The Definitive Archive of
Valve Testing, Inspection & Certification Standards

A high-fidelity, data-centric archive engineered for absolute completeness. This resource provides engineers, inspectors, and procurement specialists with a granular, side-by-side analysis of the world's primary valve testing standards. It covers general pressure integrity (API 598, EN 12266, ISO 5208), pipeline-specific protocols (API 6D), and critical performance verifications including Fire Testing (API 607, API 6FA), Cryogenic Testing (BS 6364), and Fugitive Emissions (ISO 15848).

ARCHIVE TABLE OF CONTENTS

1.1 Comparative Overview: General Pressure Testing

This table provides a high-level comparison of the most common international standards for routine hydrostatic and pneumatic pressure testing of general-purpose industrial valves. It highlights key differences in philosophy, pressure levels, and acceptance criteria.

Parameter	Test / Item	API 598 (9th Ed.)	EN 12266-1 (2012)	ISO 5208 (2015)	MSS-SP-61 (2013)	API 6D (25th Ed.)	JIS B2003 (1994)
Scope & Philosophy		Dominant in North American & API-centric projects. Prescriptive pass/fail.	Mandatory for CE Marking in Europe. Allows for defined, permissible leakage rates.	Global harmonization standard, very similar to EN 12266. Focus on leakage rate classification.	US-focused standard for commercial/utility steel valves. A "hydrostatic pressure test" standard.	Mandatory for API Monogram on pipeline & pigging valves. Highly detailed & rigorous.	General Japanese industrial valve testing standard.
Shell Test (Hydrostatic)	Test Fluid	Water (may contain corrosion inhibitor), Kerosene, or other suitable liquid of viscosity ≤ water.
	Test Pressure	≥ 1.5 × CWP @ 38°C (100°F)	≥ 1.5 × Max. allowable pressure (pₛ) at Room Temp. (RT)	≥ 1.5 × Max. allowable pressure at RT	≥ 1.5 × 100°F pressure rating	≥ 1.5 × Valve pressure rating at RT (PSL dependent)	1.5 × Max. allowable working pressure at RT.
	Acceptance	No visually detectable leakage from the pressure-boundary wall (body, bonnet, cover, end connections).
Backseat Test	Applicability	Required for all valves with a backseat feature (e.g., Gate, Globe).	Required if specified by valve product standard (Test P12).	Required if specified by valve product standard (Test F22).	Required.	Required for applicable valves.	Required for valves with backseating function.
Backseat Test	Test Pressure	≥ 1.1 × CWP @ 38°C (100ˆF)	≥ 1.1 × Max. allowable pressure at RT	≥ 1.1 × Max. allowable pressure at RT	= 100°F pressure rating	≥ 1.1 × Valve pressure rating at RT	1.1 × Max. allowable working pressure at RT.
High Pressure Closure Test (Hydrostatic)	Test Pressure	≥ 1.1 × CWP @ 38°C (100ˆF)	≥ 1.1 × Max. allowable pressure at RT (Test P11)	≥ 1.1 × Max. allowable pressure at RT (Test F21)	= 100°F pressure rating	≥ 1.1 × Valve pressure rating at RT	1.1 × Max. allowable working pressure at RT.
	Direction	Applied in one direction as specified.	Tested in direction(s) of intended sealing. Bi-directional valves tested in both directions.		Unidirectional unless specified otherwise.	Tested in both directions for bi-directional valves.	As specified by valve design.
	Acceptance (Liquid)	Zero visible leakage (0 drops).	Permissible leakage according to specified Rate (A, B, C...); Rate A is zero leakage. See Note [1].		≤ 10 ml/hr per inch of nominal pipe size.	Default: ISO 5208 Rate D. Can be specified otherwise.	No leakage.
Low Pressure Closure Test (Pneumatic)	Test Pressure	4 to 7 bar (60 to 100 psig) air or inert gas.	6 ± 1 bar (87 ± 15 psig) air or inert gas. (Test P12)	5.5 to 7 bar (80 to 100 psig) air or inert gas.	(Not a mandatory test in this standard)	5.5 to 7 bar (80 to 100 psig) air or inert gas.	0.59 MPa (~6 bar / 85 psig) air or Nitrogen.
Low Pressure Closure Test (Pneumatic)	Acceptance (Gas)	Leakage measured in bubbles/min, varies by size. See Note [2].	Permissible leakage according to specified Rate (A, B, C...); Rate A is zero bubbles. See Note [1].		N/A	Default: ISO 5208 Rate D. Can be specified otherwise.	No leakage (bubbles).

