Honeywell 705 Series User manual
Sensors Type 705
H2S Sensor and Transmitter for
Electrochemical Cells Ul Certified
Operating Instructions
MAN0362.P65 Issue 03, Mar 01 705 Sensor
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HELPING TO MAKE A SAFER WORLD
Ensure that you read and understand these operating
instructions BEFORE installing or operating any part of the
equipment.
Please pay particular attention to the Safety Warnings.
WARNINGS
1. To maintain safety standards, regular maintenance,
calibration and operation of this equipment by
qualified personnel is essential. Read and understand
this manual completely before operating or servicing.
If any further details are required which do not appear
in this manual contact Zellweger Analytics Limited or
their agent.
2. The Code of Practice regarding 'Selection, Installation
and Maintenance of Electrical Apparatus for use in
Potentially Explosive Atmospheres' must be complied
with at all times. Refer to the appropriate local or
national regulations relative to the installation site.
Elsewhere the appropriate local or national
regulations should be used.
3. Operators must be fully aware of the action to be
taken if the gas concentration exceeds an alarm
level.
CAUTION
To maintain safety standards, regular maintenance,
calibration and operation of the equipment by qualified
personnel is essential.
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IMPORTANT NOTICES
1. Zellweger Analytics Limited can take no responsibility
for installation and/or use of its equipment if this is
not done in accordance with the appropriate issue
and/or amendment of the manual.
2. The user of this manual should ensure that it is
appropriate in all details to the exact equipment to
be installed and/or operated. If in doubt, the user
should contact Zellweger Analytics Limited for advice.
3. If further details are required which do not appear in
this manual, contact Zellweger Analytics Limited or
one of their agents.
HELP US TO HELP YOU
HELPING TO MAKE A SAFER WORLD
Every effort has been made to ensure the accuracy in the
contents of our documents, however, Zellweger Analytics
Limited can assume no responsibility for any errors or
omissions in our documents or their consequences.
Zellweger Analytics Limited would greatly appreciate being
informed of any errors or omissions that may be found in the
contents of any of our documents and to this end we include
the form opposite for you to photocopy, complete and return
to us so that we may take the appropriate action.
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1. INTRODUCTION 7
1.1 General 7
1.2 Principle of Operation 8
1.3 Accessories 8
2. INSTALLATION 12
2.1 Unpacking 12
2.2 Sensor Orientation 12
2.3 Terminal Housings 12
2.4 Cable Connections 13
2.5 Fitting Sensors 14
3. FITTING ACCESSORIES 16
3.1 Collecting Cone 16
3.2 Weather Protection Housing 16
3.3 Sample Flow Housing 16
4. MAINTENANCE 18
4.1 General 18
4.2 Cleaning 18
5. CALIBRATION 19
5.1 General 19
5.2 Cross Interference From Other Gases 19
5.3 Sensor Life 19
5.4 Calibration Procedure 20
6. GASSING THE SENSOR 21
6.1 Equipment Required 21
6.2 Calibration Gassing Procedure 21
7. REPLACEMENT PARTS 23
7.1 Terminal Housings 23
7.2 Maintenance Spares 23
8. Type 705 Sensor Alternative Systems 24
9. SPECIFICATION 25
CONTENTS
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1.1 GENERAL
The 705 ECC Sensor (Figure 1) is a hydrogen sulphide toxic
gas detector certified for installation in a hazardous area.
This version uses an electrochemical sensor, in conjunction
with an electronic circuit to form a 2-wire 4 - 20mA transmitter.
The sensor comprises an aluminium housing containing an
electrochemical cell with a sintered stainless steel disc
forming the face of the sensor. The housing has a 47mm AF
body with a 3/4 NPT mounting thread at one end and an
M36 accessory thread on the other end. A plastic Filter
Housing screws on to the accessory thread that holds the
Hydrophobic Barrier in position, if accessories are not fitted.
There are a number of accessories available for the 705
Sensor which utilise the M36 accessory thread. Refer to
Section 8 for alternative systems to which the 705 Sensor
can be connected.
