ASHRAE 1997 Publication - Insulation Systems for Refrigeration Systems

This chapter will deal with insulation systems operating in below-ambient temperatures ranging from +50°F to -100°F. This is a guide to specifying insulation systems for piping, fittings, and vessels typically required in these systems.

The success of an insulation system for cold piping is contingent upon several factors which include:

• Correct refrigeration system design;
• Correct specification of insulating system;
• Correct specification of insulation thickness;
• Correct installation of the insulation and related materials such as vapor retarders; and
• Workmanship of the insulation installer.
• Adequate maintenance of the insulating system.

In steam and hot water lines it is common to use a variety of insulation materials. These systems are insulated for the following reasons:

• Heat conservation and/or freeze prevention;
• Process control;
• Personal protection; and
• Fire protection.

These systems have different insulation requirements from systems operating at below ambient temperatures. Refrigeration systems are insulated for vastly different reasons. Some of these reasons are to:

• Minimize heat gain to the refrigerant suction gas and liquid line. This improves efficiency which in turn reduces energy consumption and operating costs;
• Control surface condensation;
• Provide noise reduction; and
• Protect personnel and prevention of unsafe ice formations.

Below-ambient systems are affected by a number of properties that may affect insulation system performance. These properties include:

• Water absorption;
• Water vapor permeability;
• Thermal expansion/contraction; and
• Wicking of water.

Water absorption is the ability of material to absorb and hold liquid water. Water absorption is important on systems that may be exposed to water. This water may come from a number of external sources such as rain, surface condensation or wash down water. The property of water absorption is especially important on outdoor systems.

Water vapor permeability measured in units of perm-inches is an indication of the ability a material to allow the passage of water vapor through it. The lower the permeability, the higher is the resistance of the material to water vapor intrusion. Water vapor permeability can be a critical design consideration because water vapor has the ability to penetrate materials that are unaffected by water in the liquid form. Water vapor intrusion is a particular concern to insulation systems subjected to a thermal gradient. Driving forces are created due to pressure differences between ambient conditions and the colder operating conditions of the piping. These forces drive water vapor into the insulation system, where it may be retained as water vapor, condense to liquid water or condense and freeze to form ice. Thermal properties of insulation materials are negatively affected as the moisture or vapor content of the insulation material increases.

Thermal expansion/contraction is a concern both for insulation systems that operate continuously at below ambient conditions or systems that cycle between below-ambient conditions and elevated temperatures. Thermal contraction coefficients of insulation materials may be substantially different from those of the metal pipe. A large difference in the amount of contraction between the insulation and the piping may result in open joints of the insulation system. These open joints not only create a thermal short circuit at that point in the system, but may also affect the integrity of the entire system. Insulation materials that have large contraction coefficients, and do not have a high enough tensile strength or compressive strength to compensate, may experience shrinkage and subsequent cracking within the material. At the elevated temperature end of the cyclic process, the reverse is considered. High thermal expansion coefficients may result in warping or buckling of a material that for some insulation materials is permanent and irreversible. In this instance, the possibility of resulting stress on an external vapor retarder or weather barrier should be considered.

Wicking is the tendency of an insulation material to absorb liquid due to capillary action. Wicking is measured by partially submerging a material and measuring both the amount of liquid that is absorbed, and the amount of space by volume the liquid has consumed within the insulation material.

Open cell or fibrous materials tend to perform worse in water absorption, water vapor permeability and wicking than do closed-cell materials. The amount of closed cell structure compared to open cell structure may be to some degree an indicator of the performance of the material, however closed cell materials may still have high permeance so comparison of all specific physical properties is important.

