Emerson Rosemount 935 User manual

Reference Manual
00809-0100-4035, Rev AH
May 2022
Rosemount™ 935
Open Path Combustible Gas Detector

Legal notice
The Rosemount system described in this document is the property of Emerson.
No part of the hardware, software, or documentation may be reproduced, transmitted, transcribed, stored in a retrieval system,
or translated into any language or computer language in any form or by any means without prior written permission of Emerson.
While great efforts have been made to ensure the accuracy and clarity of this document, Emerson assumes no responsibility
resulting from any omissions in this document or from misuse of the information obtained herein. The information in this
document has been carefully checked and is believed to be entirely reliable with all the necessary information included. Emerson
does not assume any liability arising out of the application or any use of any product or circuit described herein; neither does it
convey license under its patent rights or the rights of others.
WARNING
All individuals who have or will have responsibility for using, maintaining, or servicing the product must read this manual
thoroughly.
WARNING
Physical access
Unauthorized personnel may potentially cause significant damage to and/or misconfiguration of end users’ equipment. This could
be intentional or unintentional and needs to be protected against.
Physical security is an important part of any security program and fundamental to protecting your system. Restrict physical access
by unauthorized personnel to protect end users’ assets. This is true for all systems used within the facility.
NOTICE
The source and detector are not field-repairable due to the meticulous alignment and calibration of the sensors and the respective
circuits.
Do not attempt to modify or repair the internal circuits or change their settings, as this will impair the system's performance and
void the Emerson product warranty.
Safety information
WARNING
All individuals who have or will have responsibility for using, maintaining, or servicing this product must read this manual
thoroughly.
WARNING
Physical access
Unauthorized personnel may potentially cause significant damage to and/or misconfiguration of end users’ equipment. This could
be intentional or unintentional and needs to be protected against.
Physical security is an important part of any security program and fundamental to protecting your system. Restrict physical access
by unauthorized personnel to protect end users’ assets. This is true for all systems used within the facility.
NOTICE
The device is not field-repairable due to the meticulous alignment and calibration of the sensors and the respective circuits.
Do not attempt to modify or repair the internal circuits or change their settings, as this will impair the system's performance and
void the Emerson product warranty.
2

Glossary and abbreviations
Abbreviation Meaning
Analog video Video values are represented by a scaled signal.
ATEX Atmosphere explosives
AWG American wire gauge
BIT Built-in test
CMOS Complementary metal oxide semiconductor image sensor
Digital video Each component is represented by a number representing a discrete quantization.
DSP Digital signal processing
EMC Electromagnetic compatibility
EMI Electromagnetic interference
EOL End of line
FOV Field of view
HART®Highway addressable remote transducer communication protocol
IAD Immune at any distance
IECEx International Electrochemical Commission explosion
IP Internet protocol
IPA Isopropyl alcohol
IR Infrared
IR3 Refers to the three infrared sensors
JP5 Jet fuel
Latching Refers to relays remaining in the On state even after the On condition has been removed.
LED Light-emitting diode
LEL Lower explosive limit: The minimum concentration of a substance (gas/vapor) in air mixture that can be
ignited. This mixture is different for every gas/vapor, measured in % of LEL.
LEL.m Integral of concentration in LEL units (1 LEL = 100% LEL) and the operation distance in meters (m).
