Parts supplied
Dräger Polytron Pulsar 2 5
3 Parts supplied
1 The Dräger Polytron Pulsar 2 detector comes in two parts
a Transmitter and a Receiver; each supplied with an ABS
moulded cover. Additionally the detector is supplied with
either:
{ Flying leads and Ex e junction boxes.
{ Ex d certified plugs and sockets.
2 An Optical Attenuator for use on beam paths between 4
and 16 metres, NOTE this is only supplied with 4-60m
Transmitters.
3 An installation sheet and a quick start guide are supplied
with the detector. Installation/operation manuals are also
available through local distributors or by contacting Dräger.
4 You will also require a Commissioning kit which is ordered
separately and includes:
{ Dräger Hand Held Terminal (HHT)
{ 4mm Allen key
{ Tes t She ets
{ HHT PC software
{ PC Cable (HHT version)
4 Understanding the system
4.1 Introduction
The Dräger Polytron Pulsar 2 detects hazardous releases of
flammable hydrocarbons using the open path technique. The
Dräger Polytron Pulsar 2 it adds new and unique features
which overcome common problems and annoyances in
practical installations.
A Transmitter sends a beam of infrared light through the air to
a Receiver. A release of hydrocarbon gases anywhere along
the beam is detected because they absorb particular infrared
wavelengths. Rain or snow in the air and dirt on the lenses do
not cause a false indication of gas because they do not share
the same characteristic wavelengths selectively. This 'open
path' technique can achieve a density of coverage and a speed
of response that would otherwise require an extensive array of
point detectors. The new features that Dräger Polytron
Pulsar 2 adds includes the following:
1 The light is produced by pulsed eye-safe sources with a
peak power of 30kW. With this high Transmitter power, the
Receiver is made immune from sunlight and resonance
effects associated with vibration from rotating machinery.
Having more than one source ensures that, in the unlikely
event of a failure, the system remains functional until the
Transmitter can be exchanged.
2 The performance of all open path instruments depends on
the accurate aiming of the Transmitter and Receiver
towards each other. Often the necessary detection paths
require elevated and inaccessible locations. This can make
the alignment difficult to do at the time of installation, and
difficult to check subsequently when the supporting
structures may have moved. The Dräger Polytron Pulsar 2
has internal sensors to measure the orientation of the
Transmitter with respect to the Receiver, and vice versa.
Besides being shown graphically on the Dräger Hand Held
Terminal to make installation simple, the directional
measurements are available remotely during normal
operation, allowing the alignment to be checked.
This feature also generates a pre-warning of changes in
alignment before they can affect normal operation, and
prevents a detector being commissioned before it is
correctly aligned.
3 There is a communication path for digital signals from the
Receiver to the Transmitter. The Receiver can command
the Transmitter to double its power and to increase the
flash rate from 1Hz to 4Hz, allowing an eight-fold increase
in light flux when visibility is reduced by bad weather or
(most importantly) by the mist of condensate often present
in real incidents. The higher flash rate is also triggered by
the first indication of gas, allowing a validated gas reading
to be output in a reduced response time. The link also
allows the alignment display for both Transmitter and
Receiver to be viewed at both locations, making it easy for
one person to install or maintain the system.
4 Open path instruments can suffer interference if a receiver
'sees' another transmitter mounted nearby or in line with
the intended one. The Dräger Polytron Pulsar 2 can be
switched to separate frequencies analogous to radio
channels. Each Receiver locks onto its own Transmitter
and ignores light from its neighbours.
5 The Receiver incorporates a data-logger with a non-volatile
memory, readable locally or remotely. The data provides a
valuable aid for diagnosing practical problems and
preventing unnecessary maintenance work. Internally the
information is used to monitor slow trends of signal
strength and provide a pre-warning signal when the lenses
will require cleaning, unaffected by temporary weather
conditions.
In addition to these electronic enhancements, Dräger
Polytron Pulsar 2 has a mechanical design that provides
exceptional stability and ease of adjustment. The head units
containing the optical components are mounted in lockable
gimbals that allow separate vertical and horizontal adjustments
with the other axis clamped. Each axis can be adjusted with a
controlled degree of friction provided by PTFE rings then
locked solid without disturbing the setting. An ABS moulded
cover provides mechanical protection and helps minimise the
temperature rise of the internal electronics.
4.2 Transmitter
The Transmitter is a three-wire device, with cable terminals for
(i) 24Vdc power; (ii) digital communication; and (iii) power and
signal common. The connector for the Dräger Hand Held
Terminal allows data coming from the Receiver to be viewed at
the Transmitter, including the graphical display of orientation
and signal strength needed for alignment. The Dräger Hand
Held Terminal can also configure the Transmitter with its
operating channel and a user-entered tag reference. The eyesafe optical output through the (electrically heated) Transmitter
lens is mainly infrared, although a controlled amount of deep
red light is visible. An Attenuator Plate is fitted over the lens for
operating distances below 16m. A central section in the plate
is removed for distances between 8 and 16m, retained for
distances between 4 and 8m.
There are five operating modes:
1 Normal Mode. Flashes of normal intensity are output once
a second. The flash rate appears regular to the eye,
although it is phase-coded to send directional information
to the Receiver. Occasionally a flash will be seen out of the
normal sequence as part of an internal self-test cycle.
2 Strong Mode. Flashes of increased intensity are output at
a regular 4Hz rate.
3 Alignment Mode. Flashes of normal intensity are output
four times a second. It is easily distinguishable from Strong
Mode because there is a noticeable irregularity to the flash
rate as it sends directional information to the Receiver.