SF72 Rail
Dew-Point Transmitter
User’s Manual
97503 Issue 2
April 2017
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Use this information when contacting Michell Instruments for service purposes.
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SF72 Rail Transmitter
For Michell Instruments' contact information please go to
www.michell.com
© 2017 Michell Instruments
This document is the property of Michell Instruments Ltd. and may not be copied or
otherwise reproduced, communicated in any way to third parties, nor stored in any Data
Processing System without the express written authorization of Michell Instruments Ltd.
SF72 Rail Transmitter User’s Manual
Contents
Safety ................................................................................................................................vi
Electrical Safety ...........................................................................................................vi
UL Approval .................................................................................................................vi
Pressure Safety ............................................................................................................vi
Toxic Materials .............................................................................................................vi
Repair and Maintenance ...............................................................................................vi
Calibration ...................................................................................................................vi
Safety Conformity ........................................................................................................vi
Abbreviations .....................................................................................................................vii
Warnings ...........................................................................................................................vii
1 INTRODUCTION ................................................................................................1
1.1 Features ............................................................................................................ 1
2 INSTALLATION ..................................................................................................2
2.1 Unpacking the Instrument ................................................................................... 2
2.2 Electrical Connections ......................................................................................... 3
2.2.1 Electrical Boundaries ..................................................................................... 3
2.3 Transmitter Mounting .......................................................................................... 4
2.3.1 Transmitter Mounting - Sample Block (Optional) ............................................. 5
2.3.2 Transmitter Mounting - Direct Pipeline Connection ........................................... 6
3 OPERATION ......................................................................................................7
4 MAINTENANCE ..................................................................................................8
Figures
Figure 1 Transmitter Unpacking Method ....................................................................2
Figure 2 Maximum Load of SF72 Rail - Including Cable Resistance ..............................3
Figure 3 Transmitter Mounting - Sensor Block ............................................................5
Figure 4 Transmitter Mounting - Pipe or Duct.............................................................6
Figure 5 Installation Location ...................................................................................7
Figure 6 Indication of Dead Space ............................................................................7
Figure 7 Replacement of HDPE Guard .......................................................................8
Figure 8 Dimensions ..............................................................................................11
Figure 9 Electrical Connections ............................................................................... 11
iv 97503 Issue 2, March 2017
SF72 Rail Transmitter User’s Manual
Appendices
Appendix A Technical Specifi cations .............................................................................10
A.1 Dimensions .................................................................................11
Appendix B Quality, Recycling & Warranty Information ...................................................13
Appendix C Return Document & Decontamination Declaration ........................................15
Michell Instruments v
SF72 Rail Transmitter User’s Manual
Safety
The manufacturer has designed this equipment to be safe when operated using the procedures
detailed in this manual. The user must not use this equipment for any other purpose than that
stated. Do not apply values greater than the maximum value stated.
This manual contains operating and safety instructions, which must be followed to ensure the safe
operation and to maintain the equipment in a safe condition. The safety instructions are either
warnings or cautions issued to protect the user and the equipment from injury or damage. Use
competent personnel using good engineering practice for all procedures in this manual.
Electrical Safety
The instrument is designed to be completely safe when used with options and accessories supplied
by the manufacturer for use with the instrument.
UL Approval
This product is UL approved within the operating temperature range of -20°C to +60°C. The IP66
rating of this product is outside the scope of UL Approval, but this product has been verifi ed as being
IP66 by independent, UKAS accredited, 3rd party listing.
Pressure Safety
DO NOT permit pressures greater than the safe working pressure to be applied to the instrument.
The specifi ed safe working pressure is 45 MPa (450 barg / 6526 psig). Refer to the Technical
Specifi cations in Appendix A.
Toxic Materials
The use of hazardous materials in the construction of this instrument has been minimized. During
normal operation it is not possible for the user to come into contact with any hazardous substance
which might be employed in the construction of the instrument. Care should, however, be exercised
during maintenance and the disposal of certain parts.
Repair and Maintenance
The instrument must be maintained either by the manufacturer or an accredited service agent. For
Michell Instruments’ contact information please go to www.michell.com.
Calibration
The recommended calibration interval for this instrument is 12 months unless it is to be used in a
mission-critical application or in a dirty or contaminated environment in which case the calibration
interval should be reduced accordingly. The instrument should be returned to the manufacturer,
Michell Instruments Ltd., or one of their accredited service agents for re-calibration.
