Corrosion Under Insulation Part II

SABIC Saudi CUI Forum

By

Dik BetzigHi-Temp Coatings Technology Co.

bz@hitempcoatings.comP +01 978 635 1110C +01 978 844 0238F +01 978 635 1124

Introduction

Hot liquor and other process vessels including piping creates an unsafe environment due to emission of radiant heat. Insulating the vessel creates a potential corrosion environment under the insulation. This presentation will discuss a unique Thermal Interface Coating that provides protection from corrosion, and replaces conventional insulation with metal jacketing while controlling radiant heat & condensation.

Is There a Cure for CUI?

“Corrosion Costs and Preventative Strategies in the United States” reported the direct cost of corrosion to be $276 billion per year, with that number potentially doubling when indirect costs are also considered. Corrosion costs have doubled every 10 years since 1975.– Highest incidents of leaks in chemical industries are due

to CUI– 81% occurs in piping diameters smaller than 4 inches– 60% of piping maintenance is related to CUI

Contributing Factors to CUI

• Environment• Rain water & condensation are most prominent• Water from fire protection• Water vapor penetration• Operating temperature• Ice• Chemical exposure

Operating Temperature

Optimum temperature ranges for aggressive corrosion for both carbon steel and 300 series stainless– Most aggressive 90°C – 120°C– Carbon steel is 0°C to 150°C– Stainless steel is 60°C to 150C– Below 0C corrosion is minimal due to relatively low

energy levels. Corrosion rates are dramatically reduced. The formation of ice limits the amount of oxygen available

Challenges for Insulation Systems

• Insulation and piping need to be inspected• Claddings are often exposed to UV, grease, oil,

and chemical attacks• Traditional insulation and cladding systems are

difficult to install• For complex geometries i.e. valves, flanges, and

other shapes, rigid systems are not compatible• Costs for application are significant due to

expensive equipment• Reducing noise levels with metallic insulation

systems

Solving CUI

Clearly then, for most circumstances, corrosion under insulation can be prevented in two ways:

• By using a coating system which will prevent corrosion in the potentially hot, wet conditions existing under the insulation.

• Design insulation which will not be easily damaged and will prevent water ingress either by nature of the insulation or by an alternative more effective method of cladding.

Pathway for CUI

Traditional InsulationPipe

Rockwool, fiberglass, or other traditional types of insulation promote corrosion, and also act as a carrier and spread the corrosion to other areas of the pipe or vessel.

Water

Important Insulation Concepts

• The basic law of heat transfer is that heat always flows from hot to cold.

• Heat transfer is affected but not correlated to air movement.

• Heat energy moves through matter, metal, insulation, air, etc.

Offshore Platform

Heat Transfer

The transfer of heat is normally from a high temperature object to a lower temperature object. Heat transfer changes the internal energy of both systems involved according to the First Law of Thermodynamics.

Heat Transfer Methods

• Conduction – transfer of heat through temperature differential between objects

• Convection – transfer of heat through matter caused by molecular excitation

• Radiation – Emission of electromagnetic energy waves from emitting body

• Emissivity – ratio black body radiant emission

Stefan Boltzmann’s Law

• Radiation by black body

•Hot objects other than radiators

•Emissivity of object

Constant for Thermal Conductivity

Defined as:Q=Heat through cross sectionA=Temperature difference TQ/A= Heat flux

Guarded Heat Flux Method ASTM C518 ASTM C-177 test

Thermal conductivity:

K = P / [t * (Tm - Ta)]

P = power supplied to heater

T = specimen thickness (2X)

Tm = temperature of main heater

Ta = temperature of auxiliary heater

Guarded Hot Plate Apparatus ASTM C-177

Issues Affecting Conventional Insulation

• Equipment design• Service temperatures• Insulation selection• Protective coatings• Weather barriers• Climate control• Maintenance procedures

Design & SpecificationTHE CAUSES:

– The original design of equipment is the start of CUI problems– Failure to design and specify protective coatings– Design and specifications of the insulation system itself are a

result of CUI– No single insulation, shape, size, or configuring will perform

well in every useTHE CURE:

– Understand the environment, the insulation system, purpose of the insulation, condensation control, etc.

