Envent 330S User manual

Envent Engineering Ltd.
Hydrogen Sulfide Analyzer
Model 330S & 331S
Model 330SDS & 331SDS
USER'S MANUAL
Revision 2.6
19 Nov 2021

Table of Contents
1.0 INTRODUCTION .............................................................................................................................................................1
1.1 ABOUT THIS MANUAL......................................................................................................................................................1
1.2 WARRANTY &LIABILITY STATEMENTS.................................................................................................................................1
1.21 LIMITATION OF WARRANTY ...............................................................................................................................................1
1.22 DISCLAIMER ...................................................................................................................................................................2
1.3 SAFETY INFORMATION .....................................................................................................................................................2
1.31 Key Symbols ..........................................................................................................................................................3
2.0 EQUIPMENT OVERVIEW...........................................................................................................................................4
2.1 THEORY OF OPERATION ...................................................................................................................................................4
2.2 ANALYSIS CYCLES ...........................................................................................................................................................5
2.3 Dual Sensor Analysis cycle (SDS): .........................................................................................................................7
2.4 ANALYZER SPECIFICATIONS ..............................................................................................................................................8
3.0 INSTALLATION ......................................................................................................................................................10
3.1 UNPACKING .................................................................................................................................................................10
3.1.1 Standard spare parts for 330S H2S analyzers: ....................................................................................................10
3.1.2 Standard spare parts for 331S H2S analyzers: ....................................................................................................11
3.2 SITE REQUIREMENTS.....................................................................................................................................................11
3.3 MOUNTING REQUIREMENTS............................................................................................................................................12
3.3.1 Space Requirements ...........................................................................................................................................13
3.3.2 Sample Point Selection.......................................................................................................................................14
3.3.3 Sample inlet & sample sweep.............................................................................................................................14
3.3.4 Vent line...............................................................................................................................................................14
3.3.5 Sample Volume & Flow Rate ...............................................................................................................................15
3.3.6 INSTALLATION OF ANALYZER COMPONENTS ......................................................................................................................16
4.0 OPERATION & CONFIGURATION............................................................................................................................23
4.1 START-UP PROCEDURE..................................................................................................................................................23
4.2 ANALYZER DISPLAY INTERFACE........................................................................................................................................24
4.3 CALIBRATION PROCEDURE .............................................................................................................................................25
4.3.1 H2SGAS CALIBRATION ..................................................................................................................................................25
4.3.2 RE-ZERO SENSOR PROCEDURE .......................................................................................................................................27
5.0 MAINTENANCE ......................................................................................................................................................28
5.1 H2SSENSING TAPE CHANGE PROCEDURE.........................................................................................................................29
5.2 SAMPLE CONDITIONING SYSTEM CLEANING PROCEDURE.....................................................................................................30
5.2.1 Material List .........................................................................................................................................................30
5.2.2 Procedure ............................................................................................................................................................30
6.0 TROUBLESHOOTING ............................................................................................................................................. 32
APPENDIX A - RECOMMENDED SPARE PARTS LIST ............................................................................................................. 42
APPENDIX B – SEALING COMPOUND INFORMATION ..........................................................................................................43

APPENDIX C – SAFETY DATA SHEET FOR H2S SENSING TAPE.............................................................................................. 46
APPENDIX D – RISK ASSESSMENT – SAFETY INFORMATION ...............................................................................................51
CONTACT US .....................................................................................................................................................................55
List of Figures
Figure 1. H2S Analyzer Principle of Operation Diagram............................................................................................5
Figure 2. H2S Analysis Cycle.......................................................................................................................................6
Figure 3. Space Requirements for the 330S & 331S H2S Analyzers ........................................................................13
Figure 4. 331S Recommended Venting for 331S (Same for 330S model) ..............................................................15
Figure 5. AO 4-20 mA Output Wiring Options..........................................................................................................17
Figure 6. Sample Chamber (Exploded View)...........................................................................................................18
Figure 7. Envent's Humidifier Unit for 330S & 331S................................................................................................20
Figure 8. Humidifier Unit Installed in a 331S H2S Analyzer.....................................................................................21
Figure 9. Eductor Block (Venturi Effect)..................................................................................................................22
Figure 10. 330S Display (left) & 331S Display (right)...............................................................................................24
Figure 11. 331S & 331SDS Sensing Tape Change....................................................................................................29
List of Tables
Table 1. 330S/331S H2S Analyzer Specifications......................................................................................................9
Table 2. Sample Volume and & Flow Rate ..............................................................................................................15
Table 3. Aperture Strips & Ranges...........................................................................................................................19
Table 4. Display Button Description/Function .......................................................................................................24
Table 5. Display LED Description/Function ............................................................................................................25
Table 6. Hydrogen Sulfide Properties .....................................................................................................................51
Table 7. Hydrogen Sulfide Quantities & Health Effects..........................................................................................52

