There are a number of factors that can cause an O-ring to fail, such as the selection of an unsuitable compound or incompatibility with the groove design. tippmix teljes
In this article we will review the most frequent failures, the reasons why they fail and the improvements that can be made to avoid this failure in the future.
O-ring abrasion is most common in dynamic situations. This occurs due to the continuous contact between the housing and the O-ring surface. If there is no lubrication on the O-ring when it is fitted, abrasion is more likely to occur.
To avoid this, it is essential to ensure that the sealing system is properly lubricated.
Different chemicals react differently with different O-ring materials. After a period of use, the O-ring material may harden. On the other hand, the hardness and strength of the O-ring may be reduced, causing the material to soften and the O-ring to deform from its original shape.
It is important to choose the correct O-ring material to ensure that the seal can withstand the chemicals used in the application. When temperatures are higher and the O-ring is subjected to excessive pressure, chemical decomposition occurs more quickly.
Swelling caused by chemicals
Chemical swelling of an O-ring occurs when chemicals pass through the seal and cause it to swell. The increased volume of the seal can compromise O-ring and sealing performance.
It is essential to use an O-ring material that has been approved for resistance to the chemicals used in the application.
A elasticidade do O-ring pode diminuir em altas temperaturas, o que o torna incapaz de retornar à sua forma original. A tensão na aplicação, combinada com as altas temperaturas, faz com que a forma da seção transversal mude de redonda para mais oval plana. Outra razão poderia ser uma ranhura muito apertada do O-ring.
Changing to a harder O-ring with a higher operating temperature can help to keep the O-ring in good working order. It is also worth checking the O-ring groove design to ensure that it is not too tight.
Sharp notches on the outer edge of the O-ring surface are the result of poor installation.
The O-ring was not properly lubricated and/or was placed in an application with sharp edges. The O-ring may also be chamfered during installation if it is too large or small to fit in its specified groove. Notches can be avoided by taping the edges during installation.
Biting and extrusion
At high pressures, the O-ring is pushed into the gap. The gap can open and close due to pressure surges. When the O-ring is removed from the application, it pinches into the edges of the mating surface, causing the low pressure end of the O-ring to pull out and appear wavy.
To avoid this, it is suggested to use higher durometer O-rings. If you are using 70 durometer O-rings (available in nitrile and Viton®), switch to 90 durometer O-rings. Also, the use of back-up rings in your application could reduce the chances of the O-ring clogging through the clearances.
When the molecules that make up the O-ring vaporise in a vacuum environment, it can reduce suction efficiency and pollute the environment.
It is essential to double check which O-ring material is right for the job. Examine the O-ring compound data sheets to determine the temperature ranges and recommended settings for use with the various materials. Genuine Viton®, silicone, PTFE and FFKM are some of the elastomers used to prevent outgassing.
Rapid gas decompression
What you will notice is that cracks, blisters and deep cuts may appear on the surface of the O-ring. In the worst case, the O-rings may break completely. sportfogadás adózás
Gas is absorbed and trapped in the elastomer when O-rings are exposed to high pressures and temperatures for an extended period of time. When the pressure drops rapidly, the gas escapes from the O-ring material, causing cracks and burns.
Os O-Rings de Descompressão Rápida de Gás (RGD), que vêm em Viton® 90 e 95 durometer, são recomendados.
Rounded cracks can be seen on the surface or the ring.This occurs when the ambient temperature has exceeded the temperature range of the O-ring. Higher heat can cause noticeable cracks in the hardened elastomer by increasing hardness and decreasing elasticity.
Before using the O-ring compound in the application, make sure it can withstand the temperature range. Examine the temperature ranges of the different materials, as well as the preferred and non-preferred settings for use, in the O-ring compound specification sheets.
Occurs when the outer surface of the O-ring has deep diagonal incisions around it.
Spiral marks on the O-ring can be caused by torsion in a dynamic application and even during installation. Spiral marks can occur in dynamic applications due to high friction, lack of O-ring lubrication or an uneven surface.
The use of a stiffer O-ring in the application can help prevent twisting. X-rings (also known as quad rings) are an alternative method that doubles the sealing area and avoids spiral failure.
Extrusion of thermoplastics
It is noticeable when the O-ring surface has nibbled or curled edges. Extrusion may be more prevalent on the side of the O-ring that receives less pressure if it is also in a high pressure environment.
Higher temperatures (than the O-ring is rated for) may cause the O-ring to extrude and fill the gaps.
The O-ring groove design should also be evaluated to ensure that the O-ring is not over-tightened, especially when higher temperatures may extrude material to fill the stuffing box. Review the temperature ranges of the various materials, as well as preferred and non-preferred settings for use, in the O-ring compound specification sheets.
Discolouration spots are observed along the O-ring surface. In some cases, cracking and splitting with prolonged exposure.
The cause comes when ultraviolet light carries high energy within its short wavelengths, which can manipulate the O-ring composition. online sportfogadás Prolonged exposure can have a detrimental impact, which can lead to gasket leakage.
EPDM O-rings and black Viton® O-rings are recommended for their UV resistance.