How to Conform to en 837-1 (summary)

8/18/2019 How to Conform to en 837-1 (summary)

http://slidepdf.com/reader/full/how-to-conform-to-en-837-1-summary 1/18

How to conform to EN‐837‐1 (European Standard)

Sizes and scale ranges:

1. Nominal sizes:

1.1 Industrial gauge: 40mm, 50mm, 63mm, 80mm, 100mm, 150mm,

160mm, 250mm

General tolerances (EN 22768‐1):



2. Scale Ranges:

2.1 Test gauge: Specified by the purchaser

2.2 Industrial gauge: see below (bar is the preferred unit)

In case of kPa and MPa:

0‐60 kPa up to 0‐1000 kPa, then 0‐1,6 MPa to max. 0‐160MPa.



Design and construction:

0. General – Protection against corrosion – all parts that are not inherently resistant

to corrosion, must be painted or otherwise treated

1. Case design and construction

See Nominal sizes 1.1

2. Window designs

80mm and up gauges min. 3mm thick sheet of glass (or other

similar material specified by the purchaser)

Uniform in thickness and free from defects!

3. Mounting designs

3.1 Mounting of circular surface mounting gaugesSee Nominal sizes 1.1 (check enough space for the blowout device)

3.2 Mounting of circular flush mounting gauges

See Nominal sizes 1.1 (check enough space for the blowout device)



4. Shank (connector) design and construction

4.1 Screw threads: Do NOT mix NPT and BSPT (G) threads!!!

4.2 Shank dimensions: dimensions of screw thread + hexagon/square + spigot

see below

BSPP (G): Parallel pipe threads according to ISO 228‐1



NPT (R): Taper pipe thread according to ANSI/ASME B1.20.1

4.3 Sealing washer (optional for parallel screw threads ONLY):

material depends on the pressure and the fluid to be measured

Measurements are shown below:

4.4 High pressure shank (HP) for connection with lens seal TBW



5. Bourdon tube material design and construction

6. Dials (scales) and pointers

6.1 Dials and Scales

6.1.1 Scale angle

Normally covers 270o

(for classes 0.1, 0.25 and 0.6, it may be longer)

(Dials with an accuracy of 1.6 % (2.5% and 4% too) have a stopping

and a shortened first block. With an accuracy of 1% or better, there is

no stopping and no shortened first block on the dial.)

6.1.2 Scale interval (the value (not length) between 2 scale marks)

1 x 10n, 2 x 10n or 5 x 10n (“n” can be positive, negative number or

zero)

See attachment



6.1.3 Scale marks

Thickness of scale marks < 1/5 of scale spacing

Scale spacing > 1mm

Scale spacing constant (longest and shortest spacing

difference < 1/5)

(e.g. shortest 1mm longest < 1.2mm)

6.1.4 Scale numbering

Depends on manufacturer

See attachment

6.2 Pointers

6.2.1 Pointer dimensions

Tip of pointer width < minor scale mark width

Tip of pointer falls between 1/10 and 9/10 of shortest scale markMinimum pointer length from axis to tip is shown below:

6.3 Mirror scale

Class 0.1 gauge requires a mirror scale

Class 0.25 and 0.6 gauges must minimize parallax errors e.g.

use knife edge pointers optional, but recommended: use a mirror scale

6.4 Information on dial

a) unit of pressure

b) accuracy class at the end of scale

c) optional: type of pressure element symbol (see below)



d) if gauge’s max. steady working pressure = max. scale value identifying

mark at max. scale value (see below)

e) if gauge is not calibrated for vertical use symbol of intended dial plane

angle

f) class 0.1, 0.25 and 0.6 gauges if a customer wants to use the gauge at

other than the reference temperature mark is needed

g) class 0.1, 0.25 and 0.6 gauges if the provided accuracy value of a

gauge is only for liquid or gas mark is needed

h) optional: indicate EN‐837‐1

j) name or logo of manufacturer/supplier

k) serial number class 0.1 and 0.25 (+ metrological‐related) mark

is needed

class 0.6 to 4 mark may be provided

m) if wetted parts differ from brass, bronze, tin, or hard solder mark is

needed

n) Safety pattern gauges mark is needed (see x.x.x)

o) Oxygen and acetylene gauges mark is needed (see x.x.x)



6.5 Pointer stop

Max. steady working pressure = max. scale value free zero

Max. steady working pressure = 75% of max. scale value may have

free zero

7. Safety design See also: Test section

In case of pressure element failure in a safety gauge, blast and debris cannot

leave the gauge from the front. Recommendations as seen below:

7.1 Blow‐out device (S1) on gauges (no special marking is needed)

Requirements

a) resistant to blocking by debris and dirtb) pressure needed to function < half of window burst

pressure

c) installed on liquid filled gauges

7.2 Safety pattern gauges

Types a) 40‐80 size without baffle wall (S2)

b) 40‐250 size with baffle wall (S3)

7.2.1 Energy release test See Test section

7.2.2 Window

Non‐splintering material (e.g. laminated glass, or non‐splintering

plastic)

7.2.3 Blow‐out back

See 2.2.1

Also see Test section

7.2.4 Baffle wall

Permanent wall between Bourdon tube and dial.

