Schmidt SS 23.700 Ex User manual

SCHMIDT®Flow Sensor
SS 23.700 Ex
Instructions for Use

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 2
SCHMIDT®Flow Sensor SS 23.700 Ex
Table of Contents
1Important information.......................................................................3
2Application range - General.............................................................4
3Application range - ATEX................................................................6
4Mounting instructions - General ......................................................7
5Mounting instructions - ATEX........................................................17
6Electrical connection - General .....................................................19
7ATEX - Electrical connection and protective sleeve assembly .....24
8ATEX type plate - Labelling...........................................................26
9Signaling........................................................................................27
10 Commissioning..............................................................................32
11 Information concerning operation..................................................32
12 Service information........................................................................33
13 Dimensions....................................................................................36
14 Technical data ...............................................................................37
15 Declarations of conformity.............................................................39
16 Type Examination Certificate ........................................................41
Imprint:
Copyright 2023 SCHMIDT Technology GmbH
All rights reserved
Version: 570454.02
Subject to modifications

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 3
1 Important information
The instructions for use contain all required information for a fast commis-
sioning and a safe operation of SCHMIDT®flow sensors.
These instructions for use must be read completely and observed care-
fully, before putting the unit into operation.
Any claims under the manufacturer's liability for damage resulting from
non-observance or non-compliance with these instructions will become
void.
Tampering with the device in any way whatsoever - with the exception
of the designated use and the operations described in these instructions
for use - will forfeit any warranty and exclude any liability.
The unit is designed exclusively for the use described below (refer to
chapter 2). In particular, it is not designed for direct or indirect protection
of personal or machinery.
SCHMIDT Technology cannot give any warranty as to its suitability for
a certain purpose and cannot be held liable for errors contained in these
instructions for use or for accidental or sequential damage in connection
with the delivery, performance or use of this unit.
Symbols used in this manual
The symbols used in this manual are explained in the following section.
Danger warnings and safety instructions. Read carefully!
Non-observance of these instructions may lead to injury of the
personal or malfunction of the device.
Risk of explosion - Read carefully!
Important instructions for use in areas subject to explosion haz-
ards.
General note
All dimensions are given in mm.

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 4
2 Application range - General
The SCHMIDT®Flow Sensor SS 23.700 Ex (art. no.: 569700) is designed
for the stationary measurement of flow velocity as well as the temperature
of air and gas with operating temperature from -20 … +120 °C and working
pressure
1
up to 16 bar.
The sensor is based on the measuring principle of a thermal anemometer
and measures the mass flow of the measuring medium as flow velocity
which is output in a linear way as standard velocity
2
wN(unit: m/s), based
on standard conditions of 1013.25 hPa and 20 °C. Thus, the resulting out-
put signal is independent of the pressure and temperature of the medium
to be measured.
When using the sensor outdoors, it must be protected against di-
rect exposure to the weather.
Version “PWIS-compliant”
It differs from the standard version in the following points:
Use of a special PWIS-compliant compression fitting (abbr.: DGV),
completely made of stainless steel, which seals by means of a cutting
ring (i.e. there is no O-ring or other plastic in contact with the medium).
The cutting ring is designed relatively "soft" so that it does not bite too
much when tightened and can therefore be easily loosened again, mak-
ing it unnecessary to use a lubricant. The internal thread of the com-
pression nut is finished with a coating (DURNI-COAT®) which prevents
jamming.
The packaging (foil pouch) of the sensor is also PWIS-compliant.
In addition, the sensor, together with its supplied mounting accessories
(pressure safety kit) and optional accessories, is specially cleaned in
accordance with the IEC/TR 60877:1999 standard.
The PWIS-compliant zone is limited to the actual sensor probe part only!
Only the tube-shaped probe itself (incl. its DGV and pressure
protection components) is PWIS-compliant.
By opening the shipping package, the customer assumes respon-
sibility for maintaining or restoring the PWIS-compliance of the
probe as well as the cleanliness of the rest of the sensor and its
accessories in accordance with IEC/TR 60877:1999.
1
Overpressure
2
Corresponds to the actual velocity under standard conditions

