Piping systems, tanks and structures are insulated and the purpose of the insulation is defined by the function.

 

Fire insulation

The main purpose is preventing or delaying the loss of integrity of pipes or structures due to fire.

 

Thermal insulation

The main purpose is ensuring optimal operation and/or protection of personnel. It is often distinguished between heat preservation, cold preservation, frost protection, anti-condensation/icing and personnel protection.

 

Noise insulation

Used for the purpose of reducing noise loads on personnel.

 

Insulation of penetrations

Use deck and walls to prevent the spread of fire between areas. In some cases the same insulation solution will have several desired functions.

 

The industry uses extensively insulation classes e.g NORSOK M-004 or other client specific requirements. The insulation is formed in many variants depending on it function and the object to be insulated. An example of typical build-up on a pipe is shown in Fig. 1. In this case there are two layers of insulation where the outermost layer is covered with aluminium foil and protected with stainless steel cladding. The layers may have different function, e.g. thermal insulation and fire insulation. The aluminium foil has a function of protecting the second layer while the cladding protects against water ingress and/or external fire load from the environment.

 

 

All material consists of atoms and molecules that are constantly in motion. The movements of atoms and molecules create thermal energy. In a warm material, the molecules move faster compared to cold materials. In a body that gets colder, the molecules/atoms move slower until they stop at the "absolute zero point", which is - 273.15°C.

Heat is energy that moves from one location to another due to the temperature difference. Heat conduction is the transport of heat through a substance. This occurs when the temperature is not equal throughout the substance. Heat is always transferred from an object with a higher temperature to an object with a lower temperature, and never the other way around.

 

All substances consist of atoms and molecules that are in constant motion. This movement allows the body to have heat energy or thermal energy.

 

Transfer of heat energy can take place by:

• Conduction
• Convection
• Radiation

 

Most often, the heat energy is transmitted using all three at once.

 

Conduction or thermal conduction is heat transfer that occurs by transferring heat from molecule to molecule in the material.

 

Metals and other massive materials have great molecular density and conduct heat well, while air and other gases conduct less heat due to their low molecular density.

 

Heat transfer through convection occurs by flow in gases or liquids. For example:

• When heating water, it can be seen that the warm water rises and mixes with the colder water above, i.e. natural convection. Forced convection is flow created by a fan, pump, etc.

 

Heat transfer by radiation is energy transfer through electromagnetic rays (infrared radiation, visible light or ultraviolet radiation). It is thermal energy from radiation from an object due to the temperature of the object. The thermal energy is converted into electromagnetic waves that propagate through the area. When the electromagnetic waves hit another body, the waves convert back into thermal energy.

 

The coefficient of thermal conductivity is called Lambda. (λ value)

 

The Lambda value, also called heat conduction or heat conductivity, is a number that expresses how well a material insulates. The lower the λ value of the material, the better it insulates. The unit is set in W/m·K (Watt/meter· Kelvin). The materials λ value indicates the amount of heat, which within an hour is led through a material of 1m,² with a thickness of 1m, when the temperature difference between the two surfaces is 1°C.

 

• The SI unit for heat is Joule (J)
• The SI unit of temperature is Kelvin (K)

 

 

Kelvin

Kelvin is the basic SI unit for measuring temperature and is one of the seven basic units of the SI system. The symbol for kelvin is K. The scale is defined from the absolute zero point, so that zero kelvin corresponds to this temperature.

K = °C + 273,15

°C = K − 273,15

 

The Kelvin scale is parallel to the Celsius scale, so a temperature difference of 1°C corresponds to a difference of 1K.

0­K = - 273,15°C

1­K = - 272,15°C

 

Factors affecting the heat conduction value is the type and build-up of the insulation material, humidity and temperature.

Factors affecting the heat conduction value is the type and build-up of the insulation material, humidity and temperature.

 

Type and build-up of insulation material

Insulation material consisting of cells or fibers that has gas and air enclosed in the cells or between the fibers in the insulation material. The volume/size of the air pockets greatly affect how good the material insulates. Small contact surfaces between the fibers will result in low thermal conductivity and good insulation ability.

 

Humidity
Liquid conducts heat better than gas. When an insulating material becomes wet or moist, the thermal conductivity ability will be affected. This means that a wet/moist insulation material conducts heat better than a dry material, thus, a wet/moist material will have higher thermal conductivity and worse insulation properties.

 

 

 

The lower the λ value, the better the insulation properties of the material. From the table below you can see that e.g. rock conducts much more heat than, for example, air. A good insulation material has low thermal conductivity at the operating temperature the material shall be used.

