Applicable environment analysis of butterfly valve structure and working principle??? The butterfly plate of the butterfly valve is installed in the diameter direction of the pipeline. In the cylindrical channel of the butterfly valve body, the disc shaped butterfly plate rotates around the axis with the rotation angle between 0 ° and 90 °. When the rotation angle reaches 90 °, the valve plate is fully open.???

Analysis of the failure of corrugated contraction joints in heat supply network engineering
The corrugated contraction joint is a typical low-frequency fatigue component (i.e., frequency<105). Its wave crest and wave trough are in the plastic high stress range, and it is very easy to become fatigue damaged and fail at a low cycle number. The direct buried steam pipeline suffers variable frequency vibration due to the change of medium, gas flow pulse, valve opening, sealing, branch node, elbow resistance, especially the steam water impact water hammer of the pipeline. The main causes of corrugation damage are fatigue damage, corrosion damage and distortion damage:
1) The water quality is not properly treated, and the steam contains Cl ions, forming corrugated pitting corrosion or lattice corrosion of stainless steel;
2) Escort medium high-pressure steam, line speed υ> Above 30m/s, turbulence is formed at the tee, elbow, and valve, which causes the original designed guide cylinder of the compensator to be damaged due to low frequency and large amplitude vibration, especially for the large diameter, large compensation guide cylinder L>460mm, which is more likely to occur fatigue fracture of the guide cylinder and blow off;
3) Design or operation errors, resulting in steam water impact, explosive water hammer, and serious damage (shock) to bellows elements;
4) The large diameter spiral pipe, because its internal stress has not been eliminated, causes it to restore the stress to form the corrugated joint distortion destruction; 5) When the device deflects, the fixed pier slips and the stress is out of balance, which is also one of the reasons for the change (bending), deformation and destruction of corrugated elements.
For the above points, we must pay attention to precautions in design, installation, manufacturing and operation.