VEGA PULS41 User Manual
Operating Instructions
VEGAPULS 41
®
4 … 20 mA; HART
compact sensor
Contents
Safety information ........................................................................ 3
Note Ex area ................................................................................ 3
1 Product description .................................................................. 4
1.1 Function................................................................................. 4
1.2 Application features ............................................................. 6
1.3 Adjustment ............................................................................ 7
1.4 Type survey .......................................................................... 9
1.5 Antennas............................................................................. 10
2 Mounting and installation ..................................................... 11
2.1 General installation instructions ........................................ 11
2.2 Measurement of liquids ..................................................... 14
2.3 Measurement in standpipe (surge or bypass tube) ...... 15
2.4 False echoes ...................................................................... 20
2.5 Common installation mistakes ........................................... 22
Contents
3 Electrical connection .............................................................. 25
3.1 Connection and connection cable .................................... 25
3.2 Connection of the sensor .................................................. 27
3.3 Connection of the external indicating instrument
VEGADIS 50 ....................................................................... 31
3.4 Configuration of measuring systems ............................... 32
4 Set-up ........................................................................................ 40
4.1 Adjustment media .............................................................. 40
4.2 Adjustment with PC ............................................................ 40
4.3 Adjustment with adjustment module MINICOM ............... 42
4.4 Adjustment with HART® handheld ................................... 48
5 Diagnostics............................................................................... 50
5.1 Simulation ............................................................................ 50
5.2 Error codes ........................................................................ 50
2 VEGAPULS 41 – 4 … 20 mA
26620-EN-041227
Contents
6 Technical data .......................................................................... 51
6.1 Technical data ..................................................................... 51
6.2 Approvals ........................................................................... 56
6.3 Dimensions ......................................................................... 57
Supplement..................................................................................... 59
Safet y Manual ................................................................................. 59
1 General ............................................................................... 59
1.1 Validity ................................................................................. 59
1.2 Application range ................................................................. 59
1.3 Relevant standards ............................................................. 59
1.4 Determination of safety-related characteristics .................. 60
2 Planning .............................................................................. 61
2.1 Low demand mode ............................................................... 61
2.2 High demand or continuous mode ....................................... 61
2.3 General ................................................................................ 61
3 Set-u p ................................................................................. 62
3.1 Mounting and installation..................................................... 62
3.2 Adjustment instructions and parameter adjustment ........... 62
3.3 Configuration of the processing unit ................................... 62
4 Reaction during operation and in case of failure ............. 63
5 Recurring function test ....................................................... 63
6 Safety-related characteristics ........................................... 64
SIL declaration of conformity .................................................... 65
CE conformity declaration......................................................... 66
Safety information
Please read this manual carefully, and also take
note of country-specific installation standards
(e.g. the VDE regulations in Germany) as well
as all prevailing safety regulations and accident prevention rules.
For safety and warranty reasons, any internal
Note Ex area
Please note the attached safety instructions
containing important information on installation
and operation in Ex areas.
These safety instructions are part of the operating instructions manual and come with the Ex
approved instruments.
work on the instruments, apart from that involved in normal installation and electrical connection, must be carried out only by qualified
VEGA personnel.
26620-EN-041227
VEGAPULS 41 – 4 … 20 mA 3
1 Product description
Product description
Radar sensors usually come with horn or rod
antennas. PTFE rod antennas are suitable for
many applications with chemically aggressive products, but are unsuitable for small
vessels due to their size. Also the reception
efficiency of the rod antenna is lower than that
of the (less resistant) horn antenna. The two
new radar sensors, VEGAPULS 43 with DN
50 and DN 80 process fittings and the described VEGAPULS 41 with 1½“ process
fitting, perfectly round out the instrument
series. Horn and rod antennas that protrude
into the vessel belong to the past. The antenna of VEGAPULS 41 consists of a small
40 mm TFM-PTFE cone that is suitable for
chemically aggressive environments. PTFE
has been known as the „Mercedes“ of plastic
materials for many years. They are resistant
to virtually all chemical media, such as e.g.
