GOST Flange Standard: Types, Dimensions & Comparison with ANSI/DIN (Complete Guide)

If your project is located in Russia, Kazakhstan, Ukraine, or other CIS countries, there is a strong chance your piping specification will require GOST flanges. However, outside these regions, GOST standards remain poorly explained in English, and most online resources are either repetitive or too general for real procurement.

Written from a flange manufacturer's perspective, this guide explains what GOST truly means, how different standard numbers connect, what changed in the 2015 revision, and how GOST compares with ANSI B16.5 and DIN/EN 1092-1 in practical project applications.

GOST is an acronym for Gosudarstvennyy Standart (Государственный Стандарт), which translates directly to 'State Standard' in English. It is the national standardization system originally developed in the Soviet Union and now maintained by the Euro-Asian Council for Standardization, Metrology and Certification (EASC) - an intergovernmental body covering Russia and most former Soviet republics.

GOST standards cover a wide range of industrial products. For piping systems, GOST defines the dimensional, material, pressure-temperature, and testing requirements for flanges used in oil and gas pipelines, chemical plants, water treatment systems, and power generation facilities across the CIS region.

This is where most buyers get confused - and understandably so. Over the decades, several separate GOST standards governed different flange types. The most important thing to know is that GOST 33259-2015 is the current consolidated standard that supersedes the older individual documents for most applications.

In practice, many older projects and long-running facilities still reference the 1980-era standards. If you receive a drawing marked GOST 12821-80, it refers to the old weld neck flange standard - the dimensions are still valid and widely used, but the current equivalent is covered under GOST 33259-2015. Always check your project specification to confirm which edition is required.
In our experience, about 60–70% of export inquiries we receive still reference the old 1980 standard numbers - particularly GOST 12820 and 12821. This is not wrong, but it is worth confirming with the end client whether the 2015 edition is acceptable as a direct replacement.

GOST 33259-2015 covers the following flange connection types. The naming conventions differ slightly from ANSI and DIN, so it helps to know the equivalents:

Among these, weld neck and flat (plate) flanges are by far the most commonly ordered types for CIS industrial projects. Spectacle blinds are worth noting - they are widely used in Russian oil and gas facilities but often overlooked by suppliers outside the region.

Ss Plate Flange

Weld Neck Pipe Flange

 

Blind Flange End

GOST uses the PN (Pressure Nominale) system - the same notation as DIN and EN standards. This is one area where GOST and European standards look similar on the surface, but the actual pressure-temperature ratings and dimensional data are not the same.

PN 16 and PN 40 are the two most frequently specified classes in CIS projects - covering the majority of oil and gas, chemical, and water treatment applications. If you are unsure which class to specify, PN 16 is the most common starting point for general-service pipelines.

GOST flanges use the DN (Diameter Nominal) system and metric dimensions throughout - all measurements are in millimetres. The size range under GOST 33259-2015 runs from DN 10 to DN 1600, making it one of the widest-range flange standards available.

The table below shows key dimensional parameters for GOST flat and weld neck flanges at PN 16 - the most commonly ordered class - for selected sizes:

Note: Dimensions shown are for PN 16 flat (plate) flanges per GOST 33259-2015. Weld neck and blind flange dimensions vary. Contact CNCJ for complete dimension tables across all PN classes.   sale@cncjflange.com

One of the most practical challenges in sourcing GOST flanges internationally is decoding the Russian material designations. The naming system is completely different from ASTM or EN standards, which creates confusion during procurement - especially when a project specifies a Russian steel grade but the manufacturer works primarily with ASTM materials.
A common mistake we see in procurement is assuming that matching a chemical composition is enough to confirm material equivalency. In reality, the manufacturing process, heat treatment, and testing requirements also need to align. Always request a material test certificate (MTC) and verify against the specific GOST material standard.

St20 (carbon steel) and 12Kh18N10T (stainless steel equivalent to 316Ti) are the two most frequently specified grades for GOST flanges in export projects. The stabilized titanium-bearing grade 12Kh18N10T is preferred over the basic 304/316 equivalent in high-temperature CIS applications because of its better resistance to intergranular corrosion after welding.

This is the comparison that comes up most often when a project transitions between regions - for example, when a CIS client wants to connect new ANSI-compliant equipment to an existing GOST pipeline. The short answer is: they are not interchangeable, even when the pressure ratings look similar.

In most cases, the real problem arises not during procurement but during installation - when someone on site discovers that a new ANSI flange and an existing GOST flange have different bolt circle diameters and hole counts, even though both are rated PN 16 / Class 150. This mismatch is the most common compatibility issue we encounter in mixed-standard projects.

The approximate pressure class equivalencies below are useful for initial planning - but do not use these for direct substitution without confirming bolt patterns and face dimensions:

Because both GOST and DIN/EN flanges use the PN designation and metric dimensions, it is tempting to assume they are interchangeable. They are not - and this assumption causes real problems on projects where European equipment is being connected to a GOST pipeline system.

The key differences are in bolt hole count and flange outside diameter. At DN 100 PN 16, for example, a GOST flange has 8 bolt holes on a 190 mm bolt circle, while a DIN EN 1092-1 PN 16 flange also has 8 holes but on a 180 mm bolt circle - a 10 mm difference that makes the two incompatible without an adapter.
Always verify the bolt circle diameter (PCD) and bolt hole count before specifying or ordering when mixing GOST with European-standard equipment. A simple dimensional check at the specification stage saves significant rework cost later.

GOST flanges are the standard choice for any project operating under Russian or CIS engineering codes. The most common application areas include:

• Oil & gas transmission pipelines in Russia, Kazakhstan, Azerbaijan, and Turkmenistan - where Transneft and Gazprom pipeline codes require GOST compliance
• Upstream and midstream facilities in CIS countries - including compressor stations, separator skids, and metering systems 
• District heating networks (centralized hot water systems) across Russia and Eastern Europe - PN 16 and PN 25 flat flanges dominate this application 
• Water treatment and municipal water supply infrastructure in CIS countries
• Chemical and petrochemical plants built under Soviet-era or GOST-compliant engineering standards, including maintenance and expansion projects 

GOST flanges remain essential for any project operating under Russian or CIS engineering codes. Understanding the difference between the old 1980-era standards and the current GOST 33259-2015, knowing why GOST and ANSI flanges cannot simply be swapped despite similar pressure ratings, and being able to match Russian material grades to ASTM equivalents - these are the practical details that actually matter when placing an order or reviewing a project specification.

The standard is not complicated once you know the structure. The biggest mistake is treating GOST as a loose regional variation of DIN or ANSI. It is its own system, with its own dimensional logic, and it deserves to be specified correctly.

GOST 33259-2015: Flanges for fittings, vessels and pipelines at nominal pressure up to PN 250. Euro-Asian Council for Standardization (EASC).

GOST 12820-80: Steel flat-welding flanges. USSR State Standard (historical reference).

GOST 12821-80: Steel weld-on flanges. USSR State Standard (historical reference).

EN 1092-1:2018: Flanges and their joints - circular flanges for pipes, valves, fittings and accessories. European Committee for Standardization (CEN).

ASME B16.5-2017: Pipe Flanges and Flanged Fittings. American Society of Mechanical Engineers.