ASME B40.100 vs. EN837
- Merit Instruments
- Jun 1
- 3 min read
ASME B40.100 and EN 837 are the two most widely recognized pressure gauge standards in North America and Europe, respectively. While both standards address the design, construction, performance, and safety of pressure gauges, there are several important differences.
Overview
ASME B40.100
Developed by the American Society of Mechanical Engineers.
Predominantly used in the United States, Canada, and other markets following North American engineering practices.
Covers pressure gauges and gauge attachments.
Includes extensive requirements for process gauges, safety features, and performance classifications.
EN 837
Developed by the European Committee for Standardization.
Widely used throughout Europe and many international markets.
Divided into:
EN 837-1: Bourdon tube gauges
EN 837-2: Selection and installation recommendations
EN 837-3: Diaphragm and capsule gauges
1. Accuracy Classification
ASME B40.100
Uses grade designations such as:
Grade | Typical Accuracy |
4A | ±0.1% |
3A | ±0.25% |
2A | ±0.5% |
1A | ±1.0% |
B | ±2.0% |
Accuracy is typically expressed as a percentage of span.
EN 837
Uses accuracy classes:
Class | Accuracy |
0.1 | ±0.1% |
0.25 | ±0.25% |
0.6 | ±0.6% |
1.0 | ±1.0% |
1.6 | ±1.6% |
2.5 | ±2.5% |
4.0 | ±4.0% |
EN classes are generally more granular than ASME grades.
2. Dial Size Standards
ASME B40.100
Common nominal dial sizes:
1.5"
2"
2.5"
3.5"
4.5"
6"
These reflect traditional North American gauge sizing.
EN 837
Metric nominal sizes:
40 mm
50 mm
63 mm
80 mm
100 mm
160 mm
250 mm
Metric sizing is the norm throughout Europe.
3. Pressure Range Presentation
ASME B40.100
Commonly uses:
psi
inHg
kPa
bar
compound scales
EN 837
Typically emphasizes:
bar
mbar
kPa
MPa
Dual-scale gauges are common for export applications.
4. Safety Design Requirements
One of the most significant differences.
ASME B40.100
Defines:
Solid-front gauges
Blow-out backs
Safety pattern gauges
Safety classifications include:
Type | Description |
General Purpose | Standard construction |
Solid Front | Enhanced operator protection |
Safety Pattern | Maximum protection |
This standard is widely referenced in refinery, chemical, and process industries.
EN 837
Also requires pressure-relief devices and operator protection, but classifies safety features somewhat differently and places greater emphasis on case design, venting, and conformity with European machinery and pressure equipment requirements.
5. Overpressure Requirements
ASME B40.100
Typically requires:
130% full-scale overpressure capability for many industrial gauges.
Performance testing after overpressure exposure.
EN 837
Requirements vary by gauge type and pressure range:
Generally 125% to 130% of full scale.
Specific limits depend on nominal size and pressure element design.
6. Environmental Testing
ASME B40.100
Focuses heavily on:
Vibration resistance
Pulsation resistance
Corrosion resistance
Pressure cycling
EN 837
Includes:
Temperature effects
Environmental influences
Mechanical vibration
Long-term stability
EN standards tend to provide more detailed environmental correction guidance.
7. Thread Standards
ASME B40.100
Most common:
1/8" NPT
1/4" NPT
1/2" NPT
EN 837
Most common:
G1/8
G1/4
G1/2 (BSPP)
R-thread variants (BSPT)
This is often the biggest practical issue when exporting gauges between North America and Europe.
8. Market Application
ASME B40.100 Preferred In:
Oil & gas
Chemical processing
Industrial manufacturing
HVAC (North America)
OEM equipment sold in North America
EN 837 Preferred In:
European industrial markets
OEM equipment exported to Europe
CE-marked machinery
Process and utility industries throughout the EU
At Merit Instruments, we offer our line of instrumentation manufactured in accordance with many international standards including ASME B40.100 and EN837 and EN837-1. Contact Merit Instruments or your Merit Instruments distributor if you have any questions about products being manufactured to these or other international standards.
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