How to Conform to ASME B40-100 (summary)

8/18/2019 How to Conform to ASME B40-100 (summary)

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Sizes and scale ranges

1. Nominal sizes

1.1 Gauge sizes inch (mm): 11/2 (~40), 2 (~50), 21/2 (~63), 31/2 (~80), 4 (~100),

6 (~150), 81/2, 12, 16

1.1.1 ASME gauge sizes

1.1.2 EN gauge sizes (for comparison)

2. Scale Ranges

2.1 Positive gauge pressure


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2.2 Negative gauge pressure

2.3 Compound pressure

2.4 Receiver

3. Units

3.1 SI units

3.2 MKSA units (has been replaced by SI units)


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3.3 Customary units (mainly in America)


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Design and construction

0. Common design requirements

Methods of joining: soft soldering, silver brazing, welding

1. Case design and construction

1.1 With and without pressure relief (blow‐out device)

1.2 Solid front with pressure relief back (safety pattern)

2. Window designs

2.1 Laminated glass

ANSI Z26.1 compliant reduced possibility of glass scattering (pressure

element rupture)

2.2 Tempered glass (2‐5x plain glass)

ASTM C 1048 compliant heat treated

ASTM C 1422 compliant chemically treated

2.3 Plastic

Impact, abrasive environment; temperature, corrosive atmosphere

2.4 Plain glass

Abrasion, chemical, wear resistant properties may be not suitable for

certain hazardous applications


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3. Mounting designs

2.1 Mounting types: stem, surface, flush, panel

a) Stem mounted bottom, back

b) Surface mounted bottom, backc) Flush mounted back

2.2 Mounting measurements


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4. Shank (connector) design and construction

a) Taper connection up to and for 20,000psi (~160,000kPa) (usually)

1/8”‐27 NPT; 1/4”‐18 NPT; 1/2”‐14 NPT

above 20,000psi (~160,000kPa) 1/4” and larger highpressure connection

b) Other than tapered (e.g. straight) for both lower and higher pressure

Sever vibration and stem mounting with liquid filling larger connection (1/2”

NPT instead of 1/4” NPT) and/or stronger material (SS instead of brass)

5. Bourdon

6. Dials (scales) and pointer design

4.1 Dials and scales4.1.1 Markings

a) Absolute or differential pressures are indicated (upper‐lower

both OK) ABSOLUTE/ABS; DIFFERENTIAL/DIFF; or ΔP

b) Manufacturer’s or customer’s (or both) trademark

c) Acetylene, ammonia, chemical, oxygen gauges special marking

d) Vacuum gauges (‐) sign before numbersOR mark the dial with

word VAC/VACUUM (upper‐lower both OK) (e.g. inHg (no minus sign

before numbers) place VAC under it)

4.1.2 Scale arc

270 deg. May be greater or less in special cases

4.1.3 Graduation lines

TBW (see EN recommendation)

4.1.4 Graduation near Zero

(Use of gauges near zero pressure is not recommended accuracy

problem)


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3A and 4A gauges (3rd picture) no takeup (minor graduation spacing

near zero shall be the same as at other parts of the scale)

Rest of the gauges takeup may be incorporated in this case,

indicate the pressure value where the graduation starts

a) Gauges with stop pin (1st picture) no graduation or numerals, or

both, at pointer stop position (pointer can rest against the stop pin)b) Gauges without stop pin (2nd picture) takeup should be indicated

with a perpendicular hash mark (pointer can rest anywhere within

hash mark)


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4.1.5 Dual scale dial

4.2 Pointers

4.2.1 Pointer dimensions

Tip width (Class 4A, 3A) < width of minor graduation line

4.2.2 Pointer stops

4.2.2.1 Internal stop

Retard mechanism (restrains the motion of the pressure

element or the mechanism)

4.2.2.2 Maximum stopApprox. at midway between last and first dial graduation. Motion

cannot be restrained at less than 105% of full scale pressure.

4.2.2.3 Minimum stop

Must prevent pointer motion below a point 5% lower than the

first scale graduation. (also see 4.1.4)

5. Safety design

5.1 Pressure relief means

Recommended:

a) gas pressure 400psi (2800kPa) or higher

b) liquid pressure 1000psi (7000kPa) or higher

5.1.1 Solid front with pressure relief back (safety pattern)

To reduce the likelihood of window shattering and projection of parts

through the front of the gauge

This additional protection cannot influence the gauge’s normal

operation.


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5.1.2 Open front with pressure relief (blow‐out device)

Protects against slowly built up pressure inside the gauge, but not

efficient against rapidly increasing pressure (projection of parts

through the front is possible)

5. Liquid filling

Not suitable for strong oxidizing agents, e.g. oxygen, chlorine, nitric acid,

hydrogen peroxide etc.


