Document RaXVw1XYk9EDJ6v2wXk0zLy97

Sphere coated with Vi-Cryl (CP-10), a chemical resistant weatherproofing coating, and tower, deep corrugated aluminum sheets. Also various accessory products--pre-fabricated firrint covers, strapping, a id wing seals. Insulation Practices: Protection of Thermal Insulation o v_3 cn Insulation protection cart be provided by metal jacketing, mastic coatings, or a combination of both, depending on the application, service, and economics. J. B. Marks and K. D. Holton Childers Products Co., Inc., Cleveland, Ohio It h.*> neen pro', en "'.v. :: .u: ,a:.v cr-ts ie-s to properly in01 .o:v proceo- ve-sr.; p.peo . ti:e. and flangeo. and theri 'n-erv e er.trr-. tr.-m tv . 1.te r.-: -upph j;:., on: add;::.oval he n;r; or coo.mg capae;M to cover tne ! - . r cam ,{ heat. Toe ratal m.?.,..a'.:or. :s. tneretore. a Iona nm investment In the pre-erst energy crii:.- :: be- evro even more, it bee :r?. a aef.rre neces^.ty and an cbl mm tion of some type, he it against ram. srmvv. sleet. wine., uitnviviet soiar radiation, mechanical cam,age, vapor parage, tire, chemical ravages, or any combination of ~ese. Protection can be provided in the form of meta! picketing, mastic coatings, or a combination of both, depending upon the application, service, and ocunom.c remomements. In view of the overall cost of a new lacbitv. and tne initial co't of the insulation y. 'tew, as a percentage ot 46 ; it 1974 CHEMICAL ENGINEERING PROGRESS V;| 70, No 3; ST0658896 that overall cost compared with the increased operating costs due to inefficient insulation protection, it is common sense to provide only the best protection for that long term investment, consistent with the .appropriate design and economic requirements. This article will outline just that type of protection--that is, the best available for the particular application consistent with the appropriate de sign requirements. Metal jacket system characteristics Prior to the use of metal jacketing systems, refinery and similar pipelines, vessels and tanks were covered with asphaltic roofing papers. This system offered vir tually no weather, mechanical, or fire protection. The use of 55 lb. roofing fell held with tie wire did not offer much improvement. Metal jacketing met the requirements of a more efficient, more protective and more esthetic insula tion covering. Aluminum was the first metal to be used as jacketing material. In alloys 3003, 5005, and 5010, and tempers H14 through H19, it is still the most widely used product for general purpose industrial installations, but is not recommended for use in areas requiring chemical resis tance under alkaline conditions. Its advantages are low initial cost and easy workability. Its disadvantages are low chemical resistance in pH range 7-11, low mechanical strength, and low fire resistivity, no load factor at 800'F. -- melts at 1,200'F. Clad aluminum, CAlclad) the result of a mechanical process wherein an aluminum alloy core is coated prior to rolling with an aluminum alloy anodic to the core for its electrolytic protection against corrosion, is a product with slightly better surface chemical resistance than unclad aluminum. Aluminum which has been chemically cleaned, primed with a corrosion inhibitor and then mill-coated with a polyester or acrylic resin offers greater use, flexibility, and somewhat more protection at a higher cost. Its advantages are: coating can be selected to suit the environment, offering improved corrosion resistance; its moderate cost, and easy workability. Disadvantages are that the coating can be abraded relatively easily, and polymer degradation may result in failure. Organosol-coated, electro-galvanized steel (Childer's trade name--Steel Jac) is manufactured from 0.010 in., or heavier. Type 1010, cold-rolled steel. The steel is then chemically-treated, coated on both sur faces with a vinyl acrylic primer and finally topcoated with a vinyl-organosol which is then fused to the metal. Its advantages include excellent mechanical properties, attractive vinyl finish, chemical resistance, and abrasion resistance. Its disadvantages: it is somewhat more costly than aluminum, and the organic coating, though it will not support combustion, will char at incendiary condi tions. Stainless Steel (T304 and T316) is meeting with wide acceptance resulting in large scale usage. Advantages in clude high mechanical strength, high fire retardance (melts at 2,600'F.), excellent