Edge-welded bellows is a new type of component that has arisen both domestic and abroad in recent years. It can be used as sensitive element, sealing element, isolation medium, pipe connection and temperature compensator. In addition to pressure resistance, temperature resistance, corrosion resistance, good sealing and other advantages, there are two outstanding advantages compared with the traditional formed bellows: large deformation and long life.
Edge-Welded bellows are a kind of highly flexible and telescopic metal tubes made of many thin hollow membranes formed by stamping, using precision welding, as shown in Figure 1. Its composition is composed of two formed hollow diaphragm in the form of concentric circles for the inner edge welding to form a diaphragm pair, and then a plurality of diaphragm pairs are stacked together for the outer edge welding to form a corrugated section, and then welded together at both ends and end plate metal to form a corrugated pipe group, so that the external needs can be reciprocated with other moving parts.
The choice of welding bellows material is very strict, in addition to the requirements of high temperature resistance and corrosion resistance, but also requires that the bellows have sufficient stiffness. The product welding technologies used or under development are tungsten inert gas shielded welding, micro-beam plasma welding, power beam welding and laser welding, of which micro-beam plasma welding and laser welding are more commonly used.
With the development of science and technology, the application field of welded bellows is expanding day by day. The main use of welded bellows is: as a control mechanism, transmitter or regulator detection elements can also be used as temperature, pressure and level measurement elements, can also be used as a variety of seals and energy transfer elements.
Edge-welded metal bellows can be used not only as measuring elements, but also as sealing, connecting, compensating and isolating elements, which has a wide application prospect in many fields.
1.instrument industry
Welded bellows are mainly used as pressure measuring elements in measurement and control instruments, and can be used instead of diaphragm strings. It can also be used in the gyroscope as a volume compensation element, in the control valve as a sealing isolation element, in addition to flexible coupling, pressure switch and so on.
2. Aerospace field
Welded bellows are also used in the aerospace sector. In addition to its use in some aircraft instruments, it is also used in the automatic release pressure regulator of parachutes. In addition, it can also be used as a shaft sealing door on a rocket engine.
3, electronics industry and other industries
Welded bellows are also used in electronic devices. For example, the klystron of the satellite communication ground station uses a miniature welded bellows with an outer diameter of 10mm, an inner diameter of 5mm and a wall thickness of 0.05mm. It is used as a vacuum seal, axial connector, expansion joint, oil storage, accumulator and other aspects have also been paid attention to by various departments.
The sawtooth expander widely used in the power industry is also a typical application example of welded bellows. It actually acts as a volume compensation here. The working coils of the voltage transformer and current transformer are immersed in the insulated oil tank. With the change of the ambient temperature and working current, the temperature of the insulating oil changes widely. Therefore, in a fully enclosed system, it is necessary to compensate for the volume change caused by the thermal expansion and contraction of the insulating oil.