[1] Per ISO 5208:2015 & EN 12266-1:2012, Leakage Rates. These standards quantify allowable leakage rather than a simple pass/fail. The rates are defined for both liquid (ml/s) and gas (mm³/s) tests and are a function of the valve's nominal diameter (DN). A valve can be certified to different rates depending on its design and intended service. For example:

Rate A: Zero measurable leakage (equivalent to API 598's visual liquid tightness and bubble-tight gas tests).
Rate AA: A special gas-tight category under EN 12266-1 for specific applications.
Rates B, C, D, E, F, G: Represent progressively larger allowable leakage rates. For example, Rate D is often a default for pipeline valves under API 6D.

The choice of leakage rate is a critical specification decision and must be aligned with the valve's product standard or the purchaser's specific requirements. See Section 4.1 for detailed rate tables.

[2] Per API 598, 9th Ed., Table 6: Low-Pressure Closure Test Maximum Allowable Leakage (Gas). The standard allows for a small amount of leakage, measured in bubbles per minute. The test duration must be sufficient to detect this rate.

Valve Size (NPS)	Max. Allowable Leakage (Bubbles/min)
≤ 2	0 (bubble-tight)
2½ – 8	12
10 – 18	20
≥ 20	28

Note: A "bubble" is defined as having a diameter of approximately 1/16 in. (1.6 mm). For resilient-seated valves, the requirement is 0 bubbles for all sizes.

1.2 Comparative Overview: Fire Testing

Fire testing (or "fire type-testing") is a destructive test performed on a sample valve to verify its capability to maintain pressure integrity and limit leakage after being subjected to a controlled fire. It is a design validation, not a routine production test.

Parameter	Test / Item	API 607 (7th Ed.) / ISO 10497:2010	API 6FA (4th Ed.)	API 6FD (2nd Ed.)
Primary Application		Quarter-turn soft-seated valves (Ball, Plug, Butterfly) and other general-purpose valves. The de-facto global standard.	Valves designed under API 6A (Wellhead & Christmas Tree Equipment) and API 6D (Pipeline and Piping Valves).	Check Valves.
Test Procedure	Flame Exposure	Valve is enveloped in flame, with average calorimeter temperatures reaching 761°C to 980°C (1400°F to 1800°F).
	Burn Duration	30 minutes.
	Post-Burn Action	Immediate high-volume water quench to induce thermal shock.
	Operability Cycling	One attempt to cycle open/closed during burn. One attempt to cycle after cooldown.	Three attempts to cycle open/closed after cooldown.	Valve is unseated/reseated with flow after cooldown.
Leakage Measurement	Through-Seat Leakage (Post-Burn)	Measured at both high and low pressure after cooldown. Limits are based on nominal valve size (e.g., ml/min/inch).	Measured at both high and low pressure. Limits specified in ml/min.	Measured at both high and low pressure. Limits specified in ml/min.
	External Leakage (Post-Burn)	Measured at both high and low pressure. Limits based on nominal size.	Measured at both high and low pressure. Limits specified in ml/min.
	Acceptance Criteria	Both through-seat and external leakage must be below the specified maximum allowable rates. The valve must also be operable as defined by the standard.

1.3 Comparative Overview: Fugitive Emissions Testing

Fugitive emissions testing evaluates a valve's ability to prevent unintended leakage of volatile or hazardous fluids from the stem packing and body seals over its operational life. It involves complex mechanical and thermal cycling to simulate aging and wear.

