*Case Study - Economic Justification for Replacing

Ice-laden Refrigerant Pipe Thermal

Insulation with New Insulation*

San Diego 2015

IIAR Conference & Expo

By Gordon H. Hart, P.E.

Artek Engineering, LLC

A large food processing facility

• Located in South Carolina; built in 1996

• Insulated ammonia refrigeration piping located on the roof

• Following a 2011 hail storm, the owner inspected his pipe insulation & discovered it was ice-laden and required replacement

• Owner made the decision to hire a contractor to replace all his old pipe insulation system with a new system

Pipe System Description• 4,756 LF of roof-top pipes varying from ¾” to 12”

NPS

• Pipe design temperatures vary from -25°F to 60°F

• 39 roof-top condensers

• Original thermal insulation system on pipes

• Extruded polystyrene (XPS) from 1” to 4” thick

• Traditional ASJ vapor retarder on straight pipes covered with 0.016” thick aluminum jacketing

• Vapor retarder mastic on fittings covered with 0.020” thick PVC

My role

• I visited the job to observe insulation removal & replacement one day in December, 2013

• I made no decisions regarding the insulation replacement or design of the new system

My information

• …comes from six sources:

1. owner’s Facility Maintenance Supervisor

2. insulation contractor’s Superintendent

3. original insulation specifications

4. construction drawings

5. replacement insulation manufacturer

6. my observations

Facility Owner’s Decision

• Damaging hail storm occurred in spring, 2011

• Owner noted that some damage had occurred to the PVC fitting covers prior to the storm

• Following the storm, much of the aluminum jacketing and PVC covers had holes in them

Insulation Contractor’s Work• Occurred during November – March (low

humidity) time period on precipitation free days with refrigeration system operating, over 3 years

• Insulators used hammers and chisels to first remove ice-laden insulation that was stuck to the pipes, about 6 LF at a time

• Insulators then reinsulated that section, covered with the vapor retarder, and sealed with tape

• Insulators installed aluminum jacketing afterwards

Comments on ice-laden insulation

• Full of ice and stuck to the pipe

• ASJ was soaking wet

• XPS insulation, with a permeability of 1.5 perm-inch, needed an effective vapor retarder for outdoor use and ASJ didn’t provide that

• Vapor retarder mastic on XPS fittings was probably ineffective as well

• PVC fitting covers provided insufficient physical protection in outdoor use

Owner’s Selection of aNew Insulation System

• Polyethylene pipe insulation of equal thicknesses to the XPS; sealant on outer inch of material

• Polyethylene insulation meets performance requirements of ASTM C1427

• permeability of 0.05 perm-inch

• water absorption < 0.02% by volume in 24 hours

Owner’s Selection of aNew Insulation System

• Vapor retarder consisted 4 mil thick PVDC film on straight pipe and fittings and was sealed with matching pressure sensitive adhesive tape (ASTM C1136, Type VIII; permeance = 0.01 perm)

• New 0.016” thick aluminum jacketing (ASTM C1729, Type I, Class A)

Note about the polyethylene pipe insulation used

• No longer commercially available

• Taken off the market in the fall, 2014 for business reasons

My comments on new insulation system

• Polyethylene insulation used has a much lower permeability and water absorption than XPS

• PVDC film vapor retarder has a lower permeancethan ASJ, is water repellent, and seals tightly with tape on straights & fittings

• New insulation system has a redundant vapor retarder system with a…

1. sealed, low permeability insulation and

2. sealed, low permeance vapor retarder film

Cost of new insulation system

• $550,000 contractor’s fixed price including removal of old insulation system and replacement with new insulation system, over course of 3 years

• Includes all materials, labor to remove old & install new, and contractor overhead

Estimating thermal performance of ice-laden XPS insulation

• Details described in my paper

• No publicly available thermal performance data on ice-laden insulation

• No publicly available thermal performance data on water soaked XPS insulation

• Some publicly available data on water-soaked cellular phenolic foam pipe insulation in ASHRAE RP-1356

Estimating thermal performance of ice-laden XPS insulation

• In ASHRAE RP-1356, thermal conductivity of phenolic foam increased by 56% with 5% water content by volume

• XPS has a dry density of 1.6 pcf, phenolic foam of 2.5 pcf

• I assumed the same behavior for XPS and extrapolated to soaked insulation

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Ap

par

ent

Ther

mal

Co

nd

uct

ivit

y V

alu

es, B

tu-i

n/h

r-sf

-F

% moisture by volume

Measured and predicted values for thermal conductivity of phenolic foam and XPS polystyrene insulations, at 65° F mean,

as a function of % moisture by volume

RP-1356 Test Data on wet phenolicfoam

Extrapolated Data on wet phenolicfoam

Extrapolated data on wet XPSpolystyrene

Adjusting for ice in place of water

• The thermal conductivity of ice is about 4 times greater than that of water at the same temperature

• So, I multiplied the predicted water soaked XPS thermal conductivity values by 4 to get values for ice-laden XPS at the same mean temperature

• Note that the thermal conductivity of ice decreases with increases in mean temperature

Calculations for heat loss from insulated pipes

• Used 3E Plus® (www.pipeinsulation.org) from the North American Insulation Manufacturers’ Association

• Calculated rate of heat gain per linear foot of pipe for each combination of pipe size, pipe operating temperature, and insulation thickness

• For the XPS and polyethylene insulations, I used thermal conductivity data supplied by manufacturers

Appendix A, Table 1: Heat gain savings for roof section M3.1 of the food processing facility, pipe system by pipe system

Life Cycle Cost Analysis

• Performed this on two cases:a. Leaving the old, ice-laden insulation system in

place

b. Replacing the old insulation with the new insulation system as described

• Was not able to obtain COP values for the refrigeration system from the owner

• Used a flat electricity cost of $0.10 per kWh, interest rate of 2%

Appendix B, Table 1: Tabulated results of Life Cycle Cost Analysis of both the original pipe insulation and the replacement pipe insulation

$-

$200,000

$400,000

$600,000

$800,000

$1,000,000

$1,200,000

$1,400,000

$1,600,000

$1,800,000

$2,000,000

1 1.5 2 2.5 3 3.5 4

Life

Cyc

le C

ost

, $

Coefficient of Performance, Assumed

Calculated Life Cycle Costs of Original Insulation and New Replacement Insulation

Old, original Insulation

New replacement insulation

Conclusions

• Estimated 89.4% load reduction from reinsulating pipes and a 3. 1 Billion Btus / year energy savings

• A favorable LCC for insulation replacement would be reached with a COP value < 2.75 with above assumptions

• Analysis does not include additional benefits of reduced corrosion under insulation and weight reduction of the re-insulated pipes

Recommendations1. That designers follow recommendations in

Chapter 7 of the IIAR Refrigeration Piping Handbook such as…a. Don’t use ASJ vapor retarder for applications in

unconditioned spaces, both indoors and outdoorsb. Don’t use PVC fitting covers outdoors

2. That someone (manufacturers or IIAR or ASHRAE) conduct tests to determine thermal conductivity values of wet and iced insulation materials commonly used on ammonia refrigeration pipes

Recommendations

3. That facility owners increase frequency of refrigeration pipe insulation inspections

4. That designers conduct computer modeling of simultaneous heat & moisture transport to predict long term performance of insulated refrigeration pipe insulation systems (WUFI)

5. That designers specify redundant vapor retarders for insulated refrigeration piping systems

Thank you. Questions?