Hukseflux

Thermal Sensors

USER MANUAL HF02
Flare radiation monitor / heat flux sensor
equipment model LEX30

Copyright by Hukseflux | manual v2123 | www.hukseflux.com | info@hukseflux.com

Warning statements
Follow the installation instructions of this manual. It
contains safety notes, rated operating conditions,recommendations on installation and shielding andrequirements for maintenance.
HF02 must be used under its ATEX rated operating
conditions only. The user is responsible forassessment of local conditions as well as for proper
certification of any connecting equipment.
We recommend use of HF02 in a decision-supportingrole only, and not to use measurements of HF02 as
the sole or main source of information supporting
decision making or judgements on safety.
The sensor-to-cable transition is vulnerable. The
user should provice proper strain relief of the cableso that transition is not exposed to significant force.
First install the cable including strain relief, theninstall the sensor.
Under no condition more than Umax 5V should be put
across the HF02 output wiring, Imax equals 5 x 10-3 A.

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Contents
Warning statements
Contents
List of symbols
Introduction
1.1
Ordering HF02
1.2
Included items
1.3
Quick instrument functionality check2
Instrument principle and theory
3
Specifications of HF02
3.2
Dimensions of HF02
4
Installation of HF02
4.1
Electrical connection
4.2
Site selection and installation
5
Recommended practices for use
5.1
Short user guide6
Maintenance and trouble shooting
6.1
Recommended maintenance and quality assurance
6.2
Trouble shooting
6.3
HF02 diagnostics
6.4
Calibration and checks in the field
6.5
Recoating/ repainting of sensor surfaces
7
Appendices
7.1
Appendix on calibration hierarchy
7.2
Typical heat flux ranges
7.3
EC declaration of conformity

HF02 manual v2123

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List of symbols
Quantities

SymbolUnit

Heat flux
Voltage output
Sensitivity
Temperature
Resistance

Φ
U
S
T
R

W/m²
V
V/(W/m2)°CΩ

Subscripts
N/A

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Introduction
HF02 is a sensor that measures radiant heat flux or thermal radiation in the outdoor
environment. A common application is monitoring the radiation emitted by flares. HF02 is
certified for use in potentially explosive atmospheres, and is rated for radiation levels up
to 15 x 103 W/m2. We recommend use of HF02 in a decision-supporting role only, andnot to use measurements of HF02 as the main or sole source of information for judging
safety.
The formal equipment model name of HF02 is LEX30. Hukseflux offers several shielding
options (LEX30 Option A / LEX30 Option B (standard configuration) / LEX30 Option C).
HF02 is used in alarm systems, using the heat flux measurement to issue a warning incase of high thermal radiation exposure of equipment or personnel. It is typicallyinstalled close to a flare. A common assumption is that the heat flux level in a safe
environment for personnel must not exceed 5 x 103 W/m2 (or 1.5 x 103 BTU/(hr∙ft2)).
Above that heat flux level, or when the temperature of the sensor body exceeds 70 °C,
an alarm is activated.
A typical alarm system will include multiple HF02 sensors, all aimed at the main source ofradiation, as well as other decision-supporting devices such as camera systems andtemperature sensors.
The sensor in HF02 measures the heat flux to its black (absorbing) surface, in the planeof the sensor, from a source in the field of view angle. It offers measurement of theeffective exposure for personnel and equipment from a source in the direction it is aimed
at the location of the sensor.
Using HF02 is easy. It can be connected directly to commonly used data logging systems.
The heat flux in W/m2 is calculated by dividing the HF02 output, a small voltage, by thesensitivity. The sensitivity is provided with HF02 on its calibration certificate.
The measurement function of HF02 is:Φ = U/S(Formula 0.1)

The sensor body temperature is monitored as a redundant safety precaution. In case thesensor has a temperature above a specified level, typically 70 °C, we recommend to
consider this a sign that there are strong local heat sources and to activate the alarm.
HF02 is rated for use in (potentially explosive) environments. It is supplied with aproduct certificate specifying the ATEX rating as II 2G Ex db IIC T6.
Hukseflux provides a traceable calibration. Hukseflux is ISO 9001 certified, but for heat
flux sensors not an accredited measurement laboratory according to ISO 17025.

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HF02 should be regularly inspected. The sensor performance can be verified bycomparison to a portable heat flux sensor such as model HF03.

