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

Wireless gas detectors will increase safety by higher coverage and installation flexibility, and...

… 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

8

Optical design

Wireless instrument classes

Source: Simon Carlsen, Statoil

(Modified ISA Table)

√ 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