amines, ketones, esters, acids (sulphuric
acid, phosphoric acid, hydrochloric acid,
nitric acid), alkalis (caustic soda), oxidants,
fuels and oils. These plastics do not become
brittle or age and are suitable for temperatures up to 150°C. The only limits to these
materials are applications with fluorine under
high pressure or with liquid alkali metals
(sodium or potassium), where adverse reactions may occur. The cone acts like a lens
that focuses short (0.15 mW) radar pulses
into a beam and sends them towards the
product. During the pulse intervals, the
cones operate like a unidirectional microphone with optimum reception efficiency. The
intelligent, extremely fast electronics converts
the radar echo into a precise image of the
environment and level, which is then
outputted as a 4 … 20 mA or Profibus signal.
Due to their small housing dimensions and
process fittings, the compact sensors are
unobtrusive and, above all, cost-effective
monitors of your product levels. With their
integrated display, they enable highprecision level measurements and can be
used for applications in which the
advantages of non-contact measurement
could never before be realized.
VEGAPULS radar sensors are perfectly
adapted to two-wire technology. The supply
voltage and the output signal are transmitted
via one two-wire cable. The instruments
produce an analogue 4 … 20 mA signal as
output, i.e. measuring signal.
1.1 Function
Radio detecting and ranging: Radar.
VEGAPULS radar sensors are used for noncontact, continuous distance measurement.
The measured distance corresponds to a
filling height and is outputted as level.
Measuring principle:
emission – reflection – reception
Extremely small 26 GHz radar signals are
emitted from the antenna of the radar sensor
as short pulses. The radar pulses reflected
by the sensor environment and the product
are received by the antenna as radar echoes. The running period of the radar pulses
from emission to reception is proportional to
the distance and hence to the level.
4 VEGAPULS 41 – 4 … 20 mA
26620-EN-041227
Product description
Meas.
distance
emission - reflection - reception
The radar pulses are emitted by the antenna
system as pulse packages with a pulse
duration of 1 ns and pulse intervals of
278 ns; this corresponds to a pulse package
frequency of 3.6 MHz. In the impulse intervals, the antenna system operates as a receiver. Signal running periods of less than
one billionth of a second must be processed
and the echo image evaluated in a fraction of
a second.
1 ns
278 ns
Hence, it is possible for the radar sensors to
process the slow-motion pictures of the sen-
sor environment precisely and in detail in
cycles of 0.5 to 1 second without using time-
consuming frequency analysis (e.g. FMCW,
required by other radar techniques).
Virtually all products can be measured
Radar signals display physical properties
similar to those of visible light. According to
the quantum theory, they propagate through
empty space. Hence, they are not depend-
ent on a conductive medium (air), and they
spread out like light at the speed of light.
Radar signals react to two basic electrical
properties:
- the electrical conductivity of a substance
- the dielectric constant of a substance.
All products which are electrically conductive
reflect radar signals very well. Even slightly
conductive products provide a sufficiently
strong reflection for a reliable measurement.
All products with a dielectric constant ε
more than 2.0 reflect radar pulses sufficiently
(note: air has a dielectric constant ε
Signal reflectivity grows stronger with in-
creasing conductivity or increasing dielectric
constant of the product. Hence, virtually all
products can be measured.
of 1).
r
of
r
Pulse sequence
VEGAPULS radar sensors can achieve this
through a special time transformation procedure which spreads out the more than 3.6
million echo images per second into a quasi
slow-motion picture, then freezes and processes them.
