How to Conform to ASME B40-100 (summary)
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Transcript of 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3.2 MKSA units (has been replaced by SI units)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)