Safety Conformity
This product meets the essential protection requirements of the relevant EU and US standards
and directives. Further details of applied standards may be found in the Technical Specifi cations in
Appendix A.
vi 97503 Issue 2, March 2017
SF72 Rail Transmitter User’s Manual
Abbreviations
The following abbreviations are used in this manual:
barg pressure unit (=100 kP or 0.987 atm) (bar gauge)
°C degrees Celsius
°F degrees Fahrenheit
DC direct current
g grams
in inch(es)
m micrometer
m/sec meters per second
mA milliampere
max maximum
mm millimetres
MPa megapascal
Nl/min normal liters per minute
Nm Newton meter
oz ounces
psig pounds per square inch
RH relative humidity
scfh standard cubic feet per hour
fps feet per second
T temperature
V Volts
Ohms
ø diameter
Warnings
The following general warning listed below is applicable to this instrument. It is repeated
in the text in the appropriate locations.
Where this hazard warning symbol appears in the following
sections it is used to indicate areas where potentially hazardous
operations need to be carried out.
Michell Instruments vii
SF72 Rail Transmitter User’s Manual
viii 97503 Issue 2, March 2017
SF72 Rail Transmitter User’s Manual
1 INTRODUCTION
The SF72 dew-point transmitter is a compact sensor designed for use in industrial
dryer applications at the key -50 to +10°Cdp (-58 to +50°Fdp) measuring points where
response speed, reliability and long term stability of data within a control process is
critical.
The transmitter is pressure rated to 45 MPa (450 barg / 6526 psig), ensuring process
gas safety, through the use of a 10-year, fi eld-proven stainless steel body and glass-to-
metal seal, applicable for environments with constant vibration.
Our polymer based sensor is calibrated on a high volume traceable calibration system,
providing OEM quantities of units.
The SF72 Rail Transmitter has been manufactured, tested and calibrated to the highest
available standards and should be in perfect working order, ready for installation into a
gas measurement application. If there are any questions about the instrument or how to
install and operate it, please contact a Michell representative (for Michell Instruments’
contact information go to www.michell.com).
INTRODUCTION
1.1 Features
The SF72 Rail Transmitter is a continuous on line 4-20 mA transmitter for the measurement
of moisture content in air and other non-corrosive gases, particularly in rail use.
The key features are:
• M12 electrical connector
• Dew-point measurement range -60 to +60°Cdp (-76 to +140°Fdp)
• Fast response
• 316 stainless steel IP66 construction
• Traceable calibration certifi cate
• Accuracy ±2°Cdp (±3.6°Fdp)
• G1/2” BSP process connection
• RFI/EMC certifi ed to EN 50121-3-2:2006
• Shock/vibration certifi ed to IEC 61373:1999-01
Michell Instruments 1
INSTALLATION
2 INSTALLATION
2.1 Unpacking the Instrument
On delivery, please check that all the following standard components are in the packing
box:
• SF72 Rail Transmitter
• Bonded Seal
• Certifi cate of Calibration
Unpack the dew-point transmitter box as follows:
SF72 Rail Transmitter User’s Manual
654321
Figure 1
1. Unscrew the cap (1) from the packing tube (6).
2. Remove the foam block (2).
3. Pull out the transmitter (3) from the tube, complete with the two
foam covers (4) and (5).
4. Remove the foam covers from the transmitter but leave the black
plastic protective cover in place until ready for installation.
NOTE: The transmitter sensing element is protected while in transit by a
black cover containing a small desiccant capsule. This item is not required for
the operation of the transmitter.
Transmitter Unpacking Method
2 97503 Issue 2, March 2017
SF72 Rail Transmitter User’s Manual
2.2 Electrical Connections
4-20 mA 2-wire
PIN 3 4-20 mA
PIN 4 Power supply
INSTALLATION
2.2.1 Electrical Boundaries
600
500
400
300
Resistance (ohms)
200
100
12 14 16 18 20 22 24 26 28
Supply Voltage
Figure 2
Maximum Load of SF72 Rail - Including Cable Resistance
Michell Instruments 3
INSTALLATION
2.3 Transmitter Mounting
Prior to installation of the transmitter, unscrew and remove the black plastic cover and
desiccant capsule and retain for future use. Take care to prevent any contamination
of the sensor before installation (handle the transmitter by the main body only,
avoiding contact with the sensor guard).
