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Service Life And Operating Temperature Of Bellows How Much Do You Know?

Bellows refers to the use of foldable wrinkles in the direction of folding expansion of the tube-like elastic sensitive components. Bellows in the instrumentation of a wide range of applications, the main purpose is as a pressure measuring instrument measuring elements, the pressure to convert to displacement or force. The corrugated pipe has a thin wall and a high sensitivity, measuring range of dozens of PA to dozens of MPA. The opening end is fixed, the sealing end is in a free State, and the auxiliary helical spring or reed is used to increase elasticity. When working under the action of internal pressure in the direction of the length of the pipe elongation, so that the active end produces a certain relationship with the pressure displacement. The active end of the pointer can directly indicate the size of the pressure. Bellows are often combined with displacement sensors to form a pressure sensor that is output to power, and is sometimes used as an isolating element. Because the expansion of the bellows requires larger volume changes, its response rate is lower than that of the wave-boarding tube. Bellows are suitable for measuring low pressure.


There are two states of the elastic element, one is to work under certain load and displacement, and keep the load, displacement always constant or very little change, called static work; another use is the constant cycle of load and displacement alternating. The component is in a circular working state. The modes of damage or failure of components are also different due to different working conditions. The instrument elastic sensitive element works in the elasticity range, basically is in the static work state, the service life is very long, generally achieves tens of thousands of times to hundreds of thousands of times. The corrugated pipe components used in engineering can sometimes work in the elastoplastic range or alternating stress state, and the life span can only be done in hundreds of times. The component must be given the allowable working life when working in circulation, and the number of cycles, time and frequency shall be specified.


The rated life of the elastic element is the expected service life of the component design, which requires that the component not be allowed to appear fatigue, damage or failure during this period.




The life of bellows is used under working conditions, can guarantee the minimum working time or cycle times of normal work. The elastic seal system composed of corrugated pipe is often employed under the condition of more cyclic load and larger displacement, so it is of great significance to determine the service life of corrugated pipe. Because the function of bellows is different, its service life requirements are not the same.


(1) Ripple works to compensate for the installation of the pipeline system caused by the position deviation, the life requirements only a few times enough.


(2) Bellows for high switching frequency of the thermostat controller, its life to reach 10,000 times to meet the requirements of the use.


(3) Bellows for vacuum switch as a vacuum seal, its life to reach 30,000 times to ensure normal work.


From the above three examples of use, because of the different conditions of use, bellows requirements of the service life of a large difference. The life of bellows is related to the fatigue property of the material, and also depends on the residual stress of the forming bellows, the stress concentration and the surface quality of the corrugated pipe. In addition, the service life is related to the working conditions of the corrugated pipe. For example: corrugated pipe work displacement, pressure, temperature, working medium, vibration conditions, frequency range, impact conditions.


The life span of bellows is mainly determined by the maximum stress during working process. In order to reduce the stress, it is generally achieved by reducing the working displacement of the bellows and reducing the working pressure. In general design, the working displacement of bellows should be less than half of its allowable displacement, and its working pressure should be less than half of the pressure of bellows.


The production of corrugated pipe test proved that if the bellows according to the above specifications, it will use the life of the basic soil can reach about 50,000 times.


Depending on the nature of the work pressure, the allowable displacement of bellows is also different from the general bellows only under axial load (pull or pressure), its allowable displacement can be used between the 10%~40% of the effective length of bellows, and in the corrugated pipe under the transverse concentration force, torsion torque or composite force, The allowable displacement of bellows should be reduced properly.


The application of multi-layer bellows can reduce the stress caused by stiffness and deformation, so it can improve the life of corrugated pipe greatly.


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