Influence of foam morphology on end of life U-value for subsea foamed polypropylene pipeline insulation

Transcription

1 June 7, 2017 Influence of foam morphology on end of life U-value for subsea foamed polypropylene pipeline insulation AMI s Oil & Gas Polymer Engineering Texas 2017

2 2 Foam Morphology and End of Life U-value Contents Shawcor at a glance Hydrostatic compression Triaxial compression test Simulated Service Test U-value case study Foam morphology Triaxial test results SST results Thermal design process Hypothetical designs Summary

3 3 Shawcor at glance Global Energy Services Company Provides technology-based solutions for the pipeline and pipe services market, and the petrochemical and industrial markets. Shawcor focuses on five core competencies: pipeline coating, welding inspections, composite pipe, oilfield asset management and cables and connectors ~ 5,000 Employees worldwide 80+ Global locations 25 Countries across the globe 236 Issued Patents, 86 Proprietary Formulations Solutions Driven by Innovative Technology ~ $1.8 (CAD) Billion revenues

4 4 Shawcor Products and Services Offering

5 Water Depth [m] 5 Shawcor Wet flowline insulation solutions PPFoam 150 C and 500 m High density foam. Nominal density 740 kg/m GsPU (U > 3 W / m² K) UltraSolid (U > 3 W / m² K) UltraFoam (U > 2 W / m² K) spp (U > 3 W / m² K) XtremeTemp (U > 3 W / m² K) PPFoam (U > 3 W / m² K) Design Temperature [ C]

6 6 Hydrostatic Compression Hydrostatic pressure according to water depth, from 1 MPa to 30 MPa Constant over the pipeline s lifetime ( 30 years) Initial compression component Upon installation Considered instantaneous Recoverable Creep compression component Over entire lifetime Limited recovery ISO 12736* calls for determination of hydrostatic compressive behavior of each layer of insulation At 23 C and max. rated temperature Shall be determined for each insulation layer *Standard for Petroleum and natural gas industries Wet thermal insulation coatings for pipelines, flow lines, equipment and subsea structures

7 MEASUREMENT OF HYDROSTATIC COMPRESSION Triaxial Compression Test and Simulated Service Test 7

8 8 Triaxial Compression Test Method Cylindrical test specimen Contained in cylindrical steel autoclave Piston pressing down on top of sample Produces a tri-axial stress state Mimics the stresses in pipe coating Temperature and pressure constant Compression recorded over time Measures initial compression Measures creep compression Common test on foamed insulation at Shawcor Described in ISO Annex A Essential test for design of thermal insulation

9 9 Triaxial Compression Test Creep rates increase with temperature Thick insulation is split into test sections (L1, L2, L3,.) Average temperature is calculated for each section. Cylindrical test specimen Typically Ø32 mm x 55 mm Machined to 0.03 mm tolerance Radial orientation One specimen can be made from several plugs Diameter is compensated for thermal expansion - allows a snug fit in the autoclave L1 L1 L1

10 10 Triaxial Compression Test Compression of PPFoam follows a logarithmic trend Typical test duration is 100 h Short duration is verified by long term testing Large library of historical data 20 years = h 25 years = h 30 years = h End of Life (typically 30 years) compression is extrapolated Compression is dependent on pressure, temperature, foam density and foam morphology.

11 11 Simulated Service Test SST description A 28 day test of the pipe at operational conditions: Internal operation temperature External water temperature and hydrostatic water pressure Measures heat loss and radial compression Primarily used to verify the U-value (next slide) of the pipe In some cases the SST is used to verify cool-down or thermal cycling performance The SST is not an ageing test Shawcor CR&D test vessel: Heat loss measured through surface of insulated pipe Displacement of pipe surface measured using LVDTs Shawcor CR&D vessel 6 m pipe specimen 7 electrically heated temperature zones 20 pipe surface heat flux sensors in 7 zones 12 high resolution LVDTs in 4 zones

12 Compression [%] 12 Simulated Service Test LVDT sensitivity 2,0 1,5 1,0 0,5 Internal heaters turned on 0,0 Thermal expansion -0,5-1,0 Time [minutes] Start pressurization

