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WORLD PIPELINES SEPTEMBER 2006 www.worldpipelines.com 29

2DADA=PEOKJDr. Peter Singh, Bredero Shaw, Canada, discusses the

speci cs of high temperature insulated pipeline designed

for the particular demands of oil sands development.

!ommercial exploitation of the Alberta tar sands is creating the need for high temperature insulation coat-ings for bitumen pipelines. In recent years, many large

energy companies have announced major oil sands development projects. Development plans include thermal extraction methods to separate the heavy oil from the sand and transport-ing it to markets via Edmonton using large diameter transmission pipelines.

There are two options for transport-ing the bitumen by pipeline. The diluent method uses lighter hydrocarbon frac-tions blended with the heavy bitumen to lower the viscosity and allow it to be economically pumped. After refining, the light fractions are recovered and reused. There are several drawbacks to this, one being the larger pipeline capacity needed to transport a given amount of bitumen, and a second being another pipeline is needed for recycling the light fraction.

The second option, which is now being given stronger consideration, is to heat the bitumen to a temperature where the viscosity is sufficiently lowered to make pump-ing favourable. The temperatures being considered are in the range of 110 - 150 C and even higher in some cases. In the past, this option was discounted due to the lack of economical coating and insulation solutions available for the high temperature.

2A?DJKHKCUThe coating for a high temperature pipeline includes a cor-rosion coating, an insulation layer and a protective topcoat.

The corrosion coating provides an additional safety element to protect the pipe in the event of topcoat and insulation damage, which could allow the influx of corrosive media. It is also a requirement of the Alberta Energy Utility Board that oil and gas pipelines be built according to the CSA Z662 standard, which requires both corrosion coating and cathodic protection to be applied (Figure 1).

The typical design of the pipeline requires several heat-ing stations to heat the bitumen, in order to compensate for heat losses and maintain the temperature above a critical flow temperature. The insulation should have very low thermal conductivity in order to reduce the number and proximity of required heating stations. Additionally, the pipeline should maintain a reasonable temperature long enough to allow remedial action such as pigging or injection of condensate in the event of an uncontrolled

Figure 1. Cross section of high temperature insulated

pipe system.

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30 WORLD PIPELINES SEPTEMBER 2006 www.worldpipelines.com

shutdown. Polyurethane foam insulation has been exten-sively used in oil and gas pipelines in the past. It has a very low thermal conductivity and high compressive strength, coupled with the ability to bond to the coated steel and restrain the pipeline by transferring shear forces between the steel and the soil.

The jacket system is required to protect the foam from the elements, thereby preventing degradation of the foam and reducing its insulation value. Typically, high density polyethylene material has extensive experience in this role, and has proven to be the material with the right mix of prop-erties such as moisture permeation resistance, flexibility, toughness and generally good handling characteristics.

!D=HHAJCAOSome of the challenges of a high temperature pipeline insulation system are very unique to the Canadian oil sands environment:l 110 C to 150 C temperature capability of the corro-

sion coating and insulation. The pipeline is normally designed for a lifetime in excess of 30 years. The prop-erties should remain above the minimum requirements over this period.

l Joint lengths of 25 m (80 ft) are used to reduce the

high field labour costs of welding and joint coating dur-ing installation, as well as increase pipe laying speed.

l High compressive strength greater than 480 kPa (70 psi) to resist compressive forces from pipeline/soil weight, thermal expansion as well as compensate for reduction due to ageing at the high temperature. Additionally, the long joints are normally transported using pole trailers with a limited support area near the ends. The foam must have high enough compressive strength to prevent crushing.

l Construction has to be carried out in winter and this requires handling and installation in temperatures that can reach -40 C for prolonged periods. Good flexibility and handling characteristics are required to prevent cracking and catastrophic failures of the polyethylene jacket.

l Compatible with available joint coating systems to achieve desirable production speed in the environ-ment.

l Strong bond between foam and coated steel pipe to restrain the pipeline from large thermal expansion.

l Ability to bend the insulated pipe in the field to fit the contours of the right of way, or ability to insulate induc-tion heated pre-bend.

0AOA=N?D=J@@ARAHKLIAJPHistorically, there has been little or no experience with insulated oil transmission pipelines at these high tempera-tures. Long term testing was carried out to validate the design and performance of the individual components, as well as the whole insulated pipe system.

The first stage involved evaluating the anti-corrosion coating. A high temperature fusion bonded epoxy material (FBE) was selected from a number of potential candidates. Standard coating tests referenced in CSA Z245.20 were carried out. In addition, modified adhesion and cathodic disbondment tests with higher temperature and longer exposure duration were completed. The results show that the high temperature FBE coatings performed very well and were suitable for the intended application.

The polyurethane foam insulation was evaluated using the EN 253 standard ASTM tests, as well as internal test methods. Properties such as density, compressive strength,

thermal conductivity, water absorp-tion and glass transition tempera-ture were measured.

