EDITORIAL REVISION

July 2007

Process Industry Practices

Insulation

PIP INEG1000
Insulation Design Guide
 EDITORIAL REVISION
July 2007

Process Industry Practices

Function Team

PIP INEG1000
Insulation Design Guide
Table of Contents
1. Introduction................................. 2 8. Insulation Thickness................ 16
1.1 Purpose ............................................. 2 8.1 General ............................................ 16
1.2 Scope................................................. 2 8.2 3E Plus ............................................ 16
2. References .................................. 2 9. Type Codes............................... 17
2.1 Process Industry Practices (PIP)....... 2 9.1 General ............................................ 17
2.2 Industry Codes and Standards.......... 2 9.2 Hot Insulation Types........................ 17
2.3 Other References .............................. 3 9.3 Cold Insulation Types ...................... 19
9.4 Insulation Types for Traced and
3. Insulation Materials .................... 3 Energy Transfer Jacketed
3.1 Categories ......................................... 3 Systems ........................................... 19
3.2 Closed-Cell Insulations...................... 3 9.5 AC – Acoustic Control Insulation..... 20
3.3 Fibrous Insulations ............................ 4 9.6 FP – Fire-Protection Insulation........ 20
3.4 Granular Insulations .......................... 5
Table 1: Insulation Materials Selection Table
3.5 Jacket Materials and Accessories ..... 5
(US Customary Units) .................. 22
3.6 Vapor Barriers ................................... 7
Table 1M: Insulation Materials Selection
4. Insulation System Design .......... 7 Table (SI Units)............................. 28
4.1 General .............................................. 7 Data Forms
4.2 Basic Design Criteria ......................... 8
4.3 Other Design Criteria....................... 11 INEG1000-D1 – Documentation
Requirements Sheet
5. Corrosion under Insulation...... 13 The following data forms shall be part of this
Practice only if indicated on the purchaser’s
6. Insulation Material Selection ... 14 completed Documentation Requirements Sheet.
6.1 General ............................................ 14
6.2 ASTM Considerations...................... 14 INEG1000-D2 – Hot Service Insulation
6.3 Insulation Materials Selection Design Parameters
Table................................................ 15 INEG1000-D3 – Cold Service Insulation
Design Parameters
7. Extent of Insulation .................. 15

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1. Introduction

1.1 Purpose
This Practice provides guidance for the design of insulation systems.

1.2 Scope
This Practice describes the types of insulation systems that are indicated by the
type code on the Piping and Instrumentation Diagrams (P&IDs), data sheets, and
other design documents. This Practice provides guidance on insulation design
criteria, insulation materials, extent of insulation, determination of insulation
thickness, and insulation material properties.

2. References
Applicable parts of the following Practices, industry codes and standards, and references
shall be considered an integral part of this Practice. The edition in effect on the date of
contract award shall be used, except as otherwise noted. Short titles will be used herein
where appropriate.

2.1 Process Industry Practices (PIP)

– PIP CTSE1000 – Application of External Coatings
– PIP INSC2000 – Installation of Cold Service Insulation Systems
– PIP INSH1000 – Hot Service Insulation Materials and Installation
Specification
– PIP INSR1000 – Installation of Flexible, Removable/Reusable Insulation
Covers for Hot Insulation Service
2.2 Industry Codes and Standards

• American Petroleum Institute (API)

– API RP521 – Guide for Pressure-Relieving and Depressuring Systems
– API RP2001 – Fire Protection in Refineries
– API PUBL 2218 – Fireproofing Practices in Petroleum and
Petrochemical Processing Plants
• American Society of Testing and Materials (ASTM)
– ASTM C240 – Standard Test Methods of Testing Cellular Glass Insulation
Block
– ASTM C533 – Standard Specification for Calcium Silicate Block and Pipe
Thermal Insulation
– ASTM C547 – Standard Specification for Mineral Fiber Pipe Insulation
– ASTM C552 – Standard Specification for Cellular Glass Thermal
Insulation

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– ASTM C591 – Standard Specification for Unfaced Preformed Rigid