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 5
Information concerning PWIS-compliant handling
In general, it is essential to avoid contamination, especially of the PWIS-
compliant sensor component:
- Before installing the sensor, carefully clean its mounting location.
- Make sure to use only clean tools and material for the installation.
- Before opening the packaging foil, remove dirt such as dust from its sur-
face, if necessary.
- If possible, open the packaging film and take out the sensor directly at
the installation site.
- Otherwise open the package foil at an appropriate and clean workplace
and store the sensor in an appropriate, PWIS-compliant container.
- Don’t touch the PWIS-compliant sensor parts with bare hands.
- Use clean and non-fluffy gloves or cloths or similar to handle the sensor,
preferably in PWIS-compliant models.
Version for “special gases”
The version of the SS 23.700 Ex for “special gases” receives a gas-spe-
cific adaption for the measurement of certain gases and gas mixtures.
The sensor is adjusted and calibrated in air. Then a special correction
function for the medium to be measured is applied to the sensor. This cor-
rection has been determined for many gases in real gas ducts. For gas
mixtures, the correction adaption is calculated according to the volume
based mixing ratio.
Mechanical versions
The sensor SS 23.700 Ex is available in two mechanical versions:
- Compact sensor:
The sensor probe is fixed to the main enclosure.
- Remote sensor:
The sensor probe is mechanically separated from the main enclosure.
Connection is realized by an electrical signal cable that cannot be de-
tached on either side.
The different construction types and their dimensions can be found in the
dimensional drawings in chapter 13.
The customer is responsible for observing all relevant statutory
provisions, standards and directives relating to the use of gases.

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 6
3 Application range - ATEX
As a category 3 device, the SCHMIDT®Flow Sensor SS 23.700 Ex is
equipped with the following types of protection:
o Gases (Zone 2): II 3G Ex ec ic IIC T4 Gc
o Dusts (Zone 22): II 3D Ex ic tc IIIC T135°C Dc
The sensor is only suitable for use in combustible, conductive
dusts with a smoldering temperature higher than 210 °C.
Special conditions for use ("X"):
o The internal intrinsically safe circuit is isolated
3
from the en-
closure only up to 30 V.
o A power supply with protection class III is required (PELV).
o The permissible pulling force at the connecting cable of the
remote version is limited to 20 N (25 % of the nominal value
of the standard according to Annex A, chapter A.2.3.2).
The permissible operating temperatures are:
o Electronics: -20 ... +70 °C
o Sensor probe (medium): -20 ... +120 °C
Electrical data:
o Rated voltage: 24 VDC ± 20 %
o Rated current: 250 mA
o Measurement outputs: 0 … 10 V / 4 … 20 mA
o Impulse output: f = 0 … 100 Hz
Umax = 28.8 VDC
Imax = 100 mA
o Relay output: f = 0 … 100 Hz
Umax = 30 VDC
Imax = 50 mA
Enclosure:
o Degree of protection: IP66 (main enclosure)
IP67 (sensor probe)
3
Limitation by varistor inside the sensor between GND and enclosure (ESD-protection).

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 7
4 Mounting instructions - General
Handling
The flow sensor SS 23.700 Ex is a precision instrument with high meas-
uring sensitivity. In spite of the robust construction of the sensor head,
soiling of the sensor elements can lead to distortion of measurement re-
sults (see also chapter 12).
During procedures such as transport, installation or dismounting of the
sensor that facilitates soiling as well as represent a mechanical load on
the sensor head, the protective cap supplied by SCHMIDT Technology
should generally be attached to the sensor head and only removed during
installation.
To avoid soiling and mechanical stress on the sensor head, the
protective cap should be placed over it during transport or instal-
lation.
Mounting method
The sensor SS 23.700 Ex can be mounted only by means of a compres-
sion fitting which supports the sensor tube and ensures frictional clamping.
The compression fitting as well as a pressure protection kit is included in
the scope of delivery.
Due to the variety of applications the compression fitting exists in different
versions. On the one hand they are determined by the design of the ex-
ternal thread (order option: G½ or R½), on the other hand by the materials
and properties of the sealing:
Standard: Sealing with O-Ring (NBR)
PWIS-compliant: Sealing with clamping ring (stainless steel), only G½
Systems with overpressure
The SS 23.700 EX is designed for a maximum working pressure of 16 bar.
As long as the medium to be measured is operated with overpressure,
make sure that:
There is no overpressure in the system during mounting.
Mounting and dismounting of the sensor can be carried out
only as long as the system is in a depressurized state.
Only suitable pressure-tight mounting accessories are used.
Appropriate safety measures are installed to avoid unintended discard-
ing of the sensor due to overpressure. If other accessories than the de-
livered pressure protection kit or alternative mounting solutions are
used, the customer must ensure the corresponding safety measures.

