification is generally Φ twenty-five × 0.5、 Φ twenty-five × 0.7。 The joint rubber tensile testing machine can be used to do experiments. The connection method is strength expansion, sealing and welding, and the nozzle extends out 5mm, and the pipe orifice is stuck for about 30mm in the whole process

2. Features of all position automatic tube sheet welding

the welding process of all position tube sheet welding includes flat welding, uphill welding, downhill welding, overhead welding, etc., and the stress of the weld pool varies from point to point

1. Schematic diagram of tube sheet structure

the influence of gravity on weld formation is different at each point: at the flat welding position, gravity is easy to cause the molten pool to flow into the nozzle; In overhead welding position, gravity is easy to make the weld pool deviate from the weld, resulting in uneven weld formation

in order to reduce the influence of gravity on the weld pool, pulse welding is easy to be used for all position tubesheet welding, that is, the peak value forms the weld pool, the base value maintains the arc and cools the weld pool at the same time. The weld is formed by superposition of very dense welding points, so as to form a weld with good fusion and uniform appearance

3. Requirements for automatic equipment for condenser tube sheet welding in power construction industry

according to the condenser structure, the automatic welding process of self melting without wire adding pulse TIG is adopted. The automatic welding equipment includes welding power supply and gun head. The specific requirements are as follows:

3.1 requirements for welding program-controlled power supply

1) the power supply shall have the functions of air supply in advance, air supply in delay, high-frequency arc starting, pulse current regulation, automatic rotation, counting, current attenuation, etc

2) programmable memory of power supply shall have humanized programming interface, simple operation and convenient use

3) the power supply shall have a high-performance multi CPU system with fast response, high control accuracy, stable performance and good weld reproducibility

3.2 requirements for tubesheet welding gun head:

1) reliable positioning device shall be provided with fast positioning

2) reliable gas protection device shall be provided

3) compact structure and high precision

4) the welding gun shall have external circulating water cooling to meet the requirements of long-time work

5) light weight and reduced labor intensity

4 condenser assembly, cleaning and on-site construction requirements

4.1 assembly requirements

1) the length of tube plate extending from the nozzle shall be strictly controlled 5mm

2) after one end is expanded, the other end shall be removed with a tube sheet end face machine

3) the expansion tube shall be uniform and consistent to avoid loose sticking and expansion

4.2 cleaning requirements:

1) before pipe threading, the oil stain and moisture within 25mm of the pipe hole and nozzle shall be strictly cleaned

2) after the pipe orifice is inflated, the organic solvent shall be strictly cleaned to ensure that the welding area is free of oil stain, so as to avoid pores during welding

4.3 site construction requirements:

1) a tarpaulin shall be built on site to prevent the pipe plate from absorbing water

2) during construction at one end, the nozzle at the other end should be sealed to prevent the wind passing through the pipe from affecting the arc stability

5 Welding process and efficiency

based on welding Φ 25, the time for welding one nozzle is s, and several nozzles can be welded in 8 hours

6. Welding results

the condenser in the power construction industry adopts the all position automatic tube sheet welding equipment for on-site construction welding

6.1 the weld formation is beautiful and the weld is silver white

6.2 high welding quality and good welding reproducibility

6.3 no pores and cracks in PT staining inspection

6.4 passed the field hydrostatic test

6.5 high welding efficiency. (end)

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