Cellular Polyisocyanurate Thermal Insulation
– ASTM C610 – Standard Specification for Molded Expanded Perlite Block
and Pipe Thermal Insulation
– ASTM C680 – Standard Practice for Determination of Heat Gain or Loss
and the Surfaces Temperatures of Insulated Pipe and Equipment Systems
by the Use of a Computer Program
– ASTM C800 – Standard Specification for Glass Fiber Blanket Insulation
(Aircraft Type)
– ASTM C871 – Standard Test Methods for Chemical Analysis of Thermal
Insulation Materials for Leachable Chloride, Fluoride, Silicate, and
Sodium Ions
– ASTM C1055 – Heated System Surface Conditions That Produce Contact
Burn Injuries
– ASTM C1104 – Standard Test Method for Determining the Water Vapor
Sorption of Unfaced Mineral Fiber Insulation
– ASTM E96 – Standard Test Methods for Water Vapor Transmission of
Materials
• NACE RP0198-2004 – The Control of Corrosion Under Thermal Insulation
and Fireproofing – A Systems Approach, NACE International
• North American Insulation Manufacturers Association (NAIMA) – 3E Plus

2.3 Other References

• Federal Energy Administration Report

– Economic Thickness for Industrial Insulation/ASM Metals Handbook,
“Corrosion” Volume 13, ASM International
• National Oceanic and Atmospheric Administration (NOAA), U.S. Department
of Commerce – www.noaa.gov

3. Insulation Materials

3.1 Categories
Insulation materials fall into the following three major generic categories based
on the structure of the insulation material and each has properties that give it
unique performance characteristics:
a. Closed cell
b. Fibrous
c. Granular

3.2 Closed-Cell Insulations

3.2.1 Closed-cell insulations include:

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a. Cellular glass
b. Various organic materials such as rigid polymer foams,
polyisocyanurate, polyurethane, and polystyrene
c. Elastomeric foams
3.2.2 The closed-cell structure of these materials provides a natural resistant to
absorption and permeation by external water and water vapor as well as
to absorption of leaking process chemicals. Closed-cell insulations are
frequently chosen for low-temperature applications in which control of
moisture penetration is important. ASTM E96 is a test method for water
vapor permeability that can be applied to all insulation materials.
ASTM C240 is a water absorption test method that is published for
cellular glass. Some insulation manufacturers test their materials using
both of these procedures and publish the results in their product
literature. For both test methods, the lower the value, the more resistant
the material is to absorption and permeability.
3.2.3 The upper-use temperature of the rigid polymers and elastomeric foams
is limited, and the manufacturer’s recommended maximum temperature
should be followed. Cellular glass is made from inorganic material that
gives a wider, usable temperature range and applicability in elevated
temperature service in which absorption resistance is needed.
3.2.4 In applications below ambient, most of these materials should be used
with a separate vapor barrier and with a weather-proof jacket. All outer-
layer joints should be sealed using the insulation manufacturer’s
recommended material in any application in which condensation could
occur on the insulated pipe or equipment. All the closed-cell materials
can be used for condensation control and cold conservation.
3.2.5 While the rigid foams and cellular glass have some strength, damage
resistance is not necessarily provided. The elastomeric foams are resilient
and should resist light physical abuse.
3.2.6 If exposed to ultraviolet (UV) light for extended periods of time, the
properties of most of the organic materials deteriorate. If using organic
closed-cell materials in an exterior application, a UV-protective finish
should be used.

3.3 Fibrous Insulations

3.3.1 Fibrous insulations include:
a. Fiberglass
b. Mineral fiber
c. Needled E glass
d. Ceramic fiber
3.3.2 The fundamental difference between the fibrous insulations is the raw
material from which they are made. Mineral fiber is made from volcanic

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rock; fiberglass and E glass are made from inorganic glass fibers; and
ceramic fibers are made from inorganic ceramics.
3.3.3 Fibrous insulation is not resistant to moisture permeation and can absorb
water or chemicals if exposed to liquid or vapor. There is no permeation
minimum included in the ASTM standards for any of the fibrous
materials. For this reason, fibrous insulation is not used alone for low-
temperature applications in which condensation can occur. If used at an
elevated temperature, the organic binder that helps to hold the insulation
together is burned away causing a reduction in strength and an increase
in the ability to absorb moisture.
3.3.4 The fibrous insulations, depending on form, are somewhat flexible and
have little compressive strength. As a result, piping should not be
supported through fibrous insulation, and higher strength materials
should be considered in damage-prone areas.
3.3.5 The fibrous insulations do not burn but do absorb flammable chemicals
that can burn. In cases in which leaking flammables are likely, the
fibrous materials should not be used.

