Honeywell 705 Series User manual

Sensors Type 705
Combustible Gas Sensor Ul Certified
Operating Instructions

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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.
HELPING TO MAKE A SAFER WORLD
HELP US TO HELP YOU
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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Response: Date:
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To: Marketing Communications,
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HELP US TO HELP YOU

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CONTENTS
Section Page
1. INTRODUCTION 7
1.1 General 7
1.2 Principle of Operation 6
1.3 Accessories 6
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
3.4 Filter 17
4. MAINTENANCE 18
4.1 General 18
4.2 Cleaning 18
5. GASSING THE SENSOR 19
5.1 Sensor witout Accessories 19
5.2 Sensor with Collecting Cone
or Weather Protection Housing 19
5.3 Sensor with Sample Flow Housing 19
6. REPLACEMENT PARTS 21
6.1 Terminal Housings 21
6.2 Maintenance Spares 21
7. TYPE 705 SENSOR ALTERNATIVE SYSTEMS 22
8.SPECIFICATION 23

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1.1 GENERAL
The 705 Sensor (Figure 1) is a combustible gas detector
certified for installation in a hazardous area. This version
uses the catalytic principle and in conjunction with electronic
control equipment situated in a non-hazardous area it forms
a combustible-gas detection system. The type of sensor
and the gas to be detected should always be quoted when
ordering replacement sensors.
The sensor comprises an aluminum housing containing a
pair of poison resistant detector elements, 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 and holds the filter in position, if required.
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 a filter. 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 two elements which are heated by a
supply derived from the associated electronic control
equipment. One element is sensitive to the presence of
combustible gas, the element temperature increasing in
response to catalytic oxidation of the gas. The resultant rise
in resistance of the sensitive element, proportional to gas
concentration, is processed by the associated control
module.
The non-sensitive element compensates for effects of
changes in ambient temperature.
The sensor drive current is set to a value appropriate to the
type of elements used.
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 filter. The appropriate filter must be fitted.
1. INTRODUCTION

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1. INTRODUCTION
Figure 2 Collecting Cone
Nozzle 6.35 O/D
77.6mm
165mm
42mm
A nozzle on the cone permits gassing of the Sensor with
the cone in position. Test gas is applied either direct to the
nozzle or via a permanently connected pipe-line when the
Sensor is in an inaccessible location.
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 Filter.
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.

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1. INTRODUCTION
50.8mm Dia
25.5mm
51.0mm
Figure 3 Weather Protection Housing
Figure 4 Sample Flow Housing
61mm
45mm
31mm
30mm
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 Filter is retained by the
housing and interfaces with a gasket bonded to the housing.

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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 Filters
In a clean atmosphere, and where no accessories are to be
fitted, a filter is not needed. It is however mandatory that a
filter should be fitted to provide protection appropriate to
the environment and to complete the seal when a Weather
Protection Housing or Collecting Cone is fitted.
1.3.7 Stainless Steel Filter
Two layers of stainless steel mesh in the form of a disc with
a rubber rim to provide mechanical protection of the sinter
and exclude large dust particles.
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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WARNING
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.
CAUTIONS
1. The catalytic detector element is resistant to catalyst
poisons, however, abnormally high concentrations
of halogenated hydrocarbons, vapours of heavy
metals or compounds, some silicone compounds
and sulphur compounds may cause loss of
sensitivity.
2. The type 705 Sensor must never be used in
conditions where there is insufficient Oxygen to
totally oxidise the combustible gas. For most
combustible gases, an Oxygen level of at least
15% is sufficient.
3. The sintered disc on the sensor assembly must be
kept free from contaminants. ie. Oil and dirt.
2.1 UNPACKING
On receipt the equipment must be carefully unpacked,,
observing any instructions printed on the packaging, and
the contents checked for deficiencies and transit damage.
2.2 SENSOR ORIENTATION
The sensor must be installed with the Sensor facing
downwards. In exposed locations a Weather Protection
Housing should be fitted.
2.3 TERMINAL HOUSINGS
A Terminal Housing (Figure 6) provides a mounting base
for the sensor and contains the associated electronic circuit.
The installation wiring enters the Terminal Housing via
conduit.
2. INSTALLATION

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2.4 CABLE CONNECTIONS
The sensor is connected by three wires:
Connections Colour Code
Sensitive (S) Brown
Non-sensitive (NS) Blue
Common (01) White
A 3-way terminal block is provided in the terminal enclosure
to enable connection to be made to the control unit. Earthing
facilities are available if required.
2. INSTALLATION
Cable Entry Conduit
Adalet X1HFC3L
Terminal Housing
Killark Box with
705 Sensor
Cable Entry Conduit
Figure 6 Terminal Housings

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2.5 FITTING SENSORS
WARNINGS
Before installing the sensors, isolate the power supply
by disconnecting or removing the associated control
module from the installation.
CAUTION
1. The sensitivity of catalytic sensors is impaired by
silicone compounds. Do not expose the sensors to
silicones or silicone-based products.
2. The sintered disc on the sensor assembly must be
kept free from contaminents. eg. Oil and dirt.
3. The relevant site procedures must be obeyed at all
times when opening the Terminal Housing or
removing the sensor in a hazardous areas
When fitting a sensor to a metal thread, it is recommended
that the mounting thread should be coated with an approved
anti-seize compound, such as a light petroleum grease.
Refer to Section 8 for alternative systems to which the
sensor can be connected. If replacing a sensor refer to
CAUTION 1 in the Maintenance section.
To fit the 705 Sensor proceed as follows:
(1) Remove the protection disc and fit the accessories
as required. (Refer to Section 3).
(2) Isolate the power supply and wait for five minutes.
(3) Remove the Terminal Housing lid.
(4) Pass the cable into the Terminal Housing and fit the
sensor to housing. To comply with the certification
requirements, a minimum of five threads must be
engaged.
2. INSTALLATION