Parameter	Test / Item	ISO 15848-1 (2015)	API 622 (3rd Ed.)	API 624 (2nd Ed.)
Scope & Purpose		Type test to classify valve sealing performance based on mechanical/thermal cycles, temperature, and tightness class. The most comprehensive international standard.	Type test for the GRAPHITE PACKING itself, not the valve. Establishes the performance of packing materials in a standardized fixture.	Type test for RISING-STEM valves equipped with API 622 tested packing. A simpler, more targeted test than ISO 15848-1.
Test Conditions	Mechanical Cycles	Defined by Endurance Classes: e.g., CO1 (500 cycles), CO2 (2500 cycles), CO3 (5000 cycles).	1510 mechanical cycles.	310 mechanical cycles.
	Thermal Cycles	Defined by Temperature Classes: e.g., t-RT, t-200°C, t-400°C. Involves multiple cycles between ambient and target temperature.	5 thermal cycles up to 500°F (260°C) for standard service or 850°F (454°C) for high temp.	3 thermal cycles up to 500°F (260°C).
	Test Fluid	Helium or Methane.	Methane.	Methane.
Measurement & Classification	Leakage Detection	EPA Method 21 "sniffing" technique at specified points (stem, body seals).
Measurement & Classification	Acceptance Criteria / Tightness Class	Classified by Tightness Classes (e.g., AH, BH, CH for Helium; AM, BM, CM for Methane) based on measured leakage in ppmv. AH/AM are the tightest.	Maximum allowable leakage of 500 ppmv during initial cycles, reduced to 100 ppmv for final cycles.	Maximum allowable leakage of 100 ppmv throughout the test. No gland/packing adjustment is permitted.

1.4 Comparative Overview: Cryogenic Testing

Cryogenic type-testing validates a valve's design for service at very low temperatures (typically below -50°C / -58°F). It verifies seat performance, external integrity, and operability after the valve components have been subjected to extreme cold and material contraction.

Parameter	Test / Item	BS 6364:2023	MSS SP-134 (2016)
Primary Application		The definitive global standard for testing valves intended for cryogenic service (LNG, liquid nitrogen, etc.).	North American (MSS) standard for valves with cryogenic service applications. Similar in principle to BS 6364 but with some variations.
Test Procedure	Test Temperature	Valve body is cooled by immersion in a bath of liquid nitrogen (-196°C / -321°F) or other specified cryogen.	Valve is cooled to the specified minimum design temperature, often -196°C (-321°F) using liquid nitrogen.
	Test Fluid	Helium or Nitrogen gas.	Helium gas.
	Test Sequence	Includes initial ambient tests, cooldown, multiple cryogenic seat and shell tests, and final ambient tests after warming up.	Involves a sequence of ambient pressure tests, cooldown, cryogenic seat/shell tests, and post-test ambient checks.
Acceptance Criteria	Seat Leakage (Cryogenic)	Specifies maximum allowable gas leakage rate (mm³/s) per mm of nominal bore (DN). E.g., 100 mm³/s/mm for gate/globe, 200 for quarter-turn.	Specifies maximum allowable leakage in standard cubic centimeters per minute (sccm) per inch of nominal pipe size (NPS).
Acceptance Criteria	External Leakage (Cryogenic)	Specifies maximum allowable gas leakage rate from stem seals and body joints. E.g., 200 mm³/s/mm of DN.	Specifies maximum allowable leakage from potential leak paths.

2.1 In-Depth Guide: API 598 (Valve Inspection and Testing)

API 598 is the primary standard governing the testing and inspection requirements for gate, globe, check, ball, plug, and butterfly valves. Its methodology is characterized by clear, prescriptive requirements and a "zero leakage" philosophy for many tests.