%
50
40
30
20
10
5 %
5
0
2
4 6 8 12 14 16 18
0
25 %
10
40 %
20
ε
Reflected radar power dependent on the dielectric
constant of the measured product
tt
Time transformation
26620-EN-041227
VEGAPULS 41 – 4 … 20 mA 5
r
Product description
With standard flanges of DN 50 to DN 150,
ANSI 2“ to ANSI 6“ or G 1½ A and 1½“ NPT,
the sensor antenna systems can be adapted
to various products and measuring environments.
The high-quality materials can also withstand
extreme chemical and physical conditions.
The sensors deliver stable, reproducible
analogue or digital level signals with reliability
and precision and have a long useful life.
Continuous and reliable
Unaffected by temperature, pressure and
individual gas atmospheres, VEGAPULS
radar sensors are used for quick and reliable
continuous level measurement of widely varying products.
%
0,03
0,02
0,01
0
100 500 1000 1300 ˚C
0
0,018 %
Temperature influence: Temperature error absolutely
zero (e.g. at 500°C 0.018 %)
%
10
5
0,29 %
0
10
0
1,44 %
20 30 40 60
50
Pressure influence: Error with pressure increase very
low (e.g. at 50 bar 1.44 %)
0,023 %
2,8 %
70 80 90 110 120 130 140
100
3,89 %
bar
1.2 Application features
Applications
• level measurement of any liquid
• measurement also in vacuum
• all slightly conductive materials and all
substances with a dielectric constant > 2.0
can be measured
• measuring range 0 … 10 m.
Two-wire technology
• power supply and output signal on one
two-wire cable (Loop powered)
• 4 … 20 mA output signal or HART
signal.
Rugged and abrasionproof
• non-contact
• high-resistance materials
Exact and reliable
• accuracy 0.05 %.
• resolution 1 mm
• unaffected by noise, vapours, dusts, gas
compositions and inert gas stratification
• unaffected by varying density and temperature of the medium
• measurement in pressures up to 3 bar and
product temperatures up to 150°C.
Communicative
• integrated measured value display
• optional display module separate from
sensor
• adjustment with detachable adjustment
module, pluggable in the sensor or in the
external display
• adjustment with HART
®
handheld
• adjustment with the PC.
®
output
Approvals
• CENELEC, ATEX, PTB, FM, CSA, ABS,
LRS, GL, LR, FCC.
6 VEGAPULS 41 – 4 … 20 mA
26620-EN-041227
Product description
1.3 Adjustment
Each measuring situation is unique. For that
reason, every radar sensor needs some
basic information on the application and the
environment, e.g. which level means "empty“
and which level "full“. Beside this "empty and
full adjustment“, many other settings and
adjustments are possible with VEGAPULS
radar sensors.
The adjustment and parameter setting of
radar sensors is carried out with
- the PC
- the detachable adjustment module MINICOM
- the HART
Adjustment with the PC
The set-up and adjustment of the radar sensors is generally done on the PC with the
adjustment software PACT
gram leads quickly through the adjustment
and parameter setting by means of pictures,
graphics and process visualisations.
®
handheld
ware
TM.
The pro-
The PC can be connected at any measuring
site in the system or directly to the signal
cable. It is connected by means of the twowire PC interface converter VEGACONNECT 3
to the sensor or the signal cable. The adjustment and parameter data can be saved with
the adjustment software on the PC and can
be protected by passwords. On request, the
adjustments can be quickly transferred to
other sensors.
2
PLC
2
Adjustment with the PC on the 4 … 20 mA signal and
supply cable or directly on the sensor (figure: a twowire sensor)
2
4 ...20 mA
2
Adjustment with the PC on the analogue 4 … 20 mA
signal and supply cable or directly on the sensor
(four-wire sensor)
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VEGAPULS 41 – 4 … 20 mA 7
Product description
Adjustment with the adjustment module
MINICOM
With the small (3.2 cm x 6.7 cm) 6-key adjustment module with display, the adjustment
can be carried out in clear text dialogue. The
adjustment module can be plugged into the
radar sensor or into the optional, external
indicating instrument.