LNG Liquefied natural gas
LPG Liquefied petroleum gas
mA MilliAmps (0.001 amps)
Modbus®Master-slave messaging structure
N.C. Normally closed
N.O. Normally open
N/A Not applicable
NFPA National Fire Protection Association
NPT National pipe thread
NTSC National Television System Committee (a color encoding system)
PAL Phase alternation by line (a color encoding system)
PN Part number
RFI Radio frequency interference
3

Abbreviation Meaning
RTSP Real time streaming protocol
SIL Safety integrity level
UNC Unified coarse thread
Vac Volts alternating current
Vdc Volts direct current
µm Micrometer
4

Contents
Chapter 1 Product overview.......................................................................................................7
Chapter 2 Technical description................................................................................................. 9
2.1 Features.......................................................................................................................................9
2.2 Applications...............................................................................................................................10
2.3 Principle of operation.................................................................................................................10
2.4 Models and types.......................................................................................................................13
2.5 Description................................................................................................................................ 13
Chapter 3 Operating modes..................................................................................................... 17
3.1 Operational modes.................................................................................................................... 17
3.2 Visual indicators.........................................................................................................................18
3.3 Output signals........................................................................................................................... 19
3.4 System setup............................................................................................................................. 20
Chapter 4 Installation...............................................................................................................23
4.1 Introduction.............................................................................................................................. 23
4.2 General considerations.............................................................................................................. 23
4.3 Preparations for installation....................................................................................................... 26
4.4 Certification instructions........................................................................................................... 27
4.5 Special conditions for safe use from ATEX IECEx certificate........................................................ 28
4.6 Installing conduits and cables.................................................................................................... 29
4.7 Mount detector and source to tilt mount...................................................................................30
4.8 Wire detector............................................................................................................................ 33
4.9 Wiring to detector terminals......................................................................................................34
4.10 Flash source wiring.................................................................................................................. 35
4.11 Align detector..........................................................................................................................36
Chapter 5 Operation................................................................................................................ 39
5.1 Open path system operation..................................................................................................... 39
5.2 Power up................................................................................................................................... 39
5.3 Safety precautions..................................................................................................................... 40
5.4 Verify signal............................................................................................................................... 40
5.5 Zero calibrate............................................................................................................................ 42
5.6 Functional check........................................................................................................................45
Chapter 6 Maintenance............................................................................................................47
6.1 General maintenance................................................................................................................ 47
6.2 Periodic maintenance................................................................................................................ 47
Chapter 7 Troubleshooting...................................................................................................... 49
7.1 Maintenance call........................................................................................................................49
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7.2 Detector is in constant Obscuration mode.................................................................................49
7.3 Detector is in constant Saturation mode....................................................................................49
7.4 Detector is in constant Misalignment mode...............................................................................50
7.5 Detector at V fault..................................................................................................................... 50
7.6 Internal fault.............................................................................................................................. 50
7.7 NQ Ratio below the permitted limit........................................................................................... 51
7.8 NQ Ratio above the permitted limit........................................................................................... 51
7.9 Ratio out of the limit.................................................................................................................. 51
7.10 Source fault............................................................................................................................. 51
Appendix A Ordering information...............................................................................................53
A.1 Online product configurator......................................................................................................53
A.2 Model codes.............................................................................................................................. 53
A.3 Specifications and options.........................................................................................................53
A.4 Source (Transmitter)................................................................................................................. 53
A.5 Detector (Receiver)................................................................................................................... 54
Appendix B Specifications...........................................................................................................57
B.1 General specifications................................................................................................................57
B.2 Electrical specifications..............................................................................................................57
B.3 Mechanical specifications.......................................................................................................... 59
B.4 Environmental specifications..................................................................................................... 60
Appendix C Product certifications...............................................................................................63
C.1 ATEX and IECEx..........................................................................................................................63
C.2 UK CA........................................................................................................................................ 63
C.3 FM/FMC.....................................................................................................................................63
C.4 SIL-2.......................................................................................................................................... 63
C.5 Functional approval................................................................................................................... 64
Appendix D Wiring configurations.............................................................................................. 65
D.1 RS-485 communication network...............................................................................................69
Appendix E SIL-2 features........................................................................................................... 71
E.1 Safety relevant parameters........................................................................................................ 71
E.2 General conditions for safe use.................................................................................................. 71
Appendix F Support....................................................................................................................73
F.1 Return of material...................................................................................................................... 73
Appendix G Declaration of Conformity........................................................................................75
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1 Product overview
The Rosemount 935 Gas Detector employs an advanced xenon flash source and
integrated electronics package, both housed in stainless steel housings to provide high
quality and performance, fast response, and line of sight gas monitoring. The source/
detector is backed by a three year warranty.
This device detects ambient combustible gases over a path length of up to 660 ft (201 m)
even in harsh environments where dust, fog, rain, snow, or vibration can cause a high
reduction of signal. The device can maintain operation in up to 90 percent signal
obscuration and ±0.5 degrees of misalignment.
The detector is manufactured with heated optical windows to improve performance in
icing, snow, and condensation conditions. The programmable functions are available
through a HART® port used with an intrinsically safe (I.S.) handled unit.
The source and detector unit enclosures are ATEX, IECEx, and UK CA approved Exd
flameproof with an integral segregated rear and an Exe terminal compartment to prevent
exposing the sensors and electronics to the surrounding environment. The detector also
has a plug interface for connection to a HART Field Communicator, which is intrinsically
safe.