Figure 0.1 HF02. Standard cable length is 3 m high temperature metal sheathed cableplus 3 m low temperature extension cable.

90
10
5

1
2

1

3
4

6

4

5

9
3

2

11

8

7

30

Figure 0.2 HF02 consists of a heat flux sensor (1) providing both a heat flux and asensor body temperature measurement, a sensor body (3), a radiation shield (2) andrain screen (10) to protect the sensor against the environment, a high-temperature
metal sheathed cable (4), a cable transition piece (5), a low temperature extension cable(6), mounting holes (3/8 UNC) (9) and spacers (11). The transition piece (5) to the cableend (at 7) in area 8 must be between -20 and +70 °C, and the cable end (at 7) must be
provided by the user with an enclosure certified for use in the area of installation.
Installation is the responsibility of the user. Dimensions in x 10-3 m.

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1

Ordering and checking at delivery

1.1

Ordering HF02

The standard configuration of HF02, equipment model LEX30, is with 3 m hightemperature metal sheathed cable and 3 m low temperature extension cable.
Common options are:•longer cable (specify total cable length for both cable types in m)

Specify the shielding option: the standard version has the sensor body and the hightemperature cable connected to the shield/drain wire of the low temperature plastic
cable. A shield disconnected from the high temperature metal cable and sensor body isoffered as an option.
•••

LEX30 Option A: shield not connected to high temperature cable and sensor body
LEX30 Option B: shield connected to high temperature cable and sensor body(standard configuration)
LEX30 Option C: no low temperature extension cable, high temperature metal sheathmaterial and the sensor body may act as shield

1.2

Included items

Arriving at the customer, the delivery should include:
•
•
•
•
•

heat flux sensor HF02
cables of the lengths as orderedshielding option as ordered
product certificate matching the instrument serial number
EC type examination certificate (ATEX) II 2G Ex db IIC T6

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1.3

Quick instrument functionality check

A quick test of the instrument can be done by connecting it to a multimeter.
1. Check the electrical resistance of the heat flux sensor between the black [-] and red[+] wires and the thermocouple between the green [+] and white [-] wires. Use amultimeter at the 100 Ω range. Measure the sensor resistance first with one polarity,then reverse the polarity. Take the average value. Typical resistance should be thenominal sensor resistance of 4 to 14 Ω for the thermopile sensor at standard cable
lengths, plus for additional low temperature extension cable 0.1 Ω/m (resistance permeter cable ) for the total resistance of two wires (back and forth added), for hightemperature cable 1 Ω/m. For the thermocouple work with 5 to 15 Ω at standard cable
lengths, plus additional low temperature extension cable 0.7 Ω/m resistance per meter
cable ), for high temperature cable 2 Ω/m. Infinite resistance indicates a broken circuit;zero or a lower than 1 Ω resistance indicates a short circuit.
2. Check if the heat flux sensor reacts to heat: put the multimeter at its most sensitive
range of DC voltage measurement, typically the 100 x 10-3 VDC range or lower. Expose
the sensor heat, for instance touching it with your hand. The signal should
read > 2 x 10-3 V now. Touching or exposing the black surface should generate a positive
signal. Also look at the reaction of the thermocouple to heat.
3. Check the shield connection. Measure the drain-wire to housing connection.
LEX30 Option A has: shield not connected to high temperature cable and sensor body.
LEX30 Option B has: shield connected to high temperature cable and sensor body.
Measure with a multimeter with one connection at the drain wire the other in the sensor
body.
4. Inspect the instrument for any damage.
5. Check the sensor serial number engraved on the transition piece between hightemperature cable and low temperature extension cable, against the certificate provided
with the sensor.

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2

Instrument principle and theory

HF02 is a sensor that measures heat flux. It is mainly used to measure heat flux fromflares. HF02 measures heat flux in the range of (0 to 15) x 103 W/m2. Equipped with ablack absorber, heat flux sensors of this type are designed for measurement in anenvironment in which heat flux is dominated by radiation.
HF02’s thermopile sensor generates an output voltage proportional to the incoming
irradiance.
To convert the measured voltage, U, to a heat flux Φ, the voltage must be divided by thesensitivity S, a constant that is supplied with each individual sensor.
The measurement function of HF02 is:Φ = U/S(Formula 0.1)