HVAC systems and chilled water systems are often insulated to conserve energy and prevent surface condensation or "sweating". When an open-cell material is used on these systems and the vapor retarder system fails, water vapor may move into the insulation, condense and eventually saturate the insulation material. This may lead to partial or complete insulation system failure. The problem becomes more severe as the system temperatures move lower and when the system operates continuously in the cold mode. The driving forces are greater on these systems and water vapor will condense and freeze on or within the insulation. Again, as more water vapor in absorbed, the thermal conductivity of the insulation material moves higher which leads to lower surface temperatures. These lower surface temperatures lead to more condensation which may eventually lead to insulation system freeze-up, frost-ups and "popping off" of the insulation material due to ice formation. Considering that refrigeration systems may operate at temperatures of -70°F or colder, the problem may be severe. These problems may not only lead to insulation failures but may also lead to a complete failure of the entire insulation system.

These are several components of insulation systems which include:

• Insulation material;
• Insulation joint sealant;
• Vapor retarders;
• Weather barriers;
• Weather barrier sealants;
• Jacketing;
• Pipe protection; and
• Adhesives, sealants or caulks.

The following is a brief summary of each component, but each individual component will be explored in more detail later in the chapter.

Pipe preparation

Before any type of insulation is applied, all equipment and pipe surfaces MUST be dry and clean from contaminants and rust.

Corrosion of any metal under any thermal insulation can occur for a variety of reasons. The outer surface of the pipe should be properly prepared prior to the installation of the insulation. With any insulation, the pipe can be primed to minimize the potential for corrosion. Careful consideration at the time of the insulation system design stage is essential. Specific guidelines were detailed later in this chapter.

Corrosion concerns

Insulated carbon steel surfaces that operate continuously below 25°F do not present major corrosion problems. However, equipment or piping operating either steadily or cyclically at or above these temperatures may present significant corrosion problems. These problems are aggravated by inadequate insulation thickness, improper insulation material, improper insulation system design and improper installation of insulation.

Common flaws are:

1. Incorrect insulation materials used on below-ambient systems, such as open-cell, wicking and high permeance materials;
2. Improper specification of insulation materials by generic type rather than specifying specific material properties required for the intended service; and
3. Improper or unclear application methods.

Carbon steel

Carbon steel corrodes not because it is insulated, but because it is contacted by aerated water and/or a water-borne corrosive chemical. For corrosion to occur, water must be present. Under the right conditions, corrosion can occur under all types of insulation. Improperly insulated systems create conditions that may promote corrosion. Examples include:

1. Annular space or crevice for the retention of water;
2. Insulation material that may wick or absorb water; and
3. Insulation material that may contribute contaminants that may increase the corrosion rate.

The corrosion rate of carbon steel is dependent on the temperature of the steel surface and the contaminants in the water. The two primary sources of water are infiltration of liquid water from external surfaces and condensation of water vapor on cold surfaces.

Infiltration occurs when water form external sources enters an insulated system through breaks in the vapor retarder system or breaks in the insulation itself. The breaks may be the result of inadequate design, incorrect installation, abuse or poor maintenance practices. Infiltration of external water can be reduced or prevented.

Condensation results when the metal temperature or the insulation surface temperature is lower than the dew point temperature. Insulation systems cannot always be made vaportight, so condensation must be recognized in the system design.

The main contaminants found in insulation are chlorides and sulfates. These contaminants may have been introduced during the manufacture of the insulation or from external sources. These contaminants may hydrolyze in water to produce highly corrosive free acids.

This table lists protective coating systems which can be used for carbon steel systems. The end user should select the appropriate system for the temperature range and expected duration. For other coatings or for more details, contact the coating manufacturer.

Table 1:Protective Coating Systems for Piping

(a) Coating thicknesses are typical dry film values.

(b) "Paint, Epoxy-Polyamide, General Specification for," MIL-P-24441, Part 1 (latest revision).

(c) "Paint, Epoxy-Polyamide, General Specification for," MIL-P-24441, Part 2 (latest revision).

(d) National Association of Corrosion Engineers No. 2/SSPC-SP 10 (latest revision), "Near-White Metal Blast Cleaning" (Houston, TX; NACE International, and Pittsburgh, PA : SSPC).