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 8
For measurements in media with overpressure, appropriate
safety measures must be taken to prevent unintended discard-
ing of the sensor.
The pressure-tight mounting, the fastening of the screw pipe
connection and the discarding protection must be checked be-
fore pressure is applied. These tightness checks must be re-
peated at reasonable intervals.
The components of the pressure protection kit (bolt, chain and
bracket) have to be checked regularly for integrity.
Thermal boundary conditions
In the case of medium temperatures that don’t correspond to the permis-
sible operating temperature of the electronics, cross-talk of the tempera-
ture into the electronics housing must be prevented by a thermal decou-
pling section of the sensor tube having a free-standing length of at least
50 mm (see Figure 4-1) or by means of other suitable measures.
Figure 4-1
The permissible operating temperature range of the electronics
must not be exceeded by crosstalk of the medium temperature on
the sensor housing.
Flow characteristics
Local turbulences of the medium can cause distortion of measurement
results. Therefore, appropriate mounting conditions must be guaranteed
to ensure that the gas flow is supplied to the sensor in a laminar
4
state,
i.e. quiet and low in turbulence. The corresponding measures depend on
the system properties (pipe, chamber, etc.) which are described in the fol-
lowing subchapters for different mounting variants.
Correct measurements require a (laminar) flow, low in turbulence.
4
The term “laminar” means here an air flow, low in turbulence (not according to its physical
definition saying that the Reynolds number is < 2300).
> 50 mm
2

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 9
Installation conditions
The sensor head of the SS 23.700 Ex consists of two basic elements:
Heater
The longer of the two sensor tubes at the tip of the sensor head is the
so-called heater. It consists of a heated, temperature-dependent resis-
tor that is used to measure flow velocity.
The end of the heater element, to which the length specification (L) of
the sensor also refers, represents the actual measuring point of the flow
measurement and should be placed as favourably as possible in the
flow, e.g. in the middle of the pipe.
Temperature sensing element
The shorter of the two sensor tubes at the tip of the sensor head is the
temperature sensor. It consists of an unheated, temperature-dependent
resistor, which measures the temperature of the medium.
The aerodynamically optimized design allows tilting around the longitudi-
nal axis of the sensor up to ±3° relative to the ideal measuring direction
(see Figure 4-2) without significant impact on the measurement result
5
.
The axial tilting of the sensor head relative to flow direction should
not exceed ±3°.
Position the sensor head always at the most advantageous posi-
tion for flow measurement.
The sensor measures unidirectional (see “flow arrow” in Figure
4-2) and must be adjusted correctly relative to the flow direction.
View on probe head View on enclosure cover
Figure 4-2 Alignment of sensor relative to flow direction
5
Deviation < 1 % of measured value
Alignment plane

Instructions for Use –SCHMIDT®Flow Sensor SS 23.700 Ex Page 10
Mounting in pipes with circular cross-section
Typical applications for this type are compressed air networks or burner
gas supply lines. They are characterized by long thin pipes with a typically
quasi-parabolic flow profile.
The easiest method to achieve a low-turbulence flow is to provide a suffi-
ciently long and absolutely straight distance without disturbances (such as
edges, seams, bends etc.) in front (inlet) and behind the sensor (outlet)
(see installation drawing Figure 4-3). It is also necessary to pay attention
to the design of the outlet distance because the flow is also influenced by
disturbances generating turbulences against the flow direction.
Figure 4-3
L1
Length of run-in distance
L2
Length of run-out distance
D
Inner diameter of measuring distance
The absolute length of the respective distances are determined by the in-
ner diameter D of the pipe because the flow abatement effect depends
directly on the aspect ratio of measuring distances to the diameter. There-
fore, the required abatement distances are specified as a multiple of the
inner pipe diameter D. Besides, the degree of turbulence generation by
the corresponding disturbing object plays an important role. A slightly
curved bend directs the air with a relative low-disturbance level, whereas
a valve generates massive turbulences with its abrupt change of the flow-
guiding cross-section, requiring a relatively long distance for abatement.
The following Table 1 shows the required straight pipe lengths depending
on the inner tube diameter D and different causes of disturbances.
This table lists the minimum values required in each case. If the listed
straight pipe lengths cannot be achieved, measurement accuracy may be
impaired or additional actions are required like the use of flow rectifiers
6
.
6
E.g., honeycombs made of plastic or ceramics.
Run-in distance L1
Run-out distance L2
Ø D