The sensitivity is provided with HF02 on its calibration certificate.
As the detector is essentially open (it has no protective windows) the measurement is
influenced by wind in the same way as any exposed surface such as clothing worn bypersonnel or the surface of equipment; increased wind speed leads to a reduction of themeasured heat flux. Rain on the detector can also lead to cooling and a reduction of themeasured heat flux.
To perform a heat flux measurement representative of human exposure or equipment
exposure, the sensor temperature should be as close as possible to the ambient air
temperature. This is the purpose of the rain- and radiation screens of HF02 (incombination with cooling fins). They reduce radiative heating of the sensor by the sun.
The screens also reduce the effect of wind and rain, reducing the risk of a false indicationof a safe situation.
The temperature sensor inside HF02 is a type K thermocouple. It measures the sensor
body temperature.
For readout the user only needs an accurate voltage measurement in the millivolt range,
and a type K thermocouple measurement.

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The total exposure of personnel or equipment is determined by the total heat flux, bothfrom the flare that the HF02 is aimed at and from the sun. The maximum solar radiationlevel is about 1.3 x 103 W/m2, which means it is a potentially significant contribution. If
the sun is in HF02’s field of view, solar radiation might lead to an offset of the flareirradiance. The solar radiation may also have its maximum contribution from a directionthat is not within HF02’s field of view. Users typically accept that solar radiation is part ofthe measurement in case the sun is within HF02’s field of view, and ignore the solar
contribution if the sun is not within the sensor’s field of view.
Measuring with heat flux sensors, errors may be caused by differences between
calibration reference conditions and the conditions during use. The user should analyse
his own experiment and make his own uncertainty evaluation.

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3

Specifications of HF02

HF02 measures heat flux density from 90 ° field of view angle, through the surface of the
HF02 sensor. This quantity, expressed in W/m2, is called heat flux. It also measures its
body temperature. HF02 is rated for use in environments in which the heat flux isdominated by radiation at heat flux levels up to 15 x 103 W/m2. It measures the
combined radiative and convective heat flux. HF02 is passive, using thermopile andthermocouple sensors. The thermopile generates a small output voltage proportional tothe heat flux. HF02 can only be used in combination with a suitable measurement
system. It is rated for use in potentially explosive environments. The sensor should be
used in accordance with the recommended practices this manual.
Table 3.1 Specifications of HF02 (continued on next page)
HF02 SPECIFICATIONS
Sensor typeHeat flux sensor
Measurand
Measurand in SI units
Full field of view angle
Rated measurement range
Limiting measurement range
Temperature sensor
Temperature sensor specification
Measurand
Measurand in SI units
Measurement range
Limiting temperature range
Measurement function / required
programming
Recommended number of sensors
Sensitivity (nominal)
Response time (95 %)Expected voltage output
Required readout

IP protection class
Sensor and high temperature cableLow temperature extension cable
Rated operating relative humidity range
Required sensor power
Sensor diameterStandard cable lengths
High temperature cableLow temperature extension cable

HF02 manual v2123

flare radiation monitor/ heat flux sensor
thermopile
heat flux
heat flux density in W/m2
90° (with radiation screen)
0 to 15 x 103 W/m2
150 % of rated measurement range
thermocouple type KX
ANSI MC96.1-1982 / EN 60584
temperaturetemperature in °C-30 to 100 °C
500 °C (short term exposure of sensor and hightemperature cable)
Ф = U/S
2 per measurement location
0.3 x 10-6 V/(W/m2)
180 smultiply the sensitivity by the maximum expectedheat flux
typically 4.5 x 10-3 V
heat flux sensor: 1 x differential voltage channel or 1
x single ended voltage channel
temperature sensor: 1 x Type K differential
thermocouple channel or 1 x Type K single ended
thermocouple channel
both with input resistance > 106 Ω
IP68
IP67
0 to 100 %zero (passive sensors)
25 x 10-3 m
3 m (see options)
3 m (see options)

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Table 3.1 Specifications of HF02 (started on previous page, continued on the next pages)
High temperature cable type
Low temperature extension cable typeHeat flux sensor resistance range
Low temperature extension cable: heat
flux sensor cable resistanceHigh temperature cable: heat flux sensor
cable resistance
Temperature sensor resistance range
Low temperature extension cable:temperature sensor cable resistanceHigh temperature cable: temperature
sensor cable resistanceBlack coating emissivity
High temperature cable diameter
Low temperature extension cablediameterConnection diameter
Marking

