4.6.1 Current insulation condition:
The plant had very badly insulated piping system. Its insulation was done 2 years ago and at present the condition of steam pipe insulation is very poor.
The figure 4.9 shows a photograph piping system. It is visible from picture that insulation is bad and needs repairing and also at some places insulation is missing, causing great heat loss. Glasswool used as a insulator and many places in pipes where the material is not available and it leads to the loss in the heat. So we have collected the data about different insulation material. Also we have given list of local insulation carrying consultancy. Here are some insulation material properties
Fig 4.9 Photograph of part of steam distribution system
Function of insulation are:
• To conserve energy to avoid heat loss or heat gain
• To maintain temperature of system
• To avoid heat loss from heat carrying fluid
• To stop condensation
• To avoid corrosion or exposure to corrosive atmosphere as well as fire
• Process with good efficiency like heating, ventilation and cooling.
• To absorb noise from the mechanical equipment.
Selection of insulation material is very critical and following points should be considered.
Very important. The following design and installation considerations must be noted:
• Type of insulation that is rigid, flexible, ease of handling, installation, and adjustment.
• Ease to modify, repair, and alter.
• Requirement of skilled and unskilled labor.
• Safety & environment considerations.
• Weight of insulation material and density of same
• Replacement and removal should be easy
• Performance of material.
4.6.2 Heat Gain / Loss from Cylindrical Surfaces like Pipes
To evaluate the heat gain or loss from the cylindrical surfaces it has different equation from than the equation for the flat surfaces. The heat will be transferred to pipe wall through the flowing material and after that heat will be absorbed by the atmosphere. In case of insulation the heat dissipation will be less in atmosphere.
It is not possible to calculate exact amount of heat dissipated since it is affected by:
• Color, texture, and shape of the casing.
• Vertical or horizontal orientation of the casing.
• Air movement or wind speed over the casing.
• Exposure to thermal radiation, e.g. sunlight – all of these in addition to the temperature
• Parameters, etc.
Because of the number of complicating factors, generalizations must be utilized. The theoretical methods for calculating heat transfer for pipe or any other cylindrical objects like tanks, is depends on the thickness of insulation and the area of outer surface.