Honeywell 705 Series User manual

Sensors Type 705
Combustible Gas Sensor Ul Certified
Operating Instructions

MAN0363.PM6 Issue 02, Aug 97 705 Sensor
00705M5002
2
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.

3
MAN0363.PM6 Issue 02, Aug 97 705 Sensor
00705M5002
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.

MAN0363.PM6 Issue 02, Aug 97 705 Sensor
00705M5002
4
Marked up copies attached (as appropriate): Yes / No
Please inform me of the outcome of this change: Yes / No
For Marketing Communications, Zellweger Analytics Limited:
Actioned By: Date:
Response: Date:
I suggest the following corrections/changes be made to:
Chapter ........... Section ...........
To: Marketing Communications,
Zellweger Analytics Limited,
Hatch Pond House,
4 Stinsford Road,
Nuffield Estate,
POOLE. Dorset.
BH17 0RZ.
United Kingdom.
Tel :[phone]
Fax :[phone]
email :markcom@zellweger-
analytics.co.uk
From:
Address:
Tel :
Fax :
email :
HELP US TO HELP YOU

5
MAN0363.PM6 Issue 02, Aug 97 705 Sensor
00705M5002
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

MAN0363.PM6 Issue 02, Aug 97 705 Sensor
00705M5002
6

7
MAN0363.PM6 Issue 02, Aug 97 705 Sensor
00705M5002
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

MAN0363.PM6 Issue 02, Aug 97 705 Sensor
00705M5002
8
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

9
MAN0363.PM6 Issue 02, Aug 97 705 Sensor
00705M5002
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.

MAN0363.PM6 Issue 02, Aug 97 705 Sensor
00705M5002
10
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.