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Oval section gaskets are distinguished by their shape in the form of an oval, that is, an elongated circle: with straight lines on the sides and arcs at the top and bottom.
Steel gaskets of oval section: normative and technical documentation regulating production.
The production of steel gaskets with an oval cross section in Russia is regulated by three main regulatory and technical standards.
- OST 26-845-73.
- OST 26.260.461-99.
- ATK 26-18-6-93.
The OST, GOST and ATK standards provide requirements for dimensions, design, as well as additional technical and operational characteristics.
Oval gaskets: application
Oval steel gaskets are used primarily with the RTJ connection and act as O-rings on pressurized pipelines to ensure optimum sealing. Recommended for use with flanges. Ring-type connections concentrate the bolt load in a small area, creating high seal stresses.
Since the ring-type joint material must always be softer than the mating flanges, the high stress fit causes the ring joint to "plastic flow" on the flange surfaces creating the sealing joints. Gaskets can be made from a variety of materials to suit the process application and flange.
The main types of oval gaskets
There are three main types of oval gaskets used in Russian and international practice.
- ARMCO rings. ARMCO O-Rings are precision machined metal gaskets commonly used in high pressure applications such as pipelines in the oil, gas, petrochemical and analog industries. This type of gasket is designed for use in RTJ groove flanges.
- BX RTJ. They are a modernized version of ARMCO rings.
- RX RTJ. They are a modernized version of ARMCO rings.
All modifications of sealing rings are available in different sizes. Modifications BX and RX are adequate for use in underwater conditions. Standard R types are available from R11 (1/2”) to R105 (36”) in oval or octagonal section. The octagonal section has a higher sealing efficiency than the oval section and is therefore preferred.
Oval gaskets were originally developed for the obsolete round bottom groove. Both oval and octagonal cross section are interchangeable in flat bottom groove design.
Key Specifications for Oval Gaskets
Below are the main features of the main three types of steel oval gaskets.
Rings ARMCO
- Used on high pressure lines from 300 to 1600 atmospheres.
- They are extremely reliable seals.
- Designed for flanges with standard ring type grooves.
BX RTJ
- Ring type BX connections are designed for pressures up to 1600 atmospheres.
- Oval steel gasket for API type BX flange.
- The gasket has a square cross-section with chamfered corners. The average ring diameter is slightly larger than that of the flange groove. Thus, when the ring joint sits, it remains pre-compressed in the outer diameter, creating a high seating stress.
RX RTJ
- Ring connections type RX are designed for pressure up to 300 atmospheres, they are pressure activated ring connections.
- Designed to improve tightness. The outer sealing surface of the ring joint provides initial contact with the flange. As the internal pressure increases, the contact pressure between the ring joint and the flange also increases. This is sometimes referred to as a pressure-activated ring connection due to the shape of the gasket. High landing pressure is created, increasing the tightness. This design feature makes the RX oval steel gasket more resistant to the vibrations, pressure surges, and shocks encountered in oil drilling.
Pipe fittings
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Standartinform |
Foreword
The goals and principles of standardization in the Russian Federation are established by the Federal Law of December 27, 2002 No.184-FZ"On technical regulation", and the rules for the application of national standards of the Russian Federation -GOST R 1.0-2004“Standardization in the Russian Federation. Basic Provisions»
About the standard
1 DEVELOPED by Closed Joint-Stock Company "Scientific and Production Company" Central Design Bureau of Valve Engineering "(CJSC" NPF "TsKBA")
2 INTRODUCED by the Technical Committee TC 259 "Pipeline fittings and bellows"
3 APPROVED AND INTRODUCED BY Order No. 852-st of December 15, 2009 of the Federal Agency for Technical Regulation and Metrology
4 INTRODUCED FOR THE FIRST TIME
Information about changes to this standard is published in the annually published information index "National Standards", and the text of changes and amendments - in the monthly published information indexes "National Standards". In case of revision (replacement) or cancellation of this standard, a corresponding notice will be published in the monthly published information index "National Standards". Relevant information, notification and texts are also posted in the public information system - on the official website of the Federal Agency for Technical Regulation and Metrology on the Internet
GOST R 53561-2009
NATIONAL STANDARD OF THE RUSSIAN FEDERATION
Pipe fittings
GASKETS OVAL, OCTANGULAR SECTION,
LENSED STEEL FOR FLANGES OF REINFORCEMENTS
Design, dimensions and general technical requirements
pipeline valves. Gaskets of oval, octagonal section, lens steel for valve flanges.