Hence, the combined approval:
Ex II 2(2) G D
Ex db eb ib [ib Gb] IIB+H2 T4 Gb
Ex tb IIIC T135 °C Db
Ta=-55 °C to +65 °C
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Product overview Reference Manual
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2 Technical description
2.1 Features
•Long range gas detection from 23 ft (7 m) up to 660 ft (201 m)
•Detection of methane, ethylene, or propane gases
•High sensitivity and fast response to hydrocarbon gases
•Heated optics to improve performance in icing, condensation, and snow conditions
•Continuous operation in extreme and harsh environmental conditions
•Solar blind and immune to industrial environments
•Withstands extreme vibration conditions
•Standard 0-20 mA output
•Maintenance call (3 mA)
•HART® protocol: communication protocol
•RS-485 output Modbus®-compatible for personal computer (PC) communication
network for a maximum of 247 systems
•Simple one person installation, alignment, and calibration
•ATEX, IECEx, and UK CA per:
Ex II 2(2) G D
Ex db eb ib [ib Gb] IIB + H2 T4 Gb
Ex tb [ib Db] IIIC T135 °C Db
Ta = -55 °C to 65 °C
•TUV approved per SIL2 requirements.
•FM / FMC approved per:
Class I Div. 1 Group B, C, and D
Class II/III Div. 1 Group E, F, and G
•Functional tested by FM per EN60079-29-4 and approved per FM 6325.
•Programmable configuration via the Field Communicator
•Fast connections to intrinsically safe (I.S.) approved hand-held diagnostic/calibration
unit
•Three-year warranty
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2.2 Applications
The Rosemount 935 system is an optical control fence for combustible gases as defined in
the product specification, providing perimeter monitoring and early detection in various
applications, such as:
•Petrochemical, pharmaceutical, and other chemicals storage and production areas
•Flammable chemical storage sites and hazardous waste disposal areas
•Refineries, oil platforms, pipelines, refueling stations, and fuel storage facilities
•Hazardous loading docks, transportation depots, and shipping warehouses
•Engine rooms
•Compressor and pumping stations
•Test cells
•Liquefied natural gas (LNG) and liquefied petroleum gas (LPG) systems
•Offshore floating production storage and shipping vessels (FPSO) and fixed oil rigs
2.3 Principle of operation
The system detects gases through a dual spectral range monitoring, analyzing the
absorption of radiation caused by gases in the atmosphere and comparing it to
background atmospheric absorption.
2.3.1 Spectral fingerprint
Each hazardous material is detected at a specific wavelength selected according to its
specific spectral absorption or fingerprint.
The detection process involves two separate sensors, one that absorbs a particular gas and
one that is not sensitive to it.
2.3.2 Optical path
The presence of hazardous airborne vapors, gases, or aerosols in a monitored area is
detected when the defined substance crosses/enters the optical path between the
radiation source unit and the detector.
Hazardous gases/vapors present in the atmosphere cause absorption of the radiation
pulse in the optical path between the radiation source and the detector unit at specific
wavelengths. This causes a change in the signal intensity received by the detector, which is
translated into an output related to the detector's measuring scale.
The system analyzes the defined open path at the spectral bands specific to the materials
being monitored. The automatic gain control (AGC) unit compensates for environmental
disturbances, such as fog, rain, etc., through a constant comparison with its dual spectral
beam.
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2.3.3 Microprocessor based
The built-in microprocessor analyzes the incoming signals.
A sophisticated mathematical algorithm calculates between the various functions of the
detected signal thresholds. Statistics, ratio algorithms, data communications, diagnostics,
and other functions are performed.
2.3.4 Gas sensitivity
The Rosemount 935 model uses wavelengths around 2.3 µm spectral band to measure air
flammability potential between the source and the detector.
At this wavelength, many hydrocarbon gases have an absorption peak.
This device can also detect other gases, based on cross-sensitivity. Please consult Emerson
for information on how to detect other gases.
2.3.5 Gas calibration
The detector has three calibrations that can be changed by function setup:
•Gas 1: 100 percent methane
•Gas 2: 100 percent propane
•Gas 3: 100 percent ethylene
The full scale of methane and propane is 5 LEL.m.
The full scale of ethylene is 8 LEL.m.
2.3.6 Flash source
The Rosemount 935 transmitter employs the latest generation of Xenon flash bulbs to
provide extended installation distance and maximum reliability.
2.3.7 Heated optics
The Rosemount 935 includes heated optics for the detector and source.
The heater increases the temperature of the optical surface by 5 to 8 °F (3 to 5 °C) above
the ambient temperature to improve performance in icing, condensation, and snow
conditions. Emerson has configured the heated optics to automatically operate when the
change in temperature requires heating (default).
However, you can also define the heated optics as one of the following modes:
1. Not operated (not an option source unit)
2. On continuously
3. Automatic, per temperature change (default)
When operated in Automatic mode, you can define the start temperature below which the
window will be heated (default 41 °F (5 °C)). You can define this temperature between
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32 °F (0 °C) and 122 °F (50 °C). The heating stops when the temperature is 27 °F (15 °C)
above the start temperature.
