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What is a Gasket-The Function of Gasket

A gasket is used to seal between the flange faces to prevent leakage under compression or corrosion. As the flanges are impossibly manufactured perfectly smooth, a gasket is needed to apply to provide the necessary seal. It is an ideal part to fill the deformities and connect two mating surfaces together.

Usually, flange gaskets are cut from sealing sheets such as rubber, metal, PTFE or graphite. While some other gaskets are made from metallic material with a non-metallic material to provide a functional seal, like a spiral wound gasket.

What applications a gasket is used for?

As one of the leading industrial gasket manufacturers in China, we produce gaskets that have a wide application. like cylinder head gasket, valve cover gasket, exhaust gasket, door gasket, car gasket, refrigerator gasket, toilet gasket, flexitallic gasket, oil gasket, engine gasket, liquid gasket, pump gasket and other names for gaskets that we are familiar with, is closely related to its application. Our mechanical gasket seals mainly used in the oil, gas and petrochemical industries, food & beverage, power generation, mining, military, aerospace, pharmaceutical, filtration, sanitary process industries, and nuclear installations, etc.
The gaskets are all manufactured from Ginseal gasket maker accordingly to ASME B16.20 and API or EN1514 or JIS standard. We also provide custom seals and gaskets service with free samples. As of the best China industrial gasket manufacturers, our gasket and sealing products have been exported to the USA, UK, Canada, Germany, Australia, Japan, and other more than 40 countries，obtained the trust and recognition of local customers.

How to choose a suitable gasket?

To get an adequate sealing, we need considering how to choose a suitable gasket from the best gasket manufacturers based on the below factors:

• Material Selection: Gasket material should be chosen to withstand a temperature/pressure range and the chemical properties of the fluid media under operation.
• Seating Stress: we must give a suitable pressure to seat the gasket correctly. The pressure should be limited in case of the crush of gaskets by excessive compression, at the same time the gaskets can fill the flange imperfections under the compression.
• Sealing Force: To avoid any leakage, there should be enough pressure on the sheet gasket to keep it in sufficient contact with the flange faces.
• Surface Finish: The flange finish surface should be compatible with the gasket, in this way the gaskets can provide a good seal.

What are the types of Gaskets?

Usually, our gasket manufacturing company provides gaskets in three types: metallic gasket, semi-metallic gasket or composite gasket, non-metallic gasket.

• Metallic Gasket:

Metal gaskets are manufactured from a metallic material such as soft steel, carbon steel, stainless steel, Monel, duplex stainless steel and Inconel. These gaskets are known as ring type joint gasket or ring joint gasket (RTJ).

RTJ Gasket is used in high-pressure class flanges as well as for the high-temperature environments. And high-tension bolting is required when using ring type joints.

RTJ Gasket is machined to fit in a groove on the flange to provide the seal function. Always API ring joint gaskets come in two basic types-oval and octagonal type, the octagonal type has a better sealing efficiency than the oval type as it’s a face to face sealing way. While only the oval type joints can be used for old type flanges.

Besides oval and octagonal types, there's also BX and RX ring joint gasket which is used in API 6BX and API 6B flanges and is designed for pressure up to 15000 psi. As for SRX and SBX type ring joints are used for sub-sea environment, and these types are with three vent holes with which any water trapped between a ring groove bottom and the sealing area of the gasket can escape to the equipment I.D. bore.

Usually, Ginseal also provides lens gaskets and IX rings.

Ring-type joints gaskets are manufactured according to ASME B16.20, API standards.

Custom gasket service is also available.

• Semi-metallic gasket or Composite gasket:

Semi-metallic gaskets are made up of metal material with a non-metallic material.Spiral wound gasket, kammprofile gasket, corrugated gasket, double jacketed gasket, and tanged graphite gaskets are known as semi-metallic gaskets.

• •  Spiral Wound Gasket: Its sealing element is comprising of a spiral wound V or W shaped stainless steel strip and non-metallic filler material in graphite, PTFE, asbestos-free, mica, ceramic. etc, Always has a outer ring or called center ring which can minimize the risk of material creep through over-tightening. For some critical applications, spiral wound gaskets are also required an inner ring to protect the windings from contamination and give the gasket a greater resistance to thermal shock. Some spiral wound gaskets with inner rings are also with bars that can be found in heat-exchangers, shell, channel, and cover-flange joints. Spiral wound gaskets without inner rings and outer rings are suitable for the tongue-and-groove flange.
  • Kammprofile Gasket: It is a solid metal ring with concentric grooves while a filler material, usually graphite and PTFE, is applied on both sides. It is much more expensive than spiral wound gaskets but provides better blowout resistance and easy to handle even in large diameters. Kammprofile gaskets are better for high-pressure environments.
  • Corrugated Gasket: it is made of a thin stainless steel tape compressed by a tool to form concentric corrugations and then non-metallic fillers like graphite, asbestos-free or PTFE will be applied on both sides. It cannot withstand much pressure compared to kammprofile gaskets.
  • Double Jacketed Gasket: it is also called as metal jacketed gaskets, and a soft material in graphite or asbestos or PTFE or ceramic will be enclosed in a thin stainless steel jacket. There are different ways to cover the non-metallic filler as well as different sizes and shapes. The gaskets are commonly used in heat exchangers and valves. It can be a replacement of the spiral wound gaskets without an inner and outer ring at a lower cost.
  • Tanged graphite gasket: The gaskets are cut from tanged graphite sheet which is a graphite sheet with a tanged stainless steel core. The core can be carbon steel, SS304, SS316, Duplex, Monel, Inconel, etc. It has good strength and creeps resistance, chemical stability, and high tightness as it combines excellent properties of flexible graphite and the strength of stainless steel. It is used in the chemical and petrochemical industry at high surface loads or high operating pressure. Commonly the gaskets are with inner and outer eyelets that enable the gaskets to withstand higher pressure.

