James R. Stringer
(Reference: Power Engineering Third Class Edition 2.5; Part A2; Chapter 5: Steam Traps, Water Hammer, Insulation)
Insulation around piping or fittings is used to minimize the amount of heat lost to the surrounding environment. Along with this, insulation acts to prevent the temperature within a mechanical room from becoming too high, as well as acting as a buffer to prevent injury to a person who would contact a hot surface without insulation.
The best insulations have a high insulating value, long life, non-corrosive, retain its shape and insulation values when wet, easy to install, and can defend against vermin and pests.
Thermal Conductivity
A material’s coefficient of thermal conductivity (its “k” value) is the measurement of how much heat will be transmitted through that material. By conduction, the amount of heat transferred is proportional to the cross-sectional area and temperature gradient of a body. The heat transferred would be inversely proportional to the length of the path of heat.
K-value is dependent on the temperature the insulation is exposed to. A K-value at 150 degrees Celsius may be higher at a temperature of 500 degrees Celsius. This is also expressed as the K-factor, which increases for an increase in average temperature.
K-Factor is generally the term used for the coefficient of thermal conductivity and is the measure of an insulation to conduct heat. The lower the K-Factor, the better the insulation capabilities. Insulation will normally have a K-Factor less than 1.
R-Value is another term for the insulating capabilities of insulation. It is the inverse of the K-factor and can be expressed as the insulation’s ability to resist or restrict heat flow. The higher the R-Value, the greater the insulating ability.
Brief Explanation of a Selection of Pipe Insulation Materials
| Name | Service Temperature | Notes |
| Calcium Silica | 38-650°C | Flexible, water absorbent, non-combustible |
| Glass Fibre | Up to 454°C | Non-combustible, water absorbent |
| Mineral Fibre | Up to 1040°C | Rock/slag wool, neutral pH, non-combustible, sound control |
| Expanded Silica (Perlite) | Medium to high | Volcanic rock, low shrinkage, resistant to corrosion, non-combustible |
| Elastomeric | Up to 104°C | Cost-efficient for low temperature, resilient |
| Foamed Plastic | -183 to 150°C | Light weight, moisture resistant |
| Refractory Fibre | Up to 1650°C | Ceramic fibres, thermal shock resistant, non-combustible |
| Insulating Cement | Up to 1038°C | Lower temp ranges and finish other insulation applications |
| Reflective Metal | Up to 1040°C | Baffled stainless steel, reflects radiant heat, small heat conduction |
Pipe Insulation Styles
Insulation is normally held together by metal wire or bands and can be covered with sheet metal (aluminum or galvanized steel).
Wrap and Clad is where half-cylindrical insulation is wrapped around a pipe and bound with wire or bands. Light canvas or linen covering may be pasted down and then painted which helps protect against vapour (corrosion) and helps prevent insulation from getting wet. The paint would generally reflect the piping that is being insulated (for example: red for hot water heating, blue for cooling, green for condensate). If needed, cladding of aluminum or stainless steel is used to wrap around the insulation which offers added corrosion protection as well as protects against damage while further reducing heat losses.
Molded insulation is available in standard sizes and forms around a pipe and its fittings. Well used for pipe elbows.
Insulated Blankets are easy to install and readily removed for maintenance. These are easy to use with oddly shaped components (steam traps, valves, etc). They can be used with high temperatures but do not fit tightly or provide a seal to a pipe, so they should not be used if corrosion is a concern.
Insulated Covers and Boxes are used when there are odd shaped fittings that must be insulated. These covers and boxes may be screwed together or held with clips for easy removal and are usually used when regular maintenance is required on valves, steam traps, and other fittings.
The life expectancy for insulation should be kept as long as possible. This can be accomplished as long as we avoid the insulation from getting wet, replace the insulation after servicing, remove and replace damaged insulation, and have workers avoid walking on piping or the equipment.
Wet and cracked insulation loses its ability to insulate and reduces its effectiveness. Generally, after a water leak or a flood in a mechanical room, deteriorated insulation is treated as an afterthought and left as is. Damaged insulation that is not replaced will reduce the effectiveness of systems; this means that equipment may have to work harder than it should, translating in more wear and tear on motors or pumps for example. The systems that have lower efficiency may not be able to serve occupants appropriately and result in an increase in complaints. A heating system with exposed piping can pose an increased danger to workers in mechanical areas and every opportunity for correction should be taken.
For example, refrigeration lines that have exposed piping to outside elements on a hot day will gain heat before it reaches the evaporator, thus lowering the effectiveness of heat transfer through the cooling coil. A combination of this exposed piping, with a dirty/plugged condenser coil, damaged fin coils, and/or condenser fans not working properly, may cause refrigeration compressors to go into alarm – possibly due to high head pressure. If this happens, a building can get very hot, very quickly.
Bonus Pic!
