Net Safety™ ST3
XChem Electrochemical Sensors
Reference Manual
00809-0100-4303, Rev AB
November 2020
Important instructions
Emerson designs, manufactures, and tests products to function within specific conditions. Because these products are
sophisticated technical instruments, the owner and operation personnel must strictly adhere to both the information printed on
the product nameplate and all instructions provided in this manual prior to installation, operation, and maintenance.
WARNING
Explosions and hazardous substances
Installing, operating, or maintaining this product improperly could lead to serious injury or death from explosion or exposure to
dangerous substances.
Comply with all information on the product, in this manual, and in any local and national codes that apply to this product.
Use parts and work procedures specified in this manual.
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 contents of this publication are presented for informational purposes only, and while every effort has been made to ensure
their accuracy, they are not to be construed as warranties or guarantees, expressed or implied, regarding the products or services
described herein or their use or applicability. All sales are governed by Emerson's terms and conditions, which are available upon
request.
Emerson does not assume responsibility for the selection, use, or maintenance of this product. Responsibility for proper selection,
use, and maintenance of any Net Safety product remains solely with the purchaser and end user.
To the best of Emerson's knowledge, the information herein is complete and accurate. Emerson makes no warranties, expressed
or implied, including implied warranties of merchantability and fitness for a particular purpose, with respect to this manual, and in
no event, shall Emerson be liable for any incidental, punitive, special, or consequential damages, including, but not limited to, loss
of production, loss of profits, loss of revenue, or use and costs incurred including without limitation for capital, fuel and power,
and claims of third parties.
Product names used herein are for manufacturer or supplier identification only and may be trademarks/registered trademarks of
these companies.
All rights reserved. No part of this work may be reproduced or copied in any form or by any means (graphic, electronic, or
mechanical) without first receiving written permission from Emerson.
Warranty
1. Limited Warranty. Subject to the limitations contained in Section 2 (Limitation of Remedy and Liability) herein, Seller
warrants that (a) the licensed firmware embodied in the Goods will execute the programming instructions provided by
Seller; (b) that the Goods manufactured by Seller will be free from defects in materials or workmanship under normal use
and care; and (c) Services will be performed by trained personnel using proper equipment and instrumentation for the
particular Service provided. The foregoing warranties will apply until the expiration of the applicable warranty period.
Sensors and detectors are warranted against defective part and workmanship as per warranty. Products purchased by
Seller from a third party for resale to Buyer (Resale Products) shall carry only the warranty extended by the original
manufacturer. Buyer agrees that Seller has no liability for Resale Products beyond making a reasonable commercial effort
to arrange for procurement and shipping of the Resale Products. If Buyer discovers any warranty defects and notifies Seller
thereof in writing during the applicable warranty period, Seller shall, at its option, (i) correct any errors that are found by
Seller in the firmware or Services; (ii) repair or replace FOB point of manufacture that portion of the Goods found by Seller
to be defective; or (iii) refund the purchase price of the defective portion of the Goods/Services. All replacements or
repairs necessitated by inadequate maintenance; normal wear and usage; unsuitable power sources or environmental
conditions; accident; misuse; improper installation; modification; repair; use of unauthorized replacement parts; storage
or handling; or any other cause not the fault of Seller, are not covered by this limited warranty and shall be replaced or
repaired at Buyer’s sole expense and Seller shall not be obligated to pay any costs or charges incurred by Buyer or any
other party except as may be agreed upon in writing in advance by Seller. All costs of dismantling, reinstallation, freight
and the time and expenses of Seller’s personnel and representatives for site travel and diagnosis under this limited
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warranty clause shall be borne by Buyer unless accepted in writing by Seller. Goods repaired and parts replaced by Seller
during the warranty period shall be in warranty for the remainder of the original warranty period or 90 days, whichever is
longer. This limited warranty is the only warranty made by Seller and can be amended only in a writing signed by an
authorized representative of Seller. The limited warranty herein ceases to be effective if Buyer fails to operate and use the
Goods sold hereunder in a safe and reasonable manner and in accordance with any written instructions from the
manufacturers. THE WARRANTIES AND REMEDIES SET FORTH ABOVE ARE EXCLUSIVE. THERE ARE NO REPRESENTATIONS
OR WARRANTIES OF ANY KIND, EXPRESSED OR IMPLIED, AS TO MERCHANTABILITY, FITNESS FOR PARTICULAR PURPOSE
OR ANY OTHER MATTER WITH RESPECT TO ANY OF THE GOODS OR SERVICES.