Use of materials
Net weight

metal sheathed mineral insulated signal cable
PVC signal cable with shield and drain wire
4 to 14 Ω (standard cable length)
0.1 Ω/m (nominal)
1 Ω/m (nominal)
5 to 15 Ω (standard cable length)
0.7 Ω/m (nominal)
2 Ω/m (nominal)
0.92 (nominal)
6 x 10-3 m
7.5 x 10-3 mtransition piece between high temperature and low
temperature cable: 17 x 10-3 m (including spring), 14
x 10-3 m (metal only)
1 x engraving on the transition piece, showing serial
number1 x sticker at low temperature extension cable end,
showing serial number.
stainless steel, duplex steel and PVC
approx. 3 kg (with 3 m high temperature cable and3 m low temperature extension cable)

ATEX SPECIFICTIONS AND INSTRUCTIONS
Equipment status according to directive
2014/34 EU
ATEX rated operating conditions
Rated use
Model name according to EU typeexamination
Electrical data
Rated process temperature range(sensor and high temperature cable)
Rated operating temperature range
low temperature extension wire andcable end
EC type examination certificate
Safety notes
Maintenance requirements

HF02 manual v2123

HF02 is a passive sensor which does not have its own
source of ignition. It becomes equipment in the senseof Article 2 of the directive only when operating in
combination with other equipment.
II 2G Ex db IIC T6
stationary use only
LEX30
Umax 5 V,
Imax 5 x 10-3 A-50 to +300 °C-30 to +70 °C
included in delivery
see warning statements and the chapter onrecommended practices for use
regular inspection of the sensor surface and field ofview as well as regular performance verification. See
the chapter on maintenance.

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Table 3.1 Specifications of HF02 (started on previous 2 pages, continued on the next page)
GENERAL INSTALLATION AND USE
Location
Installation
Mounting
Cable extension

Recoating
CALIBRATION
Calibration traceability
Product certificate
Calibration method
Calibration hierarchy
Calibration uncertainty
Calibration laboratory accreditation
Calibration laboratory management
system certification
Recommended recalibration interval
Calibration reference conditions
Validity of calibration
Field calibration

Temperature sensor tolerance class
Temperature sensor error limits
MEASUREMENT ACCURACY
Uncertainty of the measurement

HF02 manual v2123

HF02 is usually located at the point where safety must
be assessed, pointed at the main source of radiation.
Take into account the 90° full field of view angle.
see recommendations in this user manual.
avoid mechanical force on the sensor-to-cabletransition.
2 x mounting bolt 3/8 UNC at 30 x 10-3 m hart-to-hart
distance
extension or replacement of cables is not covered by
the product EU type examination. Cables may be
extended under user responsibility employing aconnection box certified for use in its operating
environment
the black sensor surface may be recoated with hightemperature black paint, see the appendix on thissubject
to ITS90
Included(showing calibration result and traceability)
SBGC secondary calibration according to ISO 14934-3
from SI through international standards and throughan internal mathematical procedure< 20 % (k = 2)
not accredited
ISO 9001
2 years
30 °C, heat flux of 10 x 103 W/m2
based on experience the instrument sensitivity will notchange during storage. During use the instrument“non-stability” specification is applicable.
is possible by comparison to a calibration reference
sensor. Usually mounted side by side under exposure
to a radiation source > 10 x 103 W/m2. Heat flux
sensor model HF03 may be used as a calibrationreference.
IEC Tolerance class EN60584-2: Type KX, class 2
ASTM E230-ANSI MC96.1: Type KX, standard limits
statements about the overall measurement
uncertainty can only be made on an individual basis.

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Table 3.1 Specifications of HF02 (started on previous 3 pages)
VERSIONS / OPTIONSLEX30 Option A: shield not connected to hightemperature cable and sensor body
LEX30 Option B : shield connected to hightemperature cable and sensor body(standard configuration)
LEX30 Option C: no low temperature cable, hightemperature metal sheath and sensor body may act
as shield
HF02 / model LEX30 (Option A / Option B / Option C)/ temperature cable length in m /low temperature extension cable length in m

Order code
SPARE PARTS
Spare part
Spare part

3.2

radiation screen with 4 spacers and 4 bolts
rain screen with 2 bolts

Dimensions of HF02

90
10
5

1
2

1

3

4

4

6

5

9
2

3

11

8

7

30

Figure 3.2.1 HF02 flare radiation monitor / heat flux sensor. Dimensions in x 10-3 m.

