What is an O-ring

What is an O-ring?

O-rings is a kind of rubber sealing ring with circular section. Because its section is O-type, it is called O-type rubber sealing ring, also known as O-ring. It began to appear in the mid-19th century, when it was used as the sealing element of steam engine cylinder.
Because of its low price, simple manufacture, reliable function and simple installation requirements, O-ring is the most common mechanical design for sealing. The O-ring is subjected to a pressure of tens of megapascals (kilopounds). O-rings can be used in static applications or in dynamic applications with relative motion between components, such as rotating pump shafts and hydraulic cylinder pistons.

20210916215404 19552 - What is an O-ring

Specification and standard of O-ring

The specifications and models of O-rings mainly include uhso-ring, uhp-ring, uno-ring, dho-ring, piston rod O-ring, high temperature resistant O-ring, high pressure resistant O-ring, corrosion-resistant O-ring and wear-resistant O-ring.
The standards of O-ring mainly include national standard GB 1235-76 and national standard gb3452.1-92; Japanese standard P type, G type, s type, SS/V type, F type; American Standard as568, British standard series; European standard series
The technical requirements of O-ring include appearance requirements, size requirements and material physical performance requirements.

  • Appearance requirements shall comply with GB/T3452.2-2007;
  • Material requirements shall comply with HG/T2579-2008;
  • Dimension requirements shall comply with GB/T3452.1-2005.

Application introduction of O-ring

YX O-ring for hole

Application: used for sealing piston in reciprocating hydraulic cylinder. Scope of application: TPU: general hydraulic cylinder, general equipment hydraulic cylinder. CPU: hydraulic cylinder for construction machinery and oil cylinder for high temperature and high pressure. Material: Polyurethane TPU, CPU, rubber.
Product hardness: HS85 ± 2 ° a working temperature: TPU: – 40 ~ + 80 ℃, CPU: – 40 ~ + 120 ℃, working pressure: ≤ 32Mpa, working medium: hydraulic oil and emulsion.

Retaining O-ring for YX hole

Product application: this standard is applicable to use with YX type sealing ring when the working pressure of oil cylinder is greater than 16MPa, or to protect the sealing ring when the oil cylinder is eccentrically stressed. Working temperature: – 40 ~ + 100 degrees. Working medium: hydraulic oil, emulsion and aquatic products hardness: HS 92 ± 5A material: polytetrafluoroethylene.

YX type O-ring for shaft

Application: used for sealing piston rod in reciprocating hydraulic cylinder. Scope of application: TPU: general hydraulic cylinder and general equipment hydraulic cylinder. CPU: hydraulic cylinder for construction machinery and oil cylinder for high temperature and high pressure. Material: Polyurethane TPU, CPU, rubber product hardness: HS85 ± 2 ° a working temperature: TPU: – 40 ~ + 80 ℃, CPU: – 40 ~ + 120 ℃, working pressure: ≤ 32Mpa, working medium: hydraulic oil and emulsion.
The O-ring has excellent sealing performance and high service life. The service life of dynamic pressure seal is 5-10 times higher than that of conventional rubber seal products, up to dozens of times. Under some conditions, it can have the same service life as the sealing matrix.
The friction resistance of O-ring is small, and the dynamic and static friction are equal, which is 1/2-1/4 of the friction of “0” rubber ring, which can eliminate the “crawling” phenomenon of movement at low speed and low pressure.
The O-ring is highly wear-resistant and has the function of automatic elastic compensation after the sealing surface is worn.
O-ring has good self-lubricating performance. It can be used as oil-free lubrication seal.
The O-ring has simple structure and convenient installation.
O-ring working pressure: 0-300mpa; Working speed: ≤ 15m/S; Operating temperature: – 55-250 degrees.
Applicable media of O-ring: hydraulic oil, gas, water, mud, crude oil, emulsion, water glycol, acid.

