Valve Standards Explained: Design, Flange, Face-to-Face & Testing

In valve inquiries or technical specifications, you will often see requirements such as:

• Design: EN 593
• Face-to-Face: EN 558
• Flange: EN 1092-2
• Testing: EN 12266-1

For many buyers, the first question is:

Why does one valve need to comply with so many different standards?

In fact, these standards are not repetitive requirements. Each one covers a different part of the valve specification, and together they form a complete technical requirement.

• The design standard defines how the valve should be designed.
• The face-to-face standard determines the overall installation length of the valve.
• The flange standard determines whether the valve can be correctly connected to the pipeline.
• The testing standard specifies how the valve should be tested for pressure strength and sealing performance.

Understanding what each standard covers can help buyers quickly judge whether a valve specification is complete. It can also reduce unnecessary technical clarification and avoid connection or installation problems later on.

What Are the Main Types of Valve Standards?

In industrial valve projects, commonly used standards can generally be divided into the following categories:

What Is a Valve Design Standard?

A valve design standard (also called a product standard) defines the basic requirements that a valve must meet during design and manufacturing. Depending on the valve type, it may cover areas such as valve construction, materials, pressure ratings, and basic performance requirements.

Different types of valves usually follow different design standards. For example:

It is important to note that the design standard does not define every dimensional or testing requirement. In actual projects, the face-to-face standard, flange standard, and testing standard are usually specified separately.

What Is a Valve Flange Standard?

A valve flange standard defines the dimensional and pressure-rating requirements that must be met when a valve flange is connected to a pipeline flange.

Depending on the standard, it may specify the flange outside diameter, number of bolt holes, bolt hole diameter, pitch circle diameter (PCD), flange thickness, facing type, and pressure rating.

Common valve flange standards include:

• In the EN system, common pressure ratings include PN10, PN16, PN25, and PN40.
• In the ASME system, common pressure classes include Class 150, 300, and 600.

One important point to keep in mind is that:
PN16 and Class 150 are not automatically interchangeable.

For this reason, when purchasing valves, providing only the DN/NPS size and PN/Class rating is usually not enough. Specifying the exact flange standard helps avoid problems such as misaligned bolt holes or incompatible flange dimensions after the valve arrives on site.

What Is a Face-to-Face Standard?

The face-to-face dimension of a valve is the installation length between its two connecting end faces.

Common face-to-face standards include:

The face-to-face dimension can be affected by the valve type, nominal size, pressure rating, valve construction, and the specific standard series.

For example, EN 558 includes different face-to-face series, such as:

• EN 558 Series 14
• EN 558 Series 15
• EN 558 Series 20
• EN 558 Series 48

Even if two valves have the same size and pressure rating, their installation lengths may still be different if they follow different face-to-face series.

For example:
DN300 PN16 butterfly valve

If one project requires EN 558 Series 14, while another valve is manufactured to a different series, the face-to-face dimensions may not be the same even though both valves are DN300 PN16.

This is especially important in valve replacement, maintenance projects, and installations where the existing pipeline spacing is already fixed.

If the face-to-face dimension does not match, the valve may still be impossible to install directly on site, even when the size, pressure rating, and flange dimensions are all correct.

So during project confirmation, in addition to checking:

DN + PN/Class + Flange Standard
you should also confirm:
Face-to-Face Standard / Series

What Is a Valve Testing Standard?

A valve testing standard defines which pressure and sealing tests a valve should undergo before leaving the factory, as well as how the test results are evaluated and accepted.

Common valve testing standards include:

Testing standards usually specify requirements for the shell test, seat leakage test, test pressure, holding time, test medium, allowable leakage, and acceptance criteria.

Two Common Types of Valve Tests

1. Shell Test
The shell test is mainly used to verify that the valve body, bonnet, and other pressure-containing parts can safely withstand the specified test pressure without unacceptable leakage or structural failure.

2. Seat Leakage Test
The seat leakage test is used to check whether the valve can achieve the required sealing performance when it is in the closed position.

The allowable leakage rate may vary depending on the testing standard and valve type.

For example, some soft-seated valves may require:
No visible leakage / Zero visible leakage

For some metal-seated valves, a certain amount of leakage may be permitted as long as it remains within the limits specified by the applicable standard.

What Standards Should Be Specified When Purchasing a Valve?

To reduce unclear technical requirements and avoid installation mismatches on site, it is recommended to confirm at least the following information when sending an RFQ or reviewing a valve specification:

For valve replacement projects, if the original standards are unclear, it is also best to provide the actual face-to-face dimension, flange dimensions, nameplate information, or drawings of the existing valve. This helps confirm installation compatibility more accurately.

Different valve standards cover different requirements, including valve design, face-to-face dimensions, flange connections, and testing. Understanding these differences helps buyers quickly determine whether a valve specification is complete and makes it easier to identify the real technical differences between different quotations.

For this reason, when sending an inquiry, it is recommended to specify not only the valve size and pressure rating, but also the design standard, face-to-face standard, flange standard, testing standard, and main materials.

Union Valve can review the customer’s datasheet, drawing, or existing valve specification and help confirm the appropriate standards and valve configuration, providing more accurate technical support for the project.If you have any further questions, please feel free to contact us.

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About the Author

Tina Wei

Sales Manager · Tianjin Union Valve Co., Ltd

More than 8 years of experience in the valve sales industry. Have extensive qualifications and experience.