1.1 Scope
Insulation is used to reduce the amount of heat lost or gained by hot and cold fluids within tanks and vessels respectively, thus reducing the amount of energy expended maintaining the temperature of the fluids.
Tank and Vessel Insulation is available in a range of different designs, materials and heat transfer performance. The Energy Technology List (ETL) Scheme aims to encourage the purchase of higher efficiency products.
The ETL Scheme covers four categories of product, based on the application being insulated:
- Chilled Water Tanks & Vessels
- Process Tanks & Vessels
- Domestic & Non-Domestic Hot Water Tanks & Vessels
- Domestic & Non-Domestic Heating Tanks & Vessels
1.2 Definitions
Tank and Vessel Insulation covers products that are specifically designed to be applied to the outer surfaces of Tanks or Vessels with the primary objective of reducing thermal flow into or out of the Tank or Vessel
“Tanks and Vessels” means a housing designed and built to contain fluids, including its direct attachments up the coupling point connecting it to Pipework or other equipment. This definition includes both pressurised vessels and atmospheric storage tanks.
“Maximum Permitted Heat Transfer Rate” is the amount of thermal energy into or out of the tank or vessel that the insulation allows to pass through per second, per unit area. This must be specified by the manufacturer, at the conditions noted within the referenced standard(s), which may include external air temperature, humidity, and tank/vessel surface emissivity.
“Thermal Conductivity (Q)” is the intrinsic ability of a material to transfer heat through conduction, and is the flow of heat through a defined area over a defined time. It has the SI units Watts per Meter Kelvin, W/m K.
To be eligible for inclusion on the ETL, products shall meet the requirements as set out below.
1.3 Requirements
1.3.1 Eligibility requirements
To be eligible, products shall:
- Have an appropriate Conformity Assessment mark.
1.3.2 Performance requirements
To be eligible, products shall comply with the performance requirements stated in Table 1.1 below.
Table 1.1 Performance Requirements for Tank & Vessel Insulation
|
|
Category |
Temperature |
Maximum Permitted Heat Transfer Rate. |
Relevant Standard(s) |
|
1. |
Chilled Water Tanks & Vessels
|
Fluid: > 10 °C >4.9 to < 10 °C 0 °C to 4.9 °C
|
17.2 W/m2 19.0 W/m2 20.4 W/m2
|
BS 5422:2023 Section 7 Tables 10 & 11 Annexes F & H |
|
2. |
Process Tanks & Vessels |
Hot Face: 100 °C 200 °C 300 °C 400 °C 500 °C 600 °C 700 °C |
73.3 W/m2 137.2 W/m2 204.9 W/m2 279.1 W/m2 367.7 W/m2 451.1 W/m2 577.3 W/m2 |
BS 5422:2023 Section 10 Table 21 Annexes A & H |
|
3. |
Domestic & Non-Domestic Hot Water Tanks & Vessels |
N/A |
30 .3 W/m2 |
BS 5422:2023 Sections 8 & 9 Tables 17B and 18B Annexes A & H |
|
4. |
Domestic & Non-Domestic Heating Tanks & Vessels |
Contents: ≤ 95 °C 96 – 120 °C 121 – 150 °C |
36.0 W/m2 41.8 W/m2 46.7 W/m2 |
BS 5422:2023 Sections 8 & 9 Tables 15B and 16B Annexes A & H NES Y-50 |
1.4 Measurement and Calculations
1.4.1 Performance metrics
Maximum Permitted Heat Transfer Rate is the amount of thermal energy into or out of the tank or vessel that the insulation allows to pass through per second, per unit area. This must be specified by the manufacturer, at the conditions noted within the referenced standard(s), which may include external air temperature, humidity, and tank/vessel surface emissivity.
The requirements in Table 1.1 are stated in W/m2. These have been calculated based on the requirements in BS 5422:2023 and NES Y-50, which are given in W/m (heat transfer per linear meter of pipe). It is noted the standards give values to 2 decimal places, however as there is a conversion this is limited to 1 decimal place for ETL. Formula (1) below was used for the conversion:
1.4.2 Measurement standards
The following standards, where applicable, shall be used for measuring and calculating product performance:
- BS 5422:2023 Method for specifying thermal insulating materials for pipes, tanks, vessels, ductwork and equipment operating within the temperature range -40°C to +700°C
- BS EN ISO 12241:2008 Thermal insulation for building equipment and industrial Installations. Calculation rules
- BS 5970:2012 Thermal insulation of pipework, ductwork, associated equipment and other industrial installations in the temperature range of -100°C to +870°C. Code of practice
- NES Y-50 (2011)
1.4.3 Test Requirements
Manufacturers shall provide a Declaration of Performance (DoP) to declare the thermal conductivity used to calculate pipework thickness.
Categories 3 & 4 should have their heat transfer rate determined using the assumptions in Table C.1 of BS 5422:2023, using the calculation methods in EN ISO 12241:2008.
1.4.4 Rounding
For the avoidance of doubt:
- Thermal Conductivity test data shall be presented to 3 decimal places
- Heat Transfer Rate test and/or calculation data shall be presented to 2 decimal places
1.5 Verification for ETL Listing
Any of the following testing routes may be used to demonstrate the conformity of products against the requirements:
- In-house testing – Self-certified
- In-house testing – Self-tested and verified or cross-checked by an independent body
- Witnessed testing
- Independent testing
- Representative testing (see clause 1.5.1)
Further information regarding the first three routes can be found in the ETL Testing Framework.
1.5.1 Representative testing
Where applications are being made for two or more tank and vessel insulation products that are made from the same insulation material, with the same thermal conductivity, representative testing may be used. Test data for the tank and vessel insulation material may be used to determine product performance for all tank and vessel insulation products in the representative range.
Under this test method, product performance shall be demonstrated by calculating the permitted heat loss (W/m) for the tank and vessel insulation. Manufacturers shall submit supporting information regarding the chosen calculation method, in order to determine its suitability and effectiveness. Thermal conductivity (W/m.K) i.e. the lambda value, shall be determined through product testing.
It should be noted that:
- If a manufacturer voluntarily removes the representative model from the ETL then other products linked with that representative model may or may not be permitted to remain on the ETL.
- If any product submitted under these representative model rules is later found not to meet the performance criteria when independently tested, then all products based on the same representative model will be removed from the ETL.
1.6 Conformity testing
Products listed on the ETL may be subject to the scheme’s conformity assessment programme in order to ensure listed models continue to meet the ETL requirements.
1.7 Review
1.7.1 Indicative review date
This specification is scheduled to be reviewed during the 2025/26 review cycle.
1.7.2 Illustrative future direction of the requirements
The first technical review of these criteria will consider:
- In the updated BS 5422:2023 standard the decision has been made to retain calculation methods on BS EN ISO 12241:2008, which have been superseded by those in BS EN ISO 12241:2022. Incorporation of the recalculations into BS 5422 is planned for a later update and when this is done consideration will be given to updating the ETL criteria accordingly.