The condition and type of seals used to prevent leakage or substances from entering the system.

The problem of fluid leakage in equipment such as the one shown above is one of great importance in various manufacturing industries, refineries and chemical plants where continuous processes and reactions must take place, as well as in large-scale transport and mobility such as ships and the aviation and aerospace industries. One of the most famous industrial accidents involving packaging was the tragic explosion of the US space shuttle Challenger on 28 January 1986, with seven crew members on board, 73 seconds after launch, caused by a faulty o-ring that killed all of all crews. It is a major accident that we should never forget.

In order to prevent leakage, packing and seals are one of the most important aspects of the equipment. But how are they classified and what are their characteristics?

"Seals keep internal fluids sealed and protect internal systems from external environmental conditions."

Since the surfaces of two solids using a gasket such as a gasket cannot have a perfect surface condition due to manufacturing and storage, if a seal such as a gasket does not exist between the two joints, high fluid pressure will obviously leak through the small gap that lacks airtightness.

The same is true for reciprocating and rotating machinery and rotating devices that move, and rotating bodies and fixtures with internal working fluids will have some gaps for assembly and movement, so packing materials are essential to solve this problem because it is a fundamental environment for internal fluid to leak through these gaps.

"Sealing type - Static (fixed) and Dynamic (kinetic)"

Seals, which are sealing devices, are divided into two types: fixed and movable seals, and representative types of seals used are gaskets used for piping flanges, while movable seals are mechanical seals used in fluid devices such as pumps. In addition, gland packing, which was used before mechanical seals, O-ring, which is used in small valves and reciprocating cylinders, and oil seal, which is used in various hydraulic machines, can be classified. Labyrinth seals, which are used in ultra-high pressure sealing devices such as compressors, are also one of the sealing devices you should know about. We recommend that you refer to the table below for information on the classification and scope of use of each type of seal.

While we don't know the characteristics of every seal product, we'll discuss the most common ones: oil seals, o-rings, mechanical seals, and gaskets. We'll discuss what devices each seal is used in and what you should be aware of when using them.

"Sealing Type - About the characteristics of each type"

1. Oil Seal

Oil seals are sealing products that comply with two international standards, ISO 6194 and DIN 3760, and are used for sealing applications with small hydraulic pressures. They are small in size and have a very simple and intuitive design, consisting of a lip that prevents dust from entering the seal and a main seal that performs the actual sealing. The most common applications for oil seals are hubs or housings where the housing meets the shaft. Due to their low pressure resistance, they are not used in fluidic devices where high pressure is generated.

2. O Ring

O-rings are the most basic and simple doughnut (O) shaped seals, and are classified into two types: movable o-rings, which are used on pistons, and stationary o-rings, which are deformed by internal or external pressure and used on fixed objects. O-rings are classified into several standards depending on the inner diameter and thickness of the O-ring, such as AS-568, which was the product directly at issue in the Challenger accident described above.

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?3. Mechanical Seal

A mechanical seal is a mechanical element responsible for the sealing function used in industrial high-pressure rotating machinery, mainly where the rotating surface and the stationary surface meet, and is an essential sealing element used in conditions where rotating machinery must not leak, and in fluid equipment that handles high-pressure fluids.

In terms of structural features, it is divided into stationary and rotating parts, and the actual fluid sealing mechanism is formed on the surface where these two parts meet, and the gap between the contact surfaces (perturbation surface) is compensated or reduced by the tension of the spring.

Industries that use mechanical seals include manufacturing, food, power generation (nuclear power), refining & chemicals, defence & aviation, etc.

API-682 describes mechanical seals, and ISO-21049 is also a standard worth referring to.

?4. Gasket

A gasket is a sealing device that is used between two parts that do not require movement, i.e. it seals the gap between two stationary bodies. It is a sealing element that can be found in component housings, valves and flanges, and can be found in any factory, ship or building where piping systems.

Gaskets are used in pressure ranges from as little as 10 bar to over 300 bar, and the materials and features of gaskets can vary depending on the environmental conditions, such as high temperatures or strong acids. ASME B 16.2 is the main technical reference for gaskets, and as they are often used in conjunction with bolts and flanges, the bolting force and process can have a significant impact on the reliability and life expectancy of the gasket.

Conclusion

When it comes to mechanical equipment and devices that use fluids, Sealing is crucial. There have been many cases of explosions, fires, poisoning and hazardous chemical accidents due to leakage in each industry. In process and elevated facilities where there is a risk of leakage, such as hydraulics, internal and external combustion engines, chemical facilities, power generation facilities, and building facilities, it is necessary to be familiar with the contents of fluid tightness and to be able to distinguish and identify each sealing. When replacing or reusing seals, it is necessary to carefully check and verify that the actual seals used are within the pressure range, the correct material, and the correct dimensions.