corrosion resistance, and excellent weather resistance. Disadvantages are high ini tial cost and susceptibility to stress corrosion cracking in the presence of chloride ions. Moisture barriers frequently needed Soluble salts present in most industrial insulations function as a weak electrolyte when the insulation be comes moisc. The metal pipe and the metal jacketing function as opposite poles, thus a low-voltage, galvanic cell is formed, detrimental to both poles. To prevent this attack at the metal/insulation inter face, the incorporation of an integrally laminated mois ture barrier is highly recommended. Childers Products Co. supplies two types of moisture barrier, each lami nated to 100% of the metal surface on the underside of the jacketing: One is "Poly Kraft'' moisture barrier, con sisting of one layer of 50 lb. virgin kraft paper coated on one side with one mil polyethylene film. The other is a 30-90-30 moisture barrier consisting of a uniform film of pure high-melting, oxidized asphalt, laminated be tween two sheets of 100% virgin kraft paper. Two other types of protective jackets are: "GAF'T/ N'A 100 -Jacketing'' a tough, flexible, flame-, weather-, and chemical-resistant laminate of Tedlar*, Neoprene*, and asbestos. Where a vapor barrier is required, the addi tion of one mil film of Saran (polyvinylidene chloride) to the laminate drops the vapor permeability of the system to 0.05 perms, without sacrificing any of the aforemen tioned properties. Polyvinyl chloride (PVC) jacketing is another tough, flexible system used mainly for its superior chemical resistance and flame retardance. Its limited service tem perature range and lack of dimensional stability detract from its other properties. Mastic systems useful on irregular surfaces The choice of the material used to protect the insula tion may be governed by the size, shape, and location of the insulated surface to be protected. Materials which cling to the surface by adhesion facilitate the installation of a protective covering to large, irregular surfaces offer ing no ready means of securement. Mastics may be applied by spray, brush, or trowel to large, flat surfaces which will not easily accommodate metal jacketing. They may be used in conjunction with metal jacketing in situations such as flashing between two adjacent surfaces, or around irregular shapes such as fittings, valves, etc., because they lend themselves to easy application in these areas. A weather barrier coating is applied to the outer sur face of thermal insulation primarily to protect it from the ravages of weathering. It is designed to prevent water (rain, snow, sleet, spillage, wash water, etc.) from enter ing the insulation system. There are, however, many ad ditional benefits. The tough flexible films provided by vinyl acrylic breather coatings (a breather coating is one through which vapors under pressure will pass), also afford protection from mechanical damage, chemical at tack, and fire. Mechanical damage can result from external forces in the form of shear, abrasion, impact or compression, which may occur when a sharp object is dropped, when the surface is walked on, or even from extreme weather conditions. Damage may also result from internal forces due to thermal expansion and contraction, differential movement, or vibration. An appropriate weather barrier can protect the insula tion from chemical attack of acids, alkalis, solvents, and salts, either airborne or from intermittent spillage, as well as from the effects of oxidation, infrared and ultraviolet radiation. Weather barrier coatings can even be properly formu lated and compounded so as to have a minimal contribu tory effect on the stress-corrosion cracking of austenitic stainless steel resulting from the presence of halogen ions. CHEMICAL ENGINEERING PROGRESS (Vol. 70, No. 8) August 1974 47 Catalytic cracker and alkalation unit at an oil refinery. All piping, vessels, tanks, and towers protected with 3/16-in. corrugated and deep-corrugated aluminum sheets. JL60G^9U1S "Vicryl," a Childers' product, is used both outdoors in hot, cold, and dual temperature service. It is a breather coating, thus it should be used in cold and dual tempera ture installations only in conjunction with a vapor-barrier coating, or where the insulation itself is a vapor barrier. In hot service, a breather coating allows the escape of a minimal amount of water vapor resulting from heat ap