Tank 1
m (d)
12.345
Detachable adjustment module MINICOM
Unauthorised sensor adjustments can be
prevented by removing the adjustment module.
ESC
+
-
OK
Adjustment with the HART® handheld
Series 40 sensors with 4 … 20 mA output
signal can also be adjusted with the HART
handheld. A special DDD (Data Device Description) is not necessary - the sensors can
be adjusted with the HART
®
standard menus
of the handheld.
HART Communicator
HART® handheld
To make adjustments, simply connect the
®
HART
handheld to the 4 … 20 mA output
signal cable or insert the two communication
cables of the HART
®
handheld into the ad-
justment jacks on the sensor.
®
ESC
+
-
Tank 1
m (d)
OK
12.345
2
-
Tank 1
m (d)
12.345
+
ESC
OK
4 ... 20 mA
2
4 ...20 mA
2
4
HART® handheld on the 4 … 20 mA signal cable
Adjustment with detachable adjustment module. The
adjustment module can be plugged into the radar
sensor or into the external indicating instrument
VEGADIS 50.
8 VEGAPULS 41 – 4 … 20 mA
26620-EN-041227
Types and versions
1.4 Type survey
VEGAPULS 41 sensors are manufactured
with process connection G 1½ A or 1½“ NPT.
Features
• Application preferably for liquids in storage tanks and process vessels with increased
accuracy requirements.
• Measuring range 0 … 10 m
• Ex approved in Zone 1 (IEC) or Zone 1 (ATEX) classification mark
EEx ia [ia] IIC T6.
• Integrated measured value display.
Survey
Signal output
- active (4 … 20 mA)
- passive (4 … 20 mA, loop powered)
Process connection
- G 1½ A, 1½“ NPT
Adjustment
-PC
- adjustment module in the sensor
- adjustment module in the external indicating instrument
- HART® handheld
Measuring range
- 0 … 10 m
26620-EN-041227
VEGAPULS 41 – 4 … 20 mA 9
1.5 Antennas
The antenna is the eye of the radar sensor.
An uninitiated observer would probably not
realise how carefully the antenna geometry
must be adapted to the physical properties
of electromagnetic fields. VEGAPULS 41
radar sensors are equipped with a completely encapsulated antenna.
PTFE is commonly found in hygienic applications. The small plastic cone of the
VEGAPULS 41 radar sensor, operating as
antenna, consists of a TFM-PTFE material.
This is a fluorthermoplast, which has further
distinct advantages compared to PTFE, such
as, e.g., reduced load deformation, denser
polymer structure as well as a smoother
surface (Ra < 0.8 µm). The other known advantages of PTFE, such as, e.g., high temperature resistance (up to 150°C), high
chemical resistance as well as resistance to
brittleness and ageing are still there or have
even been enhanced. Perfluorelastomers
and fluorthermoplasts are resistant to virtually
all chemical media such as, e.g., amines,
ketones, esters, acids (sulphuric acid, phosphoric acid, hydrochloric acid, nitric acid),
alkalis (caustic soda), oxidants, fuels and
oils. Beside their use in the chemical industry,
these materials are being applied more and
more in sterilisation and pharmaceutical technologies. The only limits to these materials are
in applications with fluorine under high pressure or with liquid alkali metals (sodium or
potassium), where explosive reactions may
occur.
Types and versions
10 VEGAPULS 41 – 4 … 20 mA
26620-EN-041227
Mounting and installation
2 Mounting and installation
2.1 General installation instructions
Measuring range
The reference plane for the
measuring range of the sensor
is the lower edge of the flange.
empty
full
Keep in mind that in measuring
environments where the medium can reach the sensor
flange, buildup may form on
the antenna and later cause
measurement errors.
Note: The series 40 sensors
are suitable for measurement
of solids only under certain
conditions.
Measuring range (operating range) and max. measuring distance
Note: Use of the sensors for applications with solids is limited.
