What to Consider When Choosing Your Custom Gaskets
Be sure to choose the right custom gaskets for your applications by considering the following key factors. Read more below for the details.
Choosing the wrong custom gasket can be very frustrating. All the specifications of a custom gasket, starting from the size, to its ability to withstand degradation and damage, play a major role on how perfect it can stop the escape of fluids. Knowing the type or category of gaskets will make you have the right selection.
A gasket is a layer of material placed between two mating surfaces, most times flanges, to prevent the escape of fluids or gases, or to enter a closed, confined system. The fluid; liquid or gas, may be in a relative vacuum or under pressure.
In any fluid movement chamber or compartment, there is a need for a gasket between the surfaces. These two surfaces, however, might not be perfectly straight, they have gaps that makes fluid through. A well custom gasket corrects gaps by compressing the two surfaces to effectively eliminate any leakage in the fluid path.
Types of Gaskets
Even though there are different categories of gaskets used in different industries for different applications, it is important to note the type that suits your application.
Gaskets are most times, categorized into two:
- Metallic/semi-metallic gaskets
- Non-metallic gaskets
Metallic and semi metallic gaskets are made from metals and mixture of other fabric elements. This category of gaskets has a higher sealing of fluid tendency than the non-metallic gasket. Many Engineers and technicians prefer metallic gasket to non-metallic. This is because it is designed to resist extreme temperatures, harsh chemical reactions, and high pressure.
Some examples of metallic/semi-metallic gaskets are:
- Grooved gaskets
- Corrugated metal gaskets
- Ring joints
- Metal jacketed gaskets
- Spiral wound gaskets
In the composition of a non-metallic gasket, it has zero metal. Nonmetallic gasket refers to a gasket material, which is easily compressed under the load of the flange. These non-metallic gasket materials, which is also known as soft gaskets, can be selected from a wide range of elastomers, non-asbestos compressed, PTFE, flexible graphite, and high-temperature sheet products.
Non-metallic gaskets can also be used for different applications. Examples of where it is widely used are in car bonnets, pipe flanges, heat exchangers, and compressors. The absence of non-metallic elements present in non-metallic gasket makes it to be folded into sheet or rolls of different cut shapes.
Some examples of Non-Metallic Gaskets materials are:
- Ceramic Fiber
- Elastomeric and Fiber Sheet
- Biaxially Orientated (Filled) PTFE
- PTFE Joint Sealant
- Flexible Graphite Sheet
How the Finished Quality of Mating Surfaces Affects Gasket Choice
Gaskets are materials that make effective seal between two different surfaces, to create a static seal under compression. Sealing is a direct result of the compressive forces generated by sufficient load. And also works to fill the defects on the surfaces to be sealed.
During manufacturing of machine parts, if the mating surfaces were perfectly machined, there will be a minimal need for a gasket or, most times, no gaskets. In many practical instances, surfaces manufactured are not always perfect, hence, the need for a gasket.
Physical quality like porosity, chemical composition, and quality such as hardness of the materials also have a major impact on the exact type of your custom gasket.
Flange surface finish is a fundamental aspect of performance of any gasket. Types of gaskets such as Metallic/semi-metallic and non-metallic interact differently with flange surfaces. For optimum gasket performance with the lowest leakage, each of these gasket types requires specific surface finish ranges. Metallic gaskets, however, need a smoother finish to the flange than non-metallic.
Choosing a Suitable Material for Your Custom Gaskets
When choosing a category or type of gaskets to be used in a specific operation, it is important to take cognizance of the following factors:
- Load pressure
Temperature is perhaps, the most important factor in choosing the type of your custom gasket. If the operating temperatures of a system approach a maximum continuous operating temperature threshold for the gasket materials, then the next best material should be your next option.
When gaskets are not in proper alignment to temperature of where it is applied, the rate of the gasket failure is increased. There is a suitable gasket material that fit in best for a specific range of fluid or ambient temperature. One of the first considerations when choosing your custom gasket is knowing the maximum and minimum temperature.
The chemical composition of the contained fluid where your custom gasket would be used should determine which material your gasket must be made of. Factors such as pH level, oil or water composition, oxidation and corrosion quality, and more can destroy material composition of your custom gasket with regular or irregular exposure.
Gaskets also perform differently which is hinged on the pressure levels. Non-metallic gaskets, which makes a compressed seal at relatively low pressures necessary, cannot provide adequate resistance if the contained fluid is subject to much pressure. And this can make the fluid to force a path through the gasket seal.
Taking gaskets made of synthetic rubbers for example, they often have a capacity of about 60 psi for reliable performance. Metallic gaskets, on the other hand, have resistance to extreme pressures, especially when used in oil and gas processing plants.
In some applications, gaskets will naturally have a poorer distribution of load across the mating surface or may deteriorate with use. Some gaskets, by their nature, may become stretched over time which tends to reduce their load retention and drop the torque range of the connecting faces.
As a general rule, the thinnest possible gasket material should be selected for any application. The main factor for this is that thinner materials have a surface area that is less likely to fail when it acts on pressure.
Having said that, the choice of material thickness must also be taken into account the amount of compression required to absorb any flange distortion or misalignment. And this is particularly true when using a fiber-based gasket material.
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