Application scope of O-ring

The O-ring is suitable to be installed on various mechanical equipment to seal at the specified temperature, pressure and different liquid and gas media in the static or moving state. Various types of sealing elements are widely used in machine tools, ships, automobiles, aerospace equipment, metallurgical machinery, chemical machinery, engineering machinery, construction machinery, mining machinery, petroleum machinery, plastic machinery, agricultural machinery, and various instruments and meters. O-ring is mainly used for static seal and reciprocating seal. When used for rotary motion sealing, it is limited to low-speed rotary sealing device. The O-ring is generally installed in the groove with rectangular section on the outer circle or inner circle to seal. The O-ring still plays a good role in sealing and shock absorption in the environment of oil resistance, acid-base, wear, chemical erosion and so on. Therefore, O-ring is the most widely used seal in hydraulic and pneumatic transmission system.

Advantages of O-rings

Compared with other types of sealing rings, O-ring has the following advantages:

  • Suitable for a variety of sealing forms: static sealing and dynamic sealing.
  • Suitable for various purposes, materials, sizes and grooves have been standardized and have strong interchangeability.
  • It is suitable for a variety of motion modes: rotary motion, axial reciprocating motion or combined motion (such as rotary reciprocating combined motion).
  • Suitable for a variety of different sealing media: oil, water, gas, chemical media or other mixed media.
  • By selecting appropriate rubber materials and appropriate formula design, it can effectively seal oil, water, air, gas and various chemical media. The temperature range is wide (- 60 ℃ ~ + 220 ℃), and the pressure can reach 1500kg/cm2 (used together with the reinforcing ring).
  • The utility model has the advantages of simple design, compact structure and convenient assembly and disassembly.
  • The section structure of O-ring is extremely simple, and has self sealing effect and reliable sealing performance.
  • Because the structure of the O-ring itself and the installation part are extremely simple and standardized, it is very easy to install and replace.

There are many kinds of materials:

  • It can be selected according to different fluids: nitrile rubber (NBR), fluororubber (FKM), silicone rubber (VMQ), ethylene propylene rubber (EPDM), neoprene (CR), butyl rubber (BU), polytetrafluoroethylene (PTFE), natural rubber (NR), etc.
  • Low cost.
  • The dynamic friction resistance is relatively small.

Classification and comparison of O-ring materials and their advantages and disadvantages:
1. Natural Rubber NR
Natural rubber is made of latex collected from rubber trees and is a polymer of isoprene. It has good wear resistance, high elasticity, tensile strength and elongation. It is easy to age in the air and become sticky in case of heat. It is easy to expand and dissolve in mineral oil or gasoline. It is alkali resistant but not strong acid resistant. It is the raw material for making tape, hose and rubber shoes, and is suitable for making shock-absorbing parts and products used in automotive brake oil, ethanol and other liquids with hydroxyl.
2. Styrene butadiene rubber SBR
(styrene butadiene copolymer) the copolymer of butadiene and styrene has uniform quality and less foreign matters compared with natural rubber, but its mechanical strength is weak. It can be mixed with natural rubber.
(1) Advantages:

  • low cost non oil resistant materials.
  • good water resistance, hardness below 70 and good elasticity.
  • poor compression skew at high hardness.
  • most neutral chemicals and dry and nourishing organic ketones can be used.

(2) Disadvantages:

  • it is not recommended to use strong acids, ozone, oils, oil esters, fats and most hydrocarbons.
  • widely used in tire industry, shoe industry, cloth industry and conveyor belt industry.

3. Butyl rubber IIR
(butyl rubber) is formed by polymerization of isobutene and a small amount of isoprene. A small amount of unsaturated groups are retained for sulfur addition. Because methyl has less three-dimensional barrier molecules than other polymers, it has less gas permeability, high resistance to heat, sunlight and ozone, and good electrical insulation; It has great resistance to polar solvents such as alcohol, ketone and ester, and the general service temperature range is – 54 ~ 110 ℃.
(1) Advantages:

  • impermeable to most general gases.
  • good resistance to sunlight and ozone.
  • may be exposed to animal or vegetable oils or oxidizable chemicals.

(2) Disadvantages:

  • it is not recommended to use it together with petroleum solvent, gum, kerosene and aromatic hydrogen.
  • used to make rubber parts resistant to chemicals and vacuum equipment.