Test Phase	Description	Key Parameters & Notes
Production Pressure Tests (Mandatory for each valve)
Shell Test	Verifies the integrity of the valve's pressure-containing body and bonnet. The valve is partially open, and ends are capped.	Pressure: ≥ 1.5 × Cold Working Pressure (CWP) at 38°C (100°F). Fluid: Hydrostatic (Water/Liquid). Acceptance: No visible leakage through the pressure boundary walls.
Backseat Test	Tests the seal between the stem and bonnet when the valve is fully open (back-seated). This is critical for live packing replacement.	Applicability: Only for valves with a backseat feature (Gate, Globe). Pressure: ≥ 1.1 × CWP. Acceptance: No visible leakage through the packing or stem/bonnet interface.
High-Pressure Closure Test	Tests the sealing capability of the seat(s) at high pressure.	Fluid: Hydrostatic (Water/Liquid). Pressure: ≥ 1.1 × CWP. Acceptance: Zero drops for liquid. For metal-seated check valves, a small leakage is allowed.
Low-Pressure Closure Test	Tests the sealing capability of the seat(s) at low gas pressure, which can be more difficult to achieve for metal-seated valves.	Fluid: Pneumatic (Air or Inert Gas). Pressure: 4 to 7 bar (60 to 100 psig). Acceptance: Bubble-tight for resilient-seated valves and small NPS metal-seated valves. Measured in bubbles/min for larger metal-seated valves (See Note [2] in Section 1.1).
Visual Examination	Confirms the valve meets the requirements of the relevant product standard and purchase order.	Inspection points: Markings (as per MSS-SP-25), workmanship, assembly, and coatings/paint.

2.2 In-Depth Guide: EN 12266-1 / ISO 5208

EN 12266-1 is the European standard for pressure tests of industrial valves, a mandatory requirement for CE marking. ISO 5208 is its international counterpart, with nearly identical technical content. Their key feature is the system of defined, quantifiable leakage rates.

Test (Designation)	Description	Key Parameters & Notes
Mandatory Production Tests (Part 1)
Shell Strength (Test P10)	Equivalent to API 598 Shell Test. Verifies body integrity.	Pressure: ≥ 1.5 × max. allowable pressure (pₛ) at RT. Acceptance: No visually detectable leakage.
Seat Tightness (Test P11)	Equivalent to API 598 High-Pressure Closure Test.	Pressure: ≥ 1.1 × max. allowable pressure (pₛ) at RT. Acceptance: Must meet the specified leakage rate (e.g., Rate A, B, C...). Rate A is zero leakage.
Low-Pressure Seat Tightness (Test P12)	Equivalent to API 598 Low-Pressure Closure Test. Uses gas.	Pressure: 6 ± 1 bar. Acceptance: Must meet the specified leakage rate (e.g., Rate A, B, C...). Rate A is bubble-tight.
Optional Type Tests (Part 2 - EN 12266-2)
Backseat Test (Test P21)	Verifies backseat integrity, similar to API 598.	Performed only when required by the valve's product standard.
Operability Test	Verifies that the valve can be operated at maximum differential pressure.	Torque/thrust values are measured to ensure they are within design limits.

2.3 In-Depth Guide: API 6D (Pipeline and Piping Valves)

API 6D specifies requirements and provides recommendations for the design, manufacturing, testing, and documentation of ball, check, gate, and plug valves for pipeline and piping applications. Testing under API 6D is typically more rigorous than general-purpose standards.

Test Phase	Description	Key Parameters & Notes
Hydrostatic Shell Test	Verifies pressure-containing boundary integrity.	Pressure: 1.5 × rated pressure. Duration is significantly longer for large valves than in API 598.
Hydrostatic Seat Test	Tests both seats in bi-directional valves. Includes testing of the cavity for pressure relief.	Pressure: 1.1 × rated pressure. Acceptance: Defaults to ISO 5208 Rate D, but stricter rates can be specified.
Drain / Vent Test	For trunnion ball valves, verifies the integrity of the body drain, vent, and sealant injection fittings.	A specific, additional test not found in other general standards.
Gas Seat Test (Optional)	A low-pressure gas seat test can be specified by the purchaser.	Pressure: 5.5 to 7 bar (80-100 psi).
Double Block and Bleed (DBB)	Verifies the capability of a valve to seal off pressure from both ends and allow the cavity to be bled.	This is a functional test critical for pipeline service, not just a leakage test.

2.4 In-Depth Guide: MSS-SP-61 (Pressure Testing of Steel Valves)

MSS-SP-61 was historically a standard for hydrostatic testing of steel valves in commercial and utility services. While still referenced, its application has been largely superseded by API 598 for technical procurement. Its key distinction is its focus on hydrostatic testing only.