Envent Engineering Ltd. H2S Analyzer User’s Manual – Revision 2.6 Page 1
1.0 INTRODUCTION
1.1 About This Manual
This manual provides all the necessary information to install, operate and maintain the 330S, 330SDS,
331S and 331SDS model H2S Analyzer units. This manual is intended for all technical level users.
The Envent 330S/331S H2S Analyzer is a uniquely rugged and simple design that utilizes lead acetate-
based detection which provides a linear and interference-free output of H2S concentration. This
analyzer can measure a wide range of hydrogen sulfide concentrations from parts per billion (ppb)
concentrations to parts per million (ppm) concentrations. With the addition of a dilution sample
system, it can read high concentrations in percentage up to 100%. There are other options available
such as the sample system for H2S analysis in liquids or the addition of a hydrogen reaction furnace for
total sulfur measurements.
This document will be referring to models 330S and 331S. However, the information applies equally to
the 330SDS and 3301SDS (Dual sensor), unless otherwise stated. To clarify, the difference between an
"S" model and a "SDS" model analyzer is the second sensor the "SDS" has to measure H2S giving it the
capability to measure H2S from two different samples at the same time.
1.2 Warranty & Liability Statements
Products produced and supplied by the manufacturer (Envent Engineering Ltd), unless otherwise
stated, are warranted against defects in materials and workmanship for up to 18 months from the
shipping date or up to 12 months from the start-up date (whichever comes first). During the warranty
period the manufacturer can choose to either repair or replace products which prove to be defective.
The manufacturer or its representative can provide warranty service at the buyer's facility only upon
prior agreement. In all cases, the buyer has the option of returning the product for warranty service to
a service facility designated by the manufacturer or its representative. The buyer shall prepay all
shipping charges for products returned to a service facility. The manufacturer or its representative
shall pay all shipping charges for the return of products to the buyer. The buyer may also be required
to pay round-trip travel expenses and labour charges (at prevailing labour rates) if the warranty has
been violated. The warranty may be considered violated for any of the reasons listed below.
1.21 Limitation of Warranty
The foregoing warranty shall not apply to defects arising from:
•Improper or inadequate maintenance of the product by the user

Envent Engineering Ltd. H2S Analyzer User’s Manual – Revision 2.6 Page 2
•Improper unpacking or installation procedures
•Inadequate site preparation
•Unauthorized modification or misuse of the product
•Operation of the product in unfavorable environments such as at high temperatures, high
humidity, or in corrosive atmospheres
•Operation of the product outside of the published specifications
Envent Engineering Ltd carries no responsibility for damage caused during transportation or
unpacking, unless otherwise specified in the incoterms.
An extended warranty may be available with certified start-up. Contact Envent Engineering Ltd for
details.
Envent Engineering Ltd reserves the right to change the product design and specifications at any time
without prior notice.
1.22 Disclaimer
No other warranty is expressed or implied. The manufacturer specially disclaims the implied
warranties of merchantability and fitness for a particular purpose. The sole remedy of the buyer shall
in no case exceed the purchase price of the analyzer. The manufacturer shall not be liable for personal
injury or property damage suffered in servicing the product. The product should not be modified or
repaired in any manner differing from procedures established by the manufacturer.
1.3 Safety Information
The procedures and settings outlined in this manual constitute what is considered proper use of the
equipment in question. The equipment was designed and tested under the assumption that these
procedures and settings will be adhered to. Applying values outside of the provided ranges (such as
permitting excessive pressures) or modifying provided procedures is considered improper use of the
equipment. Envent Engineering Ltd is not responsible for any injury or property damage caused by
improper use of the equipment. Once in the field, the user is solely responsible for the safe operation
of the equipment.