False echoes
Flat obstructions and struts cause strong
false echoes. They reflect the radar signal
with high energy density.
Interfering surfaces with rounded profiles
scatter the radar signals into the surrounding
space more diffusely and thus generate false
echoes with a lower energy density. Hence,
those reflections are less critical than those
from a flat surface.
Reference plane
max.
Meas. range
max.
min.
If flat obstructions in the range of the radar
signals cannot be avoided, we recommend
diverting the interfering signals with a deflector. The deflector prevents the interfering
signals from being directly received by the
radar sensor. The signals are then so lowenergy and diffuse that they can be filtered
out by the sensor.
Round profiles diffuse radar signals
Profiles with smooth interfering surfaces cause large
false signals
Cover smooth interfering surfaces with deflectors
26620-EN-041227
VEGAPULS 41 – 4 … 20 mA 11
Mounting and installation
Emission cone and false echoes
The radar signals are focused by the antenna system. The signals leave the antenna
in a conical path similar to the beam pattern
of a spotlight. This emission cone depends
on the antenna used. Any object in this beam
cone will reflect the radar signals. Within the
first few meters of the beam cone, tubes,
struts or other installations can interfere with
the measurement. At a distance of 6 m, the
false echo of a strut has an amplitude nine
times greater than at a distance of 18 m.
At greater distances, the energy of the radar
signal distributes itself over a larger area,
thus causing weaker echoes from obstructing surfaces. The interfering signals are
therefore less critical than those at close
range.
If possible, orient the sensor axis perpendicularly to the product surface and avoid
vessel installations (e.g. pipes and struts)
within the emission cone.
The illustrations of the emission cones are
simplified and represent only the main beam
- a number of weaker beams also exist. Under difficult measuring conditions, the antenna should be oriented so that the lowest
possible false echo values appear. Only
giving attention to the size of the useful echo
is not adequate when measuring conditions
are unfavourable.
In a difficult measuring environment, searching for a mounting location with the lowest
possible false echo intensity will bring the
best results. In most cases, the useful echo
will then be present with sufficient strength.
With the adjustment software PACT
ware
TM
on
the PC, you can have a look at the echo image and optimise the mounting location.
If possible, provide a "clear view“ to the
product inside the emission cone and avoid
vessel installations in the first third of the
emission cone.
Optimum measuring conditions exist when
the emission cone reaches the measured
product perpendicularly and when the emission cone is free from obstructions.
Examples of vessel echoes
The following vessel images show a typical
echo pattern in a vessel. The example shows
a process vessel with a slow double-bladed
stirrer. In the lower area, the vessel is
equipped with heating spirals. A thin, angled
inlet tube ends in the vessel centre between
the stirrer blades.
12 VEGAPULS 41 – 4 … 20 mA
26620-EN-041227
Mounting and installation
Empty vessel
When the vessel is empty, you see the echoes of the vessel installations around the
emission cone. Beside the large bottom echo,
you see a number of additional false echoes.
The false echoes of the vessel installations
are saved during a false echo recording. For
this reason, the false echo recording must be
done in an empty vessel.
False echoes from the top down:
- first inlet tube fastening
- upper stirrer blade
- second inlet tube fastening
- angled inlet tube
- upper heating tubes
- lower stirrer blade
- remaining heating tubes
- vessel bottom
¼ filling
After filling, the bottom echo is replaced by
the product echo.
½ filling
The product echo moves to the centre of the
meas. range. At the end of the meas. range,
you now see an echo at a position where the
bottom echo previously was in the empty
vessel. This echo is a multiple echo of the
product echo and is located at twice the
distance of the product echo.
26620-EN-041227
VEGAPULS 41 – 4 … 20 mA 13
Mounting and installation
Filled vessel
In a completely filled vessel, you see additional multiple echoes at two, three or four
times the distance of the product surface
echo.
