Proservo NMS8x Series intelligent tank gauges are designed for high accuracy liquid
level measurement in storage and process applications. They fulfill the exacting
demands of tank inventory management, inventory control, custody transfer, loss
control, total cost saving, and safe operation.
Typical areas of application
• Precise level, interface, and density measurement of oil (fuels), petrochemical,
chemical, and alcohol
• Tank mounted intelligence makes NMS8x ideal for single or multi-task
installation, covering a wide range of measurement functions including Liquid
level, Interface level, Spot density, Density profile, Tank bottom, and Water dip and
integrating a wide range of tank sensor measurement functions including Water
level, Temperature, and Pressure.
Your benefits
• SIL2 certified (Min, Max, Continuous level)
• SIL3 (in preparation)
• Measures liquid level to an accuracy of +/- 0.4 mm (0.016 in)
• Measurement of up to two interface levels and density of up to three liquid phases
• Liquid density profiling of up to 50 points throughout the tank or upper layer,
configurable.
• Wetted parts are completely separated from the electronic circuit
• Tank top mounting with 3” flange
• Wide range of output signals including V1, Modbus RS 485, and HART protocol
• Material and pressure rating of the wetted parts can be selected.
• Suitable for atmospheric and high pressure applications up to 6 bar/600 kPa/
87 psi
• Integration of e.g. temperature, water level, pressure, overfill prevention sensor
• Direct connection of spot or average temperature sensor
• Robust IP66/68, NEMA Type 4x/6P enclosure
• Operation and display in a wide variety of local languages
• Easy commissioning, maintenance, and diagnostics via FieldCare
Process temperature range ...................... 38
Process pressure range ......................... 38
Medium density ............................. 38
Medium density difference for interface measurement .... 39
Viscosity .................................. 39
Registered trademarks ...................... 57
Custody transfer approval ................... 40
2Endress+Hauser
Proservo NMS80
DANGER
WARNING
CAUTION
NOTICE
A
Document information
SymbolsSafety symbols
SymbolMeaning
Electrical symbols
DANGER!
This symbol alerts you to a dangerous situation. Failure to avoid this situation will
result in serious or fatal injury.
WARNING!
This symbol alerts you to a dangerous situation. Failure to avoid this situation can
result in serious or fatal injury.
CAUTION!
This symbol alerts you to a dangerous situation. Failure to avoid this situation can
result in minor or medium injury.
NOTE!
This symbol contains information on procedures and other facts which do not result in
personal injury.
SymbolMeaning
Direct current
Alternating current
Direct current and alternating current
Ground connection
A grounded terminal which, as far as the operator is concerned, is grounded via a
grounding system.
Protective ground connection
A terminal which must be connected to ground prior to establishing any other
connections.
Equipotential connection
A connection that has to be connected to the plant grounding system: This may be a
potential equalization line or a star grounding system depending on national or
company codes of practice.
Symbols for certain types of information
SymbolMeaning
Permitted
Procedures, processes or actions that are permitted.
Preferred
Procedures, processes or actions that are preferred.
Forbidden
Procedures, processes or actions that are forbidden.
Tip
Indicates additional information.
Reference to documentation
Reference to page
Reference to graphic
Visual inspection
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Symbols in graphics
1.
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SymbolMeaning
1, 2, 3 ...Item numbers
, 2., 3.…Series of steps
A, B, C, ...Views
A-A, B-B, C-C, ...Sections
Symbols at the device
SymbolMeaning
Safety instructions
Observe the safety instructions contained in the associated Operating Instructions.
Temperature resistance of the connection cables
Specifies the minimum value of the temperature resistance of the connection cables.
Proservo NMS80
Hazardous area
Indicates a hazardous area.
Safe area (non-hazardous area)
Indicates the non-hazardous area.
4Endress+Hauser
Proservo NMS80
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Function and system design
Measuring principle
NMS8x is an intelligent tank gauge for measuring liquid levels with high precision. The system is
based on the principle of gauging displacement.