2. Limitation of Remedy and Liability. SELLER SHALL NOT BE LIABLE FOR DAMAGES CAUSED BY DELAY IN PERFORMANCE.
THE REMEDIES OF BUYER SET FORTH IN THE AGREEMENT ARE EXCLUSIVE. IN NO EVENT, REGARDLESS OF THE FORM OF
THE CLAIM OR CAUSE OF ACTION (WHETHER BASED IN CONTRACT, INFRINGEMENT, NEGLIGENCE, STRICT LIABILITY,
OTHER TORT OR OTHERWISE), SHALL SELLER’S LIABILITY TO BUYER AND/OR BUYER’S CUSTOMERS EXCEED THE PRICE TO
BUYER OF THE SPECIFIC GOODS MANUFACTURED OR SERVICES PROVIDED BY SELLER GIVING RISE TO THE CLAIM OR
CAUSE OF ACTION. BUYER AGREES THAT IN NO EVENT SHALL SELLER’S LIABILITY TO BUYER AND/OR BUYER’S
CUSTOMERS EXTEND TO INCLUDE INCIDENTAL, CONSEQUENTIAL OR PUNITIVE DAMAGES. THE TERM “CONSEQUENTIAL
DAMAGES” SHALL INCLUDE, BUT NOT BE LIMITED TO, LOSS OF ANTICIPATED PROFITS, REVENUE OR USE AND COSTS
INCURRED INCLUDING WITHOUT LIMITATION FOR CAPITAL, FUEL AND POWER, AND CLAIMS OF BUYER’S CUSTOMERS.
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Reference Manual Contents
00809-0100-4303 November 2020
Contents
Chapter 1 Introduction.............................................................................................................. 7
1.1 Models covered........................................................................................................................... 7
1.2 Service support............................................................................................................................7
1.3 Return of material........................................................................................................................7
1.4 Product recycling/disposal...........................................................................................................8
Chapter 2 Install.........................................................................................................................9
2.1 Unpack and inspect..................................................................................................................... 9
2.2 Locate sensor...............................................................................................................................9
2.3 Mount sensor...............................................................................................................................9
2.4 Mounting...................................................................................................................................10
2.5 Dimensional drawings............................................................................................................... 13
2.6 Wiring........................................................................................................................................15
2.7 Calibration.................................................................................................................................18
Chapter 3 Operate....................................................................................................................19
3.1 Access sensor configuration settings......................................................................................... 19
3.2 Power up sensor........................................................................................................................ 19
3.3 Sensor end of life diagnostic...................................................................................................... 20
3.4 Sensor communication..............................................................................................................20
3.5 Configure Net Safety Millennium II Basic Transmitter.................................................................21
3.6 Fault conditions......................................................................................................................... 22
Chapter 4 Maintenance............................................................................................................23
4.1 Cross sensitivities.......................................................................................................................23
4.2 Bump testing.............................................................................................................................24
4.3 Replace sensor module..............................................................................................................24
4.4 Troubleshooting........................................................................................................................25
4.5 Storage......................................................................................................................................25
4.6 Spare parts and accessories....................................................................................................... 25
Chapter 5 Electrostatic sensitive device....................................................................................27
Chapter 6 Wire resistance table............................................................................................... 29
Chapter 7 Product certifications...............................................................................................31
7.1 Installing in North America.........................................................................................................31
7.2 North America........................................................................................................................... 31
7.3 IECEx..........................................................................................................................................31
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Contents Reference Manual
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Introduction
1 Introduction
1.1 Models covered
Emerson has designed the ST3 XChem electrochemical toxic gas sensors for use with the
Net Safety Millennium II Transmitter (models M21, M22, or M2B). This sensor is both
versatile and reliable, for fast, accurate, and continuous monitoring of gases in extreme
environments.
The sensor assembly consists of a factory sealed explosion proof enclosure (housing) rated
for hazardous locations and a replaceable sensor module. Only use this sensor with a Net
Safety Millennium II series transmitter. If you connect the sensor to any other model of
transmitter, it will not function, and the sensor or transmitter may be damaged.