Copper

External Stress Corrosion Cracking (ESCC) is a type of localized corrosion of various metals notably copper. For ESCC to occur in a refrigeration system, the copper must undergo the combined effects of a sustained stress and a specific corrodant species. During ESCC, copper degrades so that localized chemical reactions occur often at the grain boundaries in the copper. The localized corrosion attack creates a small crack which advances under the influence of the tensile stresses into the metal. The common form of ESCC in copper results from grain boundary attack (i.e. Intergranular ESCC). Once the advancing crack extends through the metal section, the pressurized refrigerant within the line will leak.

ESCC occurs in the presence of four conditions:

1. The presence of oxygen (air),
2. The presence of a tensile stress, either residual or applied. In copper, stress can be put into the metal at the time of manufacture (residual) or during installation (applied) of a refrigeration system.
3. The presence of a chemical corrodant.
4. The presence of water (or moisture) to allow the copper corrosion process to occur.

A number of precautions reduce the risk of ESCC in refrigeration systems:

• Properly seal all seams and joints of the insulation systems to prevent a path for condensation between the insulation and the copper tubing.
• Avoid introducing applied stress to copper during installation. Applied stress can be the result of any manipulation, direct or indirect, resulting in stresses in the copper tubing, for example, applying stress to a copper tube toalign with a fitting or physical damage to the copper prior to installation.
• Under no circumstances use chlorinated solvents such as 1,1,1-trichloroethane to clean a refrigeration system. Such solvents have been linked to rapid corrosion.
• Use no acidic materials such as citric acid or acetic acid (vinegar) on copper systems. Such acids are found in many cleaners.
• Make all soldered connections gas-tight, as a leak could result in failure to the section of insulated copper tubing. This prevents self-evaporating lubricating oil, and even refrigerants themselves, from reacting with moisture to produce corrosive acidic materials such as acetic acid.
• Choose the appropriate thicknesses of insulation for the environment and the operating conditions must be used to avoid condensation of the copper tubing.
• Never mechanically constrict or adhere the insulation to the copper. An example of mechanical constriction is the use of wire ties to compress the insulation. This operation may result in the pooling of water between the insulation and the copper tubing.
• Prevent extraneous chemicals or chemical-bearing materials such, such as corrosive cleaners containing ammonia and/or amine salts, wood smoke, nitrites and ground or trench water, from coming in contact with the insulation or copper.
• Prevent the entrance of water between the insulation and the copper. Where the layout of the system is such that condensation may form and run along uninsulated copper by gravitational force, the beginning run of insulation must be adhered completely to the copper and sealed or vapor stops installed.
• Use copper that complies with ASTM B 280. Buy copper from a reputable manufacture.
• When pressure testing copper tube systems, take care not to exceed the specific yield point of the copper.
• When testing copper for leaks, use only a commercial refrigerant leak detectorsolution specifically designed for that purpose. It must be assumed that all commercially available soap and detergent products contain ammoniacal or amine materials, all of which contribute to the formation of stress cracks.
• Replace any insulation that has become wetted or saturated with refrigerant lubricating oils. Such oils can react with moisture to form corrosive materials.

Stainless Steel

Certain grades of stainless steel piping are susceptible to ESCC. ESCC occurs in austenitic steel piping and equipment when chlorides in the environment or insulation material are transported in the presence of water to the hot surface of stainless steel and are then concentrated by evaporation of the water. This most commonly occurs beneath thermal insulation but the presence of insulation is not a requirement. Thermal insulation simply provides a medium to hold and transport the water with its chlorides to the metal surface.

Most ESCC failures occur when the metal temperature is in the hot water range of 120°F to 300°F. Failures are less frequent when the metal temperature are outside of this range. Below 120°F the reaction rate is slow and the evaporative concentration mechanism is not significant. Equipment that cycles through the water dew point temperature is particularly susceptible. Water that is present at the low temperature evaporates at the higher temperature. During the high temperature cycle the chloride salts dissolved in the water concentrate on the surface.