Note: New Sensors are despatched with a protection disc
in place of the Hydrophobic Barrier. This disc should
not be removed until the sensor is installed or
commissioned.
1. INTRODUCTION
Figure 1 Type 705 Sensor and Filter Housing
Mounting Thread
Accessory Thread
Sintered Disc
Hydrophobic Barrier
(fit white side out)
Filter Housing
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1.2 PRINCIPLE OF OPERATION
The sensor contains an Electrochemical Cell which generates
an electrical current in proportion to gas concentration within
the cell. Since the current output from the cell is in microamps,
this is amplified and processed by the electronics in the
terminal enclosure. The resulting signal, in the range 4 -
20mA and representing 0 - 50ppm H2S, can then be wired to
equipment in the safe area to provide alarm and concentration
indications.
1.3 ACCESSORIES
1.3.1 General
The following accessories are available for use with the
sensors:
a. Collecting Cone (Figure 2).
b. Weather Protection Housing (Figure 3).
c. Sample Flow Housing (Figure 4).
d. Hydrophobic Barrier.
e. Gassing Point Assembly (Figure 5).
1.3.2 Collecting Cone
The detection of a lighter than air gas is enhanced by the use
of a Collecting Cone. The cone fits onto the sensor accessory
thread in place of the Filter Housing and retains the
Hydrophobic Barrier.
A nozzle on the cone permits gassing of the sensor with the
cone in position. The test gas is applied either direct to the
nozzle or via a permanently connected pipeline when the
sensor is in an inaccessible location.
1. INTRODUCTION
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1.3.3 Weather Protection Housing
The Weather Protection Housing, fitted to a sensor installed
in an exposed location, affords protection from driving rain
from vertical to 30° below horizontal. When mounted close
to the ground, protection is afforded from heavy rain
rebounding off the ground. It also reduces contamination
from industrial waste and enables the application of test gas
in high wind speeds without significant error.
The housing is fitted to the sensor accessory thread in place
of the Filter Housing and retains the Hydrophobic Barrier.
Incorporated in the housing is a nozzle to facilitate gassing
of the sensor with the Weather Protection Housing in position,
either by direct application to the nozzle or via a permanently
connected pipeline. The nozzle is free to rotate within the
housing to allow removal from the sensor without
disconnecting a permanently connected pipeline, when
changing the Hydrophobic Barrier and cleaning the sensor.
1. INTRODUCTION
Figure 2 Collecting Cone
Nozzle 6.35 O/D
77.6mm
165mm
42mm
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1.3.4 Sample Flow Housing
A Sample Flow Housing provides a facility to allow sampling
of a closed system by means of two pipelines. The flow
housing is fitted to the sensor accessory thread by a locking
ring that enables the housing to be removed without
disconnecting the pipeline. The Hydrophobic Barrier is
retained by the housing and interfaces with a gasket bonded
to the housing.
1. INTRODUCTION
50.8mm Dia
25.5mm
51.0mm
Figure 3 Weather Protection Housing
Figure 4 Sample Flow Housing
61mm
45mm
31mm
30mm
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1. INTRODUCTION
1.3.5 Gassing Point Assembly
The Gassing Point Assembl assembly can be fixed in a
convenient position and permanently connected by suitable
tubing to an inaccessible sensor, thus simplifying the
application of test gas when checking sensor calibration. A
DIN Rail Mounting Assembly (00785-A-0069) is available to
enable five gassing point assemblies to be mounted side by
side.
1.3.6 Hydrophobic Barrier
The Hydrophobic Barrier consists of a layer of stainless
steel mesh with a rubber rim. A hydrophobic barrier of PTFE
is bonded to the stainless steel surface.
This MUST be fitted with the white surface faceing outwards.
Figure 5 Gassing Point Assembly
25mm
Gassing Tube Cap
Stainless Steel
Tube
120 mm Dia
Yellow Nylon Block
70mm x 38mm x 19mm
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