A small displacer is accurately positioned in a liquid medium using a stepping motor. The displacer is
then suspended on a measuring wire which is wound onto a finely grooved wire drum. NMS8x
counts the rotations of the wire drum and to calculate the traveling distance of the wire and obtain
the liquid level change.
The drum is driven via coupling magnets that are completely separated by the drum housing. Outer
magnets are connected to the wire drum, with inner magnets connected to the drive motor. As the
inner magnets turn, their magnetic attraction causes the outer magnets to turn, as well, causing the
entire drum assembly to turn. The weight of the displacer on the wire creates torque on the outer
magnets generating change of magnetic flux. These changes generated in the drum assembly are
detected by a unique electromagnetic transducer on the inner magnets. The transducer transmits the
weigh signal to a CPU using a non contact principle (patented). The drive motor is actuated to keep
the weigh signal constant at set value defined by the operating command.
When the displacer is lowered and touches a liquid, the weight of the displacer is reduced by liquid
buoyancy force, which is measured by a temperature-compensated magnetic transducer. As a result,
the torque in the magnetic coupling changes, and this is measured by six hall sensors. A signal
indicating the weight of the displacer is sent to the motor control circuit. As the liquid levels rise and
fall, the displacer position is adjusted by the drive motor. The rotation of the wire drum is
continuously evaluated to determine the level value using a magnetic rotary encoder. In addition to
gauging the level, NMS8x can measure the interfaces between up to three liquid phases, and the
tank bottom, as well as spot and profile densities.
1Operating principle
ADisplacer position data
BWeight data
1Encoder
2Motor
3Rotary transformer
4Shafts
5Gears
6Wire drum
7Measuring wire
8Displacer
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A0026724
Proservo NMS80
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HART
A
B
HART
HART
4...20mA
Integration of tank sensors
In addition to measuring the level, interfaces, tank bottom, and density, the device can also be used
to integrate of tank sensors into tank inventory systems. All measured and calculated values can be
displayed on the built-in display. They can be transferred to an inventory control system via a field
communication protocol.
A0026722
2Measuring system
AHART multidrop mode
BHART and analog mode
1Pressure transmitter
2Average temperature transmitter (NMT53x)
3Proservo NMS8x
4Field protocol transmits data to an inventory control system
Typical values measured by the sensors are:
• Level
• Spot temperature
• Average temperature
• Water level
• Pressure
• Secondary level value (for critical applications)
Major applications
The number of measuring functions and output options, as well as the compact design, enables
NMS8x to be installed in a wide range of applications at minimal cost.
Petroleum industry
From oil production to storage at an oil depot, there exists an extensive need to measure and
manage a wide variety of products. Remote tank gauging by NMS8x combined with an inventory
management system is an ideal way to measure and manage tank contents.
Chemical industry
A wide choice of options for the wetted parts ensures chemical compatibility and long product life.
Power plant
Fuel oil levels are major applications where precise measurement is required to ensure safe
operation.
6Endress+Hauser
Proservo NMS80
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Typical tank installation
3Typical tank installation
AFixed roof tank
BHigh pressure tank
CFloating roof tank with stilling well
1NMS8x
2Ball valve
3Measuring wire
4Displacer
5Stilling well
6Prothermo NMT53x
A0026725
When installing NMS8x to a floating roof tank, be sure to use a stilling well to protect the
measuring wire. Otherwise the wire may break due to an external shock.
Application
NMS8x is primarily a highly accurate level measurement gauging instrument with the added ability
to measure density. The following level measurements are supported: liquid surface level and
interface level(s) between different liquids, as well as finding tank floor or datum plate. The
Endress+Hauser7
Proservo NMS80
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following density measurements are supported: single-point (spot measurements), as well as profile
measurements of all liquid(s) in a tank.