As with copper, in order for ESCC to develop, sufficient tensile stress must be present in the stainless steel. Most mill products, such as sheet, plate, pipe and tubing, contain enough residual processing tensile stresses to develop cracks without additional applied stress. When stainless steel is used coatings may be applied to prevent ESCC. A metallurgist should be consulted to avoid catastrophic piping system failures.

Insulation systems

Five distinct components characterize a quality insulation job. It is important to define and distinguish each one.

1) Insulation The insulation itself should be a low thermal conductivity material with low water vapor permeability and it should be nonwicking.

2) Insulation Joint Sealant All insulations operating at below ambient conditions should utilize a joint sealant. The joint sealant should be resistant to liquid water, water vapor, and be able to bond to the specific insulation surface. The joint sealant is applied as a full bedding coat to all sealant joints. A properly designed and constructed insulation/sealant/insulation joint will retard liquid water and water vapor migration through the insulation system.

3) Vapor retarders Some insulation materials are commonly considered closed-cell and that as such will not absorb water. This is not exactly the case as most insulations will absorb a certain amount of water. Care should be taken to either use low permeance (water vapor permeability less than 0.1 perm-inches) insulation materials or use a continuous and effective vapor retarder system. Vapor retarders function to keep out water, water vapor and prevent water vapor infiltration, thus keeping the insulation dry. This will prevent degradation of thermal properties due to the presence of water and will prevent any moisture from reaching the cold-side surface of the pipe or vessel.

The service life of the insulation and pipe depends primarily on the in-place water vapor permeance of the vapor retarder. Therefore, the vapor retarder must be free of discontinuities and penetrations. The insulation and the vapor retarder will expand and contract with ambient temperature cycling. The vapor retarder system must be installed with a mechanism to permit this expansion and contracting without compromising the integrity of the vapor retarder. See manufacturers for design and installation instructions specific to their products.

Vapor retarders may be of the following types:

Metallic foil or all service jacket (ASJ) type applied to the surface of the insulation by the manufacturer or field applied. This type of jacket has a low (0.02 perm-inches) water vapor permeability rating under ideal conditions. This low permeability is dependent upon complete sealing of all joints and seams. There will be longitudinal joints and butt joints in the jacketing system when these systems are used. These jackets may be sealed with a contact adhesive applied to both of the overlapping surfaces. manufacturers' instructions must be strictly followed during the installation. Butt joints are sealed in a similar fashion using metallic faced ASJ material an contact adhesive. ASJ jacketing when used outdoors with metal jacketing may be installation sensitive as the metal jacketing may cause damage to the ASJ jacket. This should be considered in the system design. Self-seal lap joints and butt joints may be acceptable but seams and butt joints must be perfectly sealed.

Coatings, mastics and heavy "paints" are available as vapor retarders. Various preparations for covering insulation are available for applying by trowel, brush or spraying. The perm ratings of the material are a function of the thickness applied. Some products are recommended for indoor use only while others are available for indoor or outdoor use. These products may impart odors and manufacturers instructions should be meticulously followed. Care should also be taken to insure that the mastics used are chemically compatible with the insulation system.

Mastics should be applied in two coats (with open weave fiber reinforcing mesh) to obtain a total dry film thickness as recommended by the vapor retarder coating manufacturer. Apply the mastic as a continuous monolithic moisture vapor retarder as recommended by the Manufacturers Technical Data Sheets. The vapor retarder mastic system should extend by a minimum of 2" under any sheet type vapor retarder membrane where applicable. This is typically done at values and fittings only. These systems must be tied into the rest of the insulation system or bare pipe at the termination of the insulation preferably with a 2 inch overlap to maintain the continuity of the entire system.

Laminated membrane retarder with a rubber bitumen adhesive on a polyethylene film or PVC film. Very low perm ratings of 0.015 perms are published. Some solvent based adhesives can attach this type of vapor retarder (see manufacturer for specific details)., All joints should have a 2" overlap to insure adequate sealing.

Other types of finishes may be appropriate depending upon environmental or other factors.

4) Jacketing The purpose of jacketing on insulated pipes and vessels is to protect the vapor retarder system and the insulation. Various plastic and metallic products are available for this purpose.