13 ሶ 13 Simulated Service Test SST U-value ሶ The U-value is an engineering concept. Convenient for calculating a heat loss rate for a given temperature differential: U R ref = ref T o T i R ref - radius of a cylindrical reference surface q R ref - heat flux through the reference surface, i.e. heat loss rate per unit area T o T i - the temperature difference driving the heat loss R ref R o R i T o and T i are kept constant during the test. Shawcor will measure the heat flux qሶ R o through the outer surface of the pipe (at R o ) and calculate qሶ R ref : qሶ R ref = R o R ref qሶ R o 2R ref is defined by the Client. It is always the inner or outer diameter of the steel pipe. Shawcor will design an isulation that meets the Client s U-value requirement at 2R ref. Shawcor measure U-value at an accuracy of approx. 3 % T i T o

14 14 Simulated Service Test SST compression SST compression is reported as an average over the 28 day test duration OK for low compression materials Glass syntactic PP Solid materials PPFoam at low pressure and low temperature Caution required for high compression materials PPFoam at high pressure and high temperature Other foams with a long term creep trend. PPFoam creep compression occurs on a time scale longer than the 28 day test duration For PPFoam, less than 50 % of the total compression over the lifetime of the pipe may occur during the test duration. High compaction will increase the density of the insulation, in turn increasing the U- value. Operation temperature typically drops with time in service and lowers the minimum downstream temperature where hydrate formation is critical => EOL is important! Very limited SST compression data is available. Must cover a wide range of temperatures and pressures (and pipe/layer geometries and foam densities).

15 15 Simulated Service Test U-value as function of compression The insulation should meet the U- value criteria at the end of the life (EOL) of the pipeline. Coating compression as function of time is determined with low uncertainty and can be extrapolated to EOL Typically no significant trend to determine EOL U-value. Accurancy of U-value measurement is 3 % Shawcor will design insulations that meets the U-value at the end of life of the pipeline based on EOL compression data. Requires knowledge about the creep compression rate of the coating.

16 DESIGN CASE STUDY U-value for poor vs. improved foam morphology 16

17 17 DESIGN CASE STUDY Poor foam morphology vs. Improved foam morphology SST and triaxial compression measurements taken from full scale pipes: Pipes produced with poor foam morphology. High compression. Pipes with improved foam morphology due to process improvements. Test results are directly comparable: Same pipe OD Same foam density (740 kg/m 3 ) Same test pressure (5.6 MPa) Same test temperature Similar thicknesses Hypotetical thermal designs were made to illustrate: Impact on material consumption Impact on U-value

18 18 Foam Morphology Identification Image Segmentation Identify each foam cell Find the centroid of the cell Measure cell size, cell orientation and aspect ratio Calculate the number density of cells, i.e. number of foam cells per mm 3. If applicable: Calculate foam transport properties or mechanical properties

19 19 Foam Morphology Improvements Improvement of Morphology Use different foaming agent Pellet size and distribution Foaming agent powder size and distribution Nucleation mechanism Fine tune loading of foaming agent: Too much will cause course foam structure with much cell coalescence Set moderate melt temperature: High end temperature will increase foam cell size and reduce number density Reduce mechanical distortion of foam cells: Elongated foam cells have low compressive strength Low dosage Deformation Coalescence Improved Micrographs have the same scale Same density Cell size down 35 % Aspect radio down 40 %

20 Compression [%] 20 Triaxial Test Results 5.6 MPa Poor foam morphology: 8.1 % compression end of test and 12 % extrapolated to EOL at 73 C. Improved foam morphology: 4.3 % compression end of test and 6.4 % extrapolated to EOL at 73 C. Excellent fit to logarithmic function for all temperatures. R Same density ± 2 % Poor morphology, 30 C Poor morphology, 50 C Poor morphology, 73 C Improved morphology, 30 C Improved morphology, 50 C Improved morphology, 73 C 1 0 0,01 0, Time [h]

