General failure form of corrugated tube heat exchanger and the reason analysis
Corrugated heat exchange tube troughs or wave trough the transition part thinned craze.
In the operation of the corrugated tube heat exchanger, the corrugated heat exchange tube trough and its nearby area thinning craze, causing internal leakage is the main form of failure.
Failure reason is that in the shell side baffle plate in the trough of the corrugated tube with baffle tube hole produces vibration friction, knock against, make corrugated pipe wall thinning, so that the cracking leakage.
Now some more factories adopt baffle plate, make corrugated tube wave in contact with the pipe hole, to ensure that the tube with the smallest hole clearance, prevent vibration friction;
And in the baffle plate for corrugated pipe jacketed.
These are to avoid and reduce the failure form of corrugated pipe is better.
The corrugated heat exchange tube saddle (
Bellows instability occurred weeks to the saddle, corrugated tube heat exchanger is another failure modes.
This is mainly due to the corrugated pipe wall thickness is thin, generally below 1 mm, its ability to resist external pressure instability is very low.
In the design of heat exchanger, are generally not for checking and calculation of the bearing capacity of the heat exchange tube, so, when the pressure of shell side of heat exchange tube itself and above the critical pressure, the pipe saddle leads to instability.
Standard specified in the case of the corrugated heat exchange tube allowable external pressure calculation method.
The corrugated heat exchange tube axial bending deformation is too large,
The axial buckling)
This failure pattern is caused by the tube side pressure and the effect of temperature stress.
For austenitic stainless steel corrugated pipe material, the linear expansion coefficient is much bigger than carbon steel, in tube side and shell side phase at the same time also can produce temperature stress and temperature in the axial stiffness of the bellows is small, so, when the tube side pressure or tube wall temperature is higher than the wall temperature, are prone to moire phenomenon of the failure of heat exchange tube axial bending deformation is too large.
Specified in the standard case baffle plate without support span than specified value is small, in GB151 is consider to prevent the heat exchange tube axial buckling.
Corrugated heat exchange tube corrosion fracture and brittle failure as a whole.
The failure form is mainly due to the corrosion of the medium.
Austenitic stainless steel is the most easy to produce intercrystalline corrosion, when corrugated tube heat exchanger used in high chlorine ion and the medium such as hydrogen sulfide, corrugated heat exchange tube corrosion in the fracture.
Practice has been found that some of the heat exchange tube produced embrittlement phenomenon as a whole.
Corrugated pipe with thick wall pipe joint cracking.
The corrugated heat exchange tube is composed of corrugated pipe and connector on both ends (
As shown in figure 1)
, the girth weld joint, as a result of differences in the levels of welding technology and welding technology, welding quality is difficult to guarantee, thus cause the cracking.