PTFE, PFA, FEP, PVDF Fluoroplastic products industry experts
Leakage Causes of PTFE Gasket Failure
Classification:
Industry dynamics
Author:
PFA tube little sister
Source:
Dankai
Release time:
2022-11-21
Visits:
PTFE gasket failure will produce leakage, mainly in a gap is the sealing surface. The second is the pressure difference on both sides of the sealing part. What needs to be solved is to eliminate or reduce the gap between the sealing surfaces.
Gap. Such gaps include gaps between the sealing surfaces and gaps within the sealing device itself. Specifically, the main reasons for the leakage of PTFE gasket failure are the following.
Figure 1: PTFE gasket Source: Dankai
Teflon gasket
1. The working conditions of PTFE gasket sealing include the pressure and temperature of the medium. Under different pressure and temperature, the leakage rate is different. The pressure difference on both sides of the sealing surface is the main leakage
The driving force, the greater the pressure difference, the easier it is for the medium to overcome the resistance of the leakage channel, and the easier it is to leak. The temperature has a great influence on the sealing performance of the connection structure. Studies have shown that PTFE pads
The elastic and plastic deformation of the sheet increases with the increase of temperature, while the rebound performance decreases with the increase of temperature, and the creep increases with the increase of temperature. And with the increase of temperature, PTFE gasket
The phenomenon of aging, weightlessness, creep and relaxation will become more and more serious. In addition, the temperature also has a great influence on the viscosity of the medium. With the increase of temperature, the viscosity of the liquid decreases, while the viscosity of the gas
Increase. The higher the temperature, the more likely leakage occurs.
Figure 2: PTFE gasket Source: Dankai
2. Influence of compression stress. In order to achieve the sealing effect, it is necessary to apply enough pressure to the sealing PTFE gasket, which can cause elastic or plastic deformation to fill the unevenness of the sealing surface.
Uneven. However, during assembly, the pressing force required by the PTFE gasket cannot be reached, or the pressing bolt is loosened due to mechanical vibration during long-term operation. In addition, the material of the PTFE gasket is old.
The deformation and loss of the original elasticity will cause the PTFE gasket to fail and cause leakage. If the compression stress of the PTFE gasket is too large, it is easy to crush the PTFE gasket and lose it.
Resilience, unable to compensate for the separation of the flange surface caused by temperature and pressure, resulting in a sharp increase in leakage rate. Therefore, to maintain a good seal, the compression stress of the PTFE gasket must be kept.
within a certain range.
3. The internal organization or thickness of the material is uneven, and the cardboard with cracks or wrinkles is used, so that the PTFE gasket itself forms a gap, and the force acting on the PTFE gasket makes it poly
When the elastic deformation of the tetrafluoroethylene gasket is not sufficient to completely fill these gaps, leakage is inevitable.
4. The material of PTFE gasket is not suitable for the medium transported. Due to the diversity of the chemical properties of the chemical products transported by the pump, as well as to improve the combustion value of the fuel or to change its post-combustion life.
After adding a small amount of additives to the fuel, some properties of the fuel will change. Therefore, it is not easy to select a PTFE gasket material suitable for the conveying medium, so it is also
Often occur due to do not adapt to the PTFE gasket erosion and leakage phenomenon.
Figure 3: PTFE gasket Source: Dankai
5. The influence of size (thickness and width)
A, thickness: in the same compression load, the same medium pressure, the leakage rate decreases with the increase of the thickness of the PTFE gasket. This is due to the thick poly under the same axial load.
Teflon gasket has a large amount of compression rebound, in the case of the initial sealing conditions have been reached, the elastic reserve of large thick PTFE gasket than the thin one can compensate for the pressure caused by the medium.
The relative separation between the sealing surfaces, and the PTFE gasket surface to retain a larger residual compression stress, so that the leakage rate is reduced.
The thickness of the PTFE gasket is different, and the conditions for establishing the initial seal are also different. Due to the influence of friction on the end face, the surface of the PTFE gasket is in a three-way compressive stress state, and the deformation resistance of the material
The force is larger; and the middle part of the PTFE gasket is less affected by the end, and its deformation resistance is also smaller. Under the same preload, the middle part of PTFE gasket is more likely to produce plastic energy change than its surface.
At this time, the more difficult it is to establish an initial seal, so when its thickness reaches a certain value, the sealing performance does not change or even deteriorate. In addition, the thicker the PTFE gasket, the more permeable the leakage surface
The larger the volume, the greater the permeability leakage rate.
B, width: within a certain range, the leakage rate will decrease linearly with the increase of the width of the PTFE gasket. This is because, in the effective width of PTFE gasket medium leakage resistance and
The length of the leakage channel (proportional to the width of the PTFE gasket) is proportional. But it cannot be said that the wider the PTFE gasket, the better, because the wider the PTFE gasket, the larger the surface area, so
The same compression stress is produced on the PTFE gasket, and the bolt force of the wide PTFE gasket is much greater than that of the narrow PTFE gasket.
This article is originally created by Teflon's little sister. Welcome to pay attention and take you to grow knowledge together!
Key words:
Gasket, PTFE, seal, temperature, pressure, medium, thickness, width
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