21 Compression [%] Compression [%] 21 SST Compression Test Results 5.6 MPa SST compression data: 3,5 3,0 2,5 2,0 1,5 EOL extrapolation: 5,0 4,5 4,0 3,5 3,0 2,5 2,0 y = 0,2713ln(x) + 1,2126 R² = 0,9985 y = 0,1650ln(x) + 0,4070 R² = 0,9997 1,0 1,5 0,5 1,0 0,5 y = 0,1560ln(x) + 0,2774 R² = 0,9983 0, , Time [h] Time [h] Before improvement After improvement 1 After improvement 2 30 years Log. (After improvement 2) Log. (After improvement 1) Log. (Before improvement) Low compression critical for strapped on units requiring pretension

22 22 Triaxial vs. SST Compression 5.6 MPa Tri-axial compression Thickness EOL triaxial compression [%] Layer [mm] Before opt. After opt. FBE 0,3 0,0 0,0 Adhesive 0,3 0,0 0,0 3L 5,4 1,0 1,0 Foam layer ,8 6,4 Solid intermediate 3 1,0 1,0 Foam layer ,2 5,1 Solid intermediate 3 1,0 1,0 Foam layer ,4 3,4 Solid topcoat 4 1,0 1,0 Thickness weighed compr. [%] 8,2 4,4 SST compression Before improvement: 3.0 % end of test compression 4.7 % EOL compression After improvement: 1.3 % end of test compression 2.2 % EOL compression Shawcor SST have high accuracy on compression LVDTs. Measurement can be considered the actual compression of the pipeline. Triaxial compression results are conservative compared to SST compression results Better models are needed for the relationship between triaxial tests and actual compression (SST)

23 23 Thermal Insulation Design Process Requirements and Conditions U-value Cool-down time Max. compression Max. thickness Buoyancy Design temperature Water depth Lifetime Installation type Other input Design Select insulation system Foam density Compression Thermal properties Proven capability => Layer thicknesses U-value Cost Etc. Verification Triaxial compression Other material tests Installation tests Simulated Service Test Other system tests

24 24 Thermal Insulation Design Process U-value A thermal design defines the thickness of insulation required to reach an insulation requirement The most common requirement is U-value Insulation coatings consists of several layers Each layer in the thermal insulation is defined at start of life (SOL) and end of life (EOL) Thickness Density ρ Thermal conductivity k Foam density increases with compression Thermal conductivity increases with increasing foam density For small changes in density k EOL = k SOL ρ EOL ρ SOL U-value increases with increasing thermal conductivity n ln(rj+1 /R j ) U R ref = R ref j=1 R ref k j R j R j+1 1

25 25 Cost Impact, SST compression Poor foam morphology. U = 2.36 W/m 2 /K. Improved foam morphology. U = 2.36 W/m 2 /K. Layer Build Start of Life Material Thickn. [mm] k [W/(m K)] Dens. [kg/m 3 ] FBE 0,3 0, Adhesive 0,3 0, PP Solid 5,4 0, PP Foam Inner 30,0 0, PP Solid 3,0 0, PP Foam Mid 30,0 0, PP Solid 3,0 0, PP Foam Outer 30,0 0, PP Solid 4,0 0, Layer Build Start of Life Material Thickn. [mm] k [W/(m K)] Dens. [kg/m 3 ] FBE 0,3 0, Adhesive 0,3 0, PP Solid 5,4 0, PP Foam Inner 28,0 0, PP Solid 3,0 0, PP Foam Mid 28,0 0, PP Solid 3,0 0, PP Foam Outer 28,6 0, PP Solid 4,0 0, Total 106,0 Total 100,6 Layer Build End of Life Material Thickn. [mm] k [W/(m K)] Dens. [kg/m 3 ] FBE 0,3 0, Adhesive 0,3 0, PP Solid 5,4 0, PP Foam Inner 27,3 0, PP Solid 3,0 0, PP Foam Mid 28,6 0, PP Solid 3,0 0, PP Foam Outer 29,2 0, PP Solid 4,0 0, Total 101,0 Layer Build End of Life Coating mass [kg/m] 121,19 Coating mass [kg/m] 115,50 Coating compression 4,7 % Matching the SST compression Coating compression 2,2 % 5 % reduction in thickness and PP consumption with improved foam Material Thickn. [mm] k [W/(m K)] Dens. [kg/m 3 ] FBE 0,3 0, Adhesive 0,3 0, PP Solid 5,4 0, PP Foam Inner 27,0 0, PP Solid 3,0 0, PP Foam Mid 27,4 0, PP Solid 3,0 0, PP Foam Outer 28,2 0, PP Solid 4,0 0, Total 98,4

