What is Maximum Service Temperature (MST)?

Maximum service temperature is a measure indicating the maximum continuous temperature at which an insulation material can operate without any degradation in thermal  insulation performance. MST is either measured according to:

• EN 14706 (for flat products)
• EN 14707 (for curved products like pipe sections)
• ASTM C 447.

Maximum Service Temperature is a key parameter to evaluate the ability of a mineral wool product to withstand high temperatures. It is important for evaluation of this ability to take into account a load applied on the product as in real conditions, in many applications, a load due to additional layers of insulation and cladding will be applied. In some situations the products have to be able to support the weight of  workers walking on them as well as the weight of the equipment.

It is crucial then when tests are carried out to make sure that the products are exposed to a combination of high temperature and a load applied on them as the combination of the two is far more  demanding on insulation materials than the high temperature only.

ISOVER developed the ULTIMATE U Thermo range specifically for high temperature applications.

The U Thermo insulation solutions cover a broad range of thermal requirements in industrial applications. The Maximum Service Temperature (MST) of U Thermo insulation solutions is declared according to EN ISO 14 706 and EN ISO 14 707. The tests measure performance under a load of 250-500 Pa depending on the density of the products to simulate real life installation conditions.

ISOVER high density industrial Glasswool products (Energylite, Factorylite) usually achieve a MST of 250°C under 500Pa, or 300°C under 250 Pa. ULTIMATE and Stonewool products achieve MST under 500Pa up to 650°C.

The table below will give you some guideline to point you in the right direction:

These measurements prove that ULTIMATE performs reliably at continuous high operating temperatures.

*according to EN 12 667 for wired mattress, boards and felt, according to EN 8 497 for pipe sections

**according to EN 14 706 for wired mattress, boards and felt, according to EN 14 707 for pipe sections

Maximum Service Temperature (MST) under 500Pa – a guarantee that can be used for design

To estimate the highest continuous operating temperature at which a product can be used, a variety of methods exists.

The determination of MST under 500 Pa according to EN ISO 14 706 and EN ISO 14 707 for pipe sections includes applying a load of approximately 50 kg/m2 on the product for 72 hours at a constant high temperature. To pass the test, the decrease in thickness of the product must be less than 5% after 72hours of continuous exposure to this temperature. If successful this is the measured MST.

Values found using this method are substantially lower than with any other traditional test method but are the best guide to aid design.

This measure of MST is the most stringent and guarantees reliable results.

Alternative test methods often do not allow for a loading on the product and typically involve a rapid ramp-up of temperature resulting in an overestimation of the MST. For example, ASTM C 447 measures MST values without any loads and gives no clearly defined tolerances for passing the tests.

 Therefore MST values for mineral wool according to ASTM C447 are usually between 50 to 150°C higher than measured according to EN 14 706 and En 14 707, although they do not represent the real conditions of use for insulation products. The method for determining MST must be taken into account when doing thermal design at high temperatures.

In addition to load applied, several other factors can influence the maximum temperature maximum continuous temperature at which an insulation material can operate :

• levels of vibration,
• support/spacing of structure,
• chemical environments etc.

To give guidelines on practical maximum service temperature limits, AGI Q 101 has given correction factors based on MST according to EN standards for certain applications:

*S.C. = Support Construction
** For the calculation of the classification temperature needed