3.4 Granular Insulations

3.4.1 Granular insulations include perlite and calcium silicate because of
composition from a starting material that is granular in form.
3.4.2 Granular insulations have much higher density and compression strength
than most fibrous and closed-cell materials. Because of the higher
strength, the insulations can be used to support piping loads and to resist
damage.
3.4.3 Calcium silicate is highly absorbent and should not be used if direct
exposure to moisture or leaking chemicals is likely. At temperatures
below 500°F (260ºC), perlite resists moisture absorption and may be
used if corrosion under insulation is a concern; however, perlite is not
typically used in low-temperature applications. At temperatures above
500°F (260ºC), the organic binder that imparts the moisture resistance is
no longer effective, and moisture absorption is possible.

3.5 Jacket Materials and Accessories

3.5.1 The jacket is a key part of an insulation system. The primary function of
the jacket is to protect the insulation material from the elements,
especially water and external mechanical abuse.
3.5.2 Aluminum Jacketing
3.5.2.1 The most commonly used jacket material in chemical and
petrochemical plant applications is aluminum. The aluminum
materials are available in several thicknesses and finishes
depending on the application. The two major aluminum finishes
are stucco-embossed and smooth. Stucco-embossed aluminum
has a rough finish that is rolled into the sheet metal during
manufacture. The benefit of this finish is that minor surface

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damage is less visible. Owners prefer the appearance of the

smooth jacket rather than stucco embossed because of
appearance and ease of cleaning.
3.5.2.2 Increasing the thickness and adding corrugations improves the
damage resistance of both materials. Corrugations increase the
bending strength perpendicular to the axis of the corrugations.
3.5.2.3 Corrugated jackets should not be used on horizontal surfaces if
the corrugations are oriented parallel to the horizontal axis,
because water can be held in the troughs formed by the
corrugations on the top surface. This water can run to the joints
in the jacket and enter the insulation.
3.5.2.4 Aluminum has excellent weathering characteristics if exposed to
normal industrial atmospheres. There are specific chemicals such
as caustics and chloride salts that can damage aluminum and
aluminum should not be used if directly exposed to these
chemicals. If chemical exposure is likely, a corrosion specialist
should be consulted to determine the appropriate jacket material.
Aluminum jacket can be obtained with a coating to provide
added chemical resistance, color-coding, or increased emissivity.
3.5.3 Other Jacket Materials
3.5.3.1 Other common jacket materials are stainless steel, zinc-
aluminum alloy-coated steel, and PVC.
3.5.3.2 Stainless Steel Jacketing
1. Stainless steel jacketing is used if fire resistance is needed.
Stainless steel has a much higher melting point than
aluminum and remains intact much longer during an external
fire than aluminum. The higher melting point allows the use
of smaller relief devices on insulated pressure equipment and
provides protection for both the equipment and insulation.
2. Chemical resistance is also an important benefit of stainless
steel and can be used in areas where chemical fumes or spills
are a problem that aluminum cannot resist.
3. Stainless steel is stronger and heavier than aluminum, which
allows use in thinner sheets. The added strength improves
damage resistance in comparison to aluminum.
3.5.3.3 Zinc Aluminum Alloy-Coated Steel Jacketing
1. Zinc aluminum alloy-coated steel jacketing also is used if
mechanical strength or fire protection is needed.
2. Zinc aluminum alloy-coated jacketing should not be used on
stainless steel pipe and equipment because of the risk of zinc
embrittlement of the stainless steel in the event of a fire. Zinc
embrittlement occurs if the zinc coating melts and the liquid
zinc makes contact with austenitic stainless steel. The liquid

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zinc penetrates the stainless steel and causes cracking. Welds

are especially vulnerable to this type of cracking.
3.5.3.4 Nonmetallic Jacketing
1. Nonmetallic jackets are also commonly used. White PVC is
used in outdoor applications or if cleanliness is important.
PVC is also available in a variety of colors if the jacket must
be color-coded, however, colored PVC should not be used
outdoors.
2. Complicated shapes can be handled by fabricating the jacket
in place using mastic and reinforcing fabric. This approach is
often used in combination with metal jacket in which the
metal is used for the straight sections, and the mastic is used
for the complicated shapes. Metal fittings should be used for
tees and elbows for PIP installations.