The SF72 Rail Transmitter can be mounted either into a fl ow-through sensor sampling
block (optional) or directly into a pipe or duct. It can be operated at pressures of up to
45 MPa (450 barg / 6526 psig) when fi tted with the bonded seal.
The recommended gas fl ow rate, when mounted in the optional sampling block, is 1 to
5 Nl/min (2.1 to 10.6 scfh). However, for direct insertion applications, gas fl ow can be
from static to 10 m/sec (32.8 fps).
NOTE: Check that the bonded seal is fi tted and assemble into the sampling
location, by hand, using the wrench fl ats only. DO NOT grip and twist the
sensor cover when installing the sensor.
SF72 Rail Transmitter User’s Manual
When installed, fully tighten using a wrench until the seal is fully compressed and to the
following torque settings:
• G 1/2” BSP 56 Nm (41.3 ft-lbs)
4 97503 Issue 2, March 2017
SF72 Rail Transmitter User’s Manual
2.3.1 Transmitter Mounting - Sample Block (Optional)
The following procedure must be carried out by a qualifi ed
installation engineer.
To mount the transmitter into the sensor block (preferred method), proceed as follows,
refer to
1. Remove the protective cover (2) and the desiccant capsule (2a) from the
2. Check that the seal is fi tted behind the threaded part of the transmitter
Figure 3
tip of the transmitter (1).
body.
WARNING: Under no circumstances should the sensor
guard be handled with the fi ngers.
INSTALLATION
3. Screw the transmitter (1) into the sample block (3) and tighten to the
recommended torque setting (see Section 2.3). NOTE: Use the fl ats of
the hexagonal nut and not the sensor body.
4. Fit the transmitter cable assembly to the connector at the base of the
transmitter and tighten.
2
2a
1
3
4
Figure 3
Transmitter Mounting - Sensor Block
Michell Instruments 5
INSTALLATION
SF72 Rail Transmitter User’s Manual
2.3.2 Transmitter Mounting - Direct Pipeline Connection
The transmitter may be directly mounted into a pipe or duct as shown in
Figure 4.
CAUTION: Do not mount the transmitter too close to the
bottom of a bend where any condensate in the pipeline
might collect and saturate the probe.
The pipe or duct will require a thread to match the transmitter body thread. Fixing
dimensions are shown in
Figure 4.
For circular pipework, to ensure the integrity of a
gas tight seal, a mounting fl ange will be required on the pipework in order to provide a
fl at surface to seal against.
The following procedure must be carried out by
competent personnel.
1. Ensure that the protective cover and the desiccant capsule have been
removed from the tip of the transmitter (3).
WARNING: Under no circumstances should the
sensor guard be handled with the fi ngers.
2. Check that the seal is fi tted behind the threaded part of the transmitter
body.
3. Screw the transmitter (3) into the pipe. Tighten enough to obtain a gas
tight seal. (Torque will depend upon the pipeline material.) NOTE: Do
not overtighten or the thread on the pipework may be stripped.
1
2
3
1
2
48mm
Figure 4
3
Transmitter Mounting - Pipe or Duct
6 97503 Issue 2, March 2017
SF72 Rail Transmitter User’s Manual
3 OPERATION
Operation is very simple assuming the following installation techniques are adhered to:
Sampling Hints
Be Sure the Sample is Representative of the Gas Under Test:
The sample point should be as close to the critical measurement point as possible. Also,
never sample from the bottom of a pipe as entrained liquids may be drawn into the
sensing element.
OPERATION
Figure 5
Minimize Dead Space in Sample Lines:
Dead space causes moisture entrapment points, increased system response times and
measurement errors, as a result of the trapped moisture being released into the passing
sample gas and causing an increase in partial vapor pressure.
Figure 6
Remove Any Particulate Matter or Oil from the Gas Sample:
Particulate matter at high velocity can damage the sensing element and similarly, at
low velocity, they may ‘blind’ the sensing element and reduce its response speed. If
particulate, such as degraded desiccant, pipe scale or rust is present in the sample gas,
use an in-line fi lter, as a minimum level of protection. For more demanding applications
Michell Instruments offers a range of sampling systems (for more information contact
www.michell.com).
