Pressure gauges - EN 837 vs ASME B40

What is EN 837?

EN 837 is the European National Standard for bourbon tube pressure gauges. This standard was approved by the European Committee for Standardisation, of which the United Kingdom is a member. Due to this you may see EN 837 as BS EN 837 as the European Standard has become a British Standard.

Here at Brannan all our pressure gauges are made to EN 837. EN 837 determines the gauge size, accuracy it needs to conform to, scale divisions and calibration procedure of the gauge.

What is ASME B40?

ASME B40 is the American National Standard for bourbon tube pressure gauges and was approved by the American National Standards Institute. This, like EN 837, gives guidance on the gauge size, accuracy, divisions and calibration of gauges, however it is important to note that some of these in ASME B40 are somewhat different from that of EN 837.

What is the difference between EN 837 and ASME B40?

The main difference between the standards is that ASME B40 is advisory only, however, pressure gauges made to EN 837 must conform to the standard. Below are the main differences between EN 837 and ASME B40:

Difference	EN 837	ASME B40
Gauge size (mm)	40	40
	50	50
	63	65
	80	90
	100	115
	150	150
	250	215
		305
		405
		(Note that ASME B40 gauges are usually indicated in inches)
Accuracy (%)	0.1	0.1 (4A)
	0.25	0.25 (3A)
	0.6	0.5 (2A)
	1	1 (1A)
	1.6	2 (A)
	2.5	3 (B)
	4	4 (C)
		5 (D)
Preferred unit of pressure	Bar	PSI
Preferred pressure connection	BSP	NPT