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Types and functions of gaskets

Types and functions of gaskets

There are many kinds of gaskets, which can be divided into three categories: non-metal, semi-metal and metal gaskets.

Non-metallic gaskets

(1) Non-metallic gaskets.

Non-metallic gaskets are soft, corrosion-resistant and cheap, but have poor temperature and pressure resistance. It is mostly used for flange sealing of medium and low pressure vessels or pipes at room temperature and medium temperature.

Non-metallic gaskets include rubber pads, asbestos pads, asbestos rubber pads, flexible graphite pads and polytetrafluoroethylene pads.

① Rubber board.

The main materials for making rubber plate gaskets are natural rubber, nitrile rubber, chloroprene rubber, etc. In addition, special rubber such as fluorine rubber has also begun to be used. Rubber is widely used in the sealing of containers and pipelines because of its compact structure, soft texture, good resilience, easy shearing into various shapes, low cost and easy to buy. However, it is not resistant to high pressure, easy to dissolve and expand in mineral oil and not corrode, and easy to aging and losing resilience at high temperature.

② Asbestos.

Asbestos materials are wet asbestos and blue asbestos. Wet asbestos has good heat resistance, alkali resistance, high tensile strength and poor acid resistance. Most asbestos rubber boards are made from it. Blue asbestos is not only good in heat resistance, but also good in acid resistance, so it is mostly used to make acid-resistant asbestos rubber boards. The normal service temperature of asbestos board is below 550 degrees. Large diameter low pressure vessels can use asbestos tape or asbestos rope. When asbestos rope is used, water glass is usually impregnated. Such gaskets can also be used in medium such as acid and alkali solvents.

③ Asbestos rubber sheet.

Asbestos rubber sheet is made by pressing asbestos, rubber and fillers. General asbestos fibers account for 60% – 85%. According to its mixing technology, performance and use, there are mainly high-pressure asbestos rubber sheet, medium and low-pressure asbestos rubber sheet and oil-resistant asbestos rubber sheet.

Asbestos rubber sheet has suitable strength, elasticity, flexibility and other properties. It is convenient and cheap to make gaskets with asbestos rubber sheet. Therefore, it has been rapidly promoted and applied in chemical enterprises.

④ Flexible graphite.

Flexible graphite is a novel sealing material with good resilience, softness and temperature resistance, which has been rapidly promoted and applied in chemical enterprises.

⑤ Polytetrafluoroethylene (PTFE).

Polytetrafluoroethylene (PTFE) is known as the “king of plastics” because of its superiority in chemical resistance, heat resistance, cold resistance and oil resistance. It is not easy to aging, does not burn, and absorbs almost zero water. Its compact structure, non-polar molecular structure, as a gasket, the contact surface can be smooth, non-stick to the metal flange. In addition to being eroded by molten alkali metals and fluorine-containing gases, it can resist the corrosion of various acid, alkali, salt and grease solution media.

Polytetrafluoroethylene gaskets include pure polytetrafluoroethylene, filled polytetrafluoroethylene or expanded polytetrafluoroethylene.

Semi-metallic gaskets (also known as metal composite gaskets)

(2) Semi-metallic gaskets (also known as metal composite gaskets).

Nonmetallic materials have many advantages, such as good flexibility, compressibility and low bolt loading capacity. But its main determination is that the strength is not high, the resilience is poor, and it is not suitable for high pressure and high temperature occasions. So the bonded metal material has high strength and good resilience. Characteristic of withstanding high temperature. A gasket which combines the two structures is formed. It is a semi-metallic gasket.

(3) Metallic gaskets.

Octagonal Ring Joint Gaskets

> Ring Joint Gaskets are for oilfield and process industry duties.

> Octagonal shape gasket is belong to API 6A R series 

> These gaskets are used in pressures up to 10,000 PSI, more than Oval ring joint.

> The oval type is the only gasket that will fit a bottom radiused groove.

> Gaskets and not re-used after torque.

Octagonal Ring Joint Gasket was initially developed for high pressure and temperature applications found in the petroleum industry and is primarily used in the oil field on drilling and completion equipments. However, today this product range can also be found on valves and pipework assemblies, along with some high integrity pressure vessel joints.

> Ring Joint Gaskets are for oilfield and process industry duties.

> Oval shape gasket is belong to API 6A R series 

> These gaskets are used in pressures up to 10,000 PSI.

> The oval type is the only gasket that will fit a bottom radiused groove.

> Gaskets and not re-used after torque.

Oval Ring Joint Gasket was initially developed for high pressure and temperature applications found in the petroleum industry and is primarily used in the oil field on drilling and completion equipments. However, today this product range can also be found on valves and pipework assemblies, along with some high integrity pressure vessel joints.

Spiral Wound Gaskets

Spiral Wound Gasket can be made from a large selection of alloys and filler materials in a variety of shapes and sizes.

Yaang also provide non-round spiral wound gaskets, manhole and handhole spiral wound, and just inner & outer rings for SWG.

The Spiral Wound Gaskets is suitable for flange, valve, pump, heat exchange etc.

Corrugated/Serrated Gaskets

Corrugated/Serrated Gaskets, for ASME standard corrugated gasket.

The CMG gaskets is punched by moulds, the tolerance is strictly control.

Corrugated Metal Gasket are known as Graphonic Gaskets.

Corrugated metal gasket is widely used for pipe flange, pump, valve joint.

We supply the complete corrugated gaskets, and metal core only.

What is the role of gaskets?

  • 1. Prevent the use of spring pads in the process of screw disassembly from causing damage to the object. In the process of using, we can first make the flat cushion and the object closely connected, and then use the spring cushion outside, so that we can prevent the damage caused by the spring cushion to the object, also can play the effect of the spring cushion, and also can make the stress area more balanced. When used in this way, the spring pad can also prevent damage to the connected objects.
  • 2. It can increase the contact area. Generally, the contact area between the screw and the object is relatively small, so the force acting on the screw will be relatively small and easy to loosen. In order to make the screw more firmly lock the object, gaskets will be used to increase the contact area between the screw and the connected object.
  • 3. It can be used in some special cases. For example, if there are no threads, then we can use gaskets, and when our screw is too long, if we want to be beautiful, then we use gaskets, which can make the screw look more beautiful.
  • 4. Increase friction. In the process of using high-strength bolts, they are fixed by friction. In order to increase the friction between high-strength bolts and objects, the use of gaskets can effectively solve this problem.

Source: China Stainless Steel Gaskets Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)

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