Some specifications suggest that the jacketing should function to preserve and protect the delicate "egg-shell like" vapor retarder over the insulation. This being the case, it should be obvious that any devices used to secure the jacketing must be of the band type which holds and clamps the jacketing in place circumferentially. Pop rivets, sheet metal screws, staples or any other item that punctures should not be used because they will compromise the vapor retarder. The use of such materials may be an indication that the insulation installer does not understand the vapor retarder concept and corrective education steps should be taken.

Protective jacketing is designed to be installed over the vapor retarder and insulation to prevent weather and abrasion damage. The protective jacketing must be installed independently and in addition to any factory or field applied vapor retarder. Ambient temperature cycling will cause the jacketing to expand and contract. The jacketing must be installed with a mechanism to permit this expansion and contraction to occur without compromising the vapor retarder. See manufactures for design and installation instructions specific to their products.

Metal jacketing may be smooth, stucco, embossed, or corrugated aluminum or stainless steel with a continuous moisture retarder. PVC jacketing or other finishes may also be appropriate, depending upon the environment or other factors. PVC should be smooth, UV inhibited, in precurled rolls. The minimum thickness of PVC should be 0.030". Other types of jacketing may be appropriate depending upon environmental or other factors. Metallic type jackets are recommended for exposed roof mounted piping systems.

Protective jacketing is required whenever piping is exposed to wash downs, physical abuse or traffic. Inside of buildings where ultraviolet degradation from sunlight is not a factor, the most popular type of jacketing is white PVC. Colors can be obtained at little, if any, additional cost if desired. All longitudinal and circumferential laps should be seal welded using a solvent welding adhesive. The laps should be located at 10:00 o'clock or 2:00 o'clock positions. A sliding lap (PVC) expansion/contraction joint should be located near each end point and at immediate joints no more than twenty feet apart. Where very heavy abuse and/or hot, scalding washdowns are encountered a special CPVC material is required. These materials can withstand temperatures as high as 225°F, where standard PVC will warp and disfigure at 140°F.

Roof piping should be jacketed with a minimum 0.016 inch aluminum (embossed or smooth finish depending on aesthetic choice). On pitched lines, this jacketing should be installed with a minimum 2 inch overlap arranged to shed any water in the direction of the pitch. Only stainless steel bands should be used to install this jacketing (1/2" X 0.02" 304 stainless) and spaced every 12 inches. Jacketing on valves and fittings should match that of the adjacent piping.

Weather Barrier Joint Sealant All metal jacketed insulation systems operating at below ambient conditions should utilize a weather barrier joint sealant. The joint sealant should be a liquid water resistant elastomeric material available to bond to the specified metal surface. The joint sealant is applied to all joints to prevent driven water from migrating through the joints, accumulating within the insulation system.

Types of Insulation

Cellular Glass

Cellular Glass has excellent compressive strength but it is rigid. It is fabricated to be used on piping and vessels. When installed on applications that are subject to excessive vibration, the inner surface of the material may need to be coated. The coefficient of thermal expansion for this material is relatively close to that of carbon steel. When installed on refrigerant systems, provisions for expansion and contraction of the insulation are usually only recommended for application that cycle from below ambient to high temperatures. For outdoors or direct buried applications, a jacketing or mastic coating is recommended.

Cellular glass is suitable for temperatures between -450°F and +800°F.

ASTM C552, Standard Specification for Cellular Glass Thermal Insulation, specifies cellular glass insulation requirements.

Flame spread and smoke developed when tested according to ASTM E84 is flame spread index of 5 and a smoke developed index of 0.

The water vapor permeability as tested per ASTM E96, Procedure A is less than 0.005 perm-inches.

Thermal Conductivity in Btu/H-ft2(°F/in) as tested by ASTM C177 or ASTM C518 are

at 0°F mean temperature 0.27

at +75°F mean temperature 0.31

at +120°F mean temperature 0.33

Density can vary between 6.3 and 8.6 lb/ft3. Density does not greatly affect the thermal performance of cellular glass.

