Insulation Jacketing Information
Insulation jacketing consists of an outer covering that is wrapped around tubing or pipe insulation to protect the insulation from moisture, wear and mechanical damage. The jacket also serves to provide support for the insulation and establish the system emissivity and appearance. Insulation jacketing plays an important role in the efficiency of the insulation.
The type of jacketing used depends on the mechanical, chemical, thermal, and moisture conditions of the installation as well as cost and aesthetics requirements.
Insulation Jacketing can be broken into six functional groups.
- Weather barriers
- Vapor retarders
- Mechanical abuse coverings
Metal jackets are manufactured from metal sheets such as aluminum, stainless steel, coated steel, aluminized steel, Galvalume® steel, and zinc galvanized steel. Metal jackets come lined with bonded craft paper or surlyn. The continuous paper or surlyn thermoplastic liner is bonded to the inside surface of the jacket. This protects the metal from moisture corrosion.
Aluminum sheets are widely used in fabricating metal insulation jacketing. Aluminum has light weight and good corrosion resistance. The disadvantage of aluminum is that is has poor durability when exposed to heat. The material can have a smooth, embossed and corrugated surface finish. Smooth finishes have a more attractive and easier to clean surface, however, they show surface wear. Embossed finishes do not show surfaces damages but they do hold contamination easier than smooth surfaces. Corrugated surfaces are available in a variety of sizes and are stiffer than other jacket materials. The disadvantage of a corrugated surface is that water can collect on the top surface which can then penetrate into the insulation.
Stainless steel jacketing is often used in chemical plants to protect the underlying insulation and pipe from the corrosive fumes and leaking chemicals and other environmental conditions. This material is also used when there is a potential for fire because it melts at a much higher temperature and will remain in place much longer than aluminum. Stainless steel is more expensive than aluminum but it provides superior protection against fire and corrosion and is therefore the most commonly selected insulation jacketing material.
Zinc galvanized steel can be used in similar application as stainless steel, however, the zinc coating will most likely melt in the fire. This may cause metal embrittlement to the nearby stainless steel surfaces.
Design Tip: In addition, coatings, gels, or vapor barriers are often applied between the insulation and piping to protect the piping from corrosion under insulation (CUI) effects.
Polyvinyl chloride (PVC) is the most common plastic jacketing material used. If the insulated ducting or piping runs outside, then a weatherproof cladding of aluminum or UV resistant plastic might be selected to provide and maintain protection against weather conditions such as vapor, rain, wind, snow and UV/sunlight. PVDC plastic films such as the Saran® films from Dow Chemical are also being applied as protective jacketing materials or vapor barriers. Some of the Saran® films are only a few millimeters thick. They are used for low-temperature applications, and where cleanliness is important. Thermoplastic jackets are resistant to a wide variety of chemicals and are not damaged by water; however they cannot be used when there is risk of fire.
Foil-film laminates such aluminum service jacketing (ASJ) combine the mechanic wear, heat and tear resistance of aluminum with the vapor and chemical resistance of a plastic film. Foil scrim polyethylene (FSP) laminate adds a reinforcing layer of reinforcing fiberglass scrim to the construction. Another laminate, foil scrim kraft (FSK) consists of a thin layer of aluminum foil, glass fiber reinforcing scrim, and low cost Kraft paper. The foil laminates are often pre-applied to the outer layer of insulation batting.
Fiberglass cloth or silicone coated fiberglass jacketing or encapsulation cloth is used in some application with higher environmental conditions. In certain applications requiring higher cleanliness, hygiene, sanitation, or waterproofing; fiberglass reinforced plastic panels, multi-ply laminates or synthetic rubber laminates are used.
Fabric can be used at insulation jacketing. Fabrics have the advantage of being able to cover complicated shapes, and provide a flexible, removable, and reusable insulation. The disadvantages include reduced durability when compared to metal jackets.
Low density results in poor mechanical and wear properties. Metal cladding or plastic jacketing provides protection against impacts, tearing, snagging of the soft insulation under the covering.
Open porosity of some insulation materials can soak up water like a sponge, which would negate the layer's thermal barrier characteristics.
Different configurations of insulation jacketing are available depending on where the insulation occurs in the facility.
- Roll jacketing is used on long lengths of insulated piping or ducting because the insulation can be covered by unrolling the jacketing material and wrapping the insulation. This type of jacketing is used on moderately sized process equipment.
- Sheet jacketing is used on towers, large tanks, pressure vessels, industrial ovens, industrial furnaces, process dryers and other larger process units. Sheet jacketing, also known as corrugated jacketing, is used to cover the large flat surface of the process equipment.
Preconfigured jacketing can be used for valve, fittings and pumps for the specific shape such as elbow fitting covers, tee fitting covers and valve jackets.
Split sleeve type jackets or covers, which often have an integral insulation layer, are used on short lengths of pipes. The split sleeves are held together with banding or straps.
The video below explains the benefits of mechanical insulation.
Video credit: Bmamediagroup1
Adhesive, clips, ties, banding, strapping, springs or other fasteners are used to install and hold the jacketing material securely in place around the insulation. The video below explains various ways to install insulation jacketing.
Video credit: Generalinsulation32
- Permanent installation design: This type of jacketing cannot be removed without destroying the covering (such as adhesive-bonded roll jackets or sheet).
Removable or reusable: This type of jacketing is useful in applications with piping systems that need to be modified or changed out of different process operations. Clips, bands, springs and other mechanical fasteners are typically used on the removable insulation jackets.
Industrial Insulation Jacketing (Insulation.org)