Mechanical Insulation Design Guide - Simple Calculators

by the National Mechanical Insulation Committee (NMIC)

Last updated: 09-22-2011

Condensation Control Calculator – Horizontal Pipe

This calculator estimates the thickness of insulation required to avoid condensation on the outer surface of an insulated horizontal steel pipe. Input data includes the operating temperature, the ambient conditions (temperature, relative humidity, and wind speed) and details about the insulation system (material and jacketing).

The insulation materials included in this calculator were selected to be representative of some of the materials commonly used in the industry. The list is not exhaustive and other materials are available. Also note that some materials are not available in all of the sizes and thicknesses covered by these calculators and some are available in sizes and thicknesses not listed. Thermal conductivity data for the materials included in the calculator were taken from the appropriate ASTM material specification. The table below identifies the ASTM specification and the material type and/or grade utilized in the calculator.

MaterialInsulation Standard
Cellular GlassASTM C 552-07 Type I
ElastomericASTM C 534-08 Type II, Gr 1
FiberglassASTM C 612-09 Type I B
Mineral WoolASTM C 612-09 Type IV B
PolyethyleneASTM C 1427-07 Type II, Gr 1
PolyisocyanurateASTM C 591-08a Type IV
PolystyreneASTM C 578-09 Type XIII

Energy Loss, Emission Reduction, Surface Temperature, and Annual Return Calculators

As an aid to understanding the relationships between energy, economics, and emissions for insulated systems, simple calculators have been developed for equipment (vertical flat surfaces), and horizontal pipe applications. These calculators estimate the performance of an insulated system given the operating temperature, the ambient temperature, and other details about the system.

The algorithms used in these energy calculators are based on the calculation methodologies outlined in ASTM C 680 Standard Practice for Estimate of the Heat Gain or Heat Loss and the Surface Temperatures of Insulated Flat, Cylindrical, and Spherical Systems by use of Computer Programs. The ASTM C 680 Standard is routinely used for predicting the heat loss or gain and surface temperatures of certain thermal insulation systems that can attain one dimensional, steady- or quasi-steady-state heat transfer conditions in field operations. Users are encouraged to review the Scope and Significance and Use sections of this standard.

The Equipment Calculator estimates the heat flows through a vertical flat steel surface (typical of the sides of a large steel tank containing a heated or cooled fluid). Information concerning a hypothetical insulation system (e.g., the area, operating temperature, ambient temperature, wind speed, insulation material and surface emittance of a proposed insulation system) may be input by the user. Calculated results are given over a range of insulation types and thicknesses and include; 1) surface temperature, 2) heat flow, 3) annual cost of fuel, 4) payback period, 5) annualized rate of return, and 6) annual CO2 emissions.

The Pipe Calculator estimates the heat flows through horizontal steel piping. Information concerning a hypothetical insulation system (e.g., the length of run, pipe size, operating temperature, ambient temperature and wind speed, insulation material and surface emittance of a proposed insulation system) may be input by the user. Calculated results are given over a range of insulation types and thicknesses and include; 1) surface temperature, 2) heat flow, 3) annual cost of fuel, 4) payback period, 5) annualized rate of return, and 6) annual CO2 emissions.

It should be noted that the horizontal pipe calculator and the vertical flat surface calculator were developed to be representative of applications typical for mechanical insulation. Other orientations, geometries and base materials are certainly encountered as well and these may be analyzed with available software (e.g. 3E Plus® available at www.pipeinsulation.org).

For piping systems, orientation has a minimal effect except for bare pipe at low wind speeds. For a bare pipe in still air, vertical piping will typically have lower heat losses (by 5% or less) than horizontal piping of the same diameter. For Insulated piping, differences in heat loss (horizontal vs. vertical) will be minimal (less than 1%).

Flat horizontal surfaces in still air (e.g. the tops of heated tanks) will have higher heat losses than vertical surfaces, while horizontal surfaces with heat flow down (e.g. the bottoms of heated tanks) will have lower heat losses than vertical surfaces. Again, the differences are minimal for insulated surfaces and surfaces with moving air.

The insulation materials included in these calculators were selected to be representative of some of the materials commonly used in the industry. The list is not exhaustive and other materials are available. Also note that some materials are not available in all of the sizes and thicknesses covered by these calculators and some are available in sizes and thicknesses not listed.

Thermal conductivity data for the materials included in the calculator were taken from the appropriate ASTM material specification. The table below identifies the ASTM specification and the material type and/or grade utilized in the calculators.