Envent Engineering Ltd. H2S Analyzer User’s Manual – Revision 2.6 Page 3
1.31 Key Symbols
The following symbols are used throughout the manual to call attention to important information. We
recommend familiarizing yourself with them before reading further.
Indicates a potential hazard that, if not properly addressed, could result in damage to the equipment
or injury to the operator
Caution: hot surface.
Indicates additional information intended to help clarify an earlier statement or to aid in the reader’s
understanding of a given topic.

Envent Engineering Ltd. H2S Analyzer User’s Manual – Revision 2.6 Page 4
2.0 EQUIPMENT OVERVIEW
2.1 Theory of Operation
Envent's models 330S and 331S H2S analyzers use ASTM D4084 – 07: Standard Test Method for analysis
of hydrogen sulfide in gaseous fuels (Lead Acetate reaction rate method). This method uses lead
acetate impregnated paper. Throughout this document the term lead acetate tape will be written as
"H2S sensing tape".
The H2S sensing tape reacts when in contact with hydrogen sulfide by the compound relationship
shown below. This tape does not react to any other sulfur compounds in the gas stream. This makes it
free from interference when more than one sulfur compound is present in the sample stream. The H2S
reaction is visibly evident by a brown stain directly on the H2S sensing tape.
COOH
CHPbSCOOCHPbSH
OH
3232
2)( 2+ →+
The electronics built into the models 330S and 331S have been programmed to measure the rate of
darkening over time which, in turn, gives the hydrogen sulfide concentration level. When no H2S is in
contact with the H2S sensing tape, the analyzer sensor reads 1000 mV (+/- 100 mV).
The sensor block has a LED and a photodiode detector. The LED emits a red beam of light which is
reflected off of the H2S sensing tape to the photodiode which detects the light intensity. The darker
the H2S sensing tape becomes when in contact to H2S, the less light the photodiode detector receives
reducing the millivolt value, which in turn, increases the H2S value. The "SDS" models uniquely
measures rate of change on both sides of the H2S sensing tape, allowing for simultaneous readings of
two separate samples.

Envent Engineering Ltd. H2S Analyzer User’s Manual – Revision 2.6 Page 5
Figure 1. H2S Analyzer Principle of Operation Diagram
Figure 1 above shows a flow and pressure regulated of a filtered sample gas passing through the
humidifier into the sample chamber. An aperture in the sample chamber, which differs in sizes
depending on the application, allows the gas to come in contact with the H2S sensing tape creating a
brown stain.
Flow and pressure are the most important variables when measuring H2S and must be kept at a
constant state for the analyzer to measure H2S properly. Pressure should be kept at a constant 15 psig.
The lowest pressure found to be tolerable for proper H2S measurement is 0.5 psig. Flow must be kept
at a constant flow of 2 cm (83.63 cc/min). A change in flow of +/- 1 cm affects the reading by 10% of full
range.
2.2 Analysis Cycles
The analysis of the color rate of change on the H2S sensing tape is measured in analysis cycles. An
analysis Cycle lasts up to a maximum of 720 seconds (12 minutes).
Do not change the Maximum Analysis Time, consult Envent Engineering Ltd.
Analyzers sold prior to Mid-August 2016 are set to have a 360 second analysis cycle.