Installation Location
Deadspace
Indication of Dead Space
Use High Quality Sample Tube and Fittings:
Michell Instruments recommends that, wherever possible, stainless steel tubing and
fi ttings should be used. This is particularly important at low dew points since other
materials have hygroscopic characteristics and adsorb moisture on the tube walls,
slowing down response and, in extreme circumstances, giving false readings. For
temporary applications, or where stainless steel tubing is not practical, use high quality
thick walled PTFE tubing.
Position Transmitter away from Heat Source:
It is recommended, as good instrumentation practice, that the transmitter is placed
away from any heat source to avoid adsorption/desorption.
Michell Instruments 7
MAINTENANCE
e
4 MAINTENANCE
Calibration
Routine maintenance of the SF72 Rail Transmitter is confi ned to regular re-calibration
by exposure of the SF72 Rail Transmitter to sample gases of known moisture content to
ensure that the stated accuracy of the SF72 Rail Transmitter is maintained. Calibration
services traceable to the UK
Institute of Standards and Technology
Michell Instruments offers a re-calibration service to suit specifi c needs. A Michell
representative can provide detailed, custom advice (for Michell Instruments’ contact
information go to www.michell.com).
Sensor Guard Replacement
The sensor is supplied with a white HDPE guard (standard) or a stainless steel guard
(if specifi ed at time or order). The method of replacement is the same for both types.
HDPE Guard
SF72 Rail Transmitter User’s Manual
National Physical Laboratory
(NIST) are provided by Michell Instruments.
(NPL) and the US
National
The HDPE guard provides <10m protection to the dew-point sensor. It is designed
to show any contamination and the guard should be changed if the surface becomes
discolored.
When replacing the guard, care should be taken to handle the guard by the bottom part
only. Replacement guards (EA2-HDPE) - pack of 10 - can be obtained by contacting
Michell Instruments (www.michell.com) or your local distributor.
HANDLE,
USING
GLOVES, BY
x
BLACK PART
3
9
2
-
i
0
-
0
m
-
n
A
s
F
a
n
.
0
o
R
a
N
r
6
/
d
S
T
+
e
l
2
/
a
7
0
c
F
6
S
S
-
d
o
C
t
c
u
d
o
r
P
Stainless Steel Guard
ONLY
Figure 7
Replacement of HDPE Guard
The stainless steel guard provides <80m protection to the dew-point sensor. It is
designed to show any contamination and the guard should be changed if the surface
becomes discolored.
When replacing the guard, care should be taken to handle the guard by the bottom part
only. A replacement guard (SSG) can be obtained by contacting Michell Instruments
(www.michell.com) or your local distributor.
Bonded Seal
If the installed bonded seal gets damaged or lost, a pack of 5 replacement bonded seals
can be obtained by contacting Michell Instruments, or your local distributor, and quoting
part number 5/8-BS.
8 97503 Issue 2, March 2017
SF72 Rail Transmitter User’s Manual
APPENDIX A
Appendix A
Technical Specifi cations
Michell Instruments 9
APPENDIX A
SF72 Rail Transmitter User’s Manual
Appendix A Technical Specifi cations
Performance
Measurement Range (Dew Point) -60 to +60°Cdp (-76 to +140°Fdp)
Accuracy (Dew Point) ±2°Cdp (±3.6°Fdp)
Repeatability ±0.2°Cdp (±0.36°Cdp)
Long Term Stability <1% per year at reference conditions
Calibration Traceable 8-point calibration certifi cate
Electrical Specifi cations
Output Signal 4-20 mA (2-wire connection, current source)
Output Dew point
Analog Output Scaled Range
Supply Voltage 12 to 28 V DC
Load Resistance Max 250 @ 12 V (500 @ 24 V)
Electrical Connection M12 4-way A coded
Standard -60 to +60°C (-76 to +140°F)
Non-standard available upon request
Operating Specifi cations
Start-up Temperature
Ambient:
Gas:
Operating Temperature
Ambient:
Gas:
Storage Temperature -40 to +85°C (-40 to +185°F)
