Level Basics
Level Basics
Level Basics
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Wilockx Chris<br />
<strong>Level</strong> <strong>Basics</strong>
Physical <strong>Basics</strong> of Pressure Measurement<br />
F (force) N (Newton)<br />
P (pressure) = --------------- = ---------------- |Pa|<br />
A (surface) m2<br />
There are different pressure units:<br />
kPa: kilo Pascal mmHg: mm mercury<br />
bar: bar atm: atmosphere<br />
kg/cm2: psi: pound/inch2<br />
mmH2O: mm water inH2O: inch water
Physical <strong>Basics</strong> of Pressure Measurement<br />
pabs1<br />
Pressure Quantity<br />
Absolute Pressure<br />
Atmospheric Pressure<br />
Gauge Pressure<br />
Differential Pressure<br />
pamb.<br />
pabs. 2<br />
Symbol<br />
pabs<br />
pamb<br />
pe<br />
dp<br />
pe1 > 0<br />
pe2 < 0<br />
dp<br />
0%<br />
100%<br />
pe = 0<br />
pabs = 0<br />
(Vacum)
Physical <strong>Basics</strong> of Pressure Measurement<br />
Pressure is equal Hydrostatic Paradox<br />
in all directions P = S.g.h<br />
S = Rho = density<br />
|Pa| = |kg/m3|.|9,81m/s2|.|m|
Pressure Measurement – Pressure U - Tube<br />
U-Tube<br />
Pa = S.g.h + P0<br />
|Pa| = |kg/m3|.|9,81m/s2|.|m|
Pressure Measurement – Pressure Transmitters<br />
Boudon pressure gauge
Pressure Measurement – Pressure Transmitters<br />
p - measurement<br />
dp - measurement
Functional Principle of P and dP Transmitters<br />
Conversion of the Physical Factor<br />
(i.e.: Deflection of Diaphragm) into an Electrical Factor:<br />
Different sensors are used:<br />
• Inductive measuring principle (coil)<br />
• Capacitive measuring principle (capacitor)<br />
• Strain Gauge measuring principle (Bridge)<br />
• Piezo-resistive measuring principle (chip)
Functional principle of P and dP transmitters<br />
• inductive measuring principle:<br />
n2 . A<br />
L = µ --------l
Functional principle of P and dP transmitters<br />
• capacitive measuring principle:<br />
C1<br />
diaphragm<br />
P1 P2<br />
C2<br />
Glass<br />
Measuring<br />
diaphragm<br />
E . A<br />
C = --------d
Functional principle of P and dP transmitters<br />
• Strain Gauge measuring principle :<br />
Metal cores<br />
Bonding<br />
+<br />
Strain gages array<br />
(bonded or made<br />
directly on the<br />
substrate)<br />
Measuring<br />
diaphragm<br />
Substrate<br />
� R<br />
� R= K x<br />
x
Functional principle of P and dP transmitters<br />
• piezo-resistive measuring principle (example 265D) :<br />
DP-Sensor P abs-Sensor<br />
Measuring of resistance<br />
change via crystal<br />
lattice displacement
Functional principle of P and dP transmitters<br />
• piezo-resistive measuring principle (e.g. 265G) :<br />
lower range value<br />
span<br />
write protect<br />
measuring<br />
mechanism<br />
isolating diaphragm<br />
Microprocessor based<br />
electronics<br />
matching<br />
P e-Sensor<br />
Measuring of resistance<br />
change via crystal<br />
lattice displacement
Main Components<br />
covers<br />
vents<br />
display<br />
flanges<br />
terminal<br />
blocks<br />
gaskets<br />
housing<br />
push<br />
buttons<br />
secondary<br />
electronics integral<br />
display<br />
covers<br />
transducer<br />
bolts
Functional Specifications<br />
General<br />
Base accuracy: ABB Model 265/266 +/- 0,04%<br />
ABB Model 264 +/- 0,075%<br />
Turn Down: 1/100<br />
Ranges ABB Model 265 Pressure Transmitters:<br />
60mbar - 400mbar - 2500mbar - 10bar - 30bar - 100bar<br />
600bar<br />
Ranges ABB Model 265 dP Transmitters:<br />
10mbar - 60mbar - 400mbar – 2500mbar - 20bar – 100bar
<strong>Level</strong> – Measurement<br />
Different mounting positions?<br />
P = S.g.h<br />
h<br />
Open tank liquid measurement<br />
open to atmosphere<br />
________<br />
Dead zone
<strong>Level</strong> – Closed Tank<br />
max. level<br />
min. level<br />
4 mA = S . g . h2<br />
20 mA = S . g . (h2 + h1)<br />
S = specific gravity (medium)<br />
h1<br />
h2<br />
transmitter<br />
reference line<br />
S<br />
N2<br />
Wet Leg<br />
If the level to be maeasured is in<br />
a closed tank, a dp – transmitter<br />
is necessary.<br />
Dry Leg<br />
S = 0?