4. Hydrogenated nitrile rubber HNBR
Hydrogenate nitrile rubber is a kind of nitrile rubber. After hydrogenation, some double chains are removed. After hydrogenation, its temperature resistance and weather resistance are much higher than that of ordinary nitrile rubber, and its oil resistance is similar to that of ordinary nitrile rubber. The general operating temperature range is – 25 ~ 150 ℃.
(1) Advantages:

  • butyl eye glue has better wear resistance.
  • excellent corrosion resistance, tensile resistance, tear resistance and compression skew.
  • good resistance to ozone, sunlight and other atmospheric conditions.
  • generally, it is suitable for washing clothes or dishes.

(2) Disadvantages:

  • it is not recommended to use in alcohol, ester or aromatic solutions.
  • air conditioning refrigeration industry, which is widely used as seals in environment-friendly refrigerant R134a system.
  • automotive engine system seals.

5. Ethylene propylene rubber EPDM
Ethylene propylene rubber is formed by copolymerization of ethylene and propylene. The main chain is not double chain, so it has excellent heat resistance, aging resistance, ozone resistance and stability, but sulfur cannot be added. In order to solve this problem, a small amount of the third component with double chain is introduced into the EP main chain, and sulfur can be added to form EPDM. Generally, the service temperature range is – 50 ~ 150 ℃. Excellent resistance to polar solvents such as alcohol, ketone, ethylene glycol and phospholipid hydraulic oil.
(1) Advantages:

  • good weather resistance and ozone resistance.
  • excellent water resistance and chemical resistance.
  • alcohols and ketones can be used.
  • high temperature vapor resistance and good impermeability to gas.

(2) Disadvantages:

  • not recommended for food use or exposure to aromatic hydrogen.
  • seals for high temperature steam environment.
  • sanitary equipment seals or parts.
  • rubber parts in the braking (braking) system.
  • seals in radiators (car water tanks).

Picture 6. Butyl rubber NBR
(nitrole rubber) is formed by copolymerization of acrylonitrile and butadiene. The content of acrylonitrile ranges from 18% ~ 50%. The higher the content of acrylonitrile, the better the resistance to petrochemical oil hydrocarbon fuel oil, but the low-temperature performance becomes worse. Generally, the service temperature range is – 25 ~ 100 ℃. Nitrile rubber is one of the most commonly used rubber for oil seals and O-rings.
(1) Advantages:

  • good resistance to oil, water, solvent and high pressure oil.
  • good compression deflection, anti-wear and elongation.

(2) Disadvantages:
not suitable for use in polar solvents such as ketones, ozone, nitrohydrocarbons, MEK and chloroform.
it is used to make fuel tank, lubricating oil tank and rubber parts used in fluid media such as petroleum hydraulic oil, gasoline, water, silicone grease, silicone oil, diester lubricating oil and glycol hydraulic oil, especially sealing parts. It can be said that it is the most widely used and lowest cost rubber seal at present.
7. Chloroprene rubber Cr
(neoprene and polychloroprene) are polymerized from chlorobutene monomer. The vulcanized rubber has good elasticity and wear resistance, is not afraid of direct sunlight, has particularly good atmospheric aging resistance, is not afraid of fierce distortion, is not afraid of refrigerants such as dichlorodifluoromethane and ammonia, is resistant to dilute acid and silicon ester lubricating oil, but is not resistant to phosphate ester hydraulic oil. It is easy to crystallize and harden at low temperature, has poor storage stability, and has large expansion in mineral oil with low aniline point. The general operating temperature range is – 50 ~ 150 ℃
(1) Advantages:

  • good elasticity and good compression deformation.
  • the formula does not contain sulfur, so it is very easy to make.
  • resistant to animal and vegetable oils.
  • the physical properties will not be affected by neutral chemicals, fats, oils, and solvents.
  • flame proof.

(2) Disadvantages:

  • it is not recommended to use strong acids, nitrohydrocarbons, esters, chloroform and ketone chemicals.
  • seals resistant to R12 refrigerant.
  • rubber parts or seals on household appliances.
  • suitable for making all kinds of parts directly in contact with atmosphere, sunlight and ozone.
  • suitable for all kinds of fire-resistant and chemical corrosion-resistant rubber products.