2.2 Measurement of liquids
Most commonly, the mounting of radar sensors is done on short DIN socket pieces. The
lower side of the instrument flange is the
reference plane for the measuring range. The
socket piece should be as short as possible,
max. 70 mm.
When mounting on dished vessel tops, the
antenna length should at least correspond to
the length of the socket.
On dished vessel tops, please do not mount
the instrument in the centre or close to the
vessel wall.
Dished tank tops can act as paraboloidal
reflectors. If the radar sensor is placed in the
focal point of the parabolic tank top, the radar
sensor receives amplified false echoes. The
radar sensor should be mounted outside the
focal point. Parabolically amplified echoes are
thereby avoided.
Horn antenna directly on the vessel top
If the stability of the vessel will allow it (sensor
weight), flat mounting directly on the vessel
top is a good and economical solution. The
top side of the vessel is the reference plane.
The screwed antenna is used mainly on very
small vessels. The antenna fits into even the
smallest vessel connection openings (1
1
/2“
socket). The socket must not be longer than
70 mm.
Reference
plane
< 70 mm
Screwed antenna on1½“ mounting boss
14 VEGAPULS 41 – 4 … 20 mA
26620-EN-041227
Mounting and installation
2.3 Measurement in standpipe (surge or bypass tube)
General instructions
Measurement in a standpipe is preferred in
vessels which contain many installations, e.g.
heating tubes, heat exchangers or fast-running stirrers. Measurement is then possible
when the product surface is very turbulent,
and vessel installations can cause no false
echoes.
Due to the concentration of the radar signals
within the measuring tube, even products
with small dielectric constants (ε
3) can be reliably measured in surge or by-
pass tubes.
Surge pipes which are open at the bottom
must extend over the full measuring range
(i.e. down to 0% level), as measurement is
only possible within the tube. The tube inner
diameter should be max. 100 mm or correspond to the size of the antenna horn.
Make sure the required upper vent hole in
the surge pipe is aligned with the sensor
type label.
= 1.6 up to
r
When mounting a VEGAPULS 41 sensor on a
bypass tube (e.g. on a previous floating or
displacer unit), the radar sensor should be
placed approx. 300 mm or more from the
max. level.
For products with small dielectric constants
(< 4), the bypass tube should have a length
greater than would normally be required for
the lower tube connection. Products with
small dielectric constants are partly penetrated by the radar signals, allowing the
tube bottom to produce a stronger echo than
the product (when the bypass tube is nearly
empty). By extending the tube downward,
some liquid remains at the bottom even when
the vessel is completely empty.
Type label
> 300 mm
100 %
As an alternative to a surge pipe in the vessel, a pipe antenna system outside the vessel in a bypass tube is also possible.
0 %
300 ... 800 mm
The surge and bypass tubes must generally
be made of metal. For plastic tubes, a
closed, conductive jacket is always required.
Tube flange system as bypass tube
When using a metal tube with plastic inner
coating, make sure that the thickness of the
coating is minimal (approx. 2 … 4 mm).
If enough liquid (300 … 800 mm) remains in
the blind lower end of the tube, the portion of
Align the sensor such that the type label lies
on one axis with the tube holes or the tube
connection openings. The polarisation of the
radar signals enables a considerably stabler
measurement with this alignment.
the signal that penetrates the liquid and reflects from the tube bottom is sufficiently
damped - the sensor can then easily distinguish it from the echo of the liquid surface. In
cases where there is not enough liquid at the
bottom of the tube, a deflector situated there
will carry out the same function. It deflects
signals that reach the tube bottom into the
standard connection opening.
26620-EN-041227
VEGAPULS 41 – 4 … 20 mA 15
Connections to the bypass tube
The connections to the bypass tubes must
be fashioned in such a way that only minimal
reflections are caused by the walls of the
connecting tubes. This is especially important
for the breather connection in the upper part
of the tube. Observe the following points:
• Use small openings for the connection.
• The diameter of the connecting tubes
should not exceed 1/3 of the bypass diameter.