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4

Installation of HF02

4.1

Electrical connection

A heat flux sensor should be connected to a measurement system, typically a so-called
datalogger. HF02 is a passive sensor that does not need any power, neither for the heat
flux sensor, nor for the temperature sensor. Cables may act as a source of distortion, by
picking up capacitive noise. We recommend keeping the distance between a datalogger
or amplifier and the sensor as short as possible.
Table 4.1.1 The electrical connection of HF02
WIRE

SIGNALRed

heat flux signal [+]Blackheat flux signal [−]Green

thermocouple type K [+]White

thermocouple type K [−]BlankshieldOptions for grounding and shield connection are:•••

LEX30 Option A: shield not connected to high temperature cable and sensor body
LEX30 Option B: shield connected to high temperature cable and sensor body(standard configuration)
LEX30 Option C: no low temperature extension cable, high temperature metal sheathand sensor body may act as shield

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4.2

Site selection and installation

Table 4.2.1 Recommendations for installation of HF02 heat flux sensors
Location

HF02 measures the heat flux through the plane of the black sensor. Make
sure the orientation of the HF02 matches the orientation of the plane ofinterest.
For studies of exposure of personnel and equipment, the maximum or
worst-case heat flux is usually found by measuring at the relevant
location and by pointing the HF02 at the strongest local radiation source.
Take into account that HF02 has a 90° full field of view angle.

SafetyThe free cable end must be connected to a junction box that is certified
for use in the local environment.
For limitations to the environment: see the HF02 ATEX specifications.
Use proper terminals to connect the sensor wires
Use the ground wire if provided to connect to the safety ground
Use a suitable cable gland on the junction box to maintain the IP67
protection classification
Install sensor and cable in such a way that it they are protected against
mechanical force

Performing a
representative
measurement

we recommend using > 2 sensors per measurement location.
This redundancy also improves the assessment of the measurement
accuracy

Mechanical mounting

the sensor-to-cable transition is vulnerable.
Users should not exert significant mechanical force on the sensor or on
the sensor to cable transition.
during installation as well as operation, the user should provide proper
strain relief of the cable so that transition is not exposed to significant
force.
mounting: first install the cable including strain relief and after that install
the sensor.
use the two 3/8 UNC bolts at a hart-to-hart distance of 30 x10-3 m.

Signal amplification

HF02 manual v2123

ask the manufacturer for recommendations for signal amplification /conversion

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5

Recommended practices for use

5.1

Short user guide

Table 5.1 Recommended practices for use
HF02 RECOMMENDED PRACTICES FOR USE
1Read the full manual2

Check Ex ratingcompare HF02’s ATEX rated operating conditions to actualsite conditions

3

Determine options

choose cable lengths and shielding options

4

Design mounting andamplification

see the chapter on electrical connection and installation

5

Ordering

6

Unpack HF02

check shipment contents (see paragraph on included
items)

7

Check sensor functionality

see the paragraph on the functionality test

8

Installsee the directions on installation

9

Check performanceverify by comparing measured heat flux to a reference
measurement for example with heat flux sensor HF03

10

Check inspection /maintenance / verification
procedurescheck if the maintenance schedule contains arecalibration or performance check at an interval of 0.6
years or less. See the chapter about maintenance

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6

Maintenance and trouble shooting

6.1

Recommended maintenance and quality assurance

HF02 measures reliably at a low level of maintenance, but does require frequent
inspection. Unreliable measurement results are detected by scientific judgement, forexample by looking for unreasonably large or small measured values. The preferred way
to obtain a reliable measurement is a regular critical review of the measured data,
preferably checking against other measurements.
Table 6.1.1 Recommended maintenance of HF02. If possible the data analysis is doneon a daily basis.
MINIMUM RECOMMENDED HEAT FLUX SENSOR MAINTENANCE
INTERVALSUBJECTACTION1

after every
incident inwhich HF02
was exposed
to flames orhigh fluxes

inspection

inspect black sensor surface, inspect cable quality, inspect
mounting, inspect location of installation. The black sensor
surface should be smooth.

2

1 weekdata analysis
andinspection

compare measured data to the maximum possible or
maximum expected heat flux and to other measurements forexample from nearby or redundant instruments. Historical
records can be used as a source for expected values. Look forany patterns and events that deviate from what is normal or
expected. Compare to acceptance intervals.
verify the cleanliness quality of the black paint on the sensor
surface. The surface should be black and without scratches. A
dirty surface may be cleaned with water. If necessary theradiation screen may be removed.
verify that the field of view of the black sensor surface isunobstructed.

