Insulation properties and Materials


Insulations are defined as those materials or combinations of materials which retard the flow of heat energy by
performing one or more of the following functions:
1. Conserve energy by reducing heat loss or gain.
2. Control surface temperatures for personnel protection and comfort.
3. Facilitate temperature control of process.
4. Prevent vapour flow and water condensation on cold surfaces.
5. Increase operating efficiency of heating/ventilating/cooling, plumbing, steam, process and power systems
found in commercial and industrial installations.
6. Prevent or reduce damage to equipment from exposure to fire or corrosive atmospheres.
7. Assist mechanical systems in meeting criteria in food and cosmetic plants.
8. Reduce emissions of pollutants to the atmosphere.
The temperature range within which the term "thermal insulation" will apply, is from -75°C to 815°C. All
applications below -75°C are termed "cryogenic", and those above 815°C are termed "refractory".
Thermal insulation is further divided into three general application temperature ranges as follows:
1. From15°C through 1°C - i.e. Cold or chilled water.
2. 0°C through -40°C - i.e. Refrigeration or glycol.
3. -41°C through -75°C - i.e. Refrigeration or brine.
4. -76°C through -273°C (absolute zero) - i.e. Cryogenic. (Not addressed in this manual).
1. 16°C through 100°C - i.e. Hot water and steam condensate.
2. 101°C through 315°C - i.e. Steam, high temperature hot water.
1. 316°C through 815°C - i.e. Turbines, breechings, stacks, exhausts, incinerators, boilers.
1. Fibrous Insulation - composed of small diameter fibers which finely divide the air space. The fibers may be
perpendicular or parallel to the surface being insulated, and they may or may not be bonded together. Silica,
rock wool, slag wool and alumina silica fibers are used. The most widely used insulations of this type are
glass fiber and mineral wool. Glass fiber and mineral wool products usually have their fibers bonded together
with organic binders that supply the limited structural integrity of the products.

2. Cellular Insulation - composed of small individual cells separated from each other. The cellular material may
be glass or foamed plastic such as polystyrene (closed cell), polyisocyanurate and elastomeric.

3. Granular Insulation - composed of small nodules which may contain voids or hollow spaces. It is not
considered a true cellular material since gas can be transferred between the individual spaces. This type may
be produced as a loose or pourable material, or combined with a binder and fibers or undergo a chemical
reaction to make a rigid insulation. Examples of these insulations are calcium silicate, expanded vermiculite, perlite, cellulose, diatomaceous earth and expanded polystyrene.

Insulations are produced in a variety of forms suitable for specific functions and applications. The combined form
and type of insulation determine its proper method of installation. The forms most widely used are:
1. Rigid boards, blocks, sheets, and pre-formed shapes such as pipe insulation, curved segments, lagging etc.
Cellular, granular, and fibrous insulations are produced in these forms.
2. Flexible sheets and pre-formed shapes. Cellular and fibrous insulations are produced in these forms.
3. Flexible blankets. Fibrous insulations are produced in flexible blankets.
4. Cements (insulating and finishing). Produced from fibrous and granular insulations and cement, they may be
of the hydraulic setting or air drying type.
5. Foams. Poured or froth foam used to fill irregular areas and voids. Spray used for flat surfaces

Thermal properties are the primary consideration in choosing insulations. Refer to the following Glossary for definitions.
a. Temperature limits: Upper and lower temperatures within which the material must retain all its properties.
b. Thermal conductance "C": The time rate of steady state heat flow through a unit area of a material or
construction induced by a unit temperature difference between the body surfaces.
c. Thermal conductivity "K": The time rate of steady state heat flow through a unit area of a homogeneous
material induced by a unit temperature gradient in a direction perpendicular to that unit area.
d. Emissivity "E": The emissivity of a material (usually written ε or e) is the relative ability of its surface to emit
energy by radiation. It is the ratio of energy radiated by a particular material to energy radiated by a black
body at the same temperature.
e. Thermal resistance "R": Resistance of a material to the flow of heat.
f. Thermal transmittance "U": The overall conductance of heat flow through an "assembly".

Properties other than thermal must be considered when choosing materials for specific applications. Among them are:

a. Alkalinity (pH) or acidity: Significant when moisture is present. Also insulation must not contribute to
corrosion of the system. See Section 3.
b. Appearance: Important in exposed areas and for coding purposes.
c. Breaking load: In some installations the insulation material must "bridge" over a discontinuity in its support.
This factor is however most significant as a measure of resistance to abuse during handling.
d. Capillarity: Must be considered when material may be in contact with liquids.
e. Chemical reaction: Potential fire hazards exist in areas where flammable chemicals are present. Corrosion
resistance must also be considered.
f. Chemical resistance: Significant when the atmosphere is salt or chemical laden and when pipe content
g. Coefficient of expansion and contraction: Enters into the design and spacing of expansion/contraction
joints and/or use of multiple layer insulation applications.
h. Combustibility: One of the measures of a material's contribution to a fire hazard.
i. Compressive strength: Important if the insulation must support a load or withstand mechanical abuse
without crushing. If, however, cushioning or filling in space is needed as in expansion/contraction joints, low
compressive strength materials are specified.
l. Fire retardancy: Flame spread and smoke developed ratings are of vital importance; referred to as "surface
burning characteristics".
m. Resistance to ultraviolet light: Significant if application is outdoors and high intensity indoors.
n. Resistance to fungal or bacterial growth: Is important in all insulation applications.
o. Shrinkage: Significant on applications involving cements and mastics.
p. Sound absorption coefficient: Must be considered when sound attenuation is required, as it is in radio
stations, some hospital areas where decibel reduction is required.
q. Sound transmission loss value: Significant when constructing a sound barrier.
r. Toxicity: Must be considered in the selection of all insulating materials.
The following is a general inventory of the characteristics and properties of major insulation materials used in
commercial and industrial installations. See the Insulation Property Tables at the end of Section 2 for a comparative review
Calcium silicate insulation is composed principally of hydrous calcium silicate which usually contains reinforcing
fibers; it is available in molded and rigid forms. Service temperature range covered is 35°C to 815°C. Flexural and
compressive strength is good. Calcium silicate is water absorbent. However, it can be dried out without
deterioration. The material is non-combustible and used primarily on hot piping and surfaces. Jacketing is field

a. Glass: Available as flexible blanket, rigid board, pipe covering and other pre-molded shapes. Service
temperature range is -40°C to 232°C. Fibrous glass is neutral; however, the binder may have a pH factor.
The product is non-combustible and has good sound absorption qualities.
b. Rock and Slag: Rock and slag fibers are bonded together with a heat resistant binder to produce mineral
fiber or wool. Upper temperature limit can reach 1035°C. The same organic binder used in the production of
glass fiber products is also used in the production of most mineral fiber products. Mineral fiber products are
non-combustible and have excellent fire properties.

Available in board and block form capable of being fabricated into pipe covering and various shapes. Service
temperature range is -273C to 200°C and to 650°C in composite systems. Good structural strength, poor impact
resistance. Material is non-combustible, non-absorptive and resistant to many chemicals.

Insulation material composed of natural or expanded perlite ore to form a cellular structure; material has a low
shrinkage coefficient and is corrosion resistant; non-combustible, it is used in high and intermediate temperature
ranges. Available in pre-formed sections and blocks.
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