• The tube connections must not protrude
into the bypass.
• Large welding beads in the tubes should
be avoided.
• Additional connections to the bypass tube
must lie in the same plane as the upper
and lower vessel connection (above each
other or displaced by 180°).
Optimum connection to the bypass tube
Mounting and installation
Tube connection protrudes
Additional connection in the bypass tube in one plane
Use of guide tubes
In case of very rough inner surfaces in existing bypass tubes (e.g. due to corrosion),
large connection openings as well as bypass
tubes with more than 100 mm inner diameter,
the use of a guide tube inside the existing
bypass tube is recommended. This reduces
the noise level and increases reliability considerably. The flange of the guide tube can
be easily mounted as a sandwich flange
between vessel and sensor flange.
Welding beads too large
16 VEGAPULS 41 – 4 … 20 mA
26620-EN-041227
Mounting and installation
Seals on tube connections and tube extensions
Microwaves are very sensitive to gaps in
flange connections. If connections are made
without proper care, distinct false echoes as
well as increased signal noise can result.
Observe the following points:
• The applied seal should correspond to the
tube inner diameter.
• If possible, conductive seals such as conductive PTFE or graphite should be used.
• There should be as few seal positions as
possible in the guide tube.
Flange connections on bypass tubes
Adhesive products
In non-adhesive or slightly adhesive products, use a surge pipe with a nominal width of
e.g. 50 mm. VEGAPULS 41 radar sensors
with 26 GHz technology are for the most part
insensitive to buildup in the measuring tube.
However, buildup should not block the measuring tube.
For products with heavier buildup, the use of
a DN 80 to max. DN 100 standpipe or surge
pipe can make the measurement possible
despite buildup. With products that are extremely adhesive, measurement in a standpipe is not possible at all.
Standpipe measurement of inhomogeneous products
ø 5...15
homogeneous
liquids
inhomogeneous liquids
Openings in a surge pipe for mixing of inhomogeneous products
If you want to measure inhomogeneous or
stratified products in a surge pipe, it must
have holes, elongated holes or slots. These
openings ensure that the liquid is mixed and
corresponds to the liquid in the vessel.
The more inhomogeneous the measured
product, the closer the openings should be
spaced.
Due to radar signal polarisation, the holes or
slots must be positioned in two rows offset
by 180°. The radar sensor must then be
mounted so that the type label of the sensor
is aligned with the rows of holes.
Every wider slot causes a false echo. The
slots should therefore not exceed a width of
10 mm in order to keep the signal-to-noise
level at a minimum. Round slot ends are better than rectangular ones.
slightly inhomogeneous
liquids
ø 5...15
26620-EN-041227
VEGAPULS 41 – 4 … 20 mA 17
Mounting and installation
Type label
ø 5...15
Row of holes in one axis with the type label
Surge pipe with ball valve
If a ball valve is mounted in the surge pipe,
maintenance and servicing can be carried
out without opening the vessel (e.g. if it contains liquid gas or toxic products).
Ball valve
> 300 mm
Vent hole
ø50
Guidelines for standpipe construction
The measuring pipe must be smooth inside
(average roughness Rz ≤ 30). Use stainless
steel tubing (drawn or welded lengthwise) for
construction of the measuring pipe. Extend
the measuring pipe to the required length
with weld-on flanges or with connecting
sleeves. Make sure that no shoulders or
projections are created during welding. Before welding, join pipe and flange with their
inner surfaces flush and exactly fitting.
Avoid welding through the pipe wall. The pipe
must remain smooth inside. Roughness or
welding beads on the inner surfaces must be
carefully removed and burnished, as they
cause false echoes and encourage product
adhesion.
If the vessel contains agitated products,
fasten the measuring pipe to the vessel bottom. Provide additional fastenings for longer
measuring pipes.
