Insulation and refractories (140 °C to 800 °C)

This guarded hot-plate is an NPL designed and built national standard for thermal conductivity (or thermal resistance) of insulation and refractories at high temperatures.

Specification

• Thermal conductivity range: up to 0.5 W/m·K
• Thermal resistance range: greater than 0.07 m²·K/W
• Mean specimen temperature range: 140 °C to 800 °C
• Conforms to ISO 8302:1991

Accreditation

• UKAS accredited test service (UKAS 0002)
• Accredited under 89/106/EEC: Construction Products, Notification id: 1146

Specimen dimensions

A single specimen is required.

• Thickness: 25 mm to 50 mm
  (The thickness of each specimen is within 2% of its mean thickness over its whole area)
  Note: 50 mm is the optimum thickness of this apparatus
• Diameter: 305 mm
  (Within the range 302 mm to 315 mm)
• Flatness: The 305 mm circular faces are flat to better than 0.2 mm
  (Flatness criteria do not apply to compressible or fibrous insulations)

Note 1

Although 'thermal conductivity' is a property of a homogeneous material, it is generally accepted that the term can still be used for insulation/construction products that contain a continuous mixture of two or more materials (e.g. air and glass fibre or air and concrete) providing the size of any particles is less than a tenth of the specimen thickness. However, if your samples have either discrete layers or large particles, then 'thermal resistance' would be quoted on the Test Report, rather than 'thermal conductivity'. However, the thickness of the product during the test would be quoted in the Test Report, allowing an 'effective' thermal conductivity to be calculated by dividing the thickness (in metres) by the thermal resistance.

Note 2

For compressible or fibrous insulations, the thickness will be initially measured according to EN 823:1995. This thickness value will then be used to determine the thickness imposed on the specimen during the test.

Contact

Customer Services tel: +44 20 8943 6245
E-mail: thermal_enquiries@npl.co.uk