Design, dimensions and general technical requirements
Introduction date - 2010-04-01
1 area of use
This standard establishes the design, dimensions and general technical requirements for steel gaskets of oval, octagonal section for flanged fittings with flanges having a sealing surface of version 7 according to GOST 12815 and version J according to ISO 7005-1, as well as the design, dimensions and general technical requirements for lens gaskets with flanges having a sealing surface of version 6 according to GOST 12815. This standard applies to sealing gaskets of oval, octagonal section for flanged connections with flanges of nominal diameter DN from 10 to 400 for nominal pressure PN from 6.3 to 20 MPa (from 63 to 200 kgf / cm 2) according to GOST 12815 and ISO 7005-1, as well as for lens gaskets for flange connections with flanges of nominal diameter DN from 10 to 400 for nominal pressure PN from 6.3 to 20 MPa (from 63 to 200 kgf / cm 2) according to GOST 12815.
2 Normative references
This standard uses references to the following standards:
4.12 The design documentation for gaskets shall contain the following reliability indicators:
By durability (service life before replacement);
By keeping (shelf life);
For safety (probability of failure-free operation during the service life before replacement).
4.13 For gaskets that make up the connecting flanges of fittings and pipelines intended for hazardous production facilities, the following indicators must be indicated in the design documentation:
Assigned service life;
Assigned period of storage;
Probability of failure-free operation during the assigned service life.
Annex A
(reference)
Comparison of nominal pressure values for gaskets to flanges according to GOST 12815 Keywords: pipeline fittings, gaskets
Oval and octagonal gaskets manufactured in accordance with regulatory documents:
- Gaskets OST 26.260.461-99. Oval and octagonal steel gaskets for fittings flanges. Design, dimensions and general technical requirements.
- Gaskets OST 26-845-73. Oval and octagonal steel gaskets. Design and dimensions. Technical requirements.
- Gaskets ATK 26-18-6-93. Oval and octagonal steel gaskets. Oval pads. Octagonal pads.
- Octagonal gaskets (octagonal gaskets), GOST 28759.8-90. Gaskets metal octagonal section. Design and dimensions. Octagonal gaskets GOST 28759.8-90.
- GOST 10493-81 Rigid and compensating sealing lenses on Ru 20-100 MPa.
Standard OST 26.260.461-99 establishes the design, dimensions and general technical requirements for for flange connections of valves and pipelines for conditional pressure Pn from 6.3 to 16.0 MPa and temperature from -70 to 600°C.
Document OST 26-845-73 applies to oval and octagonal steel gaskets for flange connections of fittings and pipelines according to OST 26-838-73 and OST 26-842-73.
The use of steel gaskets
Rings Armco designed for sealing flanged joints with connecting surfaces of execution type 7 according to GOST 12815-80 fittings, pipelines, vessel flanges, devices, pumps, equipment for oil and gas production, chemical, oil refining and other industries.
Steel spacers(Armco rings) allow sealing at high pressures when other types of gaskets are not applicable. Flange gaskets steel 08KP, 10985, 08X13, 08X18H10, 08X18H10T are used for nominal pressure Ru 6.3 to 16 MPa (from 63 to 160 kgf / cm²) and temperature from -70 to 600 ° C.
Reuse of steel seals (gaskets and lenses) is not recommended. During installation and operation, the material is strengthened. When reassembling, tighter tightening of the flange bolts is required to achieve the same tightness, which can damage the sealing surfaces of the flanges.
Oval and octagonal flange gaskets (Armco rings)
OST documents provide for two types steel seals: type 1 - oval section; type 2 - octagonal section.
Oval gaskets (Armco rings)
Oval gaskets (Armco rings) have the shape of a rectangle in cross section, completed on two opposite sides by semicircles. A small area of contact under high compressive pressure of the flange fastener leads to a reliable tightness of the connection, since due to plastic deformation of the gasket, microroughnesses of the sealing surface are filled. The contact surfaces of the oval gasket and the flange must be precision machined. Some types of oval gaskets are “pressure-energized”, i.e. the sealing properties of the gaskets improve with increasing pressure. Oval gaskets can be used in conjunction with flanges having a round groove.