In products with lower dielectric values (< 4),
a part of the radar signal penetrates the
medium. If the vessel is nearly empty, echoes
are generated by both the product and the
vessel bottom. The echo from the vessel
bottom can in some cases be stronger than
the echo from the product surface. if a deflector is installed below the open end of the
measuring tube, the radar signals are scattered and prevented from reaching the vessel bottom. This ensures that, in nearly empty
vessels or with products of low dielectric
value, the product delivers a more distinct
echo than the vessel bottom.
Deflector
Due to the deflector, the useful signal and
meas. value in the nearly empty vessel are
distinct and clear - the 0 % level can thus be
Tube antenna system with ball valve cutoff in measuring tube
reliably measured.
A prerequisite for trouble-free operation is a
ball valve throat that corresponds to the pipe
diameter and provides a flush surface with
the pipe inner wall. The valve must not have
any rough edges or constrictions in its channel. The distance to the sensor flange should
be at least 300 mm.
18 VEGAPULS 41 – 4 … 20 mA
26620-EN-041227
0 %
Mounting and installation
Instead of a deflector, the standpipe or surge
pipe can be equipped with a quadrant pipe
at the end. This reflects the radar signals that
penetrate the medium diffusely to the side
and diminishes strong echoes from the tube
end or the vessel bottom.
Connecting
sleeve
Welding neck
flanges
Deburr the
holes
Deflector
0 %
100 %
150...500
~45û
2,9...6
5...10
2,9
ø 51,2
Welding of the connecting sleeves
0,0...0,4
Welding of the welding
neck flanges
1,5...2
0,0...0,4
Meas. pipe fastening
0 %
Quadrant pipe on the bypass tube end
Vessel
bottom
Quadrant pipe on the standpipe end
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Mounting and installation
2.4 False echoes
The installation location of the radar sensor
must be at a spot where no installations or
inflowing material cross the radar impulses.
The following examples and instructions
show the most frequent measuring problems
and how to avoid them.
Vessel protrusions
Vessel forms with flat protrusions can, make
measurement very difficult due to their strong
false echoes. Shields above these flat protrusions scatter the false echoes and guarantee
a reliable measurement.
Correct Incorrect
Vessel protrusions (ledge)
Intake pipes, i.e. for the mixing of materials with a flat surface directed towards the sensor - should be covered with an angled baffle
that scatters false echoes.
Vessel installations
Vessel installations, such as e.g. ladders,
often cause false echoes. Make sure when
planning your measuring location that the
radar signals have free access to the measured product.
Correct Incorrect
Ladder
Vessel installations
Ladder
Struts
Struts, like other vessel installations, can
cause strong false echoes that are superimposed on the useful echoes. Small baffles
effectively prevent a direct reception false
echoes. These false echoes are scattered
and diffused in the surrounding space are
then filtered out as "echo noise“ by the measuring electronics.
Correct Incorrect
Correct Incorrect
Struts
Vessel protrusions (intake pipe)
20 VEGAPULS 41 – 4 … 20 mA
Shields
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Mounting and installation
Inflowing material
Do not mount the instrument in or above the
filling stream. Ensure that you detect the
product surface and not the inflowing material.
Correct
Inflowing material
Incorrect
Buildup
If the sensor is mounted too close to the
vessel wall, product buildup and other deposits on the vessel wall cause false echoes.
Position the sensor at a sufficient distance
from the vessel wall. Please also note chapter
"3.1 General installation instructions“.
Correct
Incorrect
Strong product movements
Strong turbulence in the vessel, e.g. caused
by powerful stirrers or strong chemical reactions, can seriously interfere with the measurement. A surge or bypass tube (see
illustration) of sufficient size always enables
reliable and problem-free measurement even
if strong turbulence occurs in the vessel,
provided there is no product buildup in the
tube.
Correct
Strong product movements
Incorrect
100 %
75 %
0 %
Buildup
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VEGAPULS 41 – 4 … 20 mA 21
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