2. Table of Contents
PART 1: GENERAL INFORMATION 3
PART 2: THREATS AND RISKS: 5