8. Chlorosulfonated polyethylene adhesive CSM
(hypalon, polyphylene) chlorosulfonated polyethylene is a synthetic rubber patented by DuPont. Good heat resistance, weather resistance and ozone resistance; Acid resistance is also good. It is commonly used in oxidation resistant drugs (nitric acid and sulfuric acid). The general temperature range is – 45 ~ 120 ℃.
(1) Advantages:

  • good resistance to ozone, oxidation and flame.
  • the physical properties are similar to those of neoprene and have better acid resistance.
  • excellent abrasion resistance.
  • have the same low friction surface as butyl glue.
  • resistance to oil and solvent is between butyl and chloroprene.
  • it is recommended to use water to prevent leakage.

(2) Disadvantages:

  • exposure to concentrated oxidizing acids, nitrohydrocarbons, esters, ketones and aromatic hydrogen is not recommended.

9. Silicone rubber Si
(silicone rubber) the main chain of silica gel is composed of silicon (- Si-O-Si). It has excellent heat resistance, cold resistance, ozone resistance and atmospheric aging resistance. It has good electrical insulation. The tensile strength is worse than that of ordinary rubber and has no oil resistance.
(1) Advantages:

  • after the formulation, the tensile strength can reach 1500psi and the tear resistance can reach 88lbs.
  • good elasticity and compression deflection.
  • good resistance to neutral solvents.
  • excellent heat resistance.
  • excellent cold resistance.
  • excellent resistance to ozone and oxide erosion.
  • excellent electrical insulation.
  • good heat insulation and heat dissipation.

(2) Disadvantages:

  • it is not recommended to use in most concentrated solvents, oil products, concentrated acids and diluted sodium hydroxide.
  • seals or rubber parts used in the household appliance industry, such as electric kettle, electric iron and rubber parts in microwave oven.
  • seals or rubber parts in the electronics industry, such as mobile phone keys, damping pads in DVDs, seals in cable connectors, etc.
  • seals on various articles in contact with human body, such as kettle, water dispenser, etc.

10. Silicone fluororubber FLS
(fluorinated silicone rubber) silicone fluororubber is silicone rubber, which is fluorinated, and its general performance has the advantages of fluororubber and silicone rubber; It has good oil resistance, solvent resistance, fuel oil resistance and high and low temperature resistance. The general service temperature is – 50 ~ 200 ℃.
(1) Advantages:

  • suitable for special purposes, such as resistance to the corrosion of oxygen-containing chemicals, solvents containing aromatic hydrogen and solvents containing chlorine.

(2) Disadvantages:

  • it is not recommended to be exposed to brake oil, ketones and calluses.
  • on space machine parts.

11. Fluororubber FPM
Fluoro carbon rubber has various types according to fluorine content (i.e. monomer structure). At present, the widely used hexafluoride fluororubber was first listed by DuPont under the trade name of “Viton”. High temperature resistance is better than silicone rubber, with excellent chemical resistance, resistance to most oils and solvents (except ketones and esters), weather resistance and ozone resistance; The cold resistance is poor, and the general service temperature range is – 20 ~ 250 ℃. Special formula can withstand low temperature to – 40 ℃.
(1) Advantages:

  • heat resistant to 250 ℃.
  • resistant to most oils and solvents, especially all acids, aliphatic hydrocarbons, aromatic hydrocarbons and animal and vegetable oils.

(2) Disadvantages:

  • it is not recommended to use ketones, low molecular weight esters and mixtures containing nitrate.
  • automobiles, locomotives, diesel engines and fuel systems.

seals for chemical plants.
12. Perfluorinated rubber ffpm (Perfluoroelastomer)
(1) Advantages:

  • optimum heat resistance.
  • excellent chemical resistance.
  • low outgassing characteristics.
  • excellent plasma resistance.

(2) Disadvantages:

  • poor low temperature resistance.
  • high raw material prices.
  • difficult production.
  • perfluorinated series products are widely used in semiconductor industry and information related industries, including PVC, CVD and etching processes in film manufacturing process and various high vacuum sealing processes.