The choice of the most suitable displacer depends on the liquid conditions and measurement
functions. These can be classified as follows:
• Single measurement value only, e.g. level, interface, or density
• Multiple measurement application, e.g. level, interface, and density
Measurement terminology
4NMS8x with standard level, I/F x 2, Tank bottom and spot density x 3 measurement
1Upper density
2Middle density
3Lower density
4Tank bottom
5Lower I/F
6Upper I/F
7Level
8Endress+Hauser
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5Density Profile measurement
ATank profile: density profiling throughout tank
BInterface profile: density profiling withing upper phase
CManual profile: density profiling from a specific position to level
1Level
2Manual profile level
3Upper phase (oil)
4Middle phase (emulsion)
5Lower phase (water)
6Tank bottom
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Proservo NMS80
Displacer selection guide
A wide variety of displacers are available to suit different application. Proper displacer selection
ensures optimal performance and longevity. The following guidelines will assist you in selecting the
most suitable displacer for your application.
Displacer types
The following NMS8x displacers are available.
30 mm (1.18 in)50 mm (1.97 in)70 mm (2.76 in)110 mm (4.33 in)
316L/PTFE316L/Alloy C/PTFE316L316L
A0026731 A0026732
A0026729
A0026730
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Proservo NMS80
A
Ø30(1.18)
a
B
86 (3.39)
Ø30(1.18)
3.6 (0.14)
121 (4.76)
165.5 (6.52)
64 (2.52)
153.6 (6.05)
185.6 (7.31)
9.5
(0.37)
a
Displacer dimensions
A0029579
A⌀30 mm (1.18 in) 316L cylindrical displacer
B⌀30 mm (1.18 in) PTFE cylindrical displacer
aImmersion point
Item
Weight (g)261250
Volume (ml)84.3118
Balance volume (ml)41.759
⌀30 mm (1.18 in) 316L
cylindrical displacer
⌀30 mm (1.18 in) PTFE
cylindrical displacer
The weight, volume, and balance volume are individually determined by each displacer and also
might vary depending on the values stated above.
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Proservo NMS80
A
B
C
Ø50.8 (2)
a
45 (1.77)
85 (3.35)
129 (5.08)
2.5 (0.09)
Ø50.8 (2)
a
45 (1.77)
2.5 (0.09)
85 (3.35)
Ø50 (1.97)
a
35 (1.38)
82.7 (3.26)
46.7 (1.84)
11.5
(0.45)
11.5
(0.45)
129 (5.08)
A⌀50 mm (1.97 in) 316L cylindrical displacer
B⌀50 mm (1.97 in) AlloyC cylindrical displacer
C⌀50 mm (1.97 in) PTFE cylindrical displacer
aImmersion point
Item
Weight (g)253253250
Volume (ml)143143118
Balance volume (ml)70.770.759
⌀50 mm (1.97 in) 316L
cylindrical displacer
The weight, volume, and balance volume are individually determined by each displacer and also
⌀50 mm (1.97 in) AlloyC
cylindrical displacer
⌀50 mm (1.97 in) PTFE
cylindrical displacer
might vary depending on the values stated above.
A0029580
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Proservo NMS80
A
B
46.6 (1.83)
1 (0.03)
90 (3.54)
Ø70(2.76)
a
a
67 (2.64)
26 (1.02)
2 (0.07)
10 (0.39)
Ø110 (4.33)
A0029582
A⌀70 mm (2.76 in) 316L conical displacer
B⌀110 mm (4.33 in) 316L conical displacer
aImmersion point
Item⌀70 mm (2.76 in) 316L conical displacer ⌀110 mm (4.33 in) 316L conical displacer
Weight (g)245223
Volume (ml)124108
Balance volume (ml) 52.836.3
The weight, volume, and balance volume are individually determined by each displacer and also
might vary depending on the values stated above.