26 26 U-value Impact, SST compression Poor foam morhology. Thickness 106 mm. Improved foam morphology. Thickness 106 mm. Layer Build Start of Life Material Thickn. [mm] k [W/(m K)] Dens. [kg/m 3 ] FBE 0,3 0, Adhesive 0,3 0, PP Solid 5,4 0, PP Foam Inner 30,0 0, PP Solid 3,0 0, PP Foam Mid 30,0 0, PP Solid 3,0 0, PP Foam Outer 30,0 0, PP Solid 4,0 0, Total 106,0 Layer Build Start of Life Material Thickn. [mm] k [W/(m K)] Dens. [kg/m 3 ] FBE 0,3 0, Adhesive 0,3 0, PP Solid 5,4 0, PP Foam Inner 30,0 0, PP Solid 3,0 0, PP Foam Mid 30,0 0, PP Solid 3,0 0, PP Foam Outer 30,0 0, PP Solid 4,0 0, Total 106,0 Layer Build End of Life Material Thickn. [mm] k [W/(m K)] Dens. [kg/m 3 ] FBE 0,3 0, Adhesive 0,3 0, PP Solid 5,4 0, PP Foam Inner 27,3 0, PP Solid 3,0 0, PP Foam Mid 28,6 0, PP Solid 3,0 0, PP Foam Outer 29,2 0, PP Solid 4,0 0, Total 101,0 Layer Build End of Life Material Thickn. [mm] k [W/(m K)] Dens. [kg/m 3 ] FBE 0,3 0, Adhesive 0,3 0, PP Solid 5,4 0, PP Foam Inner 28,9 0, PP Solid 3,0 0, PP Foam Mid 29,3 0, PP Solid 3,0 0, PP Foam Outer 29,5 0, PP Solid 4,0 0, Total 103,6 U-value of LP on OD 2,36 W/(m 2 K) U-value of LP on OD 2,25 W/(m 2 K) Coating compression 4,7 % Matching the SST compression Coating compression 2,2 % 5 % reduction in U-value

27 27 What compression data to use in design? SST compression data U = 2.36 W/m 2 /K 4.7 % => 2.2 % compression 106 mm => 101 mm thickness kg/m PP => kg/m PP (5 % down) Triaxial compression data U = 2.36 W/m 2 /K 8.2 % => 4.4 % compression 116 mm => 105 mm thickness kg/m PP => kg/m PP (11 % down) Thickness 106 mm 4.7 % => 2.2 % compression 2.36 W/m 2 /K => 2.25 W/m 2 /K (5 % down) Thickness 116 mm 8.2 % => 4.4 % compression 2.36 W/m 2 /K => 2.18 W/m 2 /K (8 % down) Compression data - Only known after test (PQT stage) + Actual compression Compression data - Overly conservative + Wide range of historical data available In general, historical triaxial compression data is used in design. However, 8.2 % would be considered unrealistically high.

28 28 Summary ISO12736 calls for determination of hydrostatic compressive behavior Triaxial compression test is a good method for measuring creep compression, but conservative Detailed knowledge of foam compression is essential for accurate thermal designs Triaxial compression data is primary source of compression data for design Future work: Better models are needed for the relationship between triaxial test results and actual compression (SST) U-value EOL can not generally be determined in SST test Poor PPFoam morphology can double foam compression Foam morphology (aspect ratio, cell size, cell number density) can be quantified using image segmentation to show foam improvement Foam compressibility can be improved by process improvements Improved foam morphology reduces project cost

29 29 Foam Morphology and End of Life U-value Thank you for your attention. QUESTIONS? JAN PEDER HEGDAL Research Manager Global Flow Assurance Pipeline Performance Shawcor Norway A/S P.O. Box 214, N-7301 Orkanger, Norway m +44 (0) m e jphegdal@shawcor.com shawcor.com