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Accuracy, overload and other design requirements

1. Accuracy and overload

1.1 Accuracy grades

1.2 General accuracy‐related propertiesa) Elastic element material and corrosion resistance are related. Sometimes

– depending on the used media – the used material’s properties may not

be optimal may have an impact on accuracy.

b) Environmental or media temperature can both influence the accuracy of

the elastic element increases the indication error

c) Temperature changes elastic element stiffness changes

Error caused by temperature in percentage:

± 0.04 x (t2 – t1) %, where

t1 = reference temperature in oC (about 20oC)

t2 = ambient temperature in oC (actual temperature)

E.g: every 25oC change in temperature approx. 1% error of full

scale

Permanent (stable) temperature conditions (different from

reference temp.) correction calculate the approximate

error at each applied pressure and add or subtract it from

indicated value recalibrate gauge based on data

d) Sealed cases (liquid filled or not) compensation is required (pressure

relief vent)

increase in temperature increase in pressure inside gauge

decrease in indicated pressure

decrease in temperature decrease in pressure inside gauge

increase in indicated pressure

e) Retard gauges

Expanded portion of the scale this portion’s accuracy is indicated

Compressed portion of the scale different accuracy (not indicated)


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f) Suppressed gauges

TBW

g) Compound gauges

Accuracy percentage of span

h) More accurate gauge bigger gauge size (readability)

j) Mounting position affects accuracy

Normal position upright, vertical

k) Absolute pressure gauges

TBW


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Testing

1. Testing

Standard (reference device) error = 1/4 of tested gauge’s accuracy grade

e.g.: 0‐200 psi grade 1A (1%) gauge standard’s accuracy < 1/4 of 1% =

0.5 psi

(ASME PTC 19.2 to calibrate reference devices)

Reference temperature: 20C +‐1C (approx. 68F +‐2F)

Reference (barometric) pressure: 101.32 kPa (29.92 inHg) (at zero)

1.1 Testing method

a) Grades 3A and 4A apply max. indicated pressure (or vacuum) test

the gauge within 10 mins

b) All grades Increasing and decreasing pressure (value is read, gaugeslightly tapped, value is read again note value differences)

Do it 1 more time!

(Should include points within 10% of ends of dial range)c) Hysteresis refer to EN 837‐1

1.2 High temperature error test

Place it in a 60C test chamber for not less than 4 hours test it in

accordance with Point 1.1 compare data (at each point) with data

obtained during Point 1.1 (on room temperature) high temperature

error data can be received

1.3 Low temperature error test

Same as 1.2, but at ‐20C

1.4 Storage temperature test

Test gauge accuracy in accordance with Point 1.1. Place gauge into test

chamber at 70C for 24 hours. Then place it in test chamber at ‐40C for 24

hours. Repeat this 4 more times. Remove from test chamber Let it

warm up to room temperature. Test according to Point 1.1 compare

data with data obtained before temperature test = effect of storage

temperature shown in percentage

‐ Gauge shall not change its appearance

‐

Dial and pointer shall not crack, blister, change color


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1.5 Overpressure test

Test gauge according to Point 1.1 apply proof pressure for 1 min. (Proof

pressure is the maximum pressure to which a device may be exposed after

which it will return to its normal operating pressure range and perform

within specification.) Release proof pressure (wait to stabilize) Test

gauge according to Point 1.1 compare data with data obtained before

proof pressure is applied (note differences in percentage)

1.6 Rupture pressure test

Apply pressure to the gauge increase pressure by not more than 20% of

full scale per second rupture pressure is the pressure at which the

pressure element doesn’t hold pressure any longer (not reversible)

1.7 Liquid filled gauges – seal integrity and stability test

a) Mount gauge (normal position)b) Heat gauge to (supplier) recommended maximum temperature and hold

it for min. 2 hours

c) Reduce temperature to (supplier) recommended minimum temperature

and hold it for min. 2 hours

d) Repeat cycle 20x

e) Check for leakage

f) Check: dial is readable, no discoloration of fluid

1.8 Case – slow leak test(only for sealed and unvented cases)

a) Open up the elastic element

b) Open socket hole to 1/8inch diameter (3.175mm)

c) For liquid filled gauges refill gauge

d) Test is carried out at 18C to 30C

e) Apply gas pressure and slowly increase it at an approx. 1 psi/sec speed

d) Record pressure required to activate relief mechanism applied

pressure must be relieved through the relief mechanism (other parts

cannot be ejected)

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How to Conform to ASME B40-100 (summary)

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