Holes on wall cannot exceed 5% of overall area.

7.2.5 Marking (of safety pattern gauges)



40‐80 size without baffle wall “S” mark and EN 837‐1 on dial

40‐250 size with baffle wall “S” mark and EN 837‐1 on dial

7.3 Oxygen or acetylene gauges

Must be safety pattern type gauge

Material must comply with EN 29539

7.3.1 Oxygen gauges

Wetted parts must be oil and grease free.

On dial “oxygen” and no lubrication symbol “ ”

7.3.2 Acetylene gauges

On dial “acetylene”

7.4 Liquid filled gauges

Atmospheric pressure compensator device (e.g. pressure relief vent)must be installed on the gauge

7.5 Metrology gauges TBW



Accuracy, overload and temperature effects

1. Accuracy and overload

1.1 Accuracy classes

At 20C permissible errors are as follows:

1.1.1 Temperature effects: ± 0,04 x (t2 ‐ t1) %, where:

t1 = reference temperature in oC (about 20oC)

t2 = ambient temperature in oC (actual temperature)

1.2 Accuracy classes and nominal sizes

Gauges with pointer stop 10%‐100% range must be accurate

Gauges with free zero

0%‐100% range must be accurate

1.3 Endurance tests

1.3.1 Maximum steady working pressure 75% of the maximum scale

1.3.1.1 Steady pressure test

Maximum scale value for an extended period of time

1.3.1.2 Overpressure test

See below:



1.3.1.3 Cyclic pressure test

Withstands pressure fluctuation from 30% to 60% of maximum

scale value for the following number of pressure cycles:

1.3.2 Maximum steady working pressure maximum scale (see 1.4.4/d)

1.3.1.1 Steady pressure and overpressure tests

1.3x the maximum scale value for an extended period of

time

1.3.1.2 Cyclic pressure test

Withstands pressure fluctuation from 30% to 95% of maximumscale value for 200,000 cycles (for classes 0.1, 0.25, and 0.6

15,000 is enough)

1.4 Operating conditions

1.4.1 Service temperature

Ambient: ‐20C to +60C

Fluid: based on the properties of the liquid

1.4.2 Storage temperature

‐40C to +70C (gauge cannot change its appearance (neither the dial))

1.4.3 Water and dust resistance

Minimum: IP31 (indoor) (Tools, thick wires, etc. / Dripping water )

IP44 (outdoor) (Most wires, slender screws, ants etc. /

Water splashing against the enclosure from any direction)

1.4.4 Mechanical shock

Shock loads of 150 m/s2 (for accuracy classes 1‐4)

1.4.5 Mechanical vibration

(for accuracy classes 1‐4)



Three orthogonal axes: 5m/s2 acceleration (~1/2 G)

10Hz to 150Hz frequency

1 octave/min. scan rate for 2 hours/axis

After test: indicator accuracy shall fall within original

class accuracy x 1.5 (e.g. class 1.6 1.6% x

1.5 = +‐2.4%)

1.4.6 Leak rate

Shall not exceed 5 x 10‐3 mbar l/s

1.4.7 Mounting position

+‐5o tilting shall not influence the indicator more than original class x

0.5 (e.g. class 1.6 1.6% x 0.5 = +‐0.8%)



Testing

1. Testing

Reference temperature: 20C

Testing temperature (dial is in nominal position +‐3o):

Type approval tests (before a product is allowed to be sold) of all

classes, and production piece (before production gauges

prototype) tests of class 0.1, 0.25 and 0.6 gauges +‐2C

Production piece test of class 1, 1.6, 2.5, and 4 gauges +‐5C

1.1 Sample tests (type approval / production piece).

See below (table) and attachment. Group A (lowest range), Group B/C,

Group D (highest range)

1.2 Test points and hysteresis

“The number of test points shall be evenly distributed over the entire scale

as follows:

classes 0,1; 0,25 and 0,6: a minimum of 10 points;

classes 1; 1,6 and 2,5: a minimum of 5 points;

class 4: a minimum of 4 points.

Each point shall be tested with rising and falling pressure. The maximum

scale value is a test point.

Zero is a test point when it is free.

The reading shall be obtained after the gauge has been lightly tapped.

Pressure readings shall be interpolated between 1/4 and 1/10 of the

distance between two scale marks.”

“The hysteresis is calculated from the difference in applied pressure for the

same indication point or the difference in pressure indication for the same

applied pressure on falling and rising pressure.”



1.3 Temperature (difference) effect test

From reference 20C temp., in 20C steps, ambient maximum (‐20C) and

minimum (+60) shall be reached. After thermal equilibrium is reached,

tests shall be run (see 1.2).