3.6 Vapor Barriers

3.6.1 Insulation systems that operate below the ambient dew point temperature
must be protected from the inward permeation of moisture. Water vapor
permeability is measured using ASTM test method E96, and the results
are reported in “perms.” Lower perm ratings represent better resistance to
moisture penetration. Closed-cell insulation materials have low perm
ratings, while fibrous and granular materials are generally not evaluated
for permeation. Because of the low perm rating, closed-cell materials are
used for low-temperature applications.
3.6.2 As an added measure of resistance against moisture penetration, an
additional vapor barrier is added to the outer surface of the insulation.
The vapor barrier can be sheet material or vapor barrier mastic that is
applied to the outside surface of the insulation. Nonsetting joint sealer is
used to seal the joints of single-layer insulation and the outer layer of
multilayer systems.

4. Insulation System Design

4.1 General
4.1.1 An insulation system consists of the insulation material, protective
covering if needed, and accessories used to secure the insulation in place.
4.1.2 The insulation materials chosen depend upon the reasons that insulation
is being used. Many different criteria are important in the selection of an
insulation system. Not all the criteria mentioned in this Practice apply in
all cases. The criteria that apply to a project should be determined, and
priorities should be assigned to those criteria. In some cases, it may be
that only heat conservation or personnel protection are important. In
most projects, many criteria apply with some being much more important
than others. Because each project is unique, the criteria should be
assessed for each project, and selections should be made that are

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appropriate to their unique circumstances. Design criteria that should be

considered in the selection of insulation materials are described in
Section 4.2 of this Practice.

4.2 Basic Design Criteria

4.2.1 The primary reason for using insulation should be established first.
Possible reasons are:
a. Heat conservation
b. Personnel protection
c. Process stability
d. Freeze protection
e. Condensation prevention
f. Cold conservation
The possible reasons are aligned with the PIP type codes that are used on
P&IDs to designate the insulation type.
4.2.2 Heat Conservation Insulation
4.2.2.1 Heat conservation (HC) insulation is applied to prevent the
escape of thermal energy from process equipment and piping. An
optimum thickness can be determined that balances the cost of
installing and maintaining the insulation system against the value
of the energy saved. This thickness is referred to as the
“economic thickness” and can also be defined as the insulation
thickness that yields the minimum total cost of owning
insulation.
4.2.2.2 Calculation of the economic thickness depends on many
variables and must be determined on a case-by-case basis. The
National Association of Insulation Manufacturers (NAIMA) has
published software (3E Plus) that can be used to calculate
economic thickness. 3E Plus uses heat transfer calculations that
are based on ASTM C680 and economic thickness calculations
based on the Federal Energy Administration Report, Economic
Thickness for Industrial Insulation. This method assumes that
the total cost of owning an insulation system is defined as the
sum of the cost of the insulation system materials plus the cost of
the energy lost minus any tax savings.
4.2.2.3 Energy loss is reduced for a given insulation material by
increasing the insulation thickness. Increasing the thickness
raises the cost of the insulation but lowers the cost of lost energy.
At the economic thickness, the cost of adding additional
insulation thickness exceeds the value of the additional energy
saved.
4.2.2.4 The calculations made to determine the economic thickness
require the input of project-specific data on process conditions,

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ambient conditions, and economic data that is specific to the

project. To determine an accurate economic thickness, this data
must be obtained for each project. The software contains default
values for process, ambient, and economic variables. However,
the default values are subject to variation and can cause
inaccurate economic thickness calculations.
4.2.3 Personnel Protection Insulation
4.2.3.1 Personnel protection (PP) insulation is used to prevent contact
between hot operating surfaces and personnel working near the
equipment. The maximum allowable insulation system surface
temperature is 140°F (60°C).
4.2.3.2 ASTM C1055 establishes a process for the determination of
acceptable surface operating conditions for heated systems.
ASTM C1055 also defines human burn hazards and presents
methods for use in the design and evaluation of heated systems
to prevent serious injury from contact with exposed surfaces.
The method establishes a safe surface contact temperature based
on an acceptable contact time and level of injury. A graph is
included in ASTM C1055 that establishes the temperature-time
relationship for burns of specific severity. For the purposes of
this Practice, the acceptable level of injury is reversible
epidermal injury as defined in ASTM C1055, and the PIP
adopted acceptable contact time is 2 seconds. Using the
ASTM C1055 graph and the injury and time parameters leads to
the PIP maximum allowable surface temperature of 140°F
(60°C). This temperature is used to calculate the personnel
protection thickness. The personnel protection thickness is
chosen so that the outside surface temperature of the insulation
system is no more than 140°F (60°C) under the worst-case
operating conditions of highest operating temperature combined
with the highest expected ambient temperature.
4.2.3.3 Two very important variables in the calculation of outside
surface temperature are the emissivity of the jacket material and
the wind speed. As the wind speed increases, the surface
temperature falls significantly because of convective cooling.
The wind speed for indoor applications is low, resulting in
higher personnel protection thicknesses than for the same system
in an outdoor location. Choosing a jacket material with high
emissivity also reduces the surface temperature and is a method
that can be used to lower the personnel protection thickness for
indoor applications or for high temperature outdoor installations.
As the process temperature drops, increasing the emissivity
becomes less effective at lowering the surface temperature.
4.2.3.4 3E Plus or an equivalent program can be used to calculate the
personnel protection thickness.