Envent Engineering Ltd. H2S Analyzer User’s Manual – Revision 2.6 Page 6
Once an analysis cycle is complete, the motor moves the H2S sensing tape giving the sensor block new
tape surface area to start the analysis again. In normal operation, if the analyzer is being exposed to
H2S within its range, the analysis cycle should last between 150 to 210 seconds (1.5 to 2.5 min); the
cycle lasts 720 seconds if no H2S is present.
Figure 2. H2S Analysis Cycle
Figure 2 shows a complete analysis cycle from when the motor has advanced the H2S sensing tape
from a previous analysis (1), to the end of the current analysis (4). Once the H2S sensing tape has
finished moving and new tape surface area is exposed, the reflection of light from the LED to the
photodiode detector is at its maximum and results in a voltage output from the sensor block of 1000
mV (+/- 100 mV). This voltage is captured by the analyzer and it is referred to as the "Zero Voltage".
The zero voltage will vary for each surface area of the H2S sensing tape and will represent the starting
point for the H2S reading for that cycle.
From stage (2) to (4) the H2S value starts increasing as the millivolt value drops from exposure to H2S.
This stage is called "RRA Analysis". The RRA stands for Rapid Response Algorithm and it is the
instantaneous H2S readings calculated every 67 ms. As the H2S sensing tape darkens, the RRA value
starts going up every second. Although the RRA values are calculated almost instantaneously, they are
not as accurate as the final reading obtained at the "Concentration Calculation" stage (3) to (4).
However, RRA values can be used as a trigger alarms setpoint in case the application requires a rapid
response time (less than the RRA Analysis completion). The first part of the RRA Analysis (2) to (3)

Envent Engineering Ltd. H2S Analyzer User’s Manual – Revision 2.6 Page 7
completes when the mV value drops 100 mV. Once it drops 100 mV, stage (3) to (4) "Concentration
Calculation" starts.
On this stage, the H2S slope is optimal for calculating the final H2S value for that Cycle. Algorithms are
used by the controller board to calculate as accurately as possible the H2S final value. Once the final
value is obtained, it will stay at that value (shown in the display and 4-20 mA analog outputs) until the
next cycle has finished and updates the H2S current reading. This stage will always be 1/5 of the
amount of time it takes stage (2) to (3) to complete. Thus, if stage (2) to (3) took 600 seconds, then
stage (3) to (4) will take 120 seconds.
It is important that the analyzer is used for its calibrated H2S range. Do not use this unit for an
application that will require readings outside of its calibrated range. This will cause the H2S sensing
tape to run out faster and may cause less accurate readings. The range is determined by the aperture
strip in the sample chamber. For more information analyzer ranges, refer to "Aperture Strip" on page
19.
2.3 Dual Sensor Analysis cycle (SDS):
Dual sensor analyzers have two sensors that read H2S from two different samples at the same time,
e.g. Sensor 1: 0-20 ppm H2S Sensor 2: 0-200 ppm H2S. The analysis cycle process is the same per sensor
as explained earlier in this section; however, some extra algorithms have been implementing to help
with the interaction between the two sensors and their analysis cycles' timing.
Both analysis cycles for each sensor will always start at the same time. When the motor moves and
new H2S sensing tape area is exposed, a new analysis cycle has started for both sensors. However, the
analysis cycles from each sensor will finish at different times. Either sensor 1 or sensor 2 will finish its
analysis cycle first. Regardless of which sensor finishes first, it will wait for the other sensor to
complete its analysis cycle. Once both sensors have completed their analysis cycles, the motor will
move and new H2S sensing tape area is exposed for a new analysis cycle.
It is important to clarify that when the first sensor has finished its analysis cycle, even when it is
waiting for the second sensor to complete its analysis cycle, it immediately updates any outputs
associated with that sensor (Analog output 4-20 mA, alarms, display H2S value, etc.).