Test	Parameters & Notes
Shell Test	Pressure: 1.5 × 100°F rating. Acceptance: No visible leakage.
Seat Test	Pressure: 1.0 × 100°F rating. Acceptance: Specifies an allowable leakage rate in ml/hr per inch of nominal pipe size, which is less stringent than API 598's "zero drops" rule.
Pneumatic Test	Not required by this standard. This is a primary difference from API 598 and EN 12266.

3.1 Appendix A: German Standards (DIN)

The Deutsches Institut für Normung (DIN) provides a comprehensive framework for industrial components. While EN (European Norm) standards have superseded many DIN standards for valve design and testing to achieve harmonization across the EU, specific DIN standards remain highly relevant, especially for legacy systems, specific applications, and for components like flanges and materials that are integral to the valve assembly.

Standard Number	Title / Subject	Relevance & Key Features	Current Status	Superseded by / Correlates with
Primary Valve Testing & Inspection Standards
DIN 3230-3	Technical delivery conditions for valves; Compilation of tests, testing methods and acceptance criteria	This was the cornerstone of German valve testing. It defined test procedures (shell, closure, backseat), pressures, and acceptance criteria. It specified leakage rates from 1 (tight) to 3 (permissible leakage).	Withdrawn	EN 12266-1 / ISO 5208. The concepts of defined leakage rates in EN 12266 are a direct evolution of the principles in DIN 3230.
DIN 3230-4	Valves; requirements and testing for butterfly valves	Provided specific testing requirements tailored to butterfly valves, covering aspects like seat tightness and operational torque.	Withdrawn	EN 12266-1, with specific requirements now typically found in the product standard (e.g., EN 593).
DIN 3230-5	Technical delivery conditions for valves; Valves for flammable gases	Specified supplementary requirements for valves handling flammable gases, including material selection and enhanced testing for tightness (often requiring helium tests).	Withdrawn	EN 14141 (Valves for natural gas transportation in pipelines), and aspects covered by Fugitive Emissions standards like ISO 15848-1.
DIN 3230-6	Technical delivery conditions for valves; Valves for drinking water service	Focused on materials safe for potable water (e.g., KTW/DVGW approvals) and specific testing protocols to ensure public health safety.	Withdrawn	EN 1074 (Valves for water supply). National regulations (DVGW worksheets in Germany) are now primary.
Key Butterfly Valve Design & Dimension Standards (Relevant for Testing Context)
DIN 3354	Valves - General requirements	Defined general requirements for the design, materials, and marking of valves. A foundational document.	Withdrawn	Largely superseded by EN 19 (Marking of industrial valves) and specific EN product standards.
DIN EN 593	Industrial valves - Metallic butterfly valves	The current, active European standard for the design, performance requirements, and testing of metallic butterfly valves. It references EN 12266-1 for testing.	Active	Harmonized European standard, superseding national standards like DIN 3354 for butterfly valves.
DIN 3840	Industrial valves - Actuator attachment for butterfly valves	Specifies the dimensions of the mounting flange for actuators on butterfly valves, ensuring interchangeability.	Withdrawn	Superseded by ISO 5211 (Industrial valves - Part-turn actuator attachments).
Associated Flange & Connection Standards (Critical for Test Fixtures & Installation)
DIN EN 1092-1	Flanges and their joints - Circular flanges for pipes, valves, fittings and accessories, PN designated - Part 1: Steel flanges	The primary standard for steel flanges in Europe. Defines flange types (e.g., Type 01 Plate, Type 11 Welding Neck), dimensions, tolerances, materials, and pressure-temperature (PN) ratings. Essential for connecting valves for testing.	Active	Harmonized standard replacing older national standards (e.g., DIN 2501, DIN 2576, DIN 2633). Correlates with ASME B16.5 but is not interchangeable.
DIN 2501	Flanges; mating dimensions	This was the classic German standard for flange mating dimensions. It specified dimensions for PN6 to PN100.	Withdrawn	Superseded by DIN EN 1092-1. Still referenced in legacy documentation.
DIN 2527	Blind flanges	Specified dimensions for blind flanges used to cap off systems or valve ends during shell testing.	Withdrawn	Now covered within DIN EN 1092-1 (as Type 05).
DIN 2690	Flange gaskets - Steel gaskets for flanges with groove and tongue	Defined dimensions and materials for metallic tongue and groove gaskets, providing high-integrity sealing for testing and service.	Withdrawn	Now covered by standards like EN 1514-6.
Material & Certification Standards (Essential for Traceability & Verification)
DIN 50049	Types of inspection documents for metallic products	The original German standard defining material test certificates. It specified document types like 2.1, 2.2, 3.1B.	Withdrawn	Superseded by EN 10204. The terminology (e.g., "3.1B") has been directly adopted and is now "3.1". This is globally recognized.
DIN EN 10204	Metallic products - Types of inspection documents	The current, active standard defining the type of material test certificates. It ensures traceability of materials used in the valve construction.	Active	Type 2.1: Declaration of Compliance. Type 2.2: Test Report (non-specific inspection). Type 3.1: Inspection Certificate (specific inspection by manufacturer's rep). Type 3.2: Inspection Certificate (specific inspection by 3rd party).
DIN 1693	Cast iron with spheroidal graphite (Ductile Iron)	Specified material properties for ductile iron castings (e.g., GGG-40, GGG-50), a common material for butterfly valve bodies.	Withdrawn	Superseded by EN 1563 (Spheroidal graphite cast irons).
DIN 17240	Heat-resistant and highly heat-resistant materials for bolts and nuts	Defined materials for high-temperature bolting, critical for maintaining joint integrity during thermal cycling or fire tests.	Withdrawn	Superseded by EN 10269 (Steels and nickel alloys for fasteners with specified elevated and/or low temperature properties).