Related information
System setup
2.3.8 HART® protocol
This device uses the HART protocol.
HART communication is a bi-directional, industrial field communication protocol used to
communicate between intelligent field instruments and the host system. HART is the
global standard for smart instrumentation, and the majority of smart field devices installed
in plants worldwide are HART-enabled.
HART technology is easy to use and very reliable.
Through the HART connection, the detector can perform:
•Setup
•Troubleshooting
•Detector health and status
You can connect the HART communication on the 0-20 mA line or through the intrinsically
safe (I.S.) connection with a standard field communicator loaded with our device driver
(DD) software and a special harness.
2.3.9 Modbus® RS-485
For more advanced communications, the Rosemount 935 has an RS-485 Modbus-
compatible output that provides data communication.
This feature enables simple commissioning, maintenance, and configuration.
2.3.10 Tilt mount
The stainless steel tilt mount provides a small installation footprint that can conform to
limited space constraints, while the sturdy construction maintains alignment even in
constant vibration.
The X and Y axis adjustments provide quick and easy alignment for installation and
maintenance.
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2.4 Models and types
The Rosemount 935 includes four models with the same detector and different sources.
That gives the detector the ability to get detection at distances of 23 ft (7 m) to 660 ft
(201 m).
Table 2-1: Model numbers and installation distances
Model
number
Source Minimum installation
distance
Maximum installation
distance
935 T1 23 ft (7 m) 66 ft (20 m)
935 T2 50 ft (15 m) 132 ft (40 m)
935 T3 115 ft (35 m) 330 ft (101 m)
935 T4 265 ft (81 m) 660 ft (201 m)
2.5 Description
The Rosemount 935 comprises two main units:
•Flash infrared source
•Detector
This device detects gases over an open path transmitted from the source to the detector.
2.5.1 Flash source unit
The flash source unit emits infrared (IR) radiation pulses at the rate of two pulses per
second. The pulse width (5-10 µsec) is very powerful. The front of the source has a lens
that collimates the IR beam for maximum intensity. The front window is heated to
improve performance in icing, condensation, and snow conditions.
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Figure 2-1: Flash source
A. Front window section
B. Label
C. Main housing
D. Mounting plate
E. Junction box
F. Back cover
G. Indication light-emitting diode (LED)
H. Earth terminal
I. Cable inlets
J. Front window
2.5.2 Detector unit
The detector receives the transmitted pulsed radiation signals from the source. The signals
are then amplified and fed into an analog to digital signal converter to be processed by the
internal microprocessor.
When the signals drop below a prescribed level, the internal microprocessor compensates
for them. This allows the signals to be maintained even in severe weather conditions. The
data is sent to the output interface section.
The front window of the detector is heated to improve performance in icing,
condensation, and snow conditions.
There is one detector type that is suitable for all models
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Figure 2-2: Detector
A. Front window
B. Handheld fast connection
C. Weather shield
D. Front window section
E. Label
F. Main housing
G. Mounting plate
H. Junction box
I. Back cover
J. Indicator light-emitting diode (LED)
K. Earth terminal
L. Cable inlet
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3 Operating modes
3.1 Operational modes
The Rosemount 935 has four operational modes:
•Normal mode
•Maintenance call mode (3 mA output)
•Fault mode
•Zero calibration mode (1 mA output)
3.1.1 Normal mode
This mode is used for gas detection. In Normal mode, the following statuses are possible:
•Normal (N): Signal received from gas detection is at safe levels.
•Warning (W): Gases have been detected at warning levels.
•Alarm (A): Gases have been detected at alarm levels.
NOTICE
For the standard 0-20 mA output, the warning and alarm levels are not relevant. Choose
these alarm levels at the controller. The output detector is at 4 mA at zero reading and
20 mA for full-scale reading.
View warning and alarm states through the LED, RS-485, and HART®.
If using the RS-485 output, the detector changes its status from N to W at Warning level
and to A at Alarm level.
3.1.2 Maintenance call mode (3 mA output)
This mode indicates low signal that may be caused by a dirty window, misalignment, or
poor source or if one of the detector's parameters is at the limit value.
The device continues to function, but provides a (3 mA) pre-warning signal (via HART® and
Modbus®) that a maintenance procedure is required.
3.1.3 Fault mode
In the fault status, there are three fault types.
In all fault types, the LED flashes yellow at 4 Hz.
