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Thermal expansion in length

Substances react to a change in temperature with the change in their volume. This affects all areas of technology. In construction and in road, bridge and rail construction expansion joints must be planned, which absorb the longitudinal expansion of the building materials. In pipelines expansion compensators in the form of built-in pipe bends are provided. Overhead lines for the power supply must be designed in such a way that the wires do not break in winter and have sufficient distance to the ground in summer. The basis for the calculation of these and many other constructions is the thermal coefficient of linear expansion.

When storing liquids, a specified maximum filling level must be observed. Above the liquid level a space remains free, which absorbs the volume fluctuations. The calculation of such problems uses the volume expansion coefficient.
The terms derive from the fact that most substances expand when heated. With the few exceptions where substances contract when heated, the values ​​of the two sizes are negative. In the case of isotropic substances whose properties are independent of the direction considered, the volume expansion coefficient is three times the coefficient of linear expansion.

The expansion coefficients are material properties. They are determined experimentally and given in units of measure divided by Kelvin [1/K]. Kelvin is the unit of measure for absolute temperature and for differences in Celsius scale temperatures.

The exact measurement of the linear expansion is carried out with a dilatometer. The samples are heated in an oven. The temperature profile follows a precisely predetermined program, which allows the required heating rate, required temperature hold times and defined cooling processes. During this process the sample size is continuously recorded. The different dilatometers of the Linseis are optimized for special tasks and equipped with comprehensive evaluation routines.

Measuring instruments for determining the linear expansion

DIL L75 PT Vertical

DIL-L75_Vertical
  • Vertical “Zero-Friction” Dilatometer
  • Multi furnace option (up to 3 furnaces)
  • Different furnaces: -263 up to 1000/1600/1750 …2800°C
Details

DIL L75 PT Horizontal

DIL-L75_Horizontal
  • High performance horizontal single, differential or doublepushrod Dilatometer
  • Temperature range: -180 up to 1000/1600/2800°C
  • LVDT or optical Encoder
Details

DIL L76 PT

DIL-L76
  • Robust workhorse pushrod Dilatometerfor quality control applications
  • Temperature range RT up to 1000/1400/1600°C
Details

DIL L74 Optical

DIL-L74_Erhitzungsmikroskop
  • Non contact optical Dilatometer
  • Vacuum tight design
  • optional gas dosing systems
  • -100°C up to 1500/1700/2000°C
Details

DIL L74 HM

DIL-L74_Erhitzungsmikroskop
  • High performance Heating Microscope for demanding applications
  • Vacuum tight design
  • optional gas dosing systems
  • Temperature range: -100°C up to 1500/ 1700/2000°C
Details

DIL L75 Laser

DIL-L75_Laser
  • Worlds only commercial absolute Dilatometer – no zero run required
  • Resolution 0.3nm (300 picometer)
  • Temperature range: -180 up to 1000°C
Details

DIL L75 PT Quattro

DIL PT Quattro
  • High troughput vertical “Zero Friction”Dilatometer for up to 4 samples
  • Temperature range RT up to 1000/1400/1600/2000°C
Details

DIL L78 RITA

DIL L78 RITA
  • Quenching and Deformation/Tension Dilatometer family
  • determination of TTT, CHT and CCT diagrams
  • up to 2500°C/s heating and cooling
  • -150 up to 1600°C Temperature range
Details

DIL L75 120 LT

  • Vertical “Zero Friction” Dilatometer
  • up to 8 samples in one run
  • optional humidity generator
  • especially suitable for CTE determination of polymers
Details

DIL L75 High Pressure

Linseis Hochdruckdilatometer
  • The worlds only pressure Dilatometer
  • up to 150 bar variable pressure and gas dosing
  • RT up to 1000/1550/1800°C
Details