– Specify insulation system that is customized for your requirements

– Make sure to consider the need for the proper type of protection coating

MaintenanceTHE CAUSE:

– Understand sealant problems– Small holes in weather barrier– Wet insulation– Sections of insulation removed for normal operations

and inspections– Failing to reseal and patch insulation properly after

inspectionTHE CURE:

– Provide a systems approach to conventional insulation in a form of thermal interface coating to be used in conjunction with the proper corrosion protective primer

Summary

We have seen that CUI can be a huge, difficult to detect, problem that costs millions of dollars. We have highlighted how everything from design through maintenance can contribute to CUI. Finally, we will discuss how it can be easily prevented through a new technology using a thermal interface coating system.

WHAT IS A THERMAL INTERFACE COATING?

•Seamless composite insulation

•Replaces conventional insulation

•100% adherent thermal barrier

•Protection against high temperature

•Protection against high humidity

•Protection against low temperature

Characteristics

• Thermal shock resistant to 250°C• Thermal Cycling from 0°C to 200°C ASTM-2485• Ambient temperature air-dry• Prevents Stress Corrosion Cracking• Ambient and Hot Application to 300°F• VOC of <100 gram/liter.

Benefits of Insulation Coatings

• Unaffected by UV rays (past 1300 hours of accelerated aging)

• Non-combustible during application and after insulation• Low chloride content (less than 20 ppm & less than 18 ppm

halogen)• With exception of cold/wet applications the coating can be

applied without shutdown up to 150°C (300°F)• Radiant heat barrier average .39% transmittance• Remains flexible to -35°C• Contains no solvents• Cleans up with water• Dry fall during application 5-7 feet

Uses•Power Plants, Refineries

•LNG pipelines & vessels

•Chemical & Pharmaceutical Facilities

•Offshore/Marine

•Equipment for chillers

•Personnel safety ASTM-C1055

•Swage treatment plants/bio diesel tanks

R-value (Insulation)

•The R-value is measure of thermal resistance in heat transfer.

•The thermal resistance SI-units are K·m2/W

•1 ft2·°F·h/Btu ≈ 0.1761 K·m2/W

or

•1 K·m2/W ≈ 5.67446 ft2·°F·h/Btu

•Calculated from thermal conductivity, k, and thickness of material

General Performance Data I

1. Anti-condensate [atmospheric]:

HTC primer 1027 & 850 series @ 6-8 miles DFT, to-coat with XX-TIC-707.

TIC-707 80-120 mils200°F-350°F [93°C-121°C]

TIC-707 60-100 mils0°F-150°F [0°C-66°C]

General Performance Data II

2. Insulation:

HTC primer 1027 series @ 12-20 mils DFT, top-coat with TIC-707

100-200 mils DFT200°F-350°F [93°C-177°C]

80-100 mils DFT0°F-150°F [0°C-66°C]

Thermal Conductivity of TIC-707

Test specimen: TIC-707 (Insulating Coating)

Testing lab: Geosciences LTD. San Diego, CA

Size: 12” x 12” x 1” (Carbon Steel)

Testing Procedure: ASTM-C-177

Temp Range: 42oC [107°F]

Thermal Conductivity: 0.057 Btu/hr, ft, F

0.68 Btu/hr, ft2, F/in

k = 0.68 Btu, in/ ft2,hr, °F

k = 0.084 kcal/m, hr, °C

Theoretical Treatment of Heat Transfer by Conduction

A quantitative expression relating to the rate of heat transfer, the temperature gradient and the nature of the conducting medium is attributed to Fourier (1822)

q xA

= -k dT

dx

Temperature gradient along x

Heat flux= heatflow rate per unitarea in direction x

K=thermalconductivityof material

A = area normal to heat flow

Example R-valuesNote: These examples use the non-SI definition

Vacuum insulated panel 45/inAerogel 10/inPhenolic foam insulation 7/inUrethane 6/inCellulose, fiberglass, rock wool 3/inSnow 1/inAbsolute still air 5/in[Convection heat greatly reduces the insulation value to roughly R-1]

