Sealing Gasket Failure: Causes and Prevention Measures

In industrial production, gaskets are crucial components to ensure the sealing of equipment and pipelines. However, gaskets may fail during use due to various factors, leading to leaks and other issues that pose safety hazards and economic losses to production. This article will delve into the causes of gasket failure and propose corresponding preventive measures to help readers better understand and apply relevant knowledge.

In industrial equipment and pipeline systems, gaskets are key components to ensure sealing performance. However, gasket failure is a common problem that can lead to severe leaks and safety hazards. Understanding the causes of gasket failure is essential for preventing problems and enhancing the reliability of equipment. The following are some of the main reasons for gasket failure.

During equipment operation, gaskets are subjected to pressure changes and compressive forces. When the pressure is too high, the gasket may deform, get damaged, or even fail. For example, in high-pressure pipelines, if the gasket material or design cannot withstand the excessive pressure, sealing failure is likely to occur. This failure can not only cause medium leakage but also trigger safety accidents.

When in contact with adjacent components, gaskets are subjected to frictional and shearing forces. These forces can lead to surface wear of the gasket and even allow wear particles to enter the gasket surface, further exacerbating the damage. For instance, in some high-speed rotating equipment, the friction between the gasket and the rotating parts can cause rapid wear of the gasket, thereby reducing its sealing performance.

Vibration and impact of equipment generate dynamic stresses that impose additional loads on gaskets. These dynamic stresses can cause gasket fatigue and damage. For example, in large machinery or transportation equipment, frequent vibration and impact subject the gasket to continuous dynamic stresses, thereby accelerating its failure process.

The shape and roughness of flange sealing surfaces significantly affect the performance of gaskets. Generally, the sealing surface in contact with a metal gasket requires high dimensional accuracy, with a roughness between Ra6.3 and 3.2, while the sealing surface for soft gaskets can have a slightly lower precision, with a roughness of Ra25 to 12.5. If the sealing surface has radial mechanical grooves, burrs, or other mechanical damage, it will affect the sealing effect of the gasket. Moreover, the flatness of the sealing surface and its perpendicularity to the flange axis are prerequisites for ensuring uniform compression of the gasket. If the sealing surface is not clean, has mechanical damage, corrosion damage, or residual old gaskets, it will also lead to gasket sealing failure.

Gasket material is one of the main factors affecting gasket performance. The gasket material should be dense and not easily impregnated by the medium. Appropriate gasket deformation, similar to elasticity, is a necessary condition for forming a seal. Gasket deformation includes both elastic and plastic deformation. In addition, the gasket material should be able to withstand temperature and pressure fluctuations as well as medium corrosion. If the gasket material has good elasticity and flexibility, it can fit well with the sealing surface, not harden at low temperatures, nor soften or flow at high temperatures, naturally resulting in better sealing performance.

Some media are corrosive, such as acids, alkalis, and salt solutions. Long-term exposure of these media to gaskets can lead to corrosion and damage of the gasket material. Incorrect selection of gasket material or unsuitable corrosion resistance can cause the gasket to fail to withstand corrosion, thereby leading to damage.

During temperature changes, gaskets undergo dimensional changes due to thermal expansion and contraction. If the gasket cannot adapt to these changes, it will lead to damage. For example, in high-temperature environments, the gasket may become loose due to thermal expansion, while in low-temperature environments, the gasket may crack due to contraction. Moreover, frequent thermal cycling can cause thermal fatigue in gaskets, leading to degradation of material properties and damage.

Leakage in flange connections often occurs during cooling. This is because the cooling rates of flanges and bolts are different. After cooling, the compressive force on the gasket will undergo stress relaxation. In addition, the cold contraction of the pipeline generates a force in the direction of bolt tension, which promotes leakage. When selecting gaskets for low-temperature media, it is important to choose gaskets that remain elastic at low temperatures. The gasket thickness should be as small as possible, and the flange gap should be minimized. High-strength bolts should be used to reduce stress.

Incorrect installation pressure can lead to damage or failure of the gasket. If the installation is too tight, the gasket may be over-compressed, resulting in deformation or damage. If the installation is too loose, the gasket will not provide sufficient sealing force, thereby causing leakage.