3.2 Appendix B: British Standards (BS)

British Standards have historically played a major role in the oil, gas, and process industries. While many have been harmonized with EN/ISO standards, key documents like BS 6364 for cryogenic testing remain global benchmarks.

Standard Number	Title / Subject	Relevance & Key Features	Current Status	Superseded by / Correlates with
BS 6364	Valves for cryogenic service	The definitive global standard for type-testing valves at cryogenic temperatures (-196°C). It specifies test procedures, apparatus, and leakage rate acceptance criteria for both seat and external leakage.	Active (Latest edition 2023)	Correlates with MSS SP-134. No direct EN/ISO equivalent holds the same industry authority.
BS 5155	Specification for butterfly valves	The former British standard for the design and dimensions of butterfly valves.	Withdrawn	Superseded by BS EN 593.
BS 6755-1	Testing of valves. Specification for pressure testing of metallic valves	The former British standard for pressure testing.	Withdrawn	Superseded by BS EN 12266-1.
BS 6755-2	Testing of valves. Specification for fire type-testing requirements	The former British standard for fire testing.	Withdrawn	Superseded by API 607 / ISO 10497.

3.3 Appendix C: Japanese Standards (JIS)

Japanese Industrial Standards (JIS) are developed by the Japanese Industrial Standards Committee (JISC) and are widely respected in Asia and globally, particularly in shipbuilding and plant engineering.

Standard Number	Title / Subject	Relevance & Key Features	Current Status
JIS B2003	Valve inspection - General	The primary Japanese standard for general valve inspection and testing. It specifies shell tests, seat tests (hydrostatic and pneumatic), and backseat tests. Similar in scope to API 598.	Active
JIS B2032	Wafer type rubber-seated butterfly valves	Specifies the design, materials, dimensions, and testing for rubber-seated butterfly valves. References JIS B2003 for testing procedures.	Active
JIS B2220	Steel pipe flanges	Defines the pressure ratings (e.g., 5K, 10K, 20K) and dimensions for steel pipe flanges. This is the essential standard for ensuring connectivity of JIS-rated valves.	Active
JIS F7480	Shipbuilding - Steel valve fire-safe test	A fire-testing standard specifically for marine applications. While ISO 10497 is more common for industrial use, this is critical in shipbuilding contexts.	Active

3.4 Appendix D: Chinese Standards (GB/T)

GB/T (Guobiao/Tuījiàn, meaning National/Recommended) standards are the national standards of China. With China's growth as a major industrial producer, understanding these standards is crucial for global procurement and projects within the country.

