1. A study on the application of modern corrosion
resistant alloys in the upstream oil and gas
industry – Cost optimization
Presenter : Kukuh W. Soerowidjojo
Company : Sandvik Materials Technology SEA
16th – 18th August 2016

2. INTRODUCTION
Background:
• A push from the industry to have more efficient process, cost
efficient and in the same time keep the safety as paramount.
• Developed understanding of fabrication, welding and
availability of duplex stainless steel family.
• New grades in duplex family
Contents:
• Corrosion resistant materials and its mechanical and corrosion
properties
• Alloying element price and cost index
• Case study
• Summary

3. OPPORTUNITY OF COST SAVING IN
CRA SELECTION
Cost
saving
potentials
Mechanical
properties
Design change by
Utilizing higher
strength
Thinner wall,
less material
and possibly
less costly
Better CAPEX
Corrosion
properties
Longer life cycle
Less maintenance
Less loss of production
Less operation cost
Better
Present Value
with Less
OPEX
Alloy selection based
on alloying element
selection
Less expensive
alloying element
cost
Possible less
costly alloy
Better CAPEX

4. CHEMICAL COMPOSITIONS OF CRA’S
UNS #
Main alloying elements
PRE
Ni Cr Mo N
UNS S30403 8.0 - 12.0 18.0 - 20.0 max 0.1 20
UNS S31603 10.0 -14.0 16.0 - 18.0 2.0 - 3.0 max 0.1 25
UNS S32304 3.0 - 5.5 21.5 - 24.5 0.05 - 0.60 0.05 - 0.20 25
UNS S32101 1.35 - 1.70 21.0 - 22.0 0.10 - 0.80 0.20 - 0.25 27
UNS N08904 23.0 - 28.0 19.0 - 23.0 4.0 - 5.0 >35
UNS S32205 4.5 - 6.5 22.0 - 23.0 3.0 - 3.5 0.14 - 0.20 >35
UNS S31254 17.5 - 18.5 19.5 -20.5 6.0 - 6.5 0.18 - 0.22 >40
UNS S32750 6.0 - 8.0 24.0 - 26.0 3.0 - 5.0 0.24 - 0.32 >40
UNS N06625 min. 58 20.0 - 23.0 8.0 - 10.0 >50
UNS S32707 5.5 - 9.5 26.0 - 29.0 4.0 - 5.0 0.30 - 0.50 >50
UNS S33207 6.0 - 9.0 29.0 - 33.0 3.0 - 5.0 0.40 - 0.60 >50
PREN = % Cr + 3.3 x % Mo + 16 x %N

5. COMMON CORROSION AT CRA IN OIL
AND GAS OFFSHORE ENVIRONMENT

6. OTHER POSSIBLE CORROSION FORMS
• MIC – microbiological Induced Corrosion
• Mercury stress cracking
• TOL (top of line) corrosion
• Erosion corrosion
• Fatigue corrosion
• Under insulation corrosion
• Etc.

7. STRESS CORROSION CRACKING

8. CREVICE AND PITTING
0
10
20
30
40
50
60
0
20
40
60
80
100
120
CCT and CPT versus PRE graph
CCT
CPT
PRE
TemperatureoC(oF)
PRE
(68)
(104)
(140)
(176)
(212)
(248)
ASTM G48 method E and F

9. MECHANICAL PROPERTIES
Duplex family has much
higher yield strength than
austenitic SS family

10. MECHANICAL PROPERTIES
Normal Design pressure calculation based on ASME B31.3
Temperature 40°C 40°C 40°C 40°C
Grade 316/316L Alloy825 SAF2205 SAF2507
Allowable stress 20.00 23.3 30 38.7
Wall thickness tolerance % 10.0% 10.0% 10.0% 10.0%
OD (mm) 12.7 12.7 12.7 12.7
Wall thickness (mm) 1.65 1.65 1.65 1.65
Allowable internal pressure (ksi) 5.160 6.011 7.740 9.984
Allowable internal pressure (bar) 356 414 534 688
Test pressure (ksi)* 7.740 9.017 11.610 14.976
Test pressure (bar)* 533.6 621.7 800.5 1,032.6
Barlow equation
Burst pressure (ksi) 17.539 19.878 20.010 26.110
Burst pressure (bar) 1,209.3 1,370.5 1,379.6 1,800.2
API 5C3
Collapse pressure (ksi) 6.589 7.218 14.527 16.474
Collapse pressure (bar) 454.3 497.7 1,001.6 1,135.8

11. ALLOYING ELEMENTS PRICE AND
COST INDEX
• Alloying elements price
fluctuate over the time
especially nickel and
molybdenum.
• Nickel has high percentage
in CRA and Molybdenum is
the most expensive
alloying element in CRA.
• Alloying cost index could
be used as the first step of
financial analysis of
material selection.
• Cost of alloying element
50% -70%

12. CASE STUDY
A case study was conducted to propose material for :
• 2 ½” (outer diameter 73.0.3 mm) drilling riser hydraulic line for 6000 psi and 8000 psi internal
pressure with austenitic UNS S31603 as the base.
• Alternatives by considering both mechanical and corrosion properties.
• Wall thicknesses selected are standard wall thicknesses available.
• Selected materials acquire the same level or higher corrosion resistance than austenitic UNS
S31603 in seawater environment.
• Lean duplex UNS S32304, duplex UNS S32205 and super duplex UNS S32750.
• Other austenitic grades are not included since they all have higher alloying element cost indices.

13. PRESSURE CALCULATION AND PRICE
INDEX

14. DISCUSSION
• It is necessary to combine the evaluation of engineering and financial
analysis to reach a conclusion of financial benefit to choose a certain
grade of material.
• Alloying elements keep changing overtime hence corrosion resistance
materials price as well.
• Material with higher PRE has a higher resistance to marine
environment corrosion, hence it is necessary to specify minimum PRE
number in the material specification.
• Although the corrosion resistance of duplex family is well known, a few
producers took more preventive action to coat high alloyed stainless
steel pipes.
• In the case study, there is no standard size available for grade 316L for
8,000 psi rated system. Hence, the size is specially designed for the
equipment and that may increase the price significantly.

15. SUMMARY
• Cost saving could be reviewed from 3 different parameters i.e.
corrosion resistance, mechanical properties and alloying elements.
• Alloying element prices contains 50-70% in the cost structure of end
products.
• This case study only calculates the saving CAPEX by considering
both corrosion resistance and mechanical strength.
• Pressure calculations are based on ASME B31.3 (2002) and it has
revealed that duplex and super duplex grades can save significant
weight and could lead to cost saving.
• If there is any other additional corrosion protection in the system, it
should be taken into consideration to add in the cost of acquisition.
• Finally, it is important to have life cycle calculation to justify the
material selection.