Chemical Engineering April 2020 - 56

Det-Tronics
FIGURE 4. To " see " hydrogen flames, today's best
technology is multispectrum infrared flame detection,
as used in this hydrogen flame detector
mum IR filter set, some MIR devices
can detect H2 fires at about double
the range of a UV flame detector.
While the range of MIR detectors
can be reduced by the presence
of water or ice on the lens, some
detectors are equipped with lens
heaters that melt ice and accelerate
evaporation of water.
Brain of the system
To continuously monitor and analyze
data from gas and flame detectors,
F&G safety systems require controllers
that provide alarm monitoring and
some level of diagnostics. If a hazard
is detected, the controller takes the
appropriate actions based upon its
pre-programmed logic. These actions
often include providing alarm
notification and activation of suppression
systems to mitigate the hazard.
In addition to handling inputs and
outputs, the controller should be able
to provide realtime F&G safety system
status and diagnostics. It should
also facilitate programming and configuration
of flame and gas detectors,
as well as other field devices that are
part of the F&G system.
Typically, F&G safety-system controllers
have been limited to being
hardwired together using analog
or contact closures in a conventional
(that is, point-to-point) design.
Though capable of providing alarm
and fault information, the conventional
design does not give controllers
access to specific details of
fire-related events because of the
simple, binary nature of the communication
path. In addition, this design
56
provides only limited diagnostics, is
not inherently fault-tolerant and limits
configuration flexibility.
This is why today's advanced F&G
safety systems feature a redundant
control and bi-directional fault-tolerant
loop design. Systems of this type
are safety integrity level (SIL)-2 certified
and provide alarm, fault, status
and enhanced diagnostic information
that can be communicated with other
subsystems, such as process control.
The controller is in constant communication
with each device in the loop,
so it has the latest alarm and diagnostic
information, making this configuration
more reliable than point-to-point
designs as well.
Control system integration
Consider a situation in which flammable
materials continue to be
pumped into an area of a chemical
plant where fire has been detected.
To prevent potentially disastrous
scenarios like this, it is imperative
that the plant's F&G safety system
be able to communicate with the
process control system (PCS).
Any F&G system deployed in a
chemical facility should be able to
provide detection-device status in
defined process areas to the PCS so
the process owner is kept informed
about events that may threaten personnel
and/or operations. While this
level of integration is important, the
F&G system must remain independent
of the PCS, so failure of the
PCS will not affect vital fire-protection
functions in the facility.
Performance of both of the F&G
system and the PCS must be validated
to ensure they are capable of
reaching the defined risk-reduction
target for the facility. Applicable
performance requirements are contained
in codes and standards. Performance
information about specific
equipment is provided in manufacturer
documentation.
Product certification
F&G systems and equipment are covered
in fire standards such as NFPA
70 (the NFPA 70 National Electrical
Code) [5] and NFPA 72, the National
Fire Alarm and Signaling Code [6] The
surest way to know that fire-protection
equipment meets safety standards,
such as those in NFPA 70 and 72, is
to specify equipment with certification
documentation. Performance testing
and certification verify that a device
will operate as specified by the manufacturer
under a wide range of conditions.
F&G safety systems and key
components, such as controllers and
detectors, should be properly certified
for hazardous locations, performance
and functional safety.
Product testing and evaluation
should be conducted pursuant to the
requirements of a properly accredited
third-party testing and certification
agency, which provides potential
users with an independent and unbiased
product evaluation. A number
of highly regarded independent organizations
test fire-protection equipment
using their own documented
safety and performance criteria.
Manufacturers using this evaluation
approach will be able to provide proof
of certification for their products. n
Edited by Gerald Ondrey
References
1. www.thoughtco.com/most-flammable-chemical-607315
2.
Center for Industry Education Collaboration, www.
essentialchemicalindustry.org/chemicals/hydrogen.html
3. Office of Energy Efficiency & Renewable Energy,
www.energy.gov,
www.energy.gov/eere/fuelcells/
fact-month-may-2018-10-million-metric-tonshydrogen-produced-annually-united-states
4.
For more information, go to www.nfpa.org.
5. NFPA 704: Standard System for the Identification of
the Hazards of Materials for Emergency Response,
2017; www.nfpa.org
6. Chapter 17 of NFPA 72 lays out requirements for
various types of devices that can be used to detect
indications of fire.
Authors
Michael J. Hosch is lead applications
engineer at Det-Tronics (Minneapolis,
Minnesota; Phone: 952746-9100;
Email:. mike.hosch@
det-tronics.com).
Hosch has
worked with optical flame detection
for Det-Tronics for over 30 years
and has developed extensive experience
in the application of flame
detection in high-hazard environments,
ranging from the oil-and-gas industry to aircraft
hangar and munitions manufacturing.
Aaron Paterson is the Flame
Product Line manager at
Det-Tronics (same address as
Hosch, above; Phone: 952-9466471,
Email:
det-tronics.com).
aaron.paterson@
Paterson
has
been providing technical support
to Det-Tronics customers who use
flame and gas detection in challenging
and unique environments
since 2012. In his current role as Flame Product Line
manager, Paterson is responsible for recommending
product innovations and developing product roadmaps
for the flame detection product line. Paterson has a
bachelor's degree in business administration from North
Dakota State University.
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
APRIL 2020
http://www.thoughtco.com/most-flammable-chemi http://www.essentialchemicalindustry.org/chemicals/hydrogen.html http://www.energy.gov/eere/fuelcells/ http://www.energy.gov http://www.nfpa.org http://www.nfpa.org http://www.det-tronics.com http://WWW.CHEMENGONLINE.COM
Chemical Engineering April 2020

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