Standard Number	Title / Subject	Relevance & Key Features	Current Status
GB/T 13927	Industrial valves - Pressure testing	The primary general-purpose valve testing standard in China. It is largely harmonized with ISO 5208, specifying shell tests, high and low-pressure seat tests, and using a system of leakage rates.	Active
GB/T 12238	Flanged and wafer butterfly valves	The main product standard for butterfly valves, covering design, materials, face-to-face dimensions, and testing requirements. It mandates testing according to GB/T 13927.	Active
JB/T 8527	Valve packing static test procedure	A key machinery industry standard that specifies methods for testing the sealing performance of valve packing, analogous to API 622 but for the Chinese market.	Active
GB/T 9112 ~ 9124	Steel pipe flanges series	A comprehensive series of standards defining types, dimensions, and technical conditions for various steel flanges (e.g., slip-on, weld neck, blind). This series defines both PN (European) and Class (American) systems.	Active

3.5 Appendix E: Russian Standards (GOST)

GOST standards are the primary set of technical standards maintained by the Euro-Asian Council for Standardization, Metrology and Certification (EASC), and are obligatory in the Commonwealth of Independent States (CIS). They have their own distinct system for pressure classes and testing.

Standard Number	Title / Subject	Relevance & Key Features	Current Status
GOST 9544-2015	Pipeline valves. Shut-off valves seal tightness norms	The fundamental GOST standard defining leakage rate classes for valve seats and stuffing boxes. It specifies four main tightness classes: A, B, C, D. Class A signifies "no visible leaks" (gas-tight).	Active
GOST 33259-2015	Flanges of pipeline valves, fittings and pipelines. Design, dimensions and general technical requirements	The modern GOST standard for flanges, which aims to harmonize with ISO standards. It defines dimensions for flanges based on PN ratings.	Active
GOST 12815-80	Flanges for valves, fittings, pipes and apparatus	The older, but still widely encountered, GOST flange standard. It defines dimensions and joining types. It's crucial to specify which standard (GOST 33259 or GOST 12815) is required.	Superseded but widely referenced
GOST R 54808-2011	Industrial valves. Fire-type testing requirements	The Russian standard for fire testing of industrial valves, serving a similar purpose to ISO 10497 / API 607 within the CIS region.	Active

4.1 Leakage Rate Classifications (per ISO 5208 / EN 12266-1)

Unlike the simple pass/fail criteria of API 598, ISO and EN standards provide a granular classification of seat tightness. The purchaser must specify the required rate. This table summarizes the maximum allowable leakage for the most common rates.

Rate	Test Fluid	Maximum Allowable Leakage	Description / Common Application
Rate A	Liquid	0 (No visually detectable leakage)	Bubble-tight / Zero Leakage. Required for critical isolation, resilient-seated valves, and where specified. Equivalent to API 598.
Rate A	Gas	1 bubble (approx. 0.3 mm³/s) over the test duration.
Rate AA	Gas	0.01 × DN (mm³/s)	Special high-integrity gas tightness class in EN 12266-1, tighter than Rate B.
Rate B	Gas	0.3 × DN (mm³/s)	A common industrial standard for metal-seated gas valves.
Rate C	Liquid	0.1 × DN (ml/s)	Common for general purpose liquid applications with metal seats.
Rate D	Liquid	1.0 × DN (ml/s)	Often the default for large water pipeline valves. The default rate for API 6D hydrostatic seat tests.
Note on DN: DN (Diamètre Nominal) is the nominal diameter of the valve in millimeters. For example, for a DN 100 (4-inch) valve specified to Rate C, the maximum allowable liquid leakage would be 0.1 × 100 = 10 ml/s.

4.2 Archivist's Concluding Statement

This archive asserts that a valve's integrity is not defined by a single standard, but by the rigorous, verifiable, and documented application of the correct standard for its intended service. True fidelity in valve engineering and procurement is achieved only through a comprehensive understanding of these interconnected global protocols—from general pressure tests like API 598 to specialized validations like BS 6364 for cryogenics and the quantified leakage rates of ISO 5208. To specify a valve is to specify its proof of performance; this archive serves as the definitive lexicon for that proof.