MaterialBoard Insulation StandardPipe Insulation Standard
Calcium SilicateASTM C 533-09 Type IASTM C 533-09 Type I
Cellular GlassASTM C 552-07 Type IASTM C 552-07 Type II
ElastomericASTM C 534-08 Type II, Gr 1ASTM C 534-08 Type I, Gr 1
FiberglassASTM C 612-09 Type I BASTM C 547-07 Type I
Mineral WoolASTM C 612-09 Type IV BASTM C 547-07 Type II
PolyisocyanurateASTM C 591-08a Type IVASTM C 592-08a Type IV

Cost estimates for the insulation systems are provided based on industry sources and are for illustrative purposes only. These cost estimates are based on single layer installations with an aluminum jacketing finish. It should be noted that with some insulation systems and applications the use of an aluminum jacket finish may not be required. They assume unobstructed and reasonable access for the installation, no allowance for fittings, hangers or penetrations. No additional vapor retarders or sealants are included in these estimates. Actual costs will vary depending on local labor rates, productivity, complexity and geographic location of the job, actual insulation system and a multitude of other factors. A cost multiplier is provided to aid in adjusting these costs for specific insulation systems and conditions.

Financial Returns - Considerations Calculator

This calculator was developed to provide a convenient way to estimate the financial returns related to investments in mechanical insulation: Simple Payback in years, Internal Rate of Return (IRR or ROI), Net Present Value (NPV), and annual and cumulative Cash Flow. It can be used for an overall mechanical insulation project or for a small mechanical insulation investment such as insulating a valve or replacing a section of insulation.

Estimate Time to Freezing for Water in an Insulated Pipe

This calculator estimates the time for a long, fluid-filled pipe (no flow) to reach the freezing temperature.

It is important to recognize that insulation retards heat flow; it does not stop it completely. If the surrounding air temperature remains low enough for an extended period, insulation cannot prevent freezing of still water or of water flowing at a rate insufficient for the available heat content to offset heat loss. Well-insulated pipes, however, may greatly extend the time to freezing.

Personnel Protection Calculator for Horizontal Piping

This calculator estimates the maximum contact exposure time on the outer surface of a horizontal pipe insulation system based on the potential for contact burn injuries. Input requirements include the pipe size, operating temperature, ambient temperature and wind speed, and details about the insulation system (material and jacketing).

The maximum contact exposure times are estimated using the procedures outlined in ASTM C 1055-03 (Reapproved 2009) Standard Guide for Heated System Surface Conditions that Produce Contact Burn Injuries. This guide establishes a means by which the engineer, designer, or operator can determine the acceptable surface temperature of a system where contact may be made with a heated surface. The procedure requires the user to make several decisions. Careful documentation of the rational for each decision and intermediate result is an important part of the evaluation process.

For the purposes of this calculator, the maximum contact exposure times are based on an acceptable injury level of first degree burns (reversible epidermal injury, or the limit represented by the lower "Threshold B" curve shown in Figure 1 of the Standard). Acceptable contact times will depend on the application. Clearly, quite different contact times may be justified for cases as diverse as those involving infants and domestic appliances, and experienced adults operating industrial equipment. Where no available standards for these times are prescribed, The Standard recommends the following based on a survey of the medical literature:

Industrial Process   

5 sec

Consumer Items   60 sec

The insulation materials included in this calculator were selected to be representative of some of the materials commonly used in the industry. The list is not inclusive of all materials types and other materials are available. Also note that some materials are not available in all of the sizes and thicknesses covered by these calculators and some are available in sizes and thicknesses not listed.

Thermal conductivity data for the materials included in the calculator were taken from the appropriate ASTM material specification. The table below identifies the ASTM specification and the material type and/or grade utilized in the calculator.

MaterialInsulation Standard
Calcium SilicateASTM C 533-09 Type1
Cellular GlassASTM C 552-07 Type I
ElastomericASTM C 534-08 Type II, Gr 1
FiberglassASTM C 612-09 Type I B
Mineral WoolASTM C 612-09 Type IV B
PolyethyleneASTM C 1427-07 Type II, Gr 1
PolyisocyanurateASTM C 591-08a Type IV
PolystyreneASTM C 578-09 Type XIII

Temperature Drop for Air in an Insulated Duct or Fluid in an Insulated Pipe Calculators

These calculators estimate the temperature drop (or rise) of air flowing in a duct or fluid flowing in a pipe.

An example is the use of insulation to minimize temperature change (either temperature drop or rise) of a process fluid from one location to another(e.g. a hot fluid flowing down a pipe).