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4.2.4 Process Stability Insulation

Process stability (PS) insulation is used to maintain the process
temperature at a desired level. The amount of heat loss or heat gain
allowed for a process depends on the nature of the process. 3E Plus can
be used to calculate both heat loss and heat gain through insulation as a
function of insulation type and process conditions.
4.2.5 Prevention from Freezing Insulation
4.2.5.1 Prevention from freezing (PF) insulation is used to prevent water
or process fluid piping from freezing without using supplemental
heat input (either electric or steam). The system design requires
consideration of all potential heat leak paths, such as pipe
supports and terminations at enclosures. These heat leak paths
can result in localized ice formation and line plugging.
4.2.5.2 Insulation can be designed to prevent the contents of a pipe or
vessel from freezing when ambient temperatures fall below the
freeze point temperature of the insulated liquid. 3E Plus is not
used to calculate the required thickness but can be used to
calculate the heat loss rate (heat flux) from an uninsulated
surface as well as through a range of insulation thicknesses. The
important variables in making this calculation are ambient
temperature and wind speed. When the heat flux is known it can
be used to calculate the time required for the process fluid to
freeze. The volume of fluid, its heat capacity and heat of fusion
must all be known in order to calculate the amount of energy that
must be lost and the length of time required for freezing to occur.
Flow through the item to be insulated greatly complicates the
calculation. Local freezing could occur faster or slower as a
result of attachments to the insulated item. The insulation
thickness is selected to provide a specified period of time before
freezing occurs.
4.2.5.3 Caution should be exercised when calculating time to freeze
since slush can form before then and plug orifices and strainers.
This insulation approach should not be used where freezing
conditions over multiple days occur on a regular basis, or the
service is critical to process control or plant operation.
4.2.6 Cold Service Insulation
4.2.6.1 Cold service insulation (CC) is primarily intended to limit heat
gain by the process. The allowable heat gain must be determined
for each process. The required insulation thickness is determined
based on the local worst-case ambient conditions. In most cases,
the thickness should also be sufficient to keep the surface
temperature of the jacket material above the ambient dew point
temperature to prevent condensation on the jacket surface. 3E
Plus can be used to calculate heat gain, dew point, and surface
temperature.

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used. Rigid insulation materials can be selected for surfaces that are
easily accessible by personnel working on or around the equipment.
Jacket materials that are more damage resistant, such as thick aluminum
or stainless steel, can be used in conjunction with the rigid insulation to
produce a very damage-resistant system.
4.3.3 Appearance
Appearance requirements sometimes determine the type of jacket or
finish material that must be used. Applications that require a
continuously high degree of cleanliness can specify a jacket material that
has a gloss white or polished stainless steel finish to facilitate both
identification and removal of surface contamination. Embossed surface
finishes on metal jacket materials can be used to make minor surface
damage less visible to casual observation; however, it is more difficult to
clean embossed jackets. Smooth finishes are more reflective, and damage
is more easily visible.
4.3.4 Leak Detection
4.3.4.1 Leak detection is a regulatory requirement for some chemical
processes. If insulating piping and equipment that contains
chemicals that fall within the leak detection classification, it is
necessary to design the insulation to permit detection of leaks at
flanges, valves, and other locations that can be prone to leakage.
4.3.4.2 Leak detection provision can be done in hot systems by not
insulating leak-prone items or by using removable reusable
insulation as specified in PIP INSR1000. This approach is not an
option for low-temperature systems because there would be no
vapor seal and condensation or ice formation can occur. Low-
temperature systems require special consideration and should be
handled on a case-by-case basis.
4.3.5 Absorption Resistance
The absorption resistance of the insulation material is an important
attribute if insulating piping and equipment that contain flammable or
explosive chemicals. If leaks occur and the insulation absorbs the chemical,
it is possible to build up enough of the flammable or explosive chemical to
achieve auto-ignition. It may be necessary to use an appropriate closed-cell
insulation that is compatible with the chemical and does not absorb leaks. It
is desirable to provide drainage to enable the leaking chemical to escape
from the insulation in a controlled fashion.
4.3.6 Emissivity
4.3.6.1 Emissivity is a measure of a body’s ability to radiate energy. A
body that radiates a large amount of energy has an emissivity
close to 1, while a material that is a poor radiator has a low
emissivity. All materials have a characteristic emissivity. New
aluminum jacket has an emissivity of about 0.04, while PVC
jacket has an emissivity of about 0.9. The emissivity value can