<strong>Level</strong> – Closed Tank<br />
max. level<br />
min. level<br />
h1<br />
h2<br />
transmitter<br />
reference line<br />
4 mA = S1 . g . h2 – S2 . g . h4<br />
20 mA = S1 . g (h1 + h2) – S2 . g . h4<br />
S1 = specific gravity (medium)<br />
S2 = specific gravity (Wet leg)<br />
S1<br />
Wet Leg<br />
h4<br />
If the level to be maeasured is in<br />
a closed tank, a dp – transmitter<br />
is necessary.<br />
Glycol<br />
S2<br />
Wet Leg
<strong>Level</strong> – Closed Tank<br />
If condensable vapours are present use the<br />
following installation.<br />
max. level<br />
min. level<br />
transmitter<br />
reference line<br />
h1<br />
h2<br />
transmitter<br />
reference line<br />
4 mA = S1 . g . h2 – S2 . g . h4<br />
20 mA = S1 . g (h1 + h2) – S2 . g . h4<br />
S1 = specific gravity (medium)<br />
S2 = specific gravity (Wet leg)<br />
S1<br />
impuls line<br />
filled with<br />
stable fluid<br />
(Wet Leg)<br />
S2<br />
filling tee<br />
0<br />
h4
Boiler-<strong>Level</strong> Measuement<br />
Ordering data: dp transmitter with adjusted value of –300mm ... +300 mm (WC)<br />
Actual requirement: boiler level measurement<br />
level to be monitored: -300 mm ... +300 mm<br />
Distance between connection pipes: h = 1000mm<br />
Density water<br />
Tuper.: +200 C (Sup= 865 kg/m 3 ) hlow (hlow) = 200mm<br />
Tref.: +30 C (Sref= 996 kg/m 3 ) hhigh (hhigh) = 800mm<br />
Density steam<br />
Tsteam.: +200 C (Ssteam = 7.9 kg/m 3 )<br />
hlow<br />
NN<br />
hhigh<br />
h<br />
+300 mm<br />
- 300 mm
Boiler-<strong>Level</strong> Measuement<br />
DP – Transmitter with an adjusted value of: -300 ... +300 mm (WC)<br />
hl<br />
hh<br />
+300 mm<br />
H<br />
‘<br />
- 300 mm<br />
P1 (-300mm) = (-h* Sref * g + hl * Super. * g + [h-hl] * Ssteam * g) * 102 =<br />
= (-1 * 996 * 9.81 + 0.2 * 865 * 9.81 + 0.8 * 7.9 * 9.81) * 102 = -80.1 mbar<br />
P2 (+300mm) = (-h* Sref * g + hh * Super. * g + [h-hh] * Ssteam * g) * 102 =<br />
= (-1 * 996 * 9.81 + 0.8 * 865 * 9.81 + 0.2 * 7.9 * 9.81) * 102 = -29.7 mbar<br />
Adjusted value: -80.1 ... -29.7 mbar<br />
h
Remote Seals<br />
Protect Transmitters from<br />
• High temperature<br />
• Corrosive components<br />
• Media with high viscosities<br />
• Media with tendency to<br />
polymerization<br />
Useful for<br />
• Prevention of deposits in the<br />
process Connection<br />
• Adaptation to various process<br />
connections
<strong>Level</strong> – Open Tank<br />
P = S . g . h<br />