3

6 months

inspection

inspect black sensor surface, inspect cable quality, inspect
mounting, inspect location of installation

4

2 years

recalibration

recalibration by comparison to a calibration standard
instrument in the field, see following paragraphs.
alternatively: recalibration by the sensor manufacturer

5lifetime
assessment

HF02 manual v2123

judge if the instrument will be reliable for another 2 years, or
if it should be replaced

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Figure 6.1.1 Picture of HF02’s sensor surface. The sensor surface should be inspected
on a weekly basis. The picture shows that the sensor field of view is unobstructed, andthat the sensor surface is not scratched and that it is clean.

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6.2

Trouble shooting

Table 6.2.1 Trouble shooting for HF02
GeneralInspect the sensor for any damage. Inspect the quality of mounting / installation.
Verify that the sensor has a free field of view.
Inspect if the wires are properly attached to the data logger.
Check the condition of the cable.
Inspect the connection of the shield (typically connected at the datalogger side).
Check the datalogger program in particular if the right sensitivity is entered.
HF02’s sensor serial number is engraved on the transition piece between hightemperature cable and low temperature extension cable. The sensitivity can befound on the calibration certificate.
Check the electrical resistance of the heat flux sensor between the black [-] andred [+] wires and the thermocouple between the green [+] and white [-] wires.
Use a multimeter at the 100 Ω range. Measure the sensor resistance first with one
polarity, then reverse the polarity. Take the average value. Typical resistanceshould be the nominal sensor resistance of 4 to 14 Ω for the thermopile sensor atstandard cable lengths, plus for additional low temperature extension cable 0.1
Ω/m (resistance per meter cable ) for the total resistance of two wires (back andforth added), for high temperature cable 1 Ω/m. For the thermocouple work with 5
to 15 Ω at standard cable lengths, plus additional low temperature extension cable
0.7 Ω/m resistance per meter cable ), for high temperature cable 2 Ω/m. Infinite
resistance indicates a broken circuit; zero or a lower than 1 Ω resistance indicatesa short circuit.

The sensor
does not give
any signal

Check if the heat flux sensor reacts to heat: put the multimeter at its mostsensitive range of DC voltage measurement, typically the 100 x 10-3 VDC range or
lower. Expose the sensor heat, for instance touching it with your hand. The signal
should read > 2 x 10-3 V now.
Check the reaction of the thermocouple sensor to heat.
Check the data acquisition by replacing the sensor with a spare unit.

The sensor
signal isunrealisticallyhigh or low

Check the cable condition looking for cable breaks.
Check the shield connection. Measure the drain-wire to housing connection. Model
LEX30A has shield not connected to high temperature cable and sensor body while
LEX30B has shield connected to high temperature cable and sensor body. Measurewith a multimeter with one connection at the drain wire the other in the sensor
body.
Check the data acquisition by applying a 1 x 10-6 V source to it in the1 x 10-6 V range. Look at the measurement result. Check if it is as expected.
Check the data acquisition by short circuiting the data acquisition input with a
10 Ω resistor. Look at the output. Check if the output is close to 0 W/m2.

The sensor
signal shows
unexpectedvariations

Check the presence of strong sources of electromagnetic radiation (radar, radio).
Check the condition and connection of the shield.
Check the condition of the sensor cable.
Check if the cable is not moving during the measurement.

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6.3

HF02 diagnostics

The following tables are used for checking and trouble shooting HF02.
Table 6.3.1 Resistance checks for diagnostics of HF02
WIRE

WIRE

RESISTANCE ACCEPTANCE INTERVAL

Red

Black

4 to 14 Ω for standard version (*1)

Red

Green

infinite (> 106 Ω)

Red

Body

infinite (> 106 Ω)

Green

White

5 to 15 Ω for standard version (*2)

Green

Body

infinite (> 106 Ω)

Blank shield /drain wire

Body

LEX30 Option A: infinite (> 106 Ω)
LEX30 Option B: < 10 Ω*1) optionally plus 0.1 Ω/m low temperature cable plus 1 Ω/m high temperature cable (approx.)*2) optionally plus 0.7 Ω/m low temperature cable plus 2 Ω/m high temperature cable (approx.)