Typical Heat Loss for Steam Lines (MMBtu/yr)

Measuring Temperature

• Temperature on any surface is due to heat energy flux

• Electronic thermal couples only sense heat flux from visible light to near infrared range

• Glass mercury thermometer visible light to mid infrared range

• Human hand can sense heat flux from visible light to far infrared range

• TIC-707 reflect the longer wave length energy flux mostly in near and far infrared range

TIC-707 Testing Apparatus

TIC 707 Test Apparatus

TIC 707 Test Cells

HTC R&D Lab

TIC-707 Mixing

• Does not settle – but has a dry-looking layer on top• Need to Invert cans at least 8 hours before use.• Use paddle mixer and slow speed (300-500 RPM)

• Keep mixing until uniform• Use slow agitation during mixing – do not over-mix.• Pour off and re-seal material not immediately used.• Agitate during application to prevent separation.

Spray Application Equipment

Air operated jiffy mixer or heavy duty electric jiffy mixer.Paddle-type slow speed mixing blade.

(a.) Binks 2001 gun #599 Fluid Nozzle#262 Air Nozzle#54-2065 Ring

***********or***********(b.) Graco #248091 Spray gun

#287227 6.4 mm Fine Finish Nozzle

Remove all filters and screens from spray equipment.Agitate to prevent separation during application.

RecommendedSpray Guns

Hi-Temp XXTIC-707

Easy, multi-pass applicationOrange-peel finish for ambient applicationCoarse finish for hot surface applicationDries at ambient or hot applied.

Thinning: Not neededClean up: Water

Problems with traditional insulation

• If traditional insulation is chosen, it must be done ONCE installed.

• Impossible to see corrosion with traditional insulation

• Insulation / jacketing takes up more space and weighs more.

• Difficult and expensive to insulate and jacket while unit is hot.

• Insulation is subject to failure by water saturation.

Typical Application of XXTIC-707 16” DIA methane gas Pipe

• Blast to SSPC SP6 commercial blast• Apply one coat of HTC 1027 primer at @ mils DFT 8-12

hrs• Apply first coat of XX-707 40-50 mils 3-4 hours dry

time• Apply second coat XX-707 40-50 mils in tandem with

first coat• Apply final coat of XX-707 at 40-50 mils for a total of

120-150 mils DFT

Summary/ConclusionA new type of coating system has been developed to act as a thermal

interface using a system’s approach. The system is a composite design that will consist of a corrosion inhibitive/barrier primer coating as a first layer consistent with the requirements discussed in part I of this form. This will then be top-coated with a TIC thermal insulative coating, thickness will vary depending on application requirements.

The new seamless tightly adherent composite is the ultimate solution for CUI and gives the owner the capabilities of visual inspection without damage and makes restoration work cost effectively.

In addition to the ability of insulating and providing corrosion control, personal protection, sound control, and low temperature service requirements are also addressed with this new technology.

References

McGowan, Nancy. “Innovation and Environmentally Benign Solution for Corrosion Under Insulation (C.U.I.) for Steam Process Piping.” NAVSEA 1996. Jun. 6, 1996.

Abayarathna, Dharma. “Measurement of Corrosion Under Insulation and Effectiveness of Protective Coatings,” NACE 1997.

“Corrosion of Metals Under Thermal Insulation” ASTM STP 880 W.I. Pollock and J. Barnhart, Eds., for ASTM 1985.

Preventing Corrosion Under Insulation in chemical Manufacturing Facilities.” Bruce Rutherfor, JPCL, July, 1998.

“The Control of Corrosion Under Thermal Insulation and Fire Proofing Materials – A Systems Approach.” NACE RPO 198-98, Item No. 21084 NACE International 1998.