Differences and Characteristics of Familiar Sealing Parts
The sealing parts, such as gaskets and O-rings are supporting the daily use of our machine and equipments behind the scene.
There are various kinds of sealing parts for stainless steel equipment. So, what is the difference between all of them? In this article, we tried to introduce and explain the sealing parts which are commonly used, and also their characteristics and performance.
What you will learn in this article
・What is a “sealing part”?
・What is the difference between a gasket, seal, and O-ring?
・What are the different materials used for seals?
・What is the key to selecting the best seal material?
What is a "sealing part"?
A sealing part is a part (material) that prevents
the leakage of contents and the intrusion of foreign substances into the
container.
They are used in a wide range of fields
including our stainless steel containers, machinery, piping, and equipment
connections.
We don't see many of these parts in our
daily lives, but they are actually very familiar to us, such as in automobiles,
household equipment, and tap water faucets/piping.
Types of Sealing Parts
The most commonly used sealing parts are “gaskets”, “seals” and “O-rings”.
However, the same part may be called “gasket” and “seal” in two different ways.
Why are they called differently? In fact, there is a good reason for this categorization.
Gasket: Fixed, Non-moving Sealing Part
Gaskets are used to seal connections (static parts) between parts and pipes, and are available in various shapes, thicknesses, and materials to suit the connection.
Gaskets are placed between connections and fixed with bolts, etc., to seal the gaps between the connections, thereby preventing leakage of fluid or foreign substances from entering.
In order to prevent leakage and deterioration of the gasket, it is necessary to select a gasket that is compatible with the operating environment and the properties of the fluid.
Example of a flange gasket
Gasket between flange connections
Example of a flange
Other Gaskets
Thread Seal tape
This is a tape-type gasket made of PTFE material, which has excellent heat and chemical resistance.
When installing screws or valves, wrap with this tape around the threads (screw the tape in).
Liquid Gasket
Liquid gaskets do not require thickness calculation compared to general solid gaskets.
You can select the most suitable material for the application environment, such as the condition of the surface and the nature of the liquid.
Seal: Unfixed, movable sealing part
(*In NITTO KINZOKU KOGYO, we usually use the term “gasket-seal” or “gasket” to refer to those “seals” used in our containers.)
A “seal” is used to seal or protect parts that are repeatedly attached and detached, or that are subjected to rotation or reciprocating motion, and there are many different types depending on the part to be attached and the purpose.
In Japan, among seals, those are in contact with the moving part are called “contact seals”, such as oil seals for mechanical parts and gland packing seals for pump parts are also classified as “contact seals”.
**In Japan, the more familiar term for the word Seal is “Packing”(Japanese: パッキン). Knowing this may help you in better communication.
Example of Seal on a Stainless Steel Container (Type A Gasket Seal)
Three major advantages of colored seal gasket
Stainless steel airtight container with colored seal gasket
Measures against contamination
Even if the gasket seal's fragments get mixed in with contents, they can be easily detected because of their color.
Control of contents
The color of the gasket seal can be changed according to the type of contents and time of year.
Can be used as exclusive gasket seal for special contents
The color of the gasket seal can be changed according to the type of contents and time of year.
O-ring: Sealing part used as both a gasket and a seal.
O-rings are mainly installed in the grooves of parts.
O-rings are circular in cross-section and feature a self-sealing action that seals fluids using as atmospheric or hydraulic pressure.
O-rings are used in both fixed and motion applications, and are installed in stainless steel containers, such as pressure vessels.
They are also used in common faucets, so you may have the experience of replacing an O-ring when your tap water faucet was leaking.
The most common material is NBR (nitrile rubber), but the most suitable material for the operating environment and fluid can be selected.
Top: Example of O-ring
Lower: Section
Example of a pressure vessel
How O-rings work
(1) Set the O-ring in the groove.
2) The repulsive force of the O-ring seals the fluid inside.
(3) The pressure of the fluid pushes the O-ring against the groove, and the O-ring seals better.
Materials of Sealing Parts
Here are some of the materials (rubber and resin) used as sealing parts.