Envent Engineering Ltd. H2S Analyzer User’s Manual – Revision 2.6 Page 8
2.4 Analyzer Specifications
Analyzer Specification
Measurement
Method
ASTM D4084 - 07: Standard Test Method for Analysis of Hydrogen Sulfide in
Gaseous Fuels (Lead Acetate Reaction Rate Method)
Ambient
Temperature
0-50 °C (standard) consult factory for other requirements, 0 to 90% humidity
(non-condensing)
Power
12-24 VDC @ less than 3W
Or, 100-240 VAC 50/60 Hz, 5W,
(300W when total sulfur option is included)
Fuse Rating: 5 Amps, 250V, Slow blow, Size: 0.201'' Dia x 0.787'',
Package/Case: 5 mm x 20 mm
Battery (for 1d Controller Board only): Lithium 3.6V, Dia 0.571'' & 0.992''
Long
Electrical
Certification
330S-DS
Class I, Division 1 Groups B C D T3C Tamb 0 °C to + 50 °C
331S-DS
Class I, Division 2 Groups B C D T3C Tamb 0 °C to + 50 °C
For more information on Hazardous location certification, refer to the
Envent’s Website.
Output Ranges
Standard ranges are between 10-100 ppb and 0-100 ppm
Response Time
20 seconds to 90% of step change
Accuracy
±1.5% of full range on channel 1 (for SDS Models, channel 2 has an accuracy
of ± 2.0%).
For dilution (option): ±2.5%
For Total Sulfur (Option): ±2.0%
For PPB (Option): Based on "base noise average"
Display
Graphic Liquid Crystal Display; menu is scrolled by internal button or
magnetic wand (330S)
Outputs
Two 4-20mA outputs (loop power required), optional 4-20mA powered
output boards are available
Serial Communication:
(1) RS-232 Modbus protocol
(3) RS-485 Modbus protocol (One RS-485 for remote display option)
Ethernet port as an optional feature
4 SPDT relays (120 VAC 5A maximum)
4 solid state solenoid drivers
Optional Features
Total Sulfur
Utilized when all sulfur compounds need to be measured. A Total sulfur
reaction furnace is added which allows the analyzer to measure total sulfur
Dilution Sample
System
Utilized when the analyzer needs to measure ranges above 100 ppm. A
permeable membrane dilution system

Envent Engineering Ltd. H2S Analyzer User’s Manual – Revision 2.6 Page 9
Liquid Sampling
Utilized when a liquid sample conditioning system is required to measure
hydrogen sulfide in Liquids
Parts Per Billion
Utilized when analyzer requires to read in parts per billion (<1 ppm)
Low Tape Sensor
Utilized when an alarm is required when the H2S sensing tape needs to be
changed
Low Pressure
Switch
Utilized for alarming when sample pressure drops below 10 PSI
AO Powered
Boards
Utilized for loop-powered analog outputs
Expander AO
Board
Utilized when more than two analog outputs are required
Ethernet Port
Utilized for TCP/IP communication capabilities
Auto Calibration
Utilized to initiate a calibration based on time of day or manually
Table 1. 330S/331S H2S Analyzer Specifications

Envent Engineering Ltd. H2S Analyzer User’s Manual – Revision 2.6 Page 10
3.0 INSTALLATION
3.1 Unpacking
Upon arrival, the packaging should be immediately inspected for any external damage that may have
occurred during shipping. If any damage is present, please contact Envent Engineering Ltd and
request that the carrier's agent be present when the analyzer is unpacked. If a disagreement arises,
the incoterms agreed to by the seller and the customer will overrule any dispute.
Once the integrity of the packaging has been confirmed, open the shipping container and remove the
packing materials from the shipping box. Remove all provided components from the shipping
container and inspect them for any damage that may have been sustained during shipping. Compare
the provided components to the shipping manifest to ensure that all parts are present.
The 330S H2S analyzer with a standard Sample conditioning system weight approximately 105 lb.
Unpacking and transporting requires a minimum of two persons.
Make sure the start-up kit is complete (refer to list below). For some special and more complex
analyzers, there might be extra parts in the start-up kit (refer to packing slip).
3.1.1 Standard spare parts for 330S H2S analyzers:
1. 330S Customer Binder
•Customer Manual(s) and Addendums
•Factory Calibration Certificate
•Factory Configuration
•Drawing Package
•Cal Gas Certificate(s)
2. USB flash drive (containing all documentation)
3. 300' H2S Sensing Tape. Part No. 330133XS
4. 1 Liter Analyzer Fluid. Part No. 330129
5. Funnel
6. 330S Serial Comm. External Cable (USB to Mini USB). Part No. 600002
7. Humidifier (uninstalled). Part No. 330061 (Part No. 330061D for SDS)
8. Bolts For explosion proof enclosure (x22)