Recommended displacer by application
ApplicationProduct levelInterface levelDensity
Viscous liquid50 mm (1.97 in) PTFENot RecommendedNot Recommended
Crude oil50 mm (1.97 in) 316L
50 mm (1.97 in) PTFE
Black oil50 mm (1.97 in) 316L50 mm (1.97 in) 316L50 mm (1.97 in) 316L
White oil70 mm (2.76 in) 316L70 mm (2.76 in) 316L70 mm (2.76 in) 316L
Liquefied gas, LPG/LNG70 mm (2.76 in) 316L70 mm (2.76 in) 316L70 mm (2.76 in) 316L
Corrosive liquid
50 mm (1.97 in) Alloy C
50 mm (1.97 in) PTFE
50 mm (1.97 in) 316L
50 mm (1.97 in) PTFE
50 mm (1.97 in) Alloy C
50 mm (1.97 in) PTFE
50 mm (1.97 in) 316L
50 mm (1.97 in) PTFE
50 mm (1.97 in) Alloy C
50 mm (1.97 in) PTFE
Product level
In general, larger diameter displacers have better accuracy under similar conditions.
Interface level(s)
Cylindrical-shaped displacers, with rounded top and bottom, reduce resistance while moving through
liquid(s). This provides smoother movement and faster interface measurements compared to flatfaced displacers, particularly in density profile measurements that span the full tank height.
In order to move a displacer down through liquids, the displacer density (weight divided by
volume) must be higher than the liquid density.
Tank bottom and datum plate level
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70 mm (2.76 in) and 50 mm (1.97 in) displacers reduce resistance while moving through liquids.
This provides smoother movement and faster interface measurements.
Proservo NMS80
Density
Since the density is the calculated result of two measurements, a displacer with higher volume will
usually yield the most accurate density measurement. In most cases we recommend our
50 mm (1.97 in) diameter displacer for density measurement.
For non-viscous applications (e.g. white oil, LPG/LNG), the 70 mm (2.76 in) displacer also works
very well.
Level and density
When an application calls for equal emphasis on measuring both level and density, the
50 mm (1.97 in) and the 70 mm (2.76 in) diameter displacers will give the best all-around
performance.
Custody transfer
The 50 mm (1.97 in) displacer or larger is the choice for requirements per NMi.
The 110 mm (4.33 in), conical 316L displacer is the choice for requirements per PTB.
Material compatibility
Displacers are available in three different standard materials. Material compatibility should be
confirmed to ensure safe operation and optimal NMS8x performance.
316L
Stainless steel is a highly versatile industrial material that provides good compatibility with a wide
range of chemicals, including most white and black oils.
Alloy C
This high-performance material is harder than 316L, and provides excellent resistance to many of
the harshest corrosive chemical applications.
PTFE
One of the most well-known and versatile polymer materials, this high-performance material has
one of the lowest friction coefficients. It provides excellent performance in viscous/sticky liquids, and
also has excellent chemical resistance to a wide range of corrosives.
Process connection size
The process connection defines the tank process entry, and may affect the displacer size. The
standard NMS8x process connections start at 3”/DN80 and fit most tank gauging applications.
Accordingly, most applications can be covered with one of the 50mm or 70mm displacer options.
Smaller diameter displacers are available when the process connection is smaller.
When the 110 mm (4.33 in) diameter custody transfer approval (PTB) displacer is selected, a
separate calibration and maintenance chamber is recommended between the NMS8x and tank
process connection.
14Endress+Hauser
Proservo NMS80
NXA820
NXA820
NXA820
NXA820
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Measuring system
• From single tank level measurement to the largest oil refinery applications, Endress+Hauser tank
gauging devices are an integral part of tank farm management solutions. A wide variety of data
output protocols are available for seamless integration into many commonly used systems.
• A primary example is Tankvision from Endress+Hauser. Tankvision is a scalable system offering
local tank management for multiple loops via Modbus or V1 protocols. Accumulated data is
available to DCS and other plant management systems via a Host Link.