Operating Pressure 45 MPa (450 barg / 6526 psig) max
Overpressure Rating x 2 operating pressure 90 MPa (900 barg / 13,000 psig)
Flow Rate
Thermal Compensation Characterized over operating range
-40 to +50°C (-40 to +122°F)
-40 to +70°C (-40 to +158°F)
-40 to +50°C (-40 to +122°F)
-40 to +60°C (-40 to +140°F)
1 to 5 Nl/min (2.1 to 10.6 scfh) mounted in standard sampling
block;
0 to 10 m/sec (0 to 32.8 fps) direct insertion
Mechanical Specifi cations
Ingress Protection IP66 in accordance with standard BS EN60529:1992
Housing Material 316 stainless steel
Dimensions L=119mm x ø27mm (4.7” x ø1.06”)
Filter HDPE Guard < 10m
Process Connection & Material G½” BSP, 316 stainless steel
Weight 150g (5.29oz)
Digital Diagnostic
Communications
RS485, 2-wire Modbus RTU
Rail Certifi cations
Shock and Vibration IEC 61373:1999-01
RFI/EMC Emissions & Immunity EN 50121-3-2:2006
10 97503 Issue 2, March 2017
SF72 Rail Transmitter User’s Manual
A.1 Dimensions
12.7mm
(0.5”)
60.4mm
(2.4”)
APPENDIX A
46mm
(1.81”)
27mm
(1.1”)
10mm
(0.39”)
ø27mm
(1.06”)
27mm
(1.1”)
Figure 8
13mm
(0.5”)
G 1/2” thread
Bonded seal
Dimensions
4-20 mA 2-wire
PIN 3 4-20 mA
PIN 4 Power supply
Figure 9
Electrical Connections
Michell Instruments 11
APPENDIX B
SF72 Rail Transmitter User’s Manual
Appendix B
Quality, Recycling
& Warranty
Information
12 97503 Issue 2, March 2017
SF72 Rail Transmitter User’s Manual
APPENDIX B
Appendix B Quality, Recycling & Warranty Information
Michell Instruments is dedicated to complying to all relevant legislation and directives. Full information
can be found on our website at:
www.michell.com/compliance
This page contains information on the following directives:
• ATEX Directive
• Calibration Facilities
• Confl ict Minerals
• FCC Statement
• Manufacturing Quality
• Modern Slavery Statement
• Pressure Equipment Directive
• REACH
• RoHS2
• WEEE2
• Recycling Policy
• Warranty and Returns
This information is also available in PDF format.
Michell Instruments 13
APPENDIX C
SF72 Rail Transmitter User’s Manual
Appendix C
Return Document &
Decontamination Declaration
14 97503 Issue 2, March 2017
SF72 Rail Transmitter User’s Manual
Appendix C Return Document & Decontamination Declaration
'HFRQWDPLQDWLRQ&HUWL¿FDWH
IMPORTANT NOTE: Please complete this form prior to this instrument, or any components, leaving your
site and being returned to us, or, where applicable, prior to any work being carried out by a Michell
engineer at your site.
Instrument Serial Number
Warranty Repair? YES NO Original PO #
Company Name Contact Name
Address
Telephone # E-mail address
Reason for Return /Description of Fault:
APPENDIX C
Has this equipment been exposed (internally or externally) to any of the following?
Please circle (YES/NO) as applicable and provide details below
Biohazards YES NO
Biological agents YES NO
Hazardous chemicals YES NO
Radioactive substances YES NO
Other hazards YES NO
Please provide details of any hazardous materials used with this equipment as indicated above (use continuation sheet
if necessary)
Your method of cleaning/decontamination
Has the equipment been cleaned and decontaminated? YES NOT NECESSARY
Michell Instruments will not accept instruments that have been exposed to toxins, radio-activity or bio-hazardous
PDWHULDOV)RUPRVWDSSOLFDWLRQVLQYROYLQJVROYHQWVDFLGLFEDVLFÀDPPDEOHRUWR[LFJDVHVDVLPSOHSXUJHZLWKGU\
JDVGHZSRLQW&RYHUKRXUVVKRXOGEHVXI¿FLHQWWRGHFRQWDPLQDWHWKHXQLWSULRUWRUHWXUQ
Work will not be carried out on any unit that does not have a completed decontamination declaration.
Decontamination Declaration
I declare that the information above is true and complete to the best of my knowledge, and it is safe for Michell
personnel to service or repair the returned instrument.
Name (Print) Position
Signature Date
F0121, Issue 2, December 2011
Michell Instruments 15
http://www.michell.com
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