For those who needs to select the best sealing material for the chemicals:
Silicone rubber (Name in NITTO KINZOKU: Silicone)
Silicone rubber is a rubber-like material made of silicone resin, which is semi-transparent and can be colored in various ways.
In addition to sealing materials, silicone rubber is also used in a wide range of other fields such as anti-vibration rubber, molds for confectionery, electrical insulation and artificial heart lung membranes.
◆ Characteristics ◆ Weather resistance, aging resistance, high cold resistance
Fluorocarbon Rubber
Fluorocarbon rubber is a synthetic resin made by polymerizing fluorine-containing olefins. It is used for the seal of rockets, pump parts, tubes, and hoses.
This material has excellent physical properties, including the highest heat resistance.
Polychloroprene Rubber
Polychloroprene rubber is a synthetic rubber produced by the polymerization of chloroprene.
Compared to natural rubber, it has excellent weather resistance, oil resistance, and chemical resistance. It is also used for wet suits and belt conveyors because it is easy to process.
◆Characteristics ◆Average physical properties, chemical resistance, etc.
Nitrile Butadiene Rubber (NBR)
A type of synthetic rubber with excellent tensile strength and abrasion resistance.
It is also used for industrial goods such as automobiles and rubber gloves.
◆Characteristics ◆Chemical resistance, abrasion resistance, aging resistance
EPT-EPM=Ethylene-Propylene copolymer rubber / EPDM=Ethylene propylene-diene rubber
EPT is a type of synthetic rubber with excellent ozone resistance and electrical insulation properties.
It is used as an insulating material for electric wires, etc., as well as for playground equipment and ground in parks.
Characteristics ◆ Ozone resistance, resistance to polar liquids and electrical properties, weather resistance
PTFE -Polytetrafluoroethylene Plastics
PTFE is a fluoropolymer consisting of only fluorine and carbon atoms, and is chemically stable.
It has excellent chemical resistance and is the substance with the least friction (slippery). It is used for industrial products, fluorine coating of frying pans, and the roofs of stadiums.
◆ Characteristics ◆ Superior to other materials in terms of non-adhesiveness, non-wetting, heat resistance, chemical resistance, etc.
Other
Electric Conductive Silicone Rubber
This is a kind of synthetic rubber made by blending silicone with electric conductive materials. Compared to other conductive rubbers, it is superior in weather resistance, heat resistance, and cold resistance, and can be used in fields that require a cleaner environment.
Other materials
Conductive fluoroelastomer, butyl rubber, urethane rubber, acrylic rubber, and natural rubber are available.
How to select the material
It is important to select a material that is suitable for the operating environment and the substances it will come into contact with.
Therefore, it is important to select a material that is suitable for the operating environment and the substances that will come into contact with it. In addition, depending on the place of use, the material must be compliant with the Food Sanitation Law.
Food Sanitation Law of Japan
The Food Sanitation Law is a law aimed at preventing the occurrence of sanitary hazards caused by eating and drinking, improving public hygiene, and protecting health. It stipulates conformity standards not only for food and beverage products, but also for a wide range of food-related items such as machinery, containers, packaging, and labeling.
Select by characteristics
We select materials based on their properties. We recommend to select the most suitable material based on various characteristics such as physical properties, oil resistance, solvent resistance, and chemical resistance.
Gasket characteristics table
Test and Select
If you want to check the resistance of sealing parts or the influence of chemicals, you can test them with samples.
Examples of tests
Soak the sealing parts in a sample of the chemicals they will come into contact with, and then reproduce the same operating environment, etc.
Tips for Selecting Sealing Parts
・ Is it the most suitable shape for the purpose of use(standard product or custom-made)?
・Is the material compatible with the substance it will come in contact with (chemical resistance, etc.)?
・Is the material suitable for the operating environment?
We offer the most suitable sealing parts for stainless steel containers.
If you have any questions or concerns, such as “I don't know which shape or material is the most suitable” or “I want to order custom-made parts for my container,” please feel free to contact us! We will provide you with a free quote for the cost of production.