•Misalignment (2.5 mA) - non-critical
This occurs due to poor alignment. Detection is no longer possible.
•Fault 1 (2 mA output) - non-critical
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If this occurs, it is due to blockage, very low signal, partial obscuration, or full beam
block. In this situation, detection is no longer possible. The detector's proper operation
can be restored (auto reset) during operation if the condition causing the problem is
removed or resolved. This mode occurs after a delay of 60 seconds from the moment
of the fault. This delay is important to eliminate momentary obscuration due to
passing through the beam.
•Fault 2 (1 mA output) - critical
In this case, the detector is disabled due to electrical/software operational failure,
central device (memory or processor) fault, or low voltage. This fault causes the
detector to cease operation.
If there is a fault in the 0-20 mA loop, the output is 0 mA.
3.1.4 Zero calibration mode (1 mA output)
This mode zeroes the base level from which the detector reads gas.
Only do this when:
•No gases are present.
•There is a clear path between the source and the detector.
•Weather conditions are clear.
Use a field communicator or host software on your personal computer (PC) to zero
calibrate after installation, re-alignment, and window cleaning. While the device is
connected to the field communicator, you can also use the magnetic mode selector for
zero calibration.
Related information
Zero calibrate
3.2 Visual indicators
One three color LED indicator is located in the back side of the detector/source and can be
seen through the back cover window.
See Figure 2-2
The detector statuses are listed in Table 3-1.
Table 3-1: Detector LED indications
Detector status LED color LED mode
Fault Yellow 4 Hz - flashing
Alignment / Standby Yellow 1 Hz - flashing
Zero calibration Yellow Constant
Normal Green 1 Hz - flashing
Warning Red 2 Hz - flashing
Alarm Red Constant
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The source statuses are listed in Table 3-2.
Table 3-2: Source LED indications
Source status LED color LED mode
Fault Yellow 4 Hz - flashing
Normal Green 1 Hz - flashing
3.3 Output signals
The Rosemount 935 system provides the following outputs:
•0 - 20 mA current output
•RS-485 interface
3.3.1 0-20 mA current output
The 0-20 mA output provides the detector status measurements, showing a continuous
reading of exact gas concentration.
The 0-20 mA functions as current sink, but you can reconfigure it as source.
The maximum permitted load resistance for the 0-20 mA output is 500 Ω.
Table 3-3: Standard 0-20 mA current for the gas channel
Current reading Status and description
0 mA + 0.2 mA Fault in 0-20 mA loop
1 mA ± 0.2 mA Zero calibration (in progress), fault 2
2 mA ± 0.2 mA Fault 1 (non-critical)
2.5 mA ± 0.2 mA Misalignment fault
3 mA ± 0.2 mA Maintenance call
4 mA ± 0.2 mA No gas present
4 mA - 20 mA Continuous measuring of gas concentrations at a range between 0 and
full scale. For methane and propane, this translates to 3.2 mA per LEL.m
and for ethylene to 2 mA per LEL.m.
21 mA Concentration is over the range limit (more than full-scale
concentration).
3.3.2 RS-485 interface
The RS-485 input/output sends complete data information to a personal computer (PC)
and receives data or control commands from the PC.
The protocol is Modbus®-compatible. Download the Winhost software from Emerson.com
Please contact Emerson for more information.
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3.4 System setup
3.4.1 Program detection functions
The Rosemount 935 incorporates several functions that can be set by the customer using:
•WinHost software
•HART® Field Communicator: The detector is equipped with an intrinsically safe
connector to enable HART communication.
3.4.2 Setting up detection function
Related information
Setting up detector defaults
Gas calibration
You can select three gas types for maximum compatibility to gas(es) you are trying to
detect.
Gas types:
•Methane: full scale 5 LEL.m
•Propane: full scale 5 LEL.m
•Ethylene: full scale 8 LEL.m
These three calibrations are standard calibrations.
The Rosemount 935 is able to detect other gases, based on cross-sensitivity. Please
consult Emerson for information on how to detect other gases.
Setting up addresses
The detector provides up to 247 address that can be used in the RS-485 communication
link and up to 64 addresses that can be used in the HART® Field Communication link.
Setting up heated optics
Select one of the following mode's for the detector's heated optics:
Off Not operated
On Operated continuously
Auto On per temperature change (default)
When operated in Automatic mode, you can define the start temperature below which the
window will be heated between 32 °F (0 °C) and 122 °F (50 °C) The detector stops heating
the window when the temperature is 27 °F (15 °C) above the defined temperature.
This feature relates to the detector only.
Select one of the following two options for the source heated optics:
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