A0027700
6Integration of tank gauging devices into an inventory management system (typical example)
1Proservo NMS8x
2Pressure transmitter (e.g. Cerabar)
3Temperature transmitter (e.g. Prothermo)
4Tankside Monitor NRF81
5Micropilot S FMR5xx
6Micropilot NMR8x
7Field protocol (e.g. Modbus, V1)
8Tankvision Tank Scanner NXA820
9Ethernet
10 Ethernet switch
11 Internet Browser
12 Tankvision Data Concentrator NXA821
13 Tankvision Host Link NXA822
14 Modbus
15 DCS or PLC
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Input/output
Level measurementMeasured variable
Proservo is primarily a highly accurate level measurement gauging instrument, with the added
ability to measure interfaces and densities. The following level measurements are supported: liquid
surface level and interface level(s) between different liquids, as well as finding tank bottom or datum
plate. The following density measurements are supported: single-point (called “spot”
measurements), as well as profile measurements of all liquid(s) in a tank.
Measuring range
• Level and interface: Max.36 m (118 ft)(longer range is possible as special product)
• Density: 0.430 to 2.000 g/cm
The level and interface measuring range depends on the measuring wire and material compatibility
to measured medium. Measuring wires are available in three different standard materials. Material
compatibility should be confirmed to ensure safe operation and optimal measuring performance.
Measuring rangeMaterial
28 m (93.33 ft), 36 m (120 ft)316L
16 m (53.33 ft)PFA > 316L
22 m (73.33 ft)AlloyC276
Proservo NMS80
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16Endress+Hauser
Proservo NMS80
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1234
HART Ex ia/IS active input
A0027364
7HART Ex ia/IS active input
E1 HART +
E2 HART -
The device has a HART Ex ia/IS active input. Additional features are provided if the following
Endress+Hauser devices are connected:
Prothermo NMT
The measured level is transmitted to the Prothermo. Prothermo uses this level to calculate the
average temperature of the product.
Technical data
Transmitter power supply voltage23.0 V - 380 Ω ⋅ I
load
Maximum load500 Ω including signal line
Maximum current of all connected devices24 mA
The HART Ex ia/IS active input is available by default. It needs not to be chosen explicitly when
ordering a device.
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I/O modulesOverview
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NMx8x -XX xx xxxxxx...
040
NMx8x -xx XX xxxxxx...
050
8Position of the I/O modules in the terminal compartment
The terminal compartment contains up to four I/O modules, depending on the order code.
• Modules with four terminals can be in any of these slots.
• Modules with eight terminals can be in slot B or C.
The exact assignment of the modules to the slots is dependent on the device version. For a
detailed description refer to the Operating Instructions of the device in question.
The following restrictions apply when selecting the modules:
• The device may contain a maximum of four I/O modules.
• A maximum of two I/O modules with 8 terminals is possible.
Proservo NMS80
A0027363
Ordering feature 040: "Primary Output"
Option Number of I/O modulesType of I/O moduleNumber of terminalsTechnical data
A11Modbus RS4854→ 19
B11V14→ 20
E114-20mA HART Ex d/XP8→ 21
H114-20mA HART Ex i/IS8→ 21
Ordering feature 050: "Secondary IO Analogue"
Option Number of I/O
modules
A111 x "Ex d/XP 4-20mA HART + RTD input" 1 x 8→ 21
A222 x "Ex d/XP 4-20mA HART + RTD input" 2 x 8→ 21
B111 x "Ex i/IS 4-20mA HART+ RTD input"1 x 8→ 21
B222 x "Ex i/IS 4-20mA HART+ RTD input"2 x 8→ 21
C221 x "Ex i/IS 4-20mA HART + RTD input"
X00none0-
Type of I/O moduleNumber of terminals Technical data
2 x 8→ 21
1 x "Ex d/XP 4-20mA HART + RTD input"
18Endress+Hauser
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