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change as the surface characteristics of the insulation change

with time.
4.3.6.2 The surface temperature of an insulation system is a function of
the emissivity of the jacket material. On a hot insulation system,
with all other factors held constant, the outer surface temperature
of the insulation jacket is reduced by using a higher emissivity
jacket. If personnel protection is an important criteria, it may be
possible to reduce insulation thickness by using a high emissivity
jacket. On a cold insulation system, the jacket temperature can
be raised by using a higher emissivity jacket. If condensation
control is an important criteria, the surface temperature can be
raised by using a higher emissivity jacket.

5. Corrosion under Insulation

5.1 A full discussion of corrosion under insulation is beyond the scope of this
Practice. There are numerous articles available in the technical literature
referenced in this Practice. An article in the ASM Metals Handbook, Volume 13,
Ninth Edition, page 1144 through page 1147 covers the subject of corrosion
under thermal insulation.
5.2 Stress corrosion cracking (SCC) occurs if a susceptible material is exposed to a
specific cracking agent while a tensile stress is present. The stress can be directly
applied, such as internal pressure or a piping load, or it can be residual from
forming or welding operations. There is disagreement about many aspects of the
SCC cause and prevention; however, there is agreement that SCC of 300 series
austenitic stainless steel requires water at the metal surface, some level of free
chloride ion and a temperature above approximately 140°F (60°C) and below
300°F (150°C ). The source of chloride can be from leachable chloride inherent
in the insulation or from atmospheric chloride that enters the insulation system
from rain or wash down water. Certain types of insulation are higher in leachable
chloride than others. ASTM C871 describes the standard testing procedure for
determining leachable chloride in insulation material. As a general rule,
atmospheric chloride is higher close to the seashore than inland, and is higher in
industrial areas than in rural areas. The ASM Metals Handbook, Ninth Edition,
Volume 13, page 909 provides a map showing relative levels of chloride in
rainwater in the U.S.
5.3 Mitigation efforts for corrosion under insulation include the following:
a. Proper installation and maintenance of insulation weather jacketing to
prevent water ingress
b. Use of low chloride insulation materials
c. Coating the metal to prevent water contact.
NACE RP 0198-2004 describes control measures for mitigating corrosion under
thermal insulation. Common coatings for mitigating corrosion under thermal
insulation are epoxy phenolic and coal tar epoxies. PIP CTSE1000 provides more
information on coatings.

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6. Insulation Material Selection

6.1 General
6.1.1 The appropriate insulation material for a given project is selected on the
basis of design criteria that are appropriate for that specific project. Some
important design criteria are as follows:
a. Operating temperature
b. Strength, rigidity, and the ability to resist mechanical abuse and
vibration
c. Absorption resistance
d. Water vapor permeation resistance
e. Fire resistance
6.1.2 Not all insulation materials perform equally well with respect to these
design criteria. Each insulation type has strengths and weaknesses and
the strengths of the material selected for a specific job should be matched
to the most important design criteria for that job. For example, a low
permeation material should be chosen for a low-temperature application
in which permeation resistance is needed to prevent condensation on the
surface of the insulated item. A rigid high compressive strength material
should be chosen in situations in which mechanical abuse is likely.