Envent Engineering Ltd. H2S Analyzer User’s Manual – Revision 2.6 Page 11
3.1.2 Standard spare parts for 331S H2S analyzers:
1. 331S Customer Binder
•Customer Manual(s)
•Factory Calibration Certificate
•Factory Configuration
•Drawing Package
•Cal Gas Certificate(s)
2. USB flash drive (containing all documentation)
3. 300' H2S Sensing Tape. Part No. 330133XS
4. 1 Liter Analyzer Fluid. Part No. 330129
5. Funnel
6. 331S Serial Comm. External Cable (USB to Mini USB). Part No. 600002
7. Humidifier (uninstalled). Part No. 330061 (Part No. 330061D for SDS)
Envent Engineering H2S Sensing Tapes are suitalbe for use, if stored in the original sealed package, for
10 years fron date of manufacture. Tapes should be stored in a coll dry location. If the seal on the
package has been broken in storage, the H2S Sensing Tape should be discarded.
3.2 Site Requirements
The model 331S & 331SDS are designed for cETLus Class 1, Division 2, Groups BCD, Temp Code T3C
(Tamb 0°C to 50°C). These models are designed for indoor use only. Ensure that the analyzer received
is suitable for the electrical classification of the installation site.
The model 330S & 330SDS are designed for cETLus Class 1, Division 1, Groups BCD, Temp Code T3C
(Tamb 0°C to 50°C). These models are designed for indoor use only. Ensure that the analyzer received
is suitable for the electrical classification of the installation site.
Substitution of components may impair intrinsic safety and suitability for Class I, Division 1.
Substitution of components may impair suitability for Class I, Division 2.
The glass window on the XP enclosure must remain installed in order to maintain area classification.

Envent Engineering Ltd. H2S Analyzer User’s Manual – Revision 2.6 Page 12
3.3 Mounting Requirements
The analyzer should be mounted in an enclosed area in which it is not exposed to vibrations,
excessive pressures, temperatures, or environmental variations.
The selected installation site should provide adequate room for maintenance and repair procedures.
The installation site should be as close as possible to the process stream being measured. The sample
delivered to the analyzer must be representative of the stream and as such, should be taken from a
point as close as possible to the analyzer. This proximity will prevent lag times and sample
degradation in the lines.
No modifications or repairs to the flamepaths are permitted.
Substitution of components may impair flameproof safety and suitability for Class I, Division 1.
All NPT thread entries must meet the minimum requirement of 5 threads.
XP enclosures must have conduit plugs installed for unused conduit entries.
Conduit seal(s) must be installed at a minimum distance of 18'' from any XP enclosure's conduit
entries.
Conduit seals must be poured after wiring is completed and before powering up the unit.
The XP enclosure covers must be installed and fully engaged to maintain area classification. They
must be secured with the provided 6/32 x ½ set screw. A 1/16 hex key is required for removal.
When operating in low temperatures the flame arrestors and sample inlet line must be properly
insulated to prevent the cooling of the sample gas.
The analyzer’s input voltage range shown in Certification Nameplate (e.g., 120 – 240VAC) is limited
when installing external devices (e.g., Solenoids).
Before opening line pressure, be sure that all port connections, sample sweep and sample
conditioning system are securely installed.
This unit requires a disconnect device rated 24 VDC and 5A max. It must be protected by a circuit
breaker rated 24 VDC and 5A max, and it is to be installed in accordance with local electrical codes.
This unit requires a disconnect device rated 240 VDC and 5A max. It must be protected by a circuit
breaker rated 240 VDC and 5A max, and it is to be installed in accordance with local electrical codes.

