WHAT ARE THE HARDNESS OPTIONS AND SAFETY REQUIREMENTS FOR O-RINGS?

In the previous article, we learned about the phenomenon and causes of wear of O-rings. Among them, we mentioned hardness. What are the specific requirements for hardness and how should we choose? What are the safety requirements for O-rings? Let's take a look together.

O-ring hardness selection

The choice of O-ring hardness is more important. For example, the hardness of 70 (Shore) sealing ring of the pump and turbine of a power station is often peeled off or even cut off horizontally, and then a seal ring of 85 to 90 (Shore) is used, which has an ideal effect.

Although O-rings have low hardness and are easy to install, they are prone to peeling, installation damage, extrusion and even pressure explosion. The hardness is too high and the installation is inconvenient. O-ring hardness is usually 40 to 90 IRHD, but 70 IRHD is more suitable in use, except for silicone rubber, which is generally 60 IRHD.

O-ring dressing

The unvulcanized O-ring compound is a viscous fluid under high temperature and pressure. When the mold is vulcanized, the compound quickly fills the mold cavity, and the excess part (in order to prevent lack of rubber, the compound filled in the mold cavity is sure. Maintain a certain amount of excess). Once the overflow edge is formed, it must be removed in order to make the appearance neat and beautiful. This process is called trimming.

The requirements for trimming are precise size and neat appearance. In actual production, the trimming of products is often time-consuming and labor-intensive. For products with strict requirements, minor accidents in trimming may cause waste and must be treated with caution. Generally speaking, the smaller the size and the more complex the shape of the product, the more difficult the trimming and the more waste products.

Requirements for installing O-rings

Before installing the O-ring (O-ring rubber seal), check the following:

1.Whether the lead-in angle is processed according to the drawing, whether the sharp edge is chamfered or rounded;

2.Whether the inner diameter removes burrs and whether there is pollution on the surface;

3. Whether the seals and parts have been greased or lubricated (to ensure the compatibility of the elastomer, it is recommended to use the sealed liquid for lubrication);

4. Do not use grease containing solid additives, such as molybdenum disulfide, zinc sulfide.

Install O-rings manually:

1.Use tools without sharp edges;

2. Ensure that the O-ring is not twisted, and the O-ring is not stretched excessively;

3. Try to use auxiliary tools to install O-rings and ensure correct positioning;

4. For O-rings bonded with sealing strips, do not stretch at the connection.

Mounting screws and splines:

1. After the O-ring (O-ring rubber seal) is stretched, it is necessary to use a mounting mandrel when passing through screws, splines, keyways, etc. The mandrel can be made of soft, smooth metal or plastic without burrs or sharp edges.

2. When installing the compression screws, tighten the screws symmetrically, and do not tighten them in order.

Have you learned how to install a 0-ring seal through the above article? If you have any questions, please contact us in time.