 

• Non-metallic Gasket

Non-metallic gaskets are also called a soft cut gasket, and they are always cut from soft sheet material, for example, graphite, rubber, Teflon, PTFE, compressed non-asbestos fiber (CNAF). The gaskets can be provided for full-face or raised face types based on the finished flange face. Full face gaskets are suitable for flat face (FF) flanges while flat ring gaskets are suitable for raised faced (RF) flanges.

Soft flat gaskets are used with low-pressure flanges and in low temperature at the lowest cost compared with other sealing gaskets. There are rubber gaskets, non-asbestos gaskets (CNAF), Teflon gaskets, Graphite gaskets, PTFE envelope gaskets, etc.

With a full range of cutting capabilities including die cutting, waterjet cutting, laser cutting, and knife cutting, we Ginseal can provide different shapes of the flat gaskets.

• • Rubber Gasket: Rubber gaskets are always cut from rubber sheet or die-cut from rubber raw material. There usually is EPDM, Viton, Neoprene, Silicone, NBR, and the gaskets are with the properties of the corresponding rubber which is for low temperature and pressure. But it provides a high degree of deformation without permanent damage or loss of attributes.
  • Non-asbestos Gasket (CNAF): It is cut from compressed non-asbestos jointing sheet which contains fibers blended with suitable heat resistant binders and some rubber seals. They are used for a higher temperature environment compared to the rubber gasket. Asbestos-free gaskets are a replacement of asbestos gasket as asbestos is harmful to human and forbidden to be used in industries.
  • PTFE Gasket: It is a circle cut or die-cut type gasket sealer, and it has excellent chemical resistance, electrical property. PTFE gaskets are used in the presence of aggressive chemicals such as acids and alkali by offering non-corrosive, non-wetting, non-contaminating function. The gaskets can be used for the environment of the temperature from -200℃~+260℃ and also can be used for the medical and food industries.
  • Graphite Gasket: The gaskets are also cut from pure flexible graphite sheets and good for high-temperature applications. The pure graphite gasket has excellent resistance to corrosive chemicals, high temperatures, and high pressures, as well as perfect thermal conductivity. They can be used in a variety of industries such as refineries, chemical and petrochemical plants, paper mills mines and other fields.
  • PTFE Envelope Gasket: The gasket is made up of a ring gasket with usually 2mm thick and a thin PTFE envelope with 0.5mm thick leaves. The ring gasket’s material is always in rubber or non-asbestos, and the PTFE envelope is commonly supplied in slit or milled or U-shape types. The PTFE envelope can protect the ring gasket by giving good chemical resistance. In this way, the gasket is ideal for use in equipment employing flanges made from alloy, standard steel, glass-lined, plastic, ceramic, conical-end pipe, etc.

How to choose gasket material?

To know how to choose a suitable gasket material from the top gasket manufacturers, we should learn about the properties of different raw materials.

• Metallic Material
  • Carbon Steel: Recommended max. the temperature should be 538℃especially there’s an oxidizing environment. The carbon steel gasket’s hardness is 120BHN and is not good for the equipment of hot water.
  •  S304 &. S304L: Recommended max. temperature is 760℃. With lower carbon content, S304L has better resistance to corrosion.
  •  S316 &. S316L: Recommended max, working temperature range is 760℃~815℃. It is a good material to acid and alkali
  • Inconel: The material has better resistance to acid and alkali, as well as excellent resistance to heat. Good for the high-temperature environment.
• Non-metallic Material
  • Neoprene Rubber (CR): It is a composite rubber material and suitable for the environment of moderate acid and alkali and it has good resistance to commercial oil and fuel. The recommended working temperature is -51℃~121℃.
  • Viton Rubber: It has excellent heat and good physical and chemical properties as well as low deformation rate, good resilience, and long working life. The recommended working temperature is -40℃~232℃.
  •  NBR: The recommended working temperature is -51℃~121℃.
  • Silicon: It has outstanding resistance to low and high temperature, and can work at 150℃ for a long time without any property changes. And it can work at 200℃ for 10000 hours. The recommended working temperature is -70～260℃.
  • Graphite: It contains no resins or inorganic fillers and has excellent resistance to corrosion against a wide variety of acids, alkalis and salt solutions, organic compounds, heat transfer fluids, even at high temperatures.
  • PTFE: PTFE has the most advantages of all plastic material and provides excellent thermal insulation with an operating temperature range of -200℃~+260℃.

   

 How to install a gasket?

1. Proper gasket installation and correct gasket seal bolting patterns ensure the gasket’s sealability.
2. Make sure the sealing face of gaskets and flange face is clean without any scratches, bots.
3. Center the gasket on the flange.
4. Tighten the bolts to compress the gasket, but be careful the pressure should not exceed the designed one in case of any loss of resilience force under higher compression.
5. Use a torque wrench, well-lubricated fasteners, and hardened flat washers to ensure correct initial loading.
6. All bolts should be tightened in one-third increments, according to proper bolting patterns.
7. Make a final check pass at the target torque value moving consecutively from bolt to bolt.
8. Re-torque 12 to 24 hours after initial installation.
9. Never use liquid-based or metallic-based anti-stick or lubricating compounds on the gaskets.

What to do when there’s gasket failure?

• Temperature &. Pressure incompatible with the gasket
• Chemical attack
• Wrong dimensions of the gasket
• The surface finish of flanges is incompatible with the gasket
• Flange material is not right with the gasket
• Wrong gasket assembly