IEC 62862-1-6:2024

IEC 62862-1-6 ®
Edition 1.0 2024-05
INTERNATIONAL
STANDARD
Solar thermal electric plants –
Part 1-6: Silicone-based heat transfer fluids for use in line-focus concentrated
solar power applications
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IEC 62862-1-6 ®
Edition 1.0 2024-05
INTERNATIONAL
STANDARD
Solar thermal electric plants –

Part 1-6: Silicone-based heat transfer fluids for use in line-focus concentrated

solar power applications
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160  ISBN 978-2-8322-8825-2

– 2 – IEC 62862-1-6:2024 © IEC 2024
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
3.1 General definitions . 7
3.2 Relevant physical and chemical properties of heat transfer fluids . 8
4 Classification of heat transfer fluids . 12
4.1 General . 12
4.2 Mineral oil fluids . 12
4.3 Synthetic fluids . 12
4.4 Synthetic heat transfer fluids based on polydimethylsiloxanes (silicone,
SiHTF) . 12
4.5 Organic synthetic heat transfer fluids based on biphenyl / diphenyl oxide
(BP/DPO) . 12
4.6 Molten salt . 12
5 Specified fluid properties and test methods . 12
5.1 General . 12
5.2 List of technical requirements and evaluation of the quality of unused heat
transfer fluids . 13
5.3 List of additional fluid properties and test methods for silicone-based heat
transfer fluids for general layout at operating conditions . 14
5.4 List of fluid properties and test methods for heat transfer fluids in use . 14
6 Inspection interval and sampling . 15
6.1 Inspection interval . 15
6.2 HTF sampling . 16
6.3 Gas-sampling . 16
6.4 Labeling of the samples . 17
7 Reporting. 18
8 Marking, labelling and accompanied documents . 19
9 Mixing. 19
10 Recycling and disposal . 20
11 Replacement and disuse . 20
Annex A (informative) Determination of the degree of thermal degradation of
polydimethylsiloxane-based heat transfer fluids . 21
A.1 Overview. 21
A.2 Meaning of symbols M, D, T . 21
A.3 Principle . 21
A.4 Technical equipment . 23
A.5 Safety remarks . 24
A.6 Reagents . 24
A.7 Procedure . 24
A.7.1 Sample preparation . 24
A.7.2 Measurement procedure . 24
A.8 Evaluation . 25
A.8.1 Analysis of results . 25
A.8.2 Calculation of the degree of degradation . 26
A.8.3 Assessment of the result . 27

A.9 Accuracy . 27
A.9.1 General . 27
A.9.2 Addition of TM as external standard . 27
A.9.3 Repeatability . 27
A.9.4 Reproducibility . 27
A.10 Example with TM as reference substance . 27
Annex B (informative) Safety instructions and recommendations for handling
polydimethylsiloxane-based heat transfer fluids at temperatures up to 450 °C . 29
B.1 Safety information . 29
B.2 Safety instructions and recommendations . 29
B.2.1 General recommendations . 29
B.2.2 Hazardous ingredients of polydimethylsiloxane-based heat transfer
fluids under operating conditions . 30
B.2.3 Exposure controls and personal protection . 30
B.2.4 General protection and hygiene measures . 31
B.2.5 Personal protection equipment . 31
B.2.6 First aid measures after contact . 31
B.2.7 Firefighting measures . 32
Bibliography . 33

Figure 1 – Example of an aluminum bottle for sampling (new) . 16
Figure 2 – Example of a cylinder mounted with two valves (before use) e.g. for
sampling at 425 °C and 20 bar . 17
Figure A.1 – Representation of the molecular structure of M-, D-, and T-units in
polydimethylsiloxanes (PDMS) . 21
Figure A.2 – Representation of the molecular structure of polydimethylsiloxanes
(PDMS, left) and the thermally induced equilibration reaction of linear
polydimethylsiloxanes . 22
Figure A.3 – Thermally induced disproportionation of D-units in linear
polydimethylsiloxanes, into T and M units . 22
Figure A.4 – Theoretical model for describing the long-term increase in viscosity of
polydimethylsiloxane-based fluids by thermal aging . 23
Figure A.5 – Representation of a Si NMR spectrum indicating the different shift
regions . 26
Figure A.6 – Si NMR spectrum (99,3 MHz, CD Cl ) of TM with TMS as internal
2 2 3
standard . 28

Table 1 – Properties and test methods for unused heat transfer fluids . 13
Table 2 – Additional fluid properties at specified operating conditions . 14
Table 3 –Test methods for heat transfer fluids in use (basic program) . 15
Table 4 – Test methods for heat transfer fluids in use (additional program) . 15
Table A.1 – Shift regions and assignment . 25
Table B.1 – Possible hazardous ingredients of polydimethylsiloxane-based heat
transfer fluids in use . 30
Table B.2 – The product can contain the following substances of very high concern
(Regulation (EC) No. 1907/2006 (REACH), Article 57) in amounts ≥ 0,1 % . 30

– 4 – IEC 62862-1-6:2024 © IEC 2024
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SOLAR THERMAL ELECTRIC PLANTS –

Part 1-6: Silicone-based heat transfer fluids for use in
line-focus concentrated solar power applications

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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