EN 837-1 Explained: A Guide for Pressure Gauges | Manogauge
2026-05-08
The EN 837-1 standard is frequently cited on industrial pressure gauge datasheets, but its practical implications for selection and safety are often misunderstood. This technical reference decodes the standard's core requirements for Bourdon-tube pressure gauges, covering critical parameters from dimensions and accuracy to mandatory safety features. It provides engineers, OEMs, and distributors with the necessary knowledge to verify compliance, compare international standards, and select the correct instrument for demanding industrial environments, ensuring both operational reliability and personnel safety.
Core Specifications of EN 837-1
EN 837-1, 'Pressure gauges - Part 1: Bourdon tube pressure gauges - Dimensions, metrology, requirements and testing', is the definitive European standard for the most common type of mechanical pressure gauge. Its scope is to ensure interchangeability, consistent performance, and a minimum level of safety for gauges used across industrial applications. The standard precisely defines several key physical and performance characteristics.
Key metrological and dimensional parameters include:
Nominal Size (NS): This refers to the nominal case diameter in millimeters. Standard sizes are NS 40, 50, 63, 80, 100, 150, 160, and 250. This standardization ensures physical interchangeability in instrument panels and piping layouts.
Accuracy Class (KL or Cl.): The accuracy class indicates the maximum permissible error as a percentage of the full-scale value (FSV). Common classes are 0.1, 0.25, 0.6, 1.0, 1.6, 2.5, and 4.0. For example, a 100 bar gauge with KL 1.6 has a maximum permissible error of ±1.6 bar across the entire scale. Class 1.6 is typical for industrial process monitoring, while Class 2.5 is acceptable for less critical applications like filter monitoring.
Scale Ranges: The standard specifies preferred pressure ranges to promote uniformity. Ranges typically follow a 1, 1.6, 2.5, 4, 6, 10 sequence (e.g., 0-1 bar, 0-1.6 bar, 0-2.5 bar...). The scale must also include markings for the unit of pressure, most commonly 'bar' as per the standard, although kPa and MPa are also permitted.
EN 837-1 Safety Patterns: S1, S2, and S3
A critical function of EN 837-1 is to define safety systems that protect personnel in the event of a Bourdon tube rupture, a risk particularly with high-pressure gases, steam, or aggressive media. The standard outlines three levels of safety construction, identified as S1, S2, and S3.
Standard Gauge: A gauge with no specific safety pattern designation lacks features like a blow-out device or a solid front. These are suitable only for non-critical applications with low-pressure liquids.
Safety Pattern S1: These gauges feature a blow-out device, typically a rubber plug or disc on the rear of the case. In an overpressure event causing a tube leak, the case pressurizes and ejects the device, releasing pressure away from the operator. This design is common for liquid-filled gauges to relieve internal pressure buildup from temperature changes, and it provides a basic level of safety.
Safety Pattern S2: This is a solid front, blow-out back design. A solid baffle wall is placed between the dial and the internal mechanism. The entire rear of the case is designed as a blow-out back. If the Bourdon tube fails, the full force of the discharge is directed backwards, away from anyone viewing the gauge. The solid front contains any fragments.
Safety Pattern S3: The highest safety level, S3 combines the solid front and blow-out back of S2 with a laminated safety glass window. This provides maximum operator protection, as the laminated glass will not shatter and disperse fragments. S3 gauges are specified for the most hazardous applications, such as high-pressure (above 25 bar) compressible fluids like air, nitrogen, or steam, or with explosive or toxic media.
Comparison with ASME B40.100 and GB/T 1226-2017
While EN 837-1 is the dominant standard in Europe, components and equipment are often specified for a global market. Understanding its relationship with other major standards is essential for OEMs and international distributors.
ASME B40.100: This is the leading standard in North America. While conceptually similar, it differs in terminology and some specifications. Accuracy is defined by Grades (e.g., 2A, 1A, A, B) which specify error percentages over different parts of the scale, unlike the single FSV percentage of EN 837-1's Accuracy Class. Dimensions are specified in inches (e.g., 2.5", 4.5") instead of millimeters. Safety concepts like 'solid front, blow-out back' exist but are not codified into the S1/S2/S3 patterns. A gauge can be compliant with both standards, but this must be explicitly tested and declared by the manufacturer.
GB/T 1226-2017: This is the Chinese national standard for general pressure gauges. It is highly harmonized with the International Organization of Legal Metrology (OIML) recommendations, which are also the foundation for EN 837-1. As a result, GB/T 1226-2017 and EN 837-1 are very closely aligned in terms of accuracy classes, nominal sizes, and testing procedures. A gauge manufactured in compliance with EN 837-1 will generally meet the requirements of GB/T 1226-2017, simplifying specification for equipment destined for the Chinese market.
How to Verify Compliance on a Supplier Datasheet
Verifying a pressure gauge's compliance with EN 837-1 requires a careful review of the manufacturer's technical datasheet. Vague claims are insufficient; the documentation must provide specific, verifiable data points. Use the following checklist when evaluating a potential supplier.
Explicit Declaration: The datasheet must clearly state compliance, for example, "Design: EN 837-1".
Accuracy Class (KL): Look for a specific class designation, such as "Accuracy: Class 1.6 per EN 837-1". This confirms the performance has been tested against the standard's error limits.
Nominal Size (NS): The case diameter should be listed as a standard nominal size, e.g., "NS 100 (100 mm)".
Safety Pattern: If a safety gauge is required, the datasheet or model number must explicitly state the pattern, such as "Safety pattern S1" or "Solid front, S3 design per EN 837-1". If no pattern is mentioned, assume it is a standard construction.
Dial Markings: The dial image or specification should show the unit (e.g., bar), the accuracy class symbol, and the manufacturer's identity, as required by the standard.
Material and Environmental Ratings: While not part of EN 837-1 performance, check for supporting specifications like wetted parts material (e.g., 316L SS) and an Ingress Protection (IP) rating per EN 60529 (e.g., IP65) to ensure the gauge is suitable for the intended process media and environment.
Key takeaways
Verify the Accuracy Class (KL) on the datasheet; KL 1.6 is standard for industrial processes, while KL 2.5 is for general utility use.
Select the Safety Pattern (S1, S2, S3) based on media and pressure; mandate S3 (solid-front, blow-out back) for high-pressure gas applications.
EN 837-1 is a European standard using metric units (bar, mm), while ASME B40.100 is its North American counterpart using imperial units (psi, inches).
Confirm the gauge's Nominal Size (NS) and pressure range align with the standard's preferred values to ensure physical and operational interchangeability.
A datasheet must explicitly state "EN 837-1 compliant" and specify the KL and safety pattern to guarantee adherence to the standard.