Insulation Thickness Tables - Cellular Glass

Please note that insulation thickness is chosen to either prevent or minimize condensation on the outside pipe surface or limit heat gain to 8 Btu/hr-ft2 whichever thickness is greater. All thicknesses are in inches.

Table 2: Insulation Thickness Table - Cellular Glass For Indoor Design Conditions

90°F Ambient 80% Relative Humidity 0.9 Emittance 0 mph Wind Velocity

Data calculated using NAIMA 3E Plus Program

NOTE: These values do not include a safety factor. Actual operating conditions may vary. Consult a design engineer for an appropriate recommendation for your specific system.

Table 3: Insulation Thickness Table - Cellular Glass for Outdoor Design Conditions

100°F Ambient 90% Relative Humidity 0.4 Emittance 7.5 mph Wind Velocity

Data calculated using NAIMA 3E Plus Program.

Note: These values do not include a safety factor. Actual operating conditions may vary. Consult a design engineer for an appropriate recommendation for your specific system.

Flexible Elastomerics

Flexible Elastomerics are soft and flexible. It is suitable for use on non-rigid tubing. It is light weight and has low vapor permeability.

ASTM C534, Standard Specification for Preformed Flexible Elastomeric Cellular Thermal Insulation in Sheet and Tubular Form, specifies flexible elastomeric material requirements. These products can be manufactured to meet the flame spread index of 25 or less and the smoke developed index of 50 or less when tested according to ASTM E84.

Flexible elastomeric sheet is normally limited to service between -70°F up to +180°F. Around - 20°F flexible elastomeric insulation becomes stiff, but this does not affect its thermal performance or water vapor permeability.

Thermal Conductivity in Btu/h-ft2 (°F/in) as tested by ASTM C177 or ASTM C518 are

at 0°F mean temperature 0.25

at 75°F mean temperature 0.27

at 120°F mean temperature 0.29

The water vapor permeability as tested per ASTM E96, Procedure A is 0.1 perm-inches or less.

Insulation Thickness Tables - Flexible Elastomeric

Please note that insulation thickness is chosen to either prevent or minimize condensation on the outside pipe surface or limit heat gain to 8 Btu/hr-ft2 whichever thickness is greater. All thicknesses are in inches.

Table 4: Insulation Thickness Table - Flexible Elastomeric for Indoor Design Conditions

90°F Ambient 80% Relative Humidity 0.9 Emittance 0 mph Wind Velocity

Data calculated using NAIMA 3E Plus Program.

NOTE: These values do not include a safety factor. Actual operating conditions may vary. Consult a design engineer for an appropriate recommendation for your specific system.

Table 5: Insulation Thickness Table - Flexible Elastomeric For Outdoor Design Conditions

100°F Ambient 90% Relative Humidity 0.4 Emittance 7.5 mph Wind Velocity

Data calculated using NAIMA 3E Plus Program.

NOTE: These values do not include a safety factor. Actual operating conditions may vary. Consult a design engineer for an appropriate recommendations for your specific system.

Closed-cell Phenolic

Closed-cell phenolic foam insulation has a very low thermal conductivity. It is able to provide the same thermal performance as other insulations at a reduced thickness. This product can be manufactured to meet the flame spread index of 25 or less and the smoke developed index of 50 or less when tested according to ASTM E84.

ASTM C 1126, Standard Specification for Faced or Unfaced Rigid Cellular Phenolic Thermal Insulation specifies material requirements. ASTM C 1126 lists a temperature range from -290°F to +250°F.

Thermal Conductivity is Btu/h-ft2(°F/in) as tested by ASTM C177 or ASTM C518 are

at +75°F mean temperature 0.13

at +120°F mean temperature 0.15

The water vapor permeability of the unfaced material as tested per ASTM E96, Procedure A is 2.0 perm-inches or less.