1.2 Service support
For technical support, contact your local Emerson representative or the Technical Support
department at +1 866 347 3427 (toll free) or Safety.CSC@Emerson.com.
1.3 Return of material
To expedite the repair and return of this product, proper communication between the
customer and the factory is important.
Prerequisites
Before returning a product for repair, call +1 866 347 3427 (toll free) or email
Safety.CSC@emerson.com for a Return Material Authorization (RMA) number.
On the return of the equipment, include the following information:
1. RMA number provided to you by Emerson
2. Company name and contact information
3. Purchase order, from your company, authorizing repairs or request for quote
Procedure
1. Ship all equipment, prepaid to:
Emerson Automation Solutions
6021 Innovation Blvd
Shakopee, MN 55379
2. Mark all packages with Return for Repair and include RMA number and type of return
(e.g., return for evaluation).
Pack items to protect them from damage and use anti-static bags or aluminumbacked cardboard as protection from electrostatic damage.
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Introduction Reference Manual
November 2020 00809-0100-4303
Important
Ship all equipment prepaid. Emerson will not accept collect shipments.
1.4 Product recycling/disposal
Consider recycling equipment and packaging. Dispose of the product and packaging in
accordance with local and national legislations and regulations.
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Install
2 Install
2.1 Unpack and inspect
Procedure
1. Carefully remove all the components from the packaging and check them against
the enclosed packing list.
2. Inspect all components for any obvious damage, such as broken or loose parts. If
you find any components missing or damaged, notify your local Net Safety
representative or the factory immediately.
2.2 Locate sensor
Prior to the installation process, develop a plan. Although there are no absolute rules
determining the quantity of detectors or location of a sensor, consider the following
points when planning the installation.
• Carefully locate the sensor in an area where gases may potentially accumulate.
(Remember, light gases tend to rise, and heavy gases tend to accumulate in low areas).
• Use redundant systems to enhance protection and reliability.
• Consider the air movement patterns within the facility.
• Consider the construction of the facility, such as trenches where heavy gases or peaks
where light gases may accumulate.
• Seek advice from experts knowledgeable about the primary gas to be detected.
• Use common sense and refer to the regulatory publications that discuss guidelines for
your industry.
2.3 Mount sensor
You can either mount the sensor directly attached to a Net Safety Millennium II
transmitter or remotely, away from the transmitter.
Make sure the sensor is accessible for calibration and maintenance purposes. Also, make
sure the transmitter is accessible and visible.
2.3.1
Mount sensor remotely
If mounting the sensor remotely, connect it to a certified junction box. Make sure the
transmitter is located near eye level for easy access and the sensor is mounted where the
gas is likely to accumulate.
In order to ease the calibration process, you can attach a calibration cup (CCS-1) to the
bottom of the sensor housing and run calibration tubing from the calibration cup to a
convenient place for applying the calibration gas, eliminating the need to access the
sensor directly. In this case, to compensate for the effect of distance, consider decreasing
Net Safety ST3 9
Install
November 2020 00809-0100-4303
the calibration tubing length to some length where the end of the tubing to the gas
canister is still accessible or increase the calibration gas flow rate between the calibration
gas cylinder and sensor.
Refer to Figure 2-1 for an example of the sensor separation. For tubing lengths less than 10
ft. (3 m), use a 0.5 LPM regulator, and for lengths greater than 10 ft. (3 m) use a 1.0 LPM
regulator. On initial install, always confirm readings directly at the transmitter by applying
a known gas concentration to the sensor and compare the output from the transmitter.
Readings should be accurate to the gas concentration applied, taking into account the
sensor accuracy specifications in Specifications.
Figure 2-1: Sensor Separation Example
Reference Manual
A. Controller
B. Apply calibration gas.
C. Tubing for calibration gas
D. Sensor
E. Calibration cup
F. Conduit
G. Junction box
H. Approximately knee level
2.4 Mounting
Prior to mounting the sensor to the transmitter or junction box enclosure apply suitable
grease (jet lube, etc.) to the threading of the ¾-in. female national pipe thread (FNPT)
conduit entry of the enclosure as well as the threading on the sensor ¾-in. male national
pipe thread (MNPT) fitting. This aids in protecting the enclosures from water. After
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