6.2 ASTM Considerations

6.2.1 ASTM has identified many of the important material properties that
support specific design criteria. There are ASTM test methods for:
a. Strength
b. Dimensional stability
c. Surface burning characteristics
d. Water absorption
e. Water vapor permeability
f. Water wicking
g. Water vapor sorption
The ASTM standards that define the requirements for specific insulation
materials do so in terms of performance in these various tests.
6.2.2 By comparing the minimum performance requirements defined by
ASTM, it is possible to compare different material types to determine
which is best for a given application. However, it should be remembered
that the ASTM values are minimum requirements and that in some cases,
critical values are not included in the ASTM standard for a given
material. For example, the standard for mineral fiber, ASTM C547 does
not have a requirement for water absorption. Instead, mineral fiber is
evaluated for water vapor “sorption” using ASTM C1104. ASTM C1104

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detailed description of the basis for the economic analysis that goes
beyond the scope of this discussion. Among the data required by 3E Plus
is climate information that requires both ambient temperature and wind
speed. Both affect heat transfer. Climate data for many locations in the
U.S. is available at www.noaa.gov, the website of the National Oceanic
and Atmospheric Administration (NOAA). The actual climatic data used
depends upon the design criteria of the project and the location of the
item to be insulated.
8.2.3 Insulation used for condensation control should be designed for the
expected humidity conditions. 3E Plus can be used for the design of low-
temperature systems. If a low process temperature is specified, 3E Plus
should be supplied with the ambient temperature and relative humidity.
The highest expected relative humidity at the highest expected ambient
temperature can provide the worst-case dewpoint temperature. The
insulation thickness should be selected so that the surface temperature of
the insulation jacket is greater than the calculated dewpoint temperature.
The surface temperature of the insulation system can be significantly
altered by changing the emissivity of the jacket. Using a jacket material
with an emissivity close to 1 raises the temperature of the jacket surface
and reduces the thickness of insulation required. 3E Plus can be used to
calculate the effect of emissivity on surface temperature. If making
condensation control calculations, it is important to include an accurate
wind speed because the required thickness for condensation control goes
up as wind speed drops. An under estimate of wind speed can result in
excessive thickness and an over estimate can result in unwanted
condensation on the jacket surface.
8.2.4 Process stability requirements are also project specific. 3E Plus can
calculate heat loss or heat gain for user-specified operating conditions.
The allowable amount of heat loss or gain depends upon the process and
should be determined for the specific project in consultation with the
process designer.

9. Type Codes

9.1 General
9.1.1 Insulation type codes should be used on P&IDs, data sheets, piping
isometrics, and other project documents.
9.1.2 Insulation type codes consist of up to four characters. The first two
characters are defined in this Practice. The second two characters can be
used to define additional requirements such as combination systems or
special requirements.

9.2 Hot Insulation Types

9.2.1 HC - Heat Conservation Insulation
9.2.1.1 Heat conservation insulation should be designated with the
code HC.

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9.2.1.2 The primary consideration for using heat conservation insulation

should be economics.
9.2.1.3 Design of heat conservation insulation should be based on local
average ambient climatic conditions and project economics.
9.2.1.4 Heat conservation insulation should be used if normal operating
temperature exceeds 140°F (60°C), unless loss of heat is
desirable.
9.2.2 PS – Process Stability Insulation
9.2.2.1 Process stability insulation should be designated with the
code PS.
9.2.2.2 The primary consideration for using process stability insulation
should be control of process temperatures, including impact
because of sudden changes in ambient conditions.
9.2.2.3 Design of process stability insulation should be based on
anticipated extremes in ambient conditions.
9.2.3 PP – Personnel Protection Insulation
9.2.3.1 Personnel protection insulation should be designated with the
code PP.
9.2.3.2 The primary consideration for using personnel protection
insulation should be to limit the temperature of exposed surfaces.
9.2.3.3 Design of personnel protection insulation should be based on
summer dry bulb temperature and low wind velocity to reflect a
worst-case condition.
9.2.3.4 Personnel protection insulation should be used if normal
temperature of a surface exceeds 140° F (60° C) and if the
surface is in an area that is accessible to personnel. Accessible
area is defined as an area in which personnel regularly perform
duties other than maintenance during plant operation.
9.2.3.5 Personnel protection should be provided to 7 feet (2.13 m) above
grade or platforms and 3 feet (0.91 m) horizontally from the
periphery of platforms, walkways, or ladders.
9.2.3.6 Personnel protection should consist of insulation, shields,
guards, or barriers.
9.2.3.7 If corrosion under the insulation is a concern, or if heat loss is
desirable, use of fabricated shields/guards in lieu of insulation
should be considered.
9.2.3 PF – Prevention from Freezing Insulation
9.2.4.1 Freeze prevention insulation should be designated with the code
PF.
9.2.4.2 The primary consideration for the use of this category is
protection from freezing.