Octagonal gaskets
Octagonal gaskets metal (octagonal gaskets) provide a better seal than oval gaskets. Steel gaskets 08XP, 08X13, 08X18H10T are produced in accordance with GOST 28759.8-90 for P y 16 MPa.
Production of steel gaskets of oval and octagonal section
For flanges having a flat bottom recess, use oval and octagonal gaskets(allow the use of gaskets of both types). The working surfaces of the flanges must be processed to a roughness (surface finish) of 1.6 microns (according to domestic standards and ASNI B16.20), damage to the working surface is unacceptable. The material of the steel gaskets should have a lower hardness than the material of the flanges. According to GOST 28759.8-90, no more than two transverse welds are allowed on the gasket. The difference in hardness of the weld metal and the base metal should not be more than 20 Brinell units.
Steels for the manufacture of flange gaskets
Gaskets can be made of steel 08KP according to GOST 1577 and 10695 according to GOST 11036, gaskets steel 10895 according to GOST 11036, gaskets st. 08X13 according to GOST 7350 or according to GOST 5949, gaskets made of steel 08X18H10T according to GOST 7350 or according to GOST 5949. Russian standards allow the manufacture of steel gaskets from other steel grades, depending on the requirements for operation.
German DIN standard allowed production of gaskets from steel grades 1.1003, 1.0038, 1.1003, 1.0038, 1.7362, 1.4000, 1.4301, 1.4401, 1.4550. The American standard ASME B16.20 (Ring Joints) prescribes the manufacture of gaskets from Soft Iron, Low CS, 4/6 Cr ½ Mo, AISI 410, AISI 304, AISI 316, AISI 347 steels.
Gaskets steel API, ANSI, ASME
The dimensions of steel gaskets are standardized by American documents ASME B16.20, API 6A, ASME/ANSI B16.5. Gaskets steel are made of the following steels in the English nomenclature: Carbon Steel; Stainless Steel: 304, 304L, 316, 316L, 321, 347, 410; 502/501; Alloy 20 and others.
R Type Ring-joint gaskets
Oval and octagonal round gaskets are called in English literature Ring Joint Gaskets (type R), oval section - oval ring, octagonal octagonal ring. Widely used abbreviation RTJ (Ring Type Joint) - round gasket. Octagonal ring joint gaskets provide better sealing, but only oval ring joint gaskets can be used to connect older types of round groove flanges. Type R round gaskets are used for pressure classes 150 - 2500 (for ASME B 16.5 flanges), 10000 (for API 6A type 6B flanges), 900 (for ASME B 16.47 flanges). The surface roughness of the gaskets is allowed no more than 1.6 microns.
RX Type Ring-joint gaskets
Round gaskets type RX ( RX style Ring-joint gaskets) are similar in cross-sectional shape to octagonal gaskets, but their cross-section is designed to use the pressure of the conveyed medium to increase the tightness of the connection. The surface roughness of the gaskets is also allowed no more than 1.6 microns. Gaskets type RX are used for pressure classes 2000 - 5000.
BX Type Ring-joint gaskets
Round gaskets with cross section type BX ( BX style Ring-joint gaskets) differ in sectional shape from traditional oval and octagonal gaskets. Their section has the shape of a square with corners beveled at an angle of 23°. The surface roughness of the gaskets is allowed no more than 0.8 microns. Type BX gaskets are used for colossal pressure classes of 5000 - 20000 lbs.
Sealing flange lenses
Sealing lenses are used for sealing flange connections on pipelines operating under extreme temperature and barometric conditions. Sealing lenses have spherical sealing surfaces and are used to connect flanges of a special design of the sealing surface (see GOST 12815-80, version 6). The contact area of the flange with the lens is much larger than with the gasket.