13. Acrylate rubber ACM
Polyacrylate rubber is an elastomer polymerized with alkyl ester acrylate as the main component. It has good petrochemical oil resistance, high temperature resistance and weather resistance. It is weak in mechanical strength, compression deformation rate and water resistance, which is slightly worse than general oil resistant adhesives. The general operating temperature range is – 25 ~ 170 ℃.
(1) Advantages:

  • suitable for automotive transmission oil.
  • good antioxidant and weather resistance.
  • anti bending deformation function.
  • excellent resistance to oil.
  • suitable for automobile transmission system and power steering wheel.

(2) Disadvantages:

  • not suitable for hot water.
  • not applicable to brake oil.
  • no low temperature resistance.
  • not applicable to phosphate esters.
  • automotive transmission system and power system seals.

14. Polyurethane Rubber PU
Urethane rubber has quite good mechanical and physical properties, and its high hardness, high elasticity and wear resistance are difficult to compare with other rubbers; Aging resistance, ozone resistance and oil resistance are also quite good. The general operating temperature range is – 45 ~ 90 ℃.
(1) Advantages:

  • wear resistance and high pressure resistance.

(2) Disadvantages:

  • not resistant to high temperature.
  • high pressure and wear resistant seals in industry, such as hydraulic cylinder seals.
  • high voltage and high charge system.

Material name chemical description abbreviation English alias

Material name

Chemical description

English abbreviation

English alias

Acrylonitrile butadiene rubber

Acrylonitrile butadiene rubber

NBR

Buna-N

Hydrogen nitrile rubber

Hydrogenated acrylonitrile butadiene rubber

HNBR

HNBR

EPDM

Ethylene propylene diene rubber

EPDM

EP,EPT,EPR

Chloroprene

Chloroprene rubber

CR

Neoprene

silica gel

Silicone rubber

WMQ

PVMQ

Fluorosilicone

Fluorosilicone rubber

FVMQ

FVMQ

Acrylate

Acrylic rubber

ACM

ACM

Vinylacrylic acid

Ethylene acrylic rubber

AEM

Vamac

Styrene butadiene

Styrene butadiene rubber

SBR

SBR

Polyurethane

Polyester/polyether urethane

AU/Eu

AU/EU

Natural rubber

Natural rubber

NR

NR

Styrene butadiene

Styrene butadiene rubber

SBR

SBR

Use of O-ring thermometer

Basic properties

NBR

HNBR

EPDM

FKM

CR

ACM

AEM

SBR

AU/EU

VMQ

FVMQ

NR

High temperature (standard, º f)

212

300

300

390

250

350

300

212

212

390

400

220

High temperature (special, º f)

250

480

Low temperature (standard, º f)

-22

-22

-60

5

-40

0

-40

-40

-40

-65

-75

-60

Low temperature (special, º f)

-60

-40

-30

Comparison of material properties

1. Selection of O-ring material

The materials used for O-ring are nitrile rubber, carboxylic acid nitrile, fluororubber, ethylene propylene rubber, hydrogenated nitrile rubber, silicone rubber, chloroprene rubber, fluorosilicone rubber, polyurethane, chlorohydrin rubber, styrene butadiene rubber, butyl rubber, natural rubber, ethylene/propionic acid rubber, polyacrylate rubber, perfluoro rubber, etc.

For the same kind of rubber, the performance index also has great changes due to the different formula. Therefore, it is not accurate to simply fill in NBR or NBR-40 in the material column. The Ministry of materials and chemical engineering for O-ring has special standards, such as HG/T 2579, HG/T 2021, HG/T 2333, HG/T 3089, HB 5290, etc. HG/T 2579 specifically removes the specific categories of materials and only gives some performance indexes of materials.

2. It is important to choose the hardness of O-ring. For example, the hardness of the seal ring of pump turbine in a power station is 70 (Shore), which often peels off or even cuts off laterally. The sealing ring of 85-90 (Shore) is used after that, and the effect is ideal.

3. Low hardness, easy to install, but easy to appear peeling, installation damage, extrusion and even pressure explosion. The hardness is too high and the installation is inconvenient.

4. Generally, the hardness of O-ring is 40-90 IRHD, but in use, 70 IRHD is more suitable. For silicone rubber, 60 IRHD is generally used.

Source: China O-rings Manufacturer – Yaang Pipe Industry Co., Limited (www.pipelinedubai.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

If you want to have more information about the article or you want to share your opinion with us, contact us at sales@pipelinedubai.com

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