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First wireless, infrared gas detector
Safe Wireless communication for infrared gas detectors using the ISA100 standard
Niels Aakvaag, GasSecure
March 22, 2012
2
– Introduction– Principle of detection– What are the requirements for safe wireless
communication?– Why ISA100?– What are the issues and how have we solved
them– Installations present and future
Agenda
GasSecure develops the first wireless, infrared hydrocarbon gas detector
Control room
Gateway
GS01
GS01
GS01
GS01 GS01
GS0x
Features:
High reliability – SIL2 incl. SafeWirelessTM communication
Continuous monitoring with two years battery life
Fast response (5 s)
No recalibration
… reduce system costs with 60% to 80%
Wired Wireless
Installation & engineeringOther HW (cables)Detectors
60-80%
70%
20%
10%80%
5%15%
From 5 W to 0,005 Wpower consumption
– A new detection method
– Optical sensor completely redesigned
– Smart use of wireless standard
Challenge
MEMS optical filters
The optical sensor is only awake when the air composition is changing and for self testing
A new proprietary detection method using ultrasonic pre-warning
Ultrasonic sensor
gas > 2500 ppm
Opticalsensor
HC gas > 5000 ppm
Alarm
N
N
Y
Y
√ SIL2√ Multihop support√ Max 2 second
latency from node to controller
√ Based on a standard
√ 2.4GHz
Communication requirements from end-users
Choice of standard: WiHART vs ISA100
Layer WirelessHART ISA100.11a
Application HART command Object oriented
Data Link TDMA, Mesh TDMA/CSMA, Mesh
Physical 802.15.4, 2.4GHz 802.15.4, 2.4GHz
Other major differences:
o In ISA 100, the end devices can request contracts with the gateway in order to obtain a certain Quality of Service.
o ISA has defined five hopping sequences, HART only one.
o ISA supports fragmented packets, in HART this needs to be done by application
WiHART to be supported by GasSecure if sufficient demand
– IEC61508 dictates four mechanisms for safe communication
– ProfiSAFE supports all
Safe message characteristics
SafeWirelessTM: SIL2-rate safe wireless communication
Safe request 1
Safe request 2
Safe request 3
Safe response 1
Safe response 2
Safe response 3
– Initiated from controller
– Max 2 seconds latency from gas detection to packet at controller
– Max two hops
– Safe communication over grey channel
– Message:
– Gas concentration
– Temperature
– Battery status
– Diagnostic
14
– Combine contradicory requirements:
Low energy consumption rapid response
– Solution:Asymmetrical bandwidth allocation
We reserve more bandwidth uplink, but only use it whenever it's required.
Challenge and solution
Modes of operation
GatewayController GS01
20 s18 s
GatewayController GS01
request (x)
response (x)
Gas
request (x+1)
request (x+2)
response (x+1)
response (x+2)
PROFIsafe message
ISA100 message
request (x)
request (x+1)
request (x+2)
response (x+1)
response (x)
16
– 60 seconds, defined by IEC60079-29-1
– With safe message every 20 seconds three attempts
– If no safe message within process safety time:
– Detector set to safe state– Marked as unavailable to control
system– Operator intervention required to
resume
Process safety time
17
– Kårstø gas processing plant
– Seven detectors
Current installation 1 20 39 58 77 96 115134153172191210
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
Series1Series2Series3Series4Series5Series6Series7
1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 1061131201271341411481551621691761831901972042112180
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
0.045
Series1Series2Series3Series4Series5Series6Series7
RSSI
PER
18
– Gullfaks C.– Rig operated by Statoil.– 20 detectors– Schedule: August 2012
– Tor.– Rig operated by Conoco-
Phillips.– 20 detectors– Schedule: October 2012
Future installations
Detector– Dual detection principle (US and IR) gives fast response and
low power consumption
Wireless communication– SafeWirelessTM with asymmetric bandwidth allocation– ProfiSAFE
Wired communication– ProfiNET– Integration done with ABB
–Close cooperation with:– Statoil, Conoco-Phillips, NIVIS, ABB, Yokogawa, and others
Summary