Insulation Thickness Tables - Closed-cell Phenolic Foam

Please note that insulation thickness is chosen to either prevent or minimize condensation on the outside pipe surface or limit heat gain to 8 Btu/hr-ft2 whichever thickness is greater. All thickness are in inches.

Table 6: Insulation Thickness Table - Closed-cell Phenolic Foam For Indoor Design Conditions

90°F Ambient 80% Relative Humidity 0.9 Emittance 0 mph Wind Velocity

Data calculated using NAIMA 3E Plus Program.

NOTE: These values do not include a safety factor. Actual operating conditions amy vary. Consult a design engineer for an appropriate recommendation for your specific system.

Table 7: Insulation Thickness Tables - Closed-cell Phenolic Foam For Outdoor Design Conditions

100°F Ambient 90% Relative Humidity 0.4 Emittance 7.5 mph Wind Velocity

Data Calculated using NAIMA 3E Plus Program.

NOTE: These values do not include a safety factor. Actual operating conditions may vary. Consult a design engineer for an appropriate recommendation for your specific system.

Polyisocyanurate insulation

Polyisocyanurate insulation has low thermal conductivity, is light weight and has excellent compressive strength. These products can be manufactured to meet the flame spread index of 25 or less and the smoke developed index of 50 or less when tested according to ASTM E84.

ASTM C591, Standard Specification for Unfaced Rigid Cellular Polyisocyanurate Thermal Insulation specifies material requirements. ASTM C591 lists its temperature range from -297 to +300 °F.

Thermal Conductivity in Btu/h-ft2(°F/in) as tested by ASTM C177 or ASTM C518 are

at 0°F mean temperature 0.19

at +75°F mean temperature 0.19

at +120°F mean temperature 0.21

The water vapor permeability of the unfaced material as tested per ASTM E96, Procedure A is 4.5 perm-inches or less.

Insulation Thickness Tables - Polyisocyanurate Foam Insulation

Please note that insulation thickness is chosen to either prevent or minimize condensation on the outside pipe surface or limit heat gain to 8 Btu/hr-ft2 whichever thickness is greater. All thicknesses are in inches.

Table 8: Insulation Thickness Tables - Polyisocyanurate Foam Insulation for Indoor Design Conditions

90°F Ambient 80% Relative Humidity 0.9 Emittance 0 mph Wind Velocity

Data Calculated using NAIMA 3E Plus Program.

NOTE: These values do not include a safety factor. Actual operating conditions may vary. Consult a design engineer for an appropriate recommendation for your specific system.

Table 9: Insulation Thickness Table - Polyisocyanurate Foam Insulation For Outdoor Design Conditions

100°F Ambient 90% Relative Humidity 0.4 Emittance 7.5 mph Wind Velocity

Data calculated using NAIMA 3E Plus Program.

NOTE: These values do not include a safety factor. Actual operating conditions may vary. Consult a design engineer for an appropriate recommendation for your specific system.

Polystyrene insulation

Polystyrene insulation is light weight and has good compressive strength. This product does not meet the smoke developed index of 50 or less when tested according to ASTM E84. The test yields a flame spread index of 25 or less and a smoke developed index of 115.

ASTM C 578, Standard Specification for Rigid Cellular Polystyrene Thermal Insulation specifies material requirements. ASTM C 578 lists its temperature range from -65 to +165°F.

Thermal Conductivity in Btu/h-ft2(°F/in)as tested by ASTM C177 or ASTM C518 are

at +75°F mean temperature 0.24

at +120°F mean temperature 0.26

The water vapor permeability of the unfaced material as tested per ASTM E96, Procedure A is 1.5 perm-inches or less.

Insulation Thickness Tables - Polystyrene Foam Insulation

Please note that insulation thickness is chosen to either prevent or minimize condensation on the outside pipe surface or limit heat gain to 8 Btu/hr-ft2 whichever thickness is greater. All thicknesses are in inches.

Table 10: Insulation Thickness Table - Polystyrene Foam Insulation For Indoor Design Conditions

90°F Ambient 80% Relative Humidity 0.9 Emittance 0 mph Wind Velocity