plied to the moisture entrapped in the insulation, while still preventing the passage of liquid to the insulation. Glass cloth and other fabric membranes are generally used as reinforcements for weather barrier coatings. In situations subject to severe abuse, chicken wire and other metal-mesh membranes may be used. In cold and/or dual temperature service, the equip ment operates below ambient room temperature at least part of the time. Water vapor in the air seeks to move from the area of high vapor pressure (room temperature) to the area of lower pressure (the low-temperature equip ment). As the vapor passes through the insulation, the closer it comes to the low-temperature equipment, and the colder it becomes. At some point the water vapor reaches its dew-point temperature and condenses to the liquid phase. Closer to the cold surface, if the tempera ture is low enough, the liquid phase may solidify into ice. Because the thermal conductivity of water is consider ably greater than that of air, and that of ice is even greater, the value of the insulation is substantially re duced by the presence of moisture in any form. In dual temperature service, alternate freezing and thawing of the moisture in the insulation may actually destroy the in sulation. All these problems can be eliminated, or at least mini mized, by the proper application of a vapor barrier coat ing to the warm side (outside) of the insulation. Vapor barrier coatings are formulated to afford maximum pro tection from mechanical damage, chemical attack and fire, at the same time preventing the passage of vapor to the insulation. These products, whether brushed, palmed, or sprayed, are normally applied with a fabric reinforcing membrane. However, in some applications the use of membranes only at butt overlaps may be satisfactory. In addition to being used as coatings, they may also be used as joint-sealers and adhesives in special applications. Adhesives, coatings, and sealers must be considered Lagging is the process of insulating piping and cylin drical or rectangular duct work and equipment and then covering the insulating material with canvas, brattice cloth, asbestos cloth, or a similar fabric. Lagging adhesives and sizings are generally white, emulsion resin-based systems which adhere the lagging cloth to the insulation and to itself at the lap joint. They also serve to seal the fabric and secure it tightly to the surface. Combination systems which function both as adhesives and protective coatings are also available. They provide 48 August 1974 CHEMICAL ENGINEERING PROGRESS (Vol. 70, No. 8) somewhat greater protection from mechanical damage, vapor penetration, and chemical attack than the pre viously noted lagging adhesives, and this precludes the necessity of applying another material as a protective coating. The water-based system offers the versatility of a tenacious, permanent adhesive coupled with a tough, highly resistant, yet flexible and attractive coating. Decorative coating and color-coding products are heavy protective coatings that are used over masonry blocks, canvas, glass cloth, etc. bridging the unevenness of the rough surfaces and giving a smooth, tough, flexible, fire resistive finish. These coatings may be applied directly to such mate rials as polystyrene foam, polyurethane foam, cellular glass and fibrous glass. They serve as effective sealer coats over many types of asphalt. Their availability in a full spectrum of colors gives an added advantage of vir tually eliminating the need for painting and continued maintenance. Sealers in insulation work function primarily as water and vapor seals. .In many applications, however, they may also function as adhesives and expansion joints with metal, masonry, cellular glass, etc. The requirements for this type of product include low shrinkage, excellent ad hesion, and permanent flexibility. Many are virtually 100T non-volatile, and they form a skin by oxidation, remaining permanently soft and flexible under the skin. Others contain polymers dissolved or dispersed in vary ing amounts of volatile solvents; these exhibit somewhat greater shrinkage and dry by evaporation of the solvent rather than by oxidation. What a complete system requires Today there are many governmental and private indus try influences specifying, among other things, supplier and user compliance with OSHA, USDA, GSA, and Mil Spec requirements. These specifications include