Improper operation and maintenance can cause unnecessary damage to the gasket. For example, excessive torque and the use of improper tools can damage the gasket. In addition, uneven clamping force is also one of the main reasons for leakage. Uneven clamping force can be caused by various factors. First, human factors, such as asymmetric pre-tightening of bolts during construction, can easily cause unevenness, which can be eliminated during construction. In theory, when the flange is tightened, the sealing surface is absolutely parallel. However, in practice, the pipeline centerline cannot be absolutely concentric. Therefore, when tightening the bolts, a bending moment is generated on the flange, causing uneven force on the flange. This uneven connection causes more or less deformation of the sealing surface, reducing the sealing clamping force. Under operating loads, leakage is likely to occur. Finally, the bolt arrangement density also has a significant impact on the pressure distribution. The closer the bolts are, the more uniform the pressure tends to be.

After the bolts are tightened on the flange, due to factors such as mechanical vibration, temperature rise or fall, the gasket will experience stress relaxation during operation, and the bolt torque will gradually decrease, resulting in torque loss and leakage. Generally speaking, the longer the bolt, the greater the residual torque. The smaller the diameter, the more favorable it is to prevent torque loss. Therefore, using long and thin bolts is an effective way to prevent torque loss. In addition, the greater the temperature change and the longer the duration, the more serious the torque loss. Heating the bolt for a certain time to make it elongate and then maintaining the given torque is very effective in preventing torque loss. Moreover, the thinner the gasket, the smaller the torque loss. In addition, preventing strong vibrations of the machine and pipeline itself, eliminating the influence of vibrations from adjacent equipment, avoiding unnecessary impacts on the sealing surface, and not knocking on the tightened bolts can all prevent torque loss.

After understanding the various causes of gasket failure, we will now explore how to prevent these failure problems through effective measures. By making reasonable material selections, using correct installation methods, and conducting regular maintenance, the service life and sealing performance of gaskets can be significantly improved, ensuring the safe operation of equipment.

Choosing the appropriate gasket material according to the characteristics of the equipment and the medium is crucial. For example, for equipment, pipelines, and containers that transport flammable, explosive, highly toxic, and strongly corrosive media, the gasket's high-temperature and high-pressure resistance should be improved according to the operating conditions. That is, gaskets with higher temperature and pressure ratings should be selected.

During installation, it is essential to ensure that the gasket and flange surface are clean. Check for radial scratches on the gasket surface and whether the flange surface roughness is appropriate. Place the gasket in the correct position during installation, use a torque wrench correctly to achieve the correct bolt preload for the gasket. Non-metallic gaskets must be stored in a dry and cool place, not exposed to sunlight or outdoors. The box for storing gaskets must be labeled with the gasket's model, size, thickness, specifications, and other technical data to avoid misuse.

In environments with significant temperature changes, measures should be taken to reduce the impact of temperature on gaskets. For example, when selecting gaskets for low-temperature media, it is important to choose gaskets that remain elastic at low temperatures. The gasket thickness should be as small as possible, and the flange gap should be minimized. High-strength bolts should be used to reduce stress.

To prevent stress relaxation and torque loss, the following measures can be taken: use long and thin bolts to increase residual torque; after heating the bolts for a certain time to make them elongate, maintain the given torque; select thin gaskets to reduce torque loss; prevent strong vibrations of the machine and pipeline itself, eliminate the influence of vibrations from adjacent equipment, avoid unnecessary impacts on the sealing surface, and do not knock on the tightened bolts.

Regularly inspect the condition of the gasket to promptly detect and replace any damaged or aged gaskets. At the same time, conduct regular maintenance on the equipment to ensure it operates in good condition, reducing the risk of gasket failure due to equipment malfunctions.

Gaskets play a vital role in industrial production, but their failure issues should not be overlooked. By understanding the causes of gasket failure and taking corresponding preventive measures, the service life of gaskets can be effectively extended, and the sealing performance and operational safety of equipment can be improved. It is hoped that the content of this article will be helpful to readers, enabling them to better apply this knowledge in their actual work to ensure the safe operation of equipment.