1.4 Endurance test See also Point 2.2 of Section Accuracy, overload and other

design Requirements for reference

1.4.1 Maximum steady working pressure 75% of the maximum scale

1.4.1.1 Steady pressure

Max. scale value 12 hours

1.4.1.2 Over‐pressure

See below 15 minutes

1.4.1.3 Cyclic pressure

Sinusoidally fluctuating pressure between 30%+‐5% and 60%+

5% of maximum scale value at 20 – 60 cycles per minute for X(see table) cycles.

E.g.: 100 bar max. scale value 30bar+‐5bar to 60bar+‐5bar and

back to 30bar+‐5bar (1 cycle) 20‐60 cycles/minute, 50000x =

~41 hours

Above 1000bar, frequency can be reduced to 1 cycle/minute.

1.4.2 Maximum steady working pressure Maximum scale

1.4.2.1 Steady and over‐pressure

Max. scale value x 1.3 12 hours

1.4.2.2 Cyclic pressure



Sinusoidally fluctuating pressure between 30%+‐5% and 95%+

5% of maximum scale value at 20 – 60 cycles per minute for X

cycles. X can be 200000 cycles, or 15000 cycles for classes 0.1;

0.25 and 0.6.

E.g.: 100 bar max. scale value 30bar+‐5bar to 60bar+‐5bar and

back to 30bar+‐5bar (1 cycle) 20‐60 cycles/minute, 50000x =

~41 hours

Above 1000bar, frequency can be reduced to 1 cycle/minute.

1.4.3 Accuracy test (after endurance test)

Let it rest for 1 hour.

Test it according to 1.2 error cannot exceed 1.2 x class (e.g. class 1=1% x 1.2 = 1.2%)

0‐1000bar and 0‐1600bar error cannot exceed 1.5 x class

1.5 Rated temperature test

Pressure element assembly 24 hours inside climatic chamber at max.

allowed temperature (‐20C and +60C)

Up to 1000bar 2.5 x max. scale value applied pressure

Above 1000bar 1.5 x max. scale value applied pressure

Then leak test at ambient temperature (see 1.8)1.6 Rated storage temperature test

Complete unpressurized gauge 24 hours inside climatic chamber at each

(2) temperature extreme (‐40C and +70C)

Then check appearance; after 1 hour at reference temp. check accuracy,

hysteresis (see 1.2); leakage (see 1.8)

1.7 Leak test

Pressure up to max. scale value

Up to 25bar (~363psi) max. scale value gas

Above 25bar max. scale value liquid

1.8 Ingress of water and foreign particles test (IPXX)

EN 60529

1.9 Mechanical shock test

TBW, EN 60068‐2‐27

1.10 Mechanical vibration test

TBW EN 60068‐2‐6



1.11 Mounting position test

Mount the gauge in a 5o angle forwards, backwards, to the left and right to

its normal position accuracy and hysteresis test (see 1.2) error cannot

exceed 0.5 x class.

1.12 Safety test

1.12.1 Gauges with blow‐out device

1.12.1.1 Constructional requirements

Blow‐out device must be in place (inspection)

1.12.1.2 Blow‐out test

Note: Liquid filled gauges should be tested with and without

liquid

a) Seal any leakage points by low strength sealantb) Pressurize the gauge via its connection (Bourdon tube is

removed)

c) Increase pressure till blow‐out device drops out or opens up

(not more than 100kPa) window and other components

cannot be damaged in any way

d) Block the blow‐out device and measure pressure that damages

the window (burst pressure)

1.12.2 Safety pattern gauge1.12.2.1 Constructional requirements

Visual inspection. See section “Accuracy, overload and other

design requirements” 2.2.2.2 – 2.2.2.5

1.12.2.2 Energy release test

a) Gas is released into the case through gauge connection. Up to

and for 63mm gauges bore size: min. 5mm. Above 63mm

gauges bore size: min. 10mm

b) Gas shall be stored in a “storage volume”, pressurized.

c) Gas storage volume connected to a (high speed – full valve

opening within 50ms) valve that in turn is connected to the

gauge’s connector.

d) Valve (and other connected pipes etc.) flow cross section

>28mm2

e) Length of connecting piping etc. <65mm

a1) Liquid fillable gauges must be tested with and without liquid

b1) Air bubble on top correct size



c1) Protect the operator

1.12.2.2.1 Gauges without baffle wall (S2)

Release gas into the case energy (pressure x volume)

contained by pressure element at max. scale value x 1.5

1.12.2.2.2 Gauges with baffle wall (S3)

a) Up to and for 1000 bar gauges Release gas into

the case energy (pressure x volume) contained by

pressure element at max. scale value x 2.5

b) Above 1000 bar gauges Release gas into

the case energy (pressure x volume) contained by

pressure element at max. scale value x 1.5

1.12.2.3 Evaluation

Test is successful if no particles, or fluid leaves the gaugefrom the front.

How to Conform to en 837-1 (summary)

Documents

Transcript of How to Conform to en 837-1 (summary)