A valve that is perfect in every other way is useless if its flanges will not bolt to your pipe. Valve standards define the physical dimensions that make valves interchangeable: flange drilling, facing, pressure classes and thread forms. Buying across standards is one of the most common — and most expensive — mistakes in valve procurement. This guide explains the four major systems you will meet.
Why Standards Matter
Standards ensure that a valve from one manufacturer bolts onto piping built to the same standard as another manufacturer. Mixing standards is not a minor inconvenience: an ANSI flange will not line up with a JIS flange, an NPT thread will not seal in a BSP port, and a Class 300 flange has different bolt holes from a PN16 flange. Always confirm the piping standard before ordering.
ANSI / ASME Standards
The ANSI/ASME system dominates North America and much of the oil and gas industry. Valves are rated in pressure classes — Class 150, 300, 600 and higher — based on the ASME B16.34 pressure-temperature tables. Flange dimensions follow ASME B16.5, and threads follow NPT. When an international project says "Class 150 RF flange", it is quoting this system.
JIS Standards
The JIS system is common in Japan and many Asian plants. Flanges are rated by nominal pressure such as JIS 10K and 20K, with dimensions in JIS B2220. Threaded connections commonly use BSP or PT forms. JIS and ANSI flanges look similar but have different bolt circle diameters and hole counts — they are not interchangeable, and forcing them causes leaks.
DIN / EN Standards
The DIN/EN system is standard in Europe. Flanges are rated by nominal pressure PN — PN10, PN16, PN25, PN40 — and dimensions follow EN 1092-1 (successor to DIN standards). Pipe sizes use nominal diameter DN. Threaded valves commonly use BSP threads. European-built plants and machinery almost always specify this system.
GB Standards
The GB system is the Chinese national standard, widely used in domestic Chinese plants and in Chinese equipment exported worldwide. Flange and valve dimensions follow GB/T series, with pressure ratings expressed in PN classes that often align with DIN/EN. Many Chinese manufacturers build to GB as standard but can supply ANSI, JIS or DIN configurations on request — confirm which one you need when ordering.
Thread Standards: NPT vs BSP
Threaded connections are where standard mismatches hurt most. NPT (American) and BSP (British) threads look similar but have different thread angles, pitches and sealing principles — NPT seals on the thread taper, BSP seals on the face or a washer. NPT will not seal properly in a BSP port and vice versa. Always state the thread standard with threaded valves.
How to Specify Valves Correctly
- State the piping standard: ANSI/ASME, JIS, DIN/EN or GB
- State the pressure class or PN rating, and the flange facing (RF, FF, RTJ)
- State the nominal size in the right system — inches with ANSI, DN with DIN/EN
- For threaded valves, state NPT or BSP explicitly
- Confirm the design and test standard (ASME B16.34, API, EN, GB) for the body
Ask a Manufacturer Before You Spec
Getting the standard right is a one-line question that saves weeks of rework. Langtuo Valve, a Shenzhen-based manufacturer with more than 15 years of experience and ISO 9001 certification, supplies valves to ANSI, JIS, DIN and GB standards for export to over 30 countries. Tell us your piping standard and pressure class through the contact page, and we will confirm the exact flange and thread configuration.
A valve that is perfect in every other way is useless if its flanges will not bolt to your pipe. Valve standards define the physical dimensions that make valves interchangeable: flange drilling, facing, pressure classes and thread forms. Buying across standards is one of the most common — and most expensive — mistakes in valve procurement. This guide explains the four major systems you will meet.
Why Standards Matter
Standards ensure that a valve from one manufacturer bolts onto piping built to the same standard as another manufacturer. Mixing standards is not a minor inconvenience: an ANSI flange will not line up with a JIS flange, an NPT thread will not seal in a BSP port, and a Class 300 flange has different bolt holes from a PN16 flange. Always confirm the piping standard before ordering.
ANSI / ASME Standards
The ANSI/ASME system dominates North America and much of the oil and gas industry. Valves are rated in pressure classes — Class 150, 300, 600 and higher — based on the ASME B16.34 pressure-temperature tables. Flange dimensions follow ASME B16.5, and threads follow NPT. When an international project says "Class 150 RF flange", it is quoting this system.
JIS Standards
The JIS system is common in Japan and many Asian plants. Flanges are rated by nominal pressure such as JIS 10K and 20K, with dimensions in JIS B2220. Threaded connections commonly use BSP or PT forms. JIS and ANSI flanges look similar but have different bolt circle diameters and hole counts — they are not interchangeable, and forcing them causes leaks.
DIN / EN Standards
The DIN/EN system is standard in Europe. Flanges are rated by nominal pressure PN — PN10, PN16, PN25, PN40 — and dimensions follow EN 1092-1 (successor to DIN standards). Pipe sizes use nominal diameter DN. Threaded valves commonly use BSP threads. European-built plants and machinery almost always specify this system.
GB Standards
The GB system is the Chinese national standard, widely used in domestic Chinese plants and in Chinese equipment exported worldwide. Flange and valve dimensions follow GB/T series, with pressure ratings expressed in PN classes that often align with DIN/EN. Many Chinese manufacturers build to GB as standard but can supply ANSI, JIS or DIN configurations on request — confirm which one you need when ordering.
Thread Standards: NPT vs BSP
Threaded connections are where standard mismatches hurt most. NPT (American) and BSP (British) threads look similar but have different thread angles, pitches and sealing principles — NPT seals on the thread taper, BSP seals on the face or a washer. NPT will not seal properly in a BSP port and vice versa. Always state the thread standard with threaded valves.
How to Specify Valves Correctly
- State the piping standard: ANSI/ASME, JIS, DIN/EN or GB
- State the pressure class or PN rating, and the flange facing (RF, FF, RTJ)
- State the nominal size in the right system — inches with ANSI, DN with DIN/EN
- For threaded valves, state NPT or BSP explicitly
- Confirm the design and test standard (ASME B16.34, API, EN, GB) for the body
Ask a Manufacturer Before You Spec
Getting the standard right is a one-line question that saves weeks of rework. Langtuo Valve, a Shenzhen-based manufacturer with more than 15 years of experience and ISO 9001 certification, supplies valves to ANSI, JIS, DIN and GB standards for export to over 30 countries. Tell us your piping standard and pressure class through the contact page, and we will confirm the exact flange and thread configuration.