EN 558-1 is a European standard that specifically specifies the face-to-face (FTF) and center-to-face (CTF) dimensions of metal valves in flanged piping systems, and is mainly applicable to valves designated by PN (nominal pressure).
In the field of butterfly valves, the core role of EN 558-1 is to provide standardized specifications for structural length to ensure that valves produced by different manufacturers are interchangeable when installed in pipelines.
I.Core Role
For valves like butterfly valves, “structural length” is a very critical installation dimension. It refers to the distance between the two connecting end faces of the valve and determines whether the valve can be accurately installed into the pipeline system.
- Unified installation dimensions: EN 558-1 specifies standard structural lengths for flange-connected metal valves (such as butterfly valves, gate valves, check valves, etc.) according to different “Series”. This makes valves of the same series from different manufacturers interchangeable in the same diameter and pressure class.
- Applicability of butterfly valves: This standard specifically divides the sizes of butterfly valves into multiple categories such as “flange type” and “wafer type”. It is an important reference in the design and selection of butterfly valves.
II.Core Series
In the EN 558-1 standard, the structural length of butterfly valves mainly corresponds to the following series:
Series 13: Corresponds to BS 5155 standard (usually used for flange centerline butterfly valves).
Series 16: Complies with API 609 and BS 3135 standards.
Series 20: Complies with API 609 and BS 5156 standards (commonly used for wafer type butterfly valves and lug type butterfly valves).
Series 25: Complies with MSS SP 67 and BS 2080 standards.
III.Standard Version & Current Status
It is important to note that EN 558-1 has been superseded.
- This standard (such as EN 558-1:1995 or the 1996 version) has been merged and replaced by EN 558:2008, and the latest current version is EN 558:2017.
- The new version of the standard not only covers PN-specified valves, but also incorporates Class-specified valve size requirements.
IV.Example
In actual butterfly valve product specifications, you often see the serial number referencing this standard to determine the structural length. For example:
The construction length of wafer butterfly valves and lug butterfly valves may be marked in accordance with EN 558 Series 20.
The construction length of fluorine-lined butterfly valves may be marked in accordance with EN 558-1/T5 (i.e. Series 5, corresponding to ANSI B16.10 short series).
Post time: Sep-05-2026