e.g.: a seal transmitter<br />
flange mounted on the<br />
high pressure side of the<br />
transmitter is<br />
recommended in case of<br />
dirty liquid fluid or process<br />
temperature > 107 C<br />
transmitter<br />
reference line
<strong>Level</strong> – Closed Tank<br />
max. level<br />
min. level<br />
min. level may not<br />
be below this line<br />
h1<br />
h2<br />
N2<br />
e.g.: a seal transmitter<br />
flange mounted on the<br />
high pressure side of the<br />
transmitter is<br />
recommended in case of<br />
dirty liquid fluid or process<br />
temperature > 107 C<br />
transmitter<br />
reference line
<strong>Level</strong> – Closed Tank<br />
max. level<br />
min. level<br />
h1<br />
h2<br />
4 mA = S . g . h2 + Sg . G .(h4-h2) – Sc . g . h4<br />
20 mA = S . g . (h1 + h2) – Sc . g . h4<br />
S = specific gravity (medium)<br />
Sg = specific gravity (gas above fluid)<br />
Sc = specific gravity (filling oil capillary tube)<br />
Sg<br />
S<br />
filled<br />
capillary<br />
high side seal<br />
reference line<br />
low side seal<br />
reference line<br />
h4<br />
h3<br />
Sc<br />
transmitter<br />
reference line
<strong>Level</strong> Transmitter 265D<br />
Compact Version
Remote Seals Design<br />
..... with Flush or Extended Diaphragm in Flange design<br />
DN 25 Pressure Rating PN 10...PN 250<br />
DN 50 / DN 80 Pressure Rating PN 16...PN 100<br />
DN 1“ Pressure Rating 150 psi...1500 psi<br />
DN 2“ / DN 3“ Pressure Rating 150 psi...600 psi
Remote Seals<br />
.... via Capillary Tube to Transmitter
Remote Seals Design<br />
.... with Flush or Extended Diaphragm in Sandwich Design<br />
DN 50 / DN 80 Pressure Rating up to PN 400<br />
DN 2“ / DN 3“ Pressure Rating up to 2500 psi
Remote Seals Design<br />
Corrosion Resistant Materials<br />
• Stainless Steel<br />
• Hastelloy C<br />
• Monel 400<br />
• Tantal<br />
• FEP coated<br />
• Gold plated<br />
• Ect…<br />
• Capillary tube stainless steel, with<br />
PVC protective cover as an option
Remote Seals Design<br />
Filling liquids depending on the<br />
application<br />
• Silicon Oil as Standard<br />
• Carbon Fluoride for Oxygen Service<br />
• White Oil for Food and Beverage<br />
• High Temperature Oil up to 400 C<br />
Vacuum proof design with special liquid for use down to an<br />
absolute pressure of 5 mbar abs.<br />
ABB is a recognized leader in the all welded technology where Remote<br />
Seals System can be welded at every junction.