6.4

Calibration and checks in the field

The recommended calibration interval of heat flux sensors is 2 years.
Recalibration of field heat flux sensors is ideally done by the sensor manufacturer.
On-site field calibration is possible by comparison to a calibration reference sensor,
temporarily mounted side by side.
Hukseflux main recommendations for field calibrations are:1) to compare to a calibration reference for example model HF03
2) typical heat fluxes used for comparison: > 3000 W/m2
3) to correct deviations of more than ± 20 %. Lower deviations should be interpreted as
acceptable and should not lead to a revised sensitivity.
4) you may use a flare but also an artificial source such as a lamp or electrical heater

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6.5

Recoating/ repainting of sensor surfaces

Hukseflux recommendations for repainting are:Remove the radiation screen.
Verify sensor functionality. This can also be done with a non-coated sensor (see thechapter of the quick sensor test).
Purchase a matt (not glossy) black paint which is temperature resistant up to 600 °C.
Silicone based black paints are a good choice. Typically aerosol spray cans are most easy
to use, but such paints can also be used purchased in cans. In case a solvent is needed:
typically acetone is a good solvent for these paints.
Surface preparation: In case the existing sensor surface coating has small scratches but
is otherwise in good condition, apply new paint directly to the existing paint. In case ofheavy damage to sensor surface coatings: remove the existing coating, clean withacetone or ethanol. Lightly sand the metal surface.
Paint application: Spray some paint in a small cup, use a pipette to apply the paint. In
case a pipette is not available, use a small paint brush.
Recalibration: newly coated sensors should be recalibrated. We do not expect significant(> 5 %) changes relative to the original sensitivity.

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7

Appendices

7.1

Appendix on calibration hierarchy

HF02 factory calibration is traceable from SI through international standards and throughan internal mathematical procedure. The formal traceability of the generated heat flux isthrough a secondary standard calibration reference to the international temperature
standard ITS90.
The Hukseflux SBGC method follows the recommended practice of ISO 14934-3, however
we calibrate at one heat flux level only. Calibration relies on a comparison to a secondary
standard heat flux sensor under a radiant heat source.
HF02 is calibrated at a heat flux level of 10 x 103 W/m2.

7.2

Typical heat flux ranges

Table 7.2.1 Typical allowable heat flux levels in industrial environments as found inliterature. NOTE: these data should not be used as a reference.
Btu/Hr Ft2

x 103 W/m2

1

Equipment

3000

9.5

2

Human: Run

2000

6.3

3

Human: Walk

1500

4.7

4

Human: Work (static)

500

1.6

Table 7.2.2 typical ranges of heat flux levels, from ISO 14934-4
x 103 W/m2

Comment

1

300

maximum level in a fully developed fire

2

200 to 100

incident heat flux on the wall in a developed fire enclosure

3

about 100

radiation from burning house4

about 30

causing ignition of tree

5

20 to 10

causing ignition of timber

6

about 7 or 8

lowest level for causing ignition of a timber wall under a pilot
flame

7

about 4

lowest level for causing a burn8

about 2,5highest level for people to endure

9

1,5

solar constant, maximum level of solar irradiance

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7.3

EU declaration of conformity

We,

Hukseflux Thermal Sensors B.V.
Delftechpark 31
2628 XJ Delft
The Netherlands

in accordance with the requirements of the following directives:
2014/30/EU
2014/34/EU

The Electromagnetic Compatibility Directive
Equipment and Protective Systems for Use in Potentially Explosive
Atmospheres (ATEX)

hereby declare under our sole responsibility that:
Product model:
Product type:

HF02 with equipment model name LEX30
Flare radiation sensor / heat flux sensor

has been designed to comply and is in conformity with the relevant sections andapplicable requirements of the following standards:
Emission:
Immunity:
Health & Safety:

EN 61326-1: 2013
EN 61326-1: 2013
EU IEC 60079-1:2007
EU IEC 60079-0-2012

and that produced products are accompanied by a separate declaration of conformity andEC type examination certificate according to the requirements of Directive 2014/34/EU,
which together with this certificate forms a dossier as allowed by note 24.

Eric HOEKSEMA
Director
Delft
March 01, 2016

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© 2021, Hukseflux Thermal Sensors B.V.
www.hukseflux.com
Hukseflux Thermal Sensors B.V. reserves the right to change specifications without notice.