Pipe Material
Pipe Properties
1. MECHANICAL PROPERTIES
Mechanical properties of pipe and pipe fittings are very important since it defines the response and the behaviour of pipe material to the applied force. The followings are the brief explanation of the properties:
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1. MODULUS ELASTICITY 
Modulus Elasticity is the ratio of normal stress to the corresponding strain for tensile and compressive stress in elastic region. This ratio is linear through a range of stress, known as Hooke’s law. 
The material behavior in this range is elastic (meaning that if the applied load is released the material will return to its original shape). The value of the slope in the elastic range is defined as Young’s Modulus, which measured using tension test. 
Young’s Modulus, named after a British doctor, physicist, and Egyptologist, is a measure of the elasticity of the material. Young Modulus has a symbol of E. As you can see from the below table, the value of Young Modulus varies with temperature. The higher the temperature, the softer the material, and the lower its Young’s Modulus.
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2. STRESS – STRAIN
σ = E ε 
Where, σ = Stress, Psi. E = Young’s Modulus, Psi. ε = Strain 
Stress is defined as the ratio of applied force per unit area, or F/A, while Strain is deformation of material due to stress. Below graph will show the releation between σ and ε. It can be seen that the Strain increases when Stress changes until it reaches the Yield Strength and eventually to the Ultimate Strength before fracture.
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The table that showing the value of Yield Strength and Tensile Strength for some common material use in piping system, which was taken from ASME B31.3, is available on the Material Tab on this lesson.
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3. ELONGATION AND REDUCTION OF AREA 
Percent Elongation is a measurement of how much the material will deform plastically and elastically before it rupture. It basically measures the ductility, where it relates to the amount of straining that a material undergoes when subjected to a stress. 
Because, whenever the material experiencing strains, then it will also decrease the area of cross section, which called as Reduction of Area (RA). Below is the formula to calculate two of those changes, where Ao is the original cross section area, Af is final cross section area, L is the final length and Lo is the original length. 
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2. PHYSICAL PROPERTIES
The knowledge about physical properties of pipe and pipe fittings material are very important for piping engineer in performing his task, whether as piping material engineer, pipe support engineer or as piping stress engineer.
One other thing needs to be considered is the fabricability characteristics such as the ability to be bent or formed, suitability for welding or other methods of joining, ease of heat treatment, just to name a few.
There are four (4) physical properties of pipng material in this lesson:
 Density
 Thermal Conductivity
 Thermal Expansion
 Specific Heat
1. DENSITY 
Density is one of the physical parameter which plays an important role in all material states, whether solid, liquid, or gaseous. Density is the ratio of the mass of a material to its volume. The formula is: ρ = m/V, with unit of density as kg/cm^{3} or lb/in^{3}. 
2. THERMAL CONDUCTIVITY 
Thermal Conductivity is the ability of a material to transmit heat from a hightemperature source to a lower temperature and usually expressed as a coefficient of thermal conductivity, k. The lower the value of k, the more resistant the material is to the flow of thermal energy. Good insulators possess low coefficients of thermal conductivity. 
Thermal conductivity depends on the temperature of the material. For example, the coefficient of thermal conductivity of carbon steel decreases as its temperature increases, which in turn decreases its ability to transfer heat energy. Meanwhile Austenitic stainless steels, the thermal conductivity will increase when temperature increase.
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The following is the value of Density and Thermal Conductivity for some of piping material commonly used in Oil and Gas Industry:
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3. THERMAL EXPANSION 
Thermal Expansion is the coefficient of linear expansion of material. It is a ratio of the change in length of material per degree of temperature, compare to a length at a given standard temperature (such as room temperature, or the freezing point of water). See formula below. 
The units of the coefficient are the length of growth per unit length per degree of temperature. Since it depends on the temperature, then the value of the coefficient varies with temperature. This coefficient of thermal expansion is critical in the flexibility analysis of the piping system, as shown on down below table. 
Δ L = α L Δ T 
Where, Δ = Change of Length, in α = Coefficient of thermal expansion of the material, 1/^{o}F. L = Length of Material, in Δ T =Temperature Change, ^{o}F. 
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4. SPECIFIC HEAT 
Specific Heat is a measure of the quantity of heat required to raise a unit weight of a material one degree in temperature. It basically the ratio of a material’s mass per unit volume to that of water. 
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3. ELECTRICAL PROPERTIES
Electrical Properties of piping material is basically the characteristic of a pipe metal that enables the flow of electric current through or in other words to conduct electrical current. In this lesson, we will talk about 4 of electrical properties for pipe metal, namely:

1. CONDUCTIVITY
Conductivity is the ability of a material to flow electrons and conduct current through a material. Represented by the symbol kappa and having the greates value in metals, and Copper and Aluminum are the most commonly used due to having the greatest conductivity, where Aluminum has the highest conductance per unit length.
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2. RESISTIVITY
Resistivity is the measure of the resistance to the current flow. Material who has high resistivity do not charge electricity freely and therefore consider to be insulator, such as glass, teflon, rubbes and polymer.
3. CAPACITANCE
Capacitance is the ability of body to store electrical charge. The amount of energy stored is proportional to the amount of stored charge. Capacitors store electrical energy in the form of electric fields between metal plates. The gap can be filled with air or some other dialectric medium such as ceramic, or polymer, which act as insulator as well as increase capacitance.
4. PIEZOELECTRICITY
The piezoelectric property of a material is its ability to store electrical charge as a result of a stress that is applied to it. In fact, piezoelectricity means electricity as a result of pressure. Material who has piezoelectric property normally have a high elastic modulus.
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