In addition, the pneumatic butterfly valve is small and light, easy to disassemble and repair, and can be installed at any position. Simple and compact structure, small operating torque, and quick 90 ° rotation opening. The flow characteristics tend to be straight, and the regulation performance is good. The connection between the butterfly plate and the valve rod adopts a pin free structure, which overcomes the possible internal leakage point.

What is the pulling off phenomenon of bellows compensator
Bellows compensators sometimes appear to pull off in practical work and application, and this phenomenon may cause damage to the bellows expansion joint if it is small, or threaten the safety of the whole pipeline if it is large. The degree of crushing has a great relationship with the installation of fixed supports and pipe supports in the pipeline.
The following explains why the bellows expansion joint is pulled out and how to prevent it.
1、 Why does the ripple compensator pull off?
The stainless steel bellows compensator needs to adjust the pull rod device attached to the metal compensator to its compensation scale after installation rather than remove all devices.
The fixed pipe support does not need to be set up now during the pressure test of the pipeline. If the pipe support is not set up, the stainless steel metal expansion joint will be infinitely extended to its own limit with the pressure and impact force during the pressure test. At this time, the corrugated compensator has been stretched into a straight cylinder or lost its expansion function.
2、 Why is the degree of pulverization closely related to the fixed pipe rack?
First of all, it has been made clear that if the fixed pipe rack is set in strict accordance with the requirements when setting and installing, the stainless steel bellows can only be pulled off and twisted or shifted at most when the pull rod device is removed, even if it is affected by the pipeline pressure and thrust, It will not crush the equipment and pipelines of other pipe sections.
3、 How to prevent the stainless steel bellows from pulling off, and how to set the fixed pipe rack?
The best installation method is to fix the limit bolt on the expansion compensation scale of the corrugated compensator with a pull rod device during installation. Another point must be noted. When fixing the pipe support and bracket, it must ensure that the pipeline will not be displaced while being subjected to instantaneous pressure and pushing force, so that the bellows expansion joint can play its maximum role.
In the structural design of pneumatic butterfly valve, corresponding strengthening and protection measures shall be adopted. In the structural design of pneumatic butterfly valve, in order to improve the bearing capacity of bellows and avoid mechanical damage, corresponding strengthening and protection methods must be adopted. For bellows with small diameter, most of them are armored steel wire mesh sleeves.
To analyze the strength of the metal wire mesh sleeve, first make clear the structural parameters and the relationship between them.
The net sleeve is made of several strands of metal wires with diameter d, each of which has several wires. It is wrapped on the profile of corrugated pipe cylinder with necessary discipline.
Therefore, in order to reasonably operate the strength of the wire mesh sleeve, it is necessary to understand the bearing capacity of the bellows.
Since the rubber hose with wire mesh sleeve as the "tendon" is the predecessor of modern pneumatic butterfly valve, before analyzing the strength of the wire mesh sleeve of modern pneumatic butterfly valve, let's first study the environment of the wire mesh of the rubber hose under stress. The rigidity of the rubber hose is very small, so the load caused by the medium pressure is basically borne by the wire mesh. Pneumatic butterfly valves are different from rubber hoses because their lateral stiffness is much greater than the longitudinal stiffness. Therefore, a large part of the transverse load caused by the medium pressure is borne by the bellows, while the longitudinal load is mainly borne by the wire mesh.
Therefore, the braiding angle of the pneumatic butterfly valve mesh sleeve is different from that of the rubber hose wire mesh.
It can be seen from the above that the smaller the transverse load of the part immersed in the metal mesh sleeve, that is, the greater the transverse load bearing capacity of the bellows, the smaller the balanced braiding angle. Therefore, unlike the balanced braiding angle of the rubber hose, the braiding angle of the pneumatic butterfly valve mesh sleeve is often set smaller.
Due to the following difficulties in the manufacturing process: metal wire strand agglomeration; Broken wire in strand; Interleaving and uneven stretching of strands; Especially when the joint, mesh sleeve and bellows are connected in a trinity way, if the rolling welding process is adopted, the sectional area of the metal wire will be reduced; If fusion welding process is adopted, the wire will have a certain scale of heat affected zone. Therefore, there is no environment where the metal wire can bear the load evenly. Because it is absolutely true to study the influence of the above factors in an analytical way.
For pneumatic butterfly valves with larger diameters, it is not economical to use metal wire to weave the mesh in places where flexibility requirements are not high. It is understood that the pneumatic butterfly valve used to compensate the tank foundation subsidence and the pneumatic butterfly valve with small transverse compensation and large bending radius used in other places in foreign countries mainly adopts the structural form of corrugated pipe armored steel belt mesh sleeve.