GOST 10493-81 standardizes hard and compensating sealing lenses for nominal pressure Pn 20-100 MPa (200-1000 kgf/cm²) and nominal bore Dn 6-200 mm with medium temperature from -50°C to +500°C. There are 2 types of lenses: hard lens(W) and compensating lens(K), - and for each of these types - 2 versions. Compensating lenses, unlike rigid ones, have a groove on the inner surface for an insert ring, which must be made of the same steel as the lens.
| Type | Use | Har-ka | Drawing | T, °C | P y, MPa | Steel |
|---|---|---|---|---|---|---|
| AND | 1 | Rigid lens without shoulder |  | -40 … +200 | 20 - 32 | 20 |
| -50 … +200 | ||||||
| -50 … +400 | 20 - 40 | 15XM | ||||
| 20 - 50 | 18X3MV, 20X3MVF | |||||
| 2 | Rigid lens with shoulder |  | -50 … +200 | 40 - 63 | 14HGS | |
| 40 | 12X18H10T, 10X17H13M3T, 08X18H15M3T | |||||
| -50 … +400 | 50 - 80 | 30HMA | ||||
| 63 - 100 | 18X3MV, 20X3MVF | |||||
| TO | 1 | Compensating lens at pressures up to P y 50 MPa |  | -50 … +400 | 20 - 40 | 12X18H10T, 10X17H13M3T, 08X18H15M3T |
| +400 … +510 | 20 - 50 | 18X3MV, 20X3MVF | ||||
| 2 | Compensating lens at pressure P at 63 - 100 MPa |  | +400 … +510 | 63 - 100 | 18X3MV, 20X3MVF |
Sealing lenses DIN 2696 (Dichtlinse)
Also, sealing lenses can be produced according to the German standard DIN 2696 "Flange connections with lens shaped gasket (Flanschverbindungen mit Dichtlinse)" for nominal diameters Dn 10 ... 300 and nominal pressures Pn 64 ... 400.
Calculation of flange connections with gaskets
For the correct calculation of the flange connection and flange gaskets (flange gasket) it is necessary to take into account: 1) characteristics of the medium (pressure, temperature, chemical composition and their changes, additional loads, vibration); 2) the choice of components and materials of the flange connection, - and other parameters.
For calculation flange connections with gaskets there are a number of foreign standards.
DIN E 2505 is intended to regulate the detailed calculation of the system gasket flange but is under development.
The current standard DIN EN 1591 expands and deepens the previous calculations, contains detailed calculations, including additional calculations for steel gaskets. Its features - consistency with European standards and the need to know additional characteristics gaskets(for example, modulus of elasticity).
AD2000 Merkblaetter B7/ B8 limited to collar flanges.
DIN EN 13445-3 is in line with European standards, is simpler than DIN EN 1591, but the flange thickness is assumed to be large.
ASME VIII Div.1 contains calculations according to ASME codification, its advantage is a guarantee of saving the flange design, disadvantages - the case of high shrinkage of the gasket is not considered, the flange thickness is assumed to be large.
Steel gaskets of our production undergo mandatory quality control: macrostructure and microstructure control, control of mechanical properties of gaskets, control of chemical composition.
Sincerely, Hardware and Flange Plant.
The Scientific and Production Association Engineering Technologies has mastered Armco rings, these parts are used between the following connections: flange - flange, flange - valve, valve - valve.
Purpose and scope.
The use of metal gaskets is primarily due to work under high pressure, which in itself speaks of a responsible approach to the production and use of these parts.
Oval gaskets, octagonal gaskets, Armco rings are used to seal joints for flanges with pressure from 6.3 to 160 MPa. The operating temperature range is from -70 to +600 C. In the past, asbestos was used to seal flange joints, which violated the ecology of production. Oval gaskets, octagonal gaskets, Armco rings are now made exclusively of metal, moreover, the hardness of the gaskets is several units less than the hardness of the mating parts.
Example: to connect flanges made of steel, gaskets made of steel GOST 28759.8-90 are used, where the chemical composition of the steel shows that the steel of the gaskets is 4 units softer than the steel used in the flanges. Thus, the use of softer steel gaskets results in a tighter flange seal that can handle higher pressures.
It is also worth mentioning the frequency of the treated surface - it should not be lower than Rz 6.3 at the mating points, and not lower than Rz 3.2 on other surfaces of the gaskets. The high frequency of processing is due to the need - the higher it is, the tighter the mating parts fit together. And the higher the quality of the connection working under high pressure.
