4.6.1 Existing Condition Of Insulation in Plant:
The steam distribution system of plan is very badly insulated. 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 part of steam distribution system. It is clearly visible that insulation is badly needs repairing and also at some places no insulation is provided, causing great heat loss. The insulation provided on the steam pipe lines is glass wool and thickness of insulation is also not sufficient. 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 control and maintain surface temperature of vessel
• To maintain and control temperature of industrial processes
• To reduce condensation of surfaces
• Improve efficiency of processes like ventilation, plumbing, heating, steam and power system.
• To avoid corrosion or exposure to corrosive atmosphere as well as fire
• 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
• Type of vapor retarder and insulation finishes.
• 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 equivalent insulation thickness and the area of outer surface.