How to identify and choose flange gaskets?- part two

Last article we learned about some flange gaskets,today let me tell you other flange gaskets.(How to identify and choose flange gaskets-part one)

Metal jacketed gasket

A metal jacketed gasket is a composite gasket composed of a non-metallic material as the core material and cut into the desired shape, and the outer is composed of a metal thin plate having a thickness of 0.25 mm to 0.5 mm. According to the state of the jacket, it is generally divided into two types: flat type and corrugated type. This kind of gasket is also called flexible graphite metal reinforced composite gasket. It is a kind of sealing gasket which is made of composite metal plate or punched metal core plate and flexible graphite particles, and usually reinforced by flexible graphite composite. Flexible graphite metal reinforced composite gaskets can be made with stainless steel or carbon steel as needed.

ASME B16.20 S304 ring type joint gasket

ASME B16.20 S304 ring type joint gasket

The main features of metal jacketed gaskets are good resistance to high and low temperature, corrosion resistance, radiation resistance, high strength, and able to be used under high pressure conditions. The required pre-tightening force is smaller than using metal gaskets or metal wound gaskets. Due to the plasticity and good filling properties of flexible graphite, the use of such a gasket does not require precision machining of the matching flange sealing surface, and the “waterline” groove on the flange sealing surface can also be adapted, so it is relatively economical to use. The flexible graphite composite gasket type can be divided into raised face (RF) type, male and female (MFM) type, and tongue and groove face (TG) type, which are suitable for the corresponding flanges. The RF type gasket can be covered with stainless steel or carbon steel as needed, i.e. RF-E type.

Corrugated metal composite gasket

A corrugated metal composite gasket made of flexible graphite is a composite gasket coated with flexible graphite on both sides of a machined corrugated metal sheet. The gasket has both metal strength and the feature of corrugated elasticity. The highest working temperature is 650 °C, and the highest pressure can reach 26MPa. Flexible graphite corrugated metal composite gaskets are divided into three types according to their structure: basic type, type with locating ring, and type with spacer.

Metal ring joint gasket

The metal ring joint gasket is made of a metal material into a solid metal gasket with an octagonal or elliptical cross section, and has a radial self-tightening seal. Therefore, the metal ring gasket is in contact with the inner and outer sides (mainly the outer side) of the flanged trough and is sealed by pressing. The octagonal ring pad is matched with the flange groove and is mainly in the form of surface contact. Compared with the elliptical ring pad, although it is not easy to be in close contact with the flange groove, it can be used repeatedly, and because the cross section is straight, it is easy to process. The elliptical ring pad is in line contact with the flange groove, and the sealing property is good, but the processing precision is high, thereby increasing the manufacturing cost, and the elliptical ring pad cannot be reused.

Grooved metal gasket

A grooved metal gasket is a solid gasket, and the cut surface of the gasket is sawtooth. (the tooth pitch=1.5 – 2mm, the tooth height=0.65 – 0.85mm, and the tooth tip width=0.2 – 0.3mm) A number of concentric circles are lathed on the sealing surface, and the number is 7 to 16, depending on the size of the gasket.

The structure of the grooved metal gasket can be divided into basic type, type with an outer ring, type with an inner ring type, and type with inner and outer rings. Since the V-shaped ribs of the grooved metal gasket sealing surface contact area form a lot of spatial line contact with a pressure difference, the gasket’s sealing performance is reliable and its service life is long. Compared to general metal gaskets, such gaskets require less pressing force. The disadvantage is that the two flange sealing surfaces are processed each time the gasket is replaced, which is time consuming and labor intensive. In addition, the gasket is easy to leave an indentation on the flange sealing surface after use, so it is generally used for less disassembled parts.

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