ADS Environmental Services Model 3600 530002 A2 - Manual (Page 10)

Introduction 1-5
Intrinsic Safety
Intrinsic safety (IS) is a special certification awarded to equipment when its design
and manufacture meet the high standards of IS regulations . The main goal of IS
regulations is to prevent the electronic equipment from causing explosions in
potentially explosive environments. These environments are categorized as Class I,
Division 1, Groups C and D in the USA and as Zone 0 in Europe; the QS3600 flow
monitor is certified for use in these environments. IS regulations were created by
local and international standards organizations to regulate all electronic equipment
that operate in areas where hazardous gases are present (for example, in sewer
systems).
ADS field crews are trained to test all manholes for the presence of explosive gases
by sampling its atmosphere with a gas meter. When the amount of gas present
exceeds certain limits, the crew does not enter the manhole.
However, a flow monitor is mounted in a manhole for extended periods of time.
During this time, the amount of combustible gas may rise to dangerously high levels
without the field crew's knowledge. As a result, many cities require that all electronic
equipment installed in sewers be tested and certified as non-explosive. ADS
produces the QS3600 IS flow monitor to meet these requirements.
Unique Features
The QS3600 flow monitor can be configured in two ways: by using a monitor with an
internal IS modem or by using a monitor with an external modem unit (EMU).
Country specific telecommunications standards and certifications will dictate whether
the internal IS modem or EMU is required. The external modem unit (EMU) houses
the modem and the power supply outside of the monitor and the manhole. The EMU
contains special circuitry to protect the circuits entering the hazardous area.
Special features of the QS3600 flow monitor include the following.
All QS3600 flow monitors are checked carefully before being shipped. Each
component is guaranteed to meet specifications. The pre-shipping inspection
is completed by internal quality inspectors.
All QS3600 flow monitors connect to 3600 compatible sensor cables. The
female connector is located on the flow monitor lid, while the male connector
is found on the sensor cables (unlike other ADS monitors). This arrangement
of connectors prevents mismatching with non-IS sensors. .
The monitor can be equipped with either an internal IS modem and telephone
interface box or with an external modem unit (EMU).
For the internal IS modem, cables are routed from the monitor to a phone
line interface box located on a pedestal or on the telephone pole. The