■ Purpose
The Fixed gas sampling system is dedicated to the Gas Control in all Tanks,
Void Spaces or Housed adjacent to Cargo Storage Tanks and Handling Systems, in
order to detect and Gas Concentration level over programmable limits and to monitor
visible and audible alarms consequently. That system complies with ISGOTT regulation
chap. 7.8 and 8.2
These areas can be controlled by suction process sampling on one or more common
sensor(s) as well as by individual local sensors.
■ System Description
The Fixed gas sampling System is composed of:
Analysing Unit
A cabinet named Analysing Unit includes suction process sampling gas sensor(s)
and pneumatic components for up to 48 channels (pumps, solenoid valves, water
trap filter, pressure sensor,...)
A modular arrangement of solenoid valves allows easy sizing of channels number,
easy extension as well as easy maintenance.
An electronic module manages above parts, monitors up to 7 gas sensors dispatched
either in suction process or as local sensors, performs all gas measurements
from above sensors, and monitors the alarms on dry contact outputs. It comprises
2 digital RS485 communication ports Unit(s) as described hereunder, and/or and
external Monitoring System, using MODBUS RTU protocol. The Unit is powered equally
by 230 or 115 Vac: only the pumps are to be optionally changed to run under
115 VAC.
Control Unit
One or more panel(s) named Control Unit include and electronic module managing
a LCD screen for measurement and alarms display, status lamps, buzzer/dry contact
output for alarms monitoring and keyboard for System operation and configuration.
The large LCD screen increases the data availability and the man-machine interface
is simplified for easy access to functions and configuration using scrolling
menus.
One control Unit can be incorporated in the Analysing Unit or located in a
remote box, another one can be located in another place. The Control Unit is
powered by 24 VDC from the Analysing Unit, and communicates with is by RS458
link.
Suction sampling accessories
A set of suction sampling accessories is composed of non-return valves for top
wet tank fitting, flame-arrestors, shut-off valves. On each channel, a flow
regulating valve allows to get an identical flow whatever is the length of the
line, for best efficiency of the system.
Local gas sensors
When required, a set of local gas sensors of Infra-red. eagalytic, electro-chemical
or and other type. 4-20mA output, can be connected to the Analysing Unit.
■ Specifications
- Suction channel number : up to 48, connections for O.D. 6mm copper pipes
- Suction capacity : up to 400 meters w/ I.D 4mm pipes
- Sampling exhaust output : connection for O.D. 6mm copper pipe to safe area
- Circulation exhaust output : connection for O.D. 10mm copper pipe to safe
area
- Drain water trap output : connection for O.D. 6mm copper pipe to safe area
- Calibration Gas input : connection for O.D. 6mm plastic pipe
- 4-20 mA Analog calibrated inputs for sampling or loval sensors : up to 7
- Gas concentraion alarm levels : 2 adjustable, Pre-Alarm ana Alarm
- Alarm form Analysing, Unit , dry contact outputs :
- 1 for Gas Alarm
- 1 for System alarm
- 1 for remote Horn / Rotating Lamp
- 1 for Power Supply failure
- Alarm from Control Unit : 1 internal buzzer +1 dry contact output
- Communication ports : 2 RS485, 1 isolated RS232 or RS485
- Output power supply for sensors : 24VDC
- Instrument air supply for purge : 6/8bars, connection for O.D. 6mm copper
pipe
- Sensors : miscellaneous type according to gas type, Safety class according
to their location
- Operating temperature for : 0°C ~ +70°C, Analysing and Control
Units
- Location for Analysing and Control Units : Safe area in enclosed space(Control
Room, Accommodation, bridge, ...)
- Power supply : 115/230Vac
 |
Click to enlarge image
Related Keywords:
Bookmark / Share this page