Pipe Insulations are materials or combinations of materials wrapped around the pipe which retard the flow of heat energy. Pipe insulation reduces energy losses to a great extent and thereby reduce the energy cost. Piping shall be insulated as per the insulation class, operating temperature, and insulation thickness stated in the P&ID.
Functions of Pipe Insulation
A piping insulation system serves three principal purposes:
- the significant reduction in heat transfer of thermal energy to and from the surface of the piping system (Heat Conservation). So, piping insulation conserve energy
- the prevention of moisture formation and collection on the surface of the piping system due to condensation on cold surfaces (Cold Insulation).
- the prevention of potentially injurious personnel contact with the surface of the exposed piping system (Personal Protection).
However, there are various other benefits of piping insulation as listed below
- Piping insulation facilitates temperature control of the process.
- Prevent vapor flow and water condensation on cold surfaces.
- Increase the operating efficiency of heating/cooling, power, and process systems.
- Reduce major damages in the piping during fire or accidents.
- Prevent pollutant emissions to the atmosphere to a great extent.
- sometimes Steam traced/Electric traced insulation, Regeneration insulation, jacketing, etc are used as per process/licensor requirement.
- Fireproofing, fire protection, and acoustic insulation (to absorb vibration) are provided based on project specification/ ITB requirements.
Pipe Insulation Types
Piping insulation can be classified based on various parameters like
- Based on Pipe Insulation function
- Hot Insulation
- Cold Insulation
- Personal Protection Insulation
- Acoustic Insulation
- Based on Insulation Material Types
- Fibrous Insulation
- Cellular Insulation
- Granular Insulation
Piping Insulation Types Based on Function of insulation
Hot insulation is applied on the hot surfaces of the piping system to prevent the energy flow from flowing fluid. So, main aim of hot piping insulation is heat conservation. Mineral Wool, Glass Wool, Calcium Silicate, etc are normally used as Hot insulating material.
Cold Insulation is the insulation used on cold surfaces of the piping system to avoid heat gain from outside (Cold Conservation) or to avoid Condensation. Polyurethane Foam, Expanded Perlite Foam, Expanded Polystyrene Foam, etc are the widely used cold insulating materials.
Personal Protection Insulation
Personal Protection insulation is provided to avoid personal heat injury. All exposed piping surfaces that exceed 65 Deg C is provided with personal protection insulation. The areas that are not accessible by construction or operating personnel can be left exposed. An open mesh metal guard (Fig. 2), mineral wool, etc are used as personal protection insulation material.
The criteria for personal protection is that the exposed surfaces located within 600 mm horizontally or 2100 mm vertically of a normal access, walkway or work area are to be insulated.
Acoustic Insulation is provided for all piping that are considered as a potential sound source. The main purpose is to reduce the noise (vibration) to an acceptable limit. The minimum thickness for acoustic insulation is normally 75 mm. Acoustic Foam, fiberglass, polyester/polyurethane foams , rockwool, Mass Loaded Vinyl, etc are used as Acoustic Insulating material.
Piping Insulation Types based on insulation material types
Fibrous insulation consists of small diameter fibres which finely divide the air space. The fibres may be perpendicular or parallel to the surface being insulated, and they may or may not be bonded together.
Common fibres used in piping insulation are Silica, slag wool, rock wool, and alumina-silica. Among these, Glass fibre and Mineral Wool are the two most widely used piping insulations of this type. Their fibres are normally bonded with organic binders for structural integrity.
Cellular pipe insulation material comprises small individual cells separated from each other. Common cellular material used as pipe insulation is glass or foamed plastics such as cellular glass, phenolic foam, or nitrile rubber.
Small nodules containing voids or hollow spaces constitute the granular insulation. As gas can be transferred between the individual spaces, It is not considered a true cellular material. This type is manufactured as loose or pourable material or combined with a binder and fibers. Sometimes they undergo a chemical reaction to form rigid insulation. Calcium silicate and vermiculite are examples of these types of insulations.
Pipe Insulation Material
- Low-temperature insulation is frequently made of expanded cellular plastic or foam rubber material.
- Moderate temperature insulations are made from grass fibre products.
- High-temperature insulation is made of preformed cementations or refractory materials or blankets made from ceramic fibres.
- Insulation and accessory materials have to be 100% asbestos-free.
- Normally mineral fibre, cellular glass, ceramic fibre, glass fibre, polyisocyanurate, polyurethane foam etc are used as insulation material.
The following table provides details of few commonly used insulation materials:
|Pipe Insulation Material||Density (kg/m3)||Temperature Limitation|
|Mineral Glass Fibre||up to 535°C|
|Mineral Wool||140||up to 700°C|
|Rock Wool||140||up to 550°C|
|Glass Wool||80||up to 450°C|
|Calcium Silicate||200-280||up to 815°C|
|Expanded Perlite||192||up to 550°C|
|Expanded Silica||up to 535°C|
|Refractory Fiber||150||up to 1750°C|
|Polyurethane Foam||40||from -150°C to 110°C|
|Polyisocyanurate||40-64||from -150°C to 125°C|
|Cellular Glass||147||up to 350°C|
|Ceramic Fibre||250||up to 760°C|
Piping Insulation System
The main part of the Piping insulation system is the insulating material. Other elements that constitute the pipe insulation system are
- Protective Coating
- Vapor Barrier
- The cladding of the metallic sheet.
- Spacers to enable cladding to retain its shape.
- Packing to fill the cavities or voids, if any.
Pipe Insulation Forms
Insulations are manufactured in a variety of forms to suit specific applications and functions. The installation method is decided by the combined insulation form and type of insulation. The most widely used insulation forms are:
- Rigid boards, sheets, blocks, and pre-formed shapes: Cellular, granular, and fibrous insulations are produced in these forms.
- Flexible sheets and pre-formed shapes: Cellular and fibrous insulations are produced in these forms.
- Flexible blankets: Fibrous insulations are produced in flexible blankets.
- Cement (insulating and finishing): Produced from fibrous and granular insulations and cement, they may be of the hydraulic setting or airdrying type.
- Foams: Poured or froth foam used to fill irregular areas and voids. Spray used for flat surfaces.
Normally, Rock and Glasswool are preformed in two halves; Polyisocyanurate, Polyurethane, Cellular Glass are supplied in preformed cylindrical shapes to slit in half lengthwise and ceramic fibre is supplied in blanket strips.
Piping insulation Standards
The following codes and standards provide guidelines for industrial piping insulation:
- ASTM C533, ASTM C547, ASTM C552, ASTM C591, ASTM C592, ASTM C610, ASTM C612, ASTM C795, ASTM C892, ASTM C165, ASTM C240, ASTM C302, ASTM C303, ASTM C335, ASTM C356, ASTM C390, ASTM C446
- BS 1902 Part 6, BS 4370 Part 2, BS 5608
- IS 11239, IS 12436, IS 9428, IS 8183, IS 4671, IS 3690
- ISO 15665
Piping insulation thickness Calculation
Few important points related to piping insulation (May vary from project to project):
- Insulation thickness is determined based on pipe size, normal operating temperature, temperature controlling requirement (extent of heat loss/gain), etc. At a minimum 25 mm thickness is used.
- If insulation thickness is more than 75 mm then insulation is provided in two or more layers (multi-layer).
- Insulation shall not be applied until hydrostatic/ pneumatic testing.
- Insulation up to 12 inch NPS pipe shall be held with ss 304 tie wire and for >12 inch NPS ss 304 bands are used.
- All flanges will be insulated other than hydrogen service or high health hazard material services.
- All valves other than control valves and relief valves shall be insulated.