Filling Liquid Id<br />
Silicone Oil IC<br />
Carbon<br />
Fluoride<br />
High-temperature<br />
Oil<br />
L<br />
IH<br />
White Oil WB<br />
Vacuumproof<br />
Design<br />
IC-V<br />
Pressure rating in mbar abs.<br />
20°C (68°F) 100°C (212°F) 150°C (302°F) 200°C (392°F) 250°C (482°F) 400°C (752°F)<br />
> 500 > 500 > 500 > 750<br />
> 1000 > 1000 > 1000 ---<br />
> 500 > 500<br />
Application Limits<br />
> 500 > 750<br />
> 500 > 1000 > 1000 > 1000<br />
> 5 > 25 > 38 > 50<br />
> 1000 ---<br />
--- ---<br />
> 1000 > 1000<br />
> 1000 ---<br />
--- ---
Application Limits
Seals Design Performance<br />
Accuracy is primarily affected by<br />
• Fill volume change due to temperature<br />
• Capillary length<br />
• Diaphragm stiffness<br />
Low fill volume and low stiffness of diaphragm is<br />
required for high accuracy
Questionaire
Questionaire for P-/DP-Transm. with remote seals
<strong>Level</strong> – Measurement<br />
air supply<br />
regulator<br />
h<br />
Bubble measurement<br />
dP
Liquid <strong>Level</strong> (example oil on water)<br />
range of<br />
interface level<br />
S1 = H 2O<br />
S2 = oil<br />
4 mA = S2 . 9,81 . h (only oil)<br />
20 mA = S1 . 9,81 . h (only H 2O)<br />
(simplified illustration; without the influence of capillary tube S3)<br />
Interface level measurement<br />
S2<br />
interface level<br />
S1<br />
h<br />
LT<br />
S3
Density<br />
S1 = low specific gravity<br />
S2 = higher specific gravity<br />
S3 = specific gravity of filling oil in capillary tube<br />
4 mA = (S1 . h – S3 . h) . 9.81<br />
20 mA = (h * SG2 – h * SG3) * 9.81<br />
Density measurement<br />
h
<strong>Level</strong> measuement in a spheric tank<br />
output<br />
(volume)<br />
v = 1/3 pi * h 2 (3r – h)<br />
input (level = h)<br />
Input [%]<br />
(<strong>Level</strong> = h)<br />
0.00<br />
3.75<br />
7.75<br />
11.75<br />
16.75<br />
22.00<br />
28.00<br />
35.25<br />
45.75<br />
55.00<br />
65.00<br />
72.25<br />
78.50<br />
83.75<br />
88.25<br />
92.50<br />
96.25<br />
100.00<br />
Ouput [%]<br />
(Volume)<br />
0.00<br />
0.41<br />
1.71<br />
3.82<br />
7.48<br />
12.39<br />
19.13<br />
28.52<br />
43.64<br />
57.48<br />
71.82<br />
81.17<br />
88.12<br />
92.94<br />
96.18<br />
98.40<br />
99.59<br />
100.00
<strong>Level</strong> measuement - warning<br />
• Pressure (vacuum)<br />
• Temperature<br />
• Medium<br />
• Foam<br />
• Agitator<br />
• Flow inlet
Intelligent Transmitters<br />
Conventional<br />
1965<br />
HART<br />
1987<br />
Fieldbus<br />
1985/95/97/99<br />
A<br />
A<br />
A<br />
E<br />
E + #<br />
#<br />
4 ... 20 mA<br />
4 ... 20 mA + superimposed,<br />
digital communication<br />
FSK-Modem
Intelligent Transmitters<br />
Functionality<br />
Traditional<br />
4-20mA<br />
Value<br />
HART<br />
SMART<br />
Value<br />
Device<br />
Parameter<br />
Fieldbus<br />
Fieldbus<br />
More values<br />
Multi variabel<br />
High resolution<br />
Diagnostic data<br />
Quality signal<br />
Status<br />
Decentral Functions<br />
Distributed Control<br />
Bi-directional<br />
Asset Optimization<br />
Graphics<br />
Time
Intelligent Transmitters<br />
Value (measuring)<br />
Status<br />
Scaling<br />
Filter time<br />
Alarm / warn limits<br />
Alarm summary<br />
TAG<br />
Device diagnostic<br />
Manufacture<br />
specific<br />
parameter<br />
Cyclic<br />
services<br />
(Analog value)<br />
Acyclic<br />
services<br />
(Hart)<br />
Spontaneous<br />
services<br />
Acyclic<br />
services
Intelligent Transmitters<br />
400 mbar<br />
200 mbar<br />
0 mbar<br />
-400 mbar<br />
