Views: 101 Author: Site Editor Publish Time: 2020-09-17 Origin: Site
The surface of gaskets plays a significant role in sealing performance, usually, if the surface is smoother, the sealing performance is better. This could explain why elbow fitting or vacuum valve is always smooth. However, the perfectly smooth surface is just an ideal model and does not exist in reality. To obtain higher evenness of the surface, suitable pressure should be applied in gaskets. There are three common reasons causing gaskets to lose their functions:
1. The compressive force is not enough during the manufacturing process.
2. Long-time mechanical vibration incurs the compression bolt is loose.
3. Plastic deformation might occur due to aging. It follows that gaskets could not prevent mediums from leaking.To avoid aging, elbow joint or union connector such connection part will apply protective agents.
The stress which is exerted on gaskets must be in a reasonable range. If the compressive force is beyond the maximum value, the gaskets are easily broken and lose their elasticity. In this case, the separation of the flange face caused by pressure and temperature could not be fixed. Thus, the rate of leakage will dramatically increase. To maintain a good sealing performance, the gasket compressive stress must be kept in a precise range.
It shows that pressure and temperature have a great effect on the leak rate. The pressure gas between the inside and outside of gaskets is the main reason resulting in leakage. The medium could overcome resistance easily in the channel of leakage if the pressure difference is large. Therefore, the rate of leakage is increasing. Thus, the gaskets which are used in the high-pressure environment, like the stainless-steel pressure tank, should always check its sealing properties.
The sealing property of connection parts is influenced by temperature. According to research, it shows that the deformation degree increases as the temperature rises. What is more, the resilience ability decreases and creep function increases owing to overheating. This required the factories need to check and maintain the seal performance of heat exchanger otherwise it will cause an accident.
The viscosity of the medium varies with different temperature conditions. The fluid viscosity decreases as the gas viscosity increases, thus leakage will happen.
Seal failure because of chemical incompatibility is now becoming one of the common issues. To reduce contamination of the environment and save money, hydraulic systems are popularly used in the industry. Since the mediums have different chemical properties, then the gasket's materials could not be suitable for all the fluids then leakage happens. In the factory, this situation common happens in stainless steel solvent tank. To avoid this from happening, it is necessary to change seal methods.
Another reason causing chemical incompatibility is the medium will have chemical reactions with other chemicals or some additives are adding to the mediums, thus their chemical properties are changing. The medium might corrosive the gaskets so that the gaskets could not work properly.
Because of this, oil extractor and oil distillation column are needed to inspect from time to time. However, choosing the correct material for the sealing medium is a practical problem.
Physical property has a great effect on the leakage rate as well. Under the same seal methods and same working conditions, gas is easier to leak than fluids. Viscosity is a determining factor. Medium which has high viscosity tends to have a low leakage rate. Because of this, different types of columns, such as oil distillation column and methanol distillation column, are needed in the factory.
There are some gaps in gaskets because the inert structure or thickness of the material is not uniform. The leakage could not be avoided when those gaps could not be filled with gasket elasticity.