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(5) Connect the sensor cable to the terminal block. (See
label adjacent to connector).
(6) After mounting the Terminal Housing in the required
location, connect the associated Control Module wiring
to the terminal block (see label).
(7) Replace and secure Terminal Housing lid.
(8) If not already replaced by accessories, unscrew the
Filter Housing, remove the protection disc and replace
Filter Housing and gasket.
Note: The Hydrophobic Barrier is retained in position by
the Filter Housing, or one of the accessories.
(9) Connect power supply to the Sensor by reconnecting
or replacing the associated Control Module.
(10) Calibrate the system as detailed in the control
equipment manual.
2. INSTALLATION

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3.1 COLLECTING CONE (00780-A-0032)
To fit the Collecting Cone Assembly to a sensor, carry out
the following:
(1) Remove the Filter Housing and gasket from the
sensor.
(2) Fit the Stainless Steel Filter.
(3) Screw the Collecting Cone assembly onto the sensor
accessory thread and tighten firmly by hand.
3.2 WEATHER PROTECTION HOUSING
(00780-A-2076)
To fit a Weather Protection Housing to a sensor carry out
the following:
(1) Remove the Filter Housing and gasket from the
sensor.
(2) Fit the Stainless Steel Filter.
(3) Screw the Weather Protection Housing on to sensor
accessory thread and tighten firmly by hand.
3.3 SAMPLE FLOW HOUSING (00780-A-0035)
To fit a Sample Flow Housing to the sensor, carry out the
following:
(1) Remove the Filter Housing and gasket from the
sensor.
(2) Ensure that the Sample Flow Housing is fitted with its
gasket (00780-C-0017).
(3) Apply a thin coating of anti-seize compound, such as
a light petroleum grease, to the sensor accessory
thread.
3. FITTING ACCESSORIES

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(4) If required fit the Stainless Steel Filter, screw the
Sample Flow Housing on to the sensor and tighten
with a 40mm A/F spanner.
(5) Set the sample flow rate to 1.5 ± 0.1 litres per minute,
unless otherwise directed in System installation
instructions.
3.4 FILTER
The filter is retained in position on the sensor by either the
Filter Housing, or one of the above accessories. When
fitting a filter, keep it free from oil and dirt and other
contaminants.
3. FITTING ACCESSORIES

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4.1 GENERAL
Maintenance consists of cleaning the sensor and
accessories, replacing gasket and the Hydrophobic Barrier
and gassing the sensor when testing the system.
CAUTIONS
1. The sensitivity of Catalytic Sensors is impaired by
silicone compounds. Do not expose to silicones or
silicone based products.
2. Dismantling of a sensor or a sensor installation by
other than authorised engineers invalidates
certification.
In the event of exposure to contaminant or prolonged
exposure to high concentration of gas, the sensor should
be operated for 24 hours in a clean environment and then
recalibrated.
Note: If the sensor is found to be faulty, or cannot be
calibrated, the complete sensor must be discarded
and replaced.
4.2 CLEANING
Sensor and accessories may be cleaned using an industrial
grade of methanol, providing the appropriate safety
precautions are taken when handling this solvent. Whenever
cleaning takes place, a new Filter must be fitted and the
following precautions must be observed:
a. Isolate power supply from the sensor by withdrawing
the associated Control Module from the installation.
b. Do not remove sensor from the installation.
4. MAINTENANCE

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5.1 SENSOR WITHOUT ACCESSORIES
Where there are no accessories fitted, it is recommended
that a Sample Flow Housing is used when gassing the
sensor. Where this is not possible, a suitable plastic bag
may be used.
5.2 SENSOR WITH COLLECTING CONE OR
WEATHER PROTECTION HOUSING
(1) Using the rubber tubing, connect the test gas to the
gassing nozzle or to the permanently connected tubing
if fitted.
CAUTIONS
1. Upward pressure on the gassing nozzle of a
Weather Protection Housing forces the nozzle
against the sinter. Rotation of the nozzle may
damage the sinter if a filter is not fitted.
2. Direct gassing of the sensor via the nozzle on the
Collecting Cone in wind speeds of greater than 5
metres per second may cause errors.
(2) Set the flow rate to 1.5 ± 0.1 litres per minute and test
the system in accordance with the instructions in the
appropriate system equipment manual.
(3) On completion, shut off the test gas and disconnect
the rubber tubing.
5.3 SENSOR WITH SAMPLE FLOW HOUSING
(1) Shut off the sample flow to the flow housing.
(2) Disconnect the input pipeline from the input nozzle of
the flow housing.
5. GASSING THE SENSOR

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(3) Using the rubber tubing, connect the test gas to the
flow housing input nozzle.
(4) Set the flow rate to 1.5 ± 0.1 litres per minute and test
the system in accordance with the instructions in the
appropriate system equipment manual.
(5) On completion, shut off the test gas and disconnect
the rubber tubing.
(6) Reconnect the input pipeline to the flow housing input
nozzle and restore the sample flow.
5. GASSING THE SENSOR