 

Some materials and their λ values

Material	W/mK
Aerogel	0,017
Air	0,024
Glass wool/Mineral wool	0,03 - 0,04
Cork	0,07
Snow	0,05 - 0,25
Wood	0,1 - 0,2
Vacuum	0,006 - 0,008
Water	0,5
Ice	2
Rock	2 - 4
Cast iron	55
Copper	401
Diamond	900

The U-value tells us how much heat passes through a material or heat loss. The heat loss is indicated in the Joules per second, or the number of Watts per m² of the material, when the temperature difference between hot and cold side is 1K. The lower the U-value of a material, the better the insulation capacity of the material. The U-value is also called coefficient of thermal transmittance.

 

Material	U-value W/m2K
Single layer window	5,7
Sealed 3-layer window	1,5
Mineral wool 50 mm	1,9

 

Specific thermal (heat) capacity – example calculation

Heating 2 liters of water requires double amount of heat as needed for 1 liter. This means that the heat capacity of a substance is proportional to the mass of the substance.

 

Q = c × m × ( T2 - T1 )

 

50 kg of Mineral wool is heated from 20 °C to 60 °C. Specific heat capacity of the material is 0.8 kJ/kg K. How much heat is supplied?

 

M = 50 kg

T_{2 ^-} T₁ = 60 – 20 = 40 K

c = 0,8 kJ/kg K = 800 J/kg K.

 

Our calculation will then be:

Q = 800 x 50 x 40 = 1600000J = 1600kJ

In the oil and gas industry, insulation is largely motivated by the following three main topics:

• Fire safety
• Process conditions
• Health, safety and environment (HSE)

 

Ensuring fire safety

• To prevent an uncontrollable fire from becoming critical, the components and process equipment are protected with fire insulation
• The fire insulation shall ensure that protected structure, pipelines and equipment have sufficient fire resistance in a given fire scenario

 

Fire insulation is typically used for:

• Fire divisions/fire walls
• Penetrations in fire divisions to assure the integrity of the fire division
• PFP (Passive Fire Protection) on pipes and process equipment
• PFP on structures

 

If a fire gets out of control, escape routes can be blocked, personnel can be harmed, evacuation of personnel out of process areas may delayed or impossible, and in the worst scenario, a fire out of control can cause collapse of the structure and installation.

 

PFP is used as a common term for fire insulation by use of insulation materials

 

 

Insulation due to process conditions

• For reduction of heat loss to the environment
• Maintain optimum temperature on the substance
• Reduce possibility of creation of wax or hydrates (plugging)
• Prevent condensation of liquid in a gas
• Reduce heat transfer to the environment
• Avoid freezing
• Prevent external condensation and ice formation.

 

 

Insulation for Health and Safety

Personnel protection

To protect the surroundings and personnel against hot and cold surfaces

 

 

Noise insulation

Reduce noise from ppipes and process equipment.

 

Noise is defined as undesirable sound and are divided into two types:

• Irritating noise from e.g. ventilation system, fan in PC and similar.
• Harmful noise from noisy environment more than 80 dB impulse sound more than 130 dB

 

The frequency of sound is defined as the number of sound fluctuations per second and is measured in Hertz (Hz). Noise level is measured in decibels (dB). A normal conversation is around 65 dB, while a shout reaches about 80 dB. The scale build-up is that every time the sound effect doubles, the decibel level increases by three dBs. The sound effect of 83 dB will therefore be twice as high as that of 80 dB. It's not just the noise level that determines whether a sound is harmful or not. How long and how often you are exposed is also important. Therefore, noise is measured over time. As a rule, measuring noise in the workplace is based on overall noise exposure over an entire working day. Rule of thumb: If the noise level is reduced/increased by 3 dB, you will perceive it as a half/double the noise level.

 

Documenting noise insulation of pipes, flanges and valves should be carried out in accordance with ISO 15665. Noise insulation is done to reduce noise levels of process equipment to the environment. Noise-insulating properties shall be tested. Definitions of sound insulation classes are given in ISO 15665, paragraph 4. The standard specifies the minimum reduction for each class related to the current pipe diameter.

 

Insertion loss gives the effect of the insulation, i.e., the difference between noise before and after insulation. ISO 15665 has high requirements to the noise reduction, depending on the noise frequency. The insertion loss for a insulation class must be fulfilled for all frequencies. All insulation systems shall be tested, and the insertion loss shall be documented in accordance with the procedure specified in chapter 10 of ISO 15665.

ISO 15665 defines the acoustic insertion loss of three classes (A, B and C) of the pipe insulation. It also specifies three types of constructions that will fulfill the acoustic insertion loss requirements. In addition, it defines a standardized test method to measure the acoustic insertion loss for all types of constructions, thus, existing and new constructions can be assessed against the three classes.

 

ISO 15665 applies for acoustic insulation of cylindrical steel pipes and its components. It is valid for pipes up to 1 meter in diameter with a minimum wall thickness of 4,2 mm for diameters less than 300 mm and 6,3 mm for diameters 300 mm and above. This does not apply to acoustic insulation of rectangular ducts or machines.