Basic range value<br />
Analog Technology Bus Technology<br />
20 mA<br />
4 mA<br />
Sensor range limits<br />
Floating Point 32 bit
Communication mode: Point-to-Point<br />
2600T<br />
U S > 10.5 ... 45 V DC (HART)<br />
R > 250 Ohms<br />
FSK modem<br />
e.g. power<br />
supply
Communication mode: FSK Bus<br />
2600T TZN 128<br />
FSK modem<br />
e.g. power<br />
supply<br />
TZN 128<br />
FSK modem
SmartVision
SmartVision
SmartVision
Communication Requirements<br />
Connecting cable<br />
Communication between transmitter and PC/laptop requires<br />
shielded and twisted pair lines.<br />
The minimum wire diameter should be:<br />
- 0.51 mm for lines up to 1500 m<br />
- 0.81 mm for lines longer than 1500 m<br />
The maximum line length is limited to:<br />
- 3000 m for twin-core cable<br />
- 1500 m for multicore cable
Electrical Safety - Explosion Protection<br />
• The areas where this can occur are classified depending upon the<br />
“probability” that gas/vapour, in dangerous combination with air, is<br />
present.<br />
• In Europe and some part of the world, except the American continent,<br />
the classification is as follows, according to IEC Publication 79-10:<br />
• ZONE 0: an area in which an explosive gas-air mixture is present<br />
continuously or for long periods.<br />
• ZONE 1: an area in which an explosive gas-air mixture is likely to occur<br />
in normal operation.<br />
• ZONE 2: an area in which an explosive gas-air mixture is not likely to<br />
occur in normal operation, and if it occurs, it will exist only for a short<br />
time.
Electrical Safety - Explosion Protection<br />
In North America, the classification refers to only two divisions, which<br />
may be briefly defined as follows, according to NEC article 500:<br />
Division 1: hazard may be present in normal operation.<br />
Division 2: hazard may be present only in abnormal<br />
operation.<br />
Therefore the following rough equivalence apply:<br />
CONTINUOUS<br />
HAZARD<br />
(> 100 h / y)<br />
INTERMITTENT<br />
HAZARD<br />
(1 - 100 h / y)<br />
ABNORMAL<br />
CONDITIONS<br />
(0.01 - 1 h / y)<br />
EUROPE (IEC) ZONE 0 ZONE 1 ZONE 2<br />
North America * DIVISION 1 DIVISION 1<br />
*Note: The “Zone” classification like IEC is now possible also for North America<br />
according to article 505 of the NEC/Edition 1996, ANSI/NFPA70
Electrical Safety - Explosion Protection<br />
The various gases/vapours are grouped considering their "likeness" in terms of<br />
ignition energy.<br />
Each group has a "representative gas". Representative gases and relevant minimum<br />
ignition energy (microjouls) are shown here below:<br />
Representative Gas IEC / CENELEC<br />
(EUROPE)<br />
Note: according to IEC classification “II” means “surface industries”<br />
(as an alternative to mining atmosphere)<br />
NORTH AMERICA Minimum Ignition<br />
Energy [micro joules]<br />
Acetylene II C Class I Group A 20 µJ<br />
Hydrogen II C Class I Group B 20 µJ<br />
Ethylene II B Class I Group C 60 µJ<br />
Propane II A Class I Group D 180 µJ
Electrical Safety - Explosion Protection<br />
The temperature classification relates to the maximum attainable temperature<br />
of the transmitter, or part of it (normally assuming a 40 C ambient), to the<br />
ignition temperature of a gas / vapour.<br />
Max. Temp.<br />
[ C]<br />
North America<br />
200 T3<br />
180 T3A<br />
165 T3B<br />
160 T3C<br />
135 T4<br />
Max. Temp.<br />
[ C]<br />
IEC/CENELEC<br />
(EUROPE)<br />
450 T1<br />
300 T2<br />
200 T3<br />
135 T4<br />
100 T5<br />
85 T6