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9.2.4.3 Design of prevention from freezing insulation should be based

on local climatic conditions.
9.2.4.4 Prevention from freezing insulation can be combined with other
types of insulation.

9.3 Cold Insulation Types

9.3.1 CC – Cold Service Insulation
9.3.1.1 Cold service insulation should be designated with the code CC.
9.3.1.2 The primary consideration for using cold service insulation
should be based on maximum allowable heat gain.
9.3.1.3 The design of cold service insulation should be based on control
of heat gain and limiting surface condensation if the operating
temperature is below ambient.
9.3.1.4 Cold service insulation should be sealed against atmospheric
moisture intrusion and subsequent wetting/icing of the
insulation. Sealing normally involves special consideration for
design of equipment and insulation support details.
9.3.2 CP – Condensation Control Insulation
9.3.2.1 Condensation control insulation should be designated with the
code CP.
9.3.2.2 The only consideration for use of condensation control insulation
should be control of external surface condensation.
9.3.2.3 Design of condensation control insulation should be based on the
normal operating temperature and local climatic conditions. In
some humid climates, it is impractical to prevent condensation
100 percent of the time.
9.3.2.4 Use of surface finishes to control surface emissivity can be
considered to reduce insulation thickness.

9.4 Insulation Types for Traced and Energy Transfer Jacketed Systems
9.4.1 General Considerations
9.4.1.1 The primary consideration for using tracing or heat transfer
jacketing and associated insulation should be control of process
temperatures.
9.4.1.2 Design of insulation should be based on the operating
temperature, heat transfer jacketing temperature, or the tracer
temperature. The same insulation thickness as that for heat
conservation (HC) or cold service (CC), as appropriate, should
be used unless design optimization dictates a different thickness.
9.4.1.3 Optimization of the tracer or heat transfer jacketing design and
insulation thickness should be required if specified.

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9.4.1.4 Oversize insulation should be considered to accommodate

tracer(s) or heat transfer jacketing.
9.4.1.5 Grooving of insulation to accommodate tracing is not allowed,
unless specified by the purchaser.
9.4.2 ET – Electric Traced
Electric tracing and associated insulation should be designated with the
code ET.
9.4.3 ST – Steam Traced
Steam tracing and associated insulation should be designated with the
code ST.
9.4.4 SJ – Steam Jacketed
Steam jacketing and associated insulation should be designated with the
code SJ.
9.4.5 HT – Hot Fluid Traced
Hot fluid tracing (except steam) and associated insulation should be
designated with the code HT.
9.4.6 HJ – Hot Fluid Jacketed
Hot fluid jacketing and associated insulation should be designated with
the code HJ.
9.4.7 CT – Chilled Fluid Traced
Chilled fluid tracing and associated insulation should be designated with
the code CT.
9.4.8 CJ – Chilled Fluid Jacketed
Chilled fluid jacketing and associated insulation should be designated
with the code CJ.

9.5 AC – Acoustic Control Insulation

9.5.1 Acoustic control insulation should be designated with the code AC.
9.5.2 The primary consideration for use of acoustic control insulation should
be control of noise.
9.5.3 Normally, acoustic control insulation should have a dedicated design for
each application.
9.5.4 Special consideration of insulation materials and jacketing is normally
required.
9.5.5 Acoustic control insulation can be combined with other types of
insulation.

9.6 FP – Fire-Protection Insulation

9.6.1 Fire-protection insulation should be designated with the code FP.

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9.6.2 The primary consideration for use of fire-protection insulation should be

control of the rate of heat gain in a fire.
9.6.3 Design of fire-protection insulation should be based on maximum
allowable heat gain, fire case characteristics, allowable time duration,
and process characteristics.
9.6.4 Refer to API RP521, API Publication 2218, and API RP2001 for
additional information on fire protective insulation.
9.6.4 Fire-protection insulation can be combined with other types of
insulation.

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