consid eration of the following conditions or questions: Solvent or water based system? Care must be taken that the system will not attack the substrate to which it is applied. It must dry in the time required and under the conditions to which it will be exposed. Toxicity. What is the threshold limit value of each ingredient, and what steps must be taken to prevent exceeding that level? What ts the flammability of the system (in the wet state), and will it create an undesirable hazard9 What is the flame-retardance of the dry film, and will it meet all the necessary requirements? Is the material UL (Underwriters Laboratories) listed? What are its Tunnel Test ratings (ASTM E-84)9 Flame spread9 Fuel-contributed? Smoke-developed? What is its resistance to various mechanical factors, including expansion and contraction, vibration, shear, abrasion, impact, and compression9 Thermal factors: application temperature limits, freeze thaw stability, and service temperature requirements. Chemical resistance factors: acid resistance, alkali re sistance, and solvent resistance Method of application - trowel, brush, or spray. Sample recommendations for eleven different kinds of applications are given in the following. Petrochemicals operation. 0.016-0,019 in. aluminum; 0.019-0.024 in. deep corrugated aluminum on vertical vessels and 0.024 in. smooth aluminum on horizontal vessels. Type 304 stainless steel is to be used in areas where the atmosphere contains curro>i\e vapors of a highly acid or highly alkaline nature. All metal jacketing is to have a moisture barrier. "Vicrvl" is to be used to give protection to any irregular shape or surface where the application of a metal jacketing system is impracti cal. Detergent alkylate unit. Steel Jac with moisture bar rier, or Type 304 stainless steel with moisture barrier, is recommended due to aluminum's intolerance for caustics. (Vicryl to be used where necessary.) Power house. 0.016 in. acrylic-coated aluminum is sug gested for improved appearance. Polykraft moisture barrier is recommended. The acrylic coating facilitates washing down the surface. Food processing. Type 304 stainless steel was once the only recommendation made. However, today more and more aluminum jacketing is being used. T/NA lO'f ap plications are also being used extensively, as are USDAapproved mastic systems. Urea plant. Steel Jac with moisture barrier, or Type 304 stainless steel with 30-90-^0 moisture barrier, is recommended due to the wide range of extremely corro sive acidic and basic process chemicals present (e g., nitric acid, ammonium nitrate). Chlor-alkali plants. Steel Jac with Polykraft moiscure barrier is recommended due to the high degTee of soluble chlorides existing. (Stainless steel is weak under these conditions, and aluminum fails in caustic areas.) Off-site steam lines. Since only weather protection is necessary, aluminum jacketing with Polykraft moisture barrier, or an application of Vicryl, is all that is required. Nuclear containment vessels. Type 304 stainless steel used in conjunction with chloride-free, nuclear grade mastics. Roofing applications over sprayed urethane. A weather-resistant, moisture-resistant, ultraviolet bar rier is required to protect the urethane insulation. SSGfLNG (synthetic natural and liquefied natural gas.) As with all cold piping installations, the application of a vapor barrier coating over the insulation will prevent the passage of moisture vapor from the warm (outside) surface to the cold surface, thereby preserving the in tegrity and utility of the insulation. Aluminum jacketing will do the job in thicknesses from 0.016 to 0.040 in., depending upon the specific requirements. Paper mills. Where formerly Type 316 stainless steel was the only recommendation, it has been found that Steel Jac and Vicryl work well under conditions of inter mittent spillage in areas of white, black and green liquor make-up and storage. # J. B. Marks is a technical director of the Coatings, Adhesives and Sealants Div. of Childers Products Co. Marks attended Brooklyn College, Upsala College and Seaton Hofl Univ. He has been with the Coatings, Adhesives and Sealants Div. of Childers since 1956. K. D. Holton is general sales manager for Childers Products Co. He is a graduate of Lafayette College with a degree in chem istry. He has been active in the thermal insulation industry since 1955. CHEMICAL ENGINEERING PROGRESS <Vol. 70. No 3) Ann..< !OT4