Oval gaskets, octagonal gaskets, Armco rings are used in all critical flange connections - cracking columns, shipbuilding fittings, pipeline transport, petrochemical complex.
Products are manufactured according to the following standards:
- GOST R 53561-2009 Pipe fittings. Gaskets of oval, octagonal section, lens steel for fittings flanges. Design, dimensions and general technical requirements
- Oval and octagonal steel gaskets for fittings flanges. Design, dimensions and general technical requirements.
- OST 26-845-73 Design and dimensions. Technical requirements.
- ATK 26-18-6-93 Oval and octagonal steel gaskets.
- Gaskets metal octagonal section. Design and dimensions. Technical requirements.
This standard applies to gaskets of octagonal section to the flanges of vessels and apparatus with steel butt welded according to GOST 28759.4-90
The requirements of paragraph 1, with the exception of the indicators "Nominal pressure, MPa" and "Mass, kg"; pp. 2.1, 2.3 and 2.4 of this standard are mandatory, other requirements of this standard are recommended. The design and dimensions of octagonal gaskets must comply with the drawing.
- GOST 10493-81 Rigid and compensating sealing lenses for Ru 20-100 MPa.
For the manufacture of gaskets of oval and octagonal section, the following steel grades are used: 08kp; 08X13; 08X18H10.
Oval and octagonal gaskets (also known as ARMCO rings, aka RTJ= API rings) and O-rings types RX and BX
In the Russian Federation, oval and octagonal gaskets are manufactured in accordance with the following regulatory documents:
- OST 26-845-73 “Design and dimensions. Technical requirements";
- OST 26.260.461-99 “Oval and octagonal steel gaskets for reinforcement flanges. Design, dimensions and general technical requirements”;
- ATK 26-18-6-93 "Oval and octagonal steel gaskets";
- GOST 28759.8-90 “Metal octagonal gaskets. Design and dimensions. Technical requirements".
In international practice, gaskets of this type are called API rings, and connections using them are called RTJ (ring - type joint). Gaskets of this type are described in ASME B 16.20 and API 6 A, and flanges in ASME / ANSI B 16.5. Suitable for pressures up to ANSI 5000 psi. Gaskets are laid in recesses on flanges having walls with an angle of 23° to the vertical.
Application: Armco rings (steel and iron gaskets, RTJ) are designed for sealing flange joints with connecting surfaces of type Execution 7 according to GOST 12815-80 of fittings, pipelines, vessels, apparatuses, pumps and similar equipment for oil and gas production, chemical, oil refining and some other industries industry.
Advantages: allow to create seals at high operating pressures when other types of gaskets are not applicable.
They are used for conditional pressure Ru 6.3 to 16.0 MPa (from 63 to 160 kgf / cm 2) and temperature from -70 to 600 ° C. They can be made from steel 08kp according to GOST 1577 and 10695 according to GOST 11036, steel 08X13 according to GOST 7350 or according to GOST 5949, from steel 08X18H10 according to GOST 7350 or according to GOST 5949. According to Russian regulatory documents, it is allowed to manufacture these gaskets from other steel grades in depending on operating requirements.
Octagonal gaskets provide a better seal than oval gaskets and are therefore preferred. However, only oval-shaped gaskets can be used with flanges having a recess with a round bottom (previously produced). Newer flanges have a flat bottom recess and accept both types of gaskets. The working surfaces of the flanges must be machined to a roughness of 1.6 microns, damage to the working surface is unacceptable. The gasket material must always be less hard than the flange material.
Optional: o-ring typesRXAndBX
RX type gaskets have a similar profile to conventional octagonal gaskets, but have different bevel angles on the outside and inside of the ring, making them self-sealing (working pressure ensures better sealing of the gasket against the flange). Used in conjunction with flanges made in accordance with API 6 A . Type BX gaskets also have an octagonal profile. It is obtained from a square by chamfering at 4 corners. They are used in conjunction with flanges made in accordance with API 6 BX, and the flanges, after tightening the bolts, come into contact with each other. Both types of gaskets are used for very high pressure classes up to ANSI 20000 psi.