Envent Engineering Ltd. H2S Analyzer User’s Manual – Revision 2.6 Page 13
3.3.1 Space Requirements
Figure 3. Space Requirements for the 330S & 331S H2S Analyzers

Envent Engineering Ltd. H2S Analyzer User’s Manual – Revision 2.6 Page 14
Make sure to leave at least 1 foot of extra space on the left side of the 330S H2S analyzer. This will
allow proper opening of the side door located at the upper blue chassis where the H2S sensing tape is
located.
3.3.2 Sample Point Selection
The sample to the 330S/331S H2S analyzer must be representative of the process stream and should
be taken from a point as close as possible to the analyzer to avoid lag times and sample degradation
in the tubing. A probe must be installed vertically on a horizontal section of pipe ensuring that the
sample is drawn from the middle third of the pipeline.
An optional Genie GPR Probe regulator may be used. The function of this probe is to ensure a clean
dry sample to the analyzer and to reduce the pressure of the sample. The lower pressure will improve
the response time of the analyzer. Refer to Figure 4.
It is advisable that the probe is not installed on a vertical pipe.
3.3.3 Sample inlet & sample sweep
1/4 inch 316 stainless steel tubing and fittings are recommended for the sample inlet and sample
sweep tubing. Sample sweep can be connected to a flare line if available. Refer to Figure 4.
1/8 inch 316 stainless steel tubing can also be used if the response time of the analyzer is of particular
concern.
3.3.4 Vent line
3/8 inch stainless steel tubing and fittings are recommended for the vent line to a maximum of 6 feet
in length. 1/2 inch stainless steel tubing should be used for vent lines exceeding 6 feet. The tubing
should be installed with a slight downward slope and should be as short as possible. Refer to Figure 4.
The sample vent line must be tubed to atmospheric pressure outside and cannot be connected to a
flare line or header.

Envent Engineering Ltd. H2S Analyzer User’s Manual – Revision 2.6 Page 15
Figure 4. 331S Recommended Venting for 331S (Same for 330S model)
3.3.5 Sample Volume & Flow Rate
The sample should be supplied to the 330S/331S H2S analyzer at 10-15 psig and at a flow of 83.63
cc/min (set flowmeter at 2.0). A bypass sweep is recommended to reduce sample lag time in the
sample line if it is at high pressure or it is longer than 15 feet (The Standard H2S conditioning sample
system has a bypass sweep). The standard sample tubing material is 1/4" 316 stainless steel; however,
1/8" stainless steel tubing can be used if the response time is critical (refer to
Table 2).
Table 2. Sample Volume and & Flow Rate
Carbon steel sample line and/or fittings are not acceptable.
Tube
Si
ze
(
")
Tube
Ga
uge
ID (")
ID (cm)
Flow
(S
CFH)
Flow
Std.
(cc/min)
Pressure
(PS
IA)
Lag
Time per
100' (min)
Lag
Time per
100' (sec)
3/8
20
0.319
0.810
5
2359
800
36.30
2178
3/8
20
0.319
0.810
5
2359
200
9.07
544
3/8
20
0.319
0.810
5
2359
50
2.27
136
1/4
20
0.181
0.459
5
2359
800
11.69
701
1/4
20
0.181
0.459
5
2359
200
2.92
175
1/4
20
0.181
0.459
5
2359
50
0.73
44
1/8
20
0.081
0.205
5
2359
800
2.34
140
1/8
20
0.081
0.205
5
2359
200
0.59
35
1/8
20
0.081
0.205
5
2359
50
0.15
9

Envent Engineering Ltd. H2S Analyzer User’s Manual – Revision 2.6 Page 16
3.3.6 Installation of Analyzer Components
In this section, the description and installation of the main components of the 330S & 331S H2S
analyzers are covered.
Total Sulfur and Dilution system options are not covered in this section. Please refer to Total Sulfur
and Dilution manuals.
3.3.6.1 Analog Outputs
The H2S controller board has two isolated loop power 4-20mA outputs which can be set up for
different variable outputs. Loop power (10-32 Volts) sourced from the end device (PLC) is required for
the analog to output. Figure 5 shows the different wiring set ups for the analog outputs.
The third wiring option shown in Figure 5 uses Envent's powered AO board(s) to provide self-powered
analog outputs. These boards are available at Envent Engineering Ltd.