Insulation is provided primarily to reduce the heat loss from equipment. Insulation is provided for personal protection, also. Insulation is generally provided on the out side of the piping. Outer casing of light thickness (1.6mm) is provided to protect the insulation. The insulation is made of fibrous materials, such as slag wool, mineral wool and glass wool. Outer casing is made of aluminum or galvanized iron (GI) sheets. Thickness of the insulation is calculated considering heat loss and personal protection considerations.
Refractory is made of refractory clay. Refractory is applied on the inner of the piping. Refractory is applied to reduce pipe metal temperature and improve economics. Inner casing (liner) is provided to retain the refractory in place. Where the pipe inside temperature is high (above 700 Degree C), insulation retainers are provided. Insulation retainers can be welded with the pipe inner or bolted.
The following gives the calculation for loss of heat through the piping insulation (hollow cylindrical shape):
Q = heat transferred, kcal/hr
Dt = temperature difference, Degree C
R = resistance for flow of heat, hr - Degree C/kcal
L = Length of pipe, m
Ti = pipe inside fluid temperature, Degree C
To = pipe outside ambient temperature, Degree C
Hi = convective heat transfer co-efficient inside pipe,k cal/hr-Degree C-sq m
Ho = convective heat transfer co-efficient outside pipe, k cal/hr-Degree C-sq m
K1 = thermal conductivity of pipe material, k cal/hr-Degree C-m
K2 = thermal conductivity of insulation material, k cal/hr-Degree C-m