The complete insulated pipe system was evaluated for mechani-cal properties such as impact, shear strength of the jacket and insulation to the pipe, and flexibility at cold temperature. Full scale flex-ibility testing was carried out with the insulated pipe system being bent up to 1.5 per pipe diameter at -25 C without cracking in the foam or jacket.

Accelerated heat ageing was carried out following the procedure outlined in the EN 253 standard on pre-insulated bonded pipe systems. The test involves the ageing of pipes at temperatures above the design temperature. This accelerates the effects of ageing of the insulation,

Table 1. Summary of test results

Property Bredero Shaw Type-1 HT Foam EN 253:2003 requirements

Test pipe size x foam thickness (mm)

114.3 x 50 60.3 x 28 (typ.)

Anticorrosion coating FBE None

Density (kg/m3) 84.2 *60

Compressive strength (MPa)

0.7 *0.3

Water absorption (%) 6.1 )10

Closed cell content (%) 90 *88

Un-aged axial shear at 23 C (MPa)

0.205 *0.12

Un-aged axial shear at 140 C (MPa)

0.118@ 150 C

*0.08

Un-aged tangential shear at 23 C (MPa)

0.445 *0.20

Un-aged tangential shear at 140 C (MPa)

0.338@ 150 C

Not specified

Figure 2. Accelerated heat ageing apparatus.

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32 WORLD PIPELINES SEPTEMBER 2006 www.worldpipelines.com

which can then be measured in shorter test durations. The test results are then used to extrapolate to the estimated maximum operating temperature for the design lifetime.

Initial, as well as thermally aged, performance results indicate that the system has a maximum operating tem-perature of 150 C (Figure 2).

.NK@Q?PEKJBredero Shaw has extensive experience with sprayed and molded polyurethane foam used in pre-insulated pipes. The pipe is coated in two processes. The first is the application of anti-corrosion FBE coating. Then, the pipe is taken to the insulation plant where polyurethane foam is spray applied and a polyethylene outer jacket is extruded over the foam (Figures 3 and 4).

The foam insulation is produced by the mix-ing of two fast reacting liquid components along with a cyclopentane blowing agent, to achieve the required density and performance proper-ties.

!KJOPNQ?PEKJATLANEAJ?AInsulated pipe systems have been used for a long time in oil and gas pipelines in Western Canada. They are used to prevent hydrate forma-tion in gas production and to prevent the build up of waxes and asphaltenes in oil pipelines. Considerable expertise exists in the design-ing and construction of long, buried insulated pipelines. Innovative techniques and equipment are being used in transportation, field bending, field foaming and pre-stressing. In general, with thousands of kilometers of buried insulated pipelines, there is very good operating experi-ence and high integrity of these pipelines.

$EAH@FKEJPThe field joint to be used is a Canusa Supercase CSC. It provides a comparable level of insu-lation to complement the insulation coating on the line pipe. The CSC is heat shrink-able and combines a cross-linked, high density polyethylene casing with a high shear and peel strength adhesive to provide a high quality, reli-able system for protection and sealing of joints. As a result of its design, the ends of the CSC

casing preferentially shrink. This innovation makes it per-fect for foam-in-place applications.l Specially designed to allow complete foam fill.l Air-pressure testability ensures a quality installation.l High performance, user friendly adhesive ensures long-

term sealing protection.

Figure 3. Step 1 - FBE application.

Figure 4. Step 2 - HT insulation application.

Figure 5. PIpeline right of way.

Figure 6. Insulated coated pipe.

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WORLD PIPELINES SEPTEMBER 2006 www.worldpipelines.com 33

l Cross-linked backing results in excellent field handling and does not pre-shrink in direct sunlight.

l Retains its shape and high stress resistance over the lifetime of the pipeline.

l Non-cross-linked enhancements provide a conduit for standard weldable plugs.

l Meets and exceeds the European Standard EN489 for district heating joints.

!KJ?HQOEKJShaw Pipe Protection Limited, part of Bredero Shaw, is a premier provider of insulated pipes for the oil and gas industry in western Canada. Pipeline operators, designers and contractors have gained extensive experience with the product and are affirmative in its implementation in existing and new projects. With ongoing developments in the oil sands of Alberta, Bredero Shaw has continuously improved and developed new products to meet the rising challenges.

The company has developed a high temperature insu-lation system for application in bitumen transportation. Extensive validation testing shows that the system will meet the requirements expected in the design of a high temperature pipeline up to 150 C. The system uses a spray-applied polyurethane foam, which has high tempera-ture capability, and is superior in both performance and economics compared to molded foam district heating insu-lation systems. The polyethylene jacket provides excellent damage and moisture resistance and can be expected to handle well during winter construction.

Figure 7. Insulated pipe being bent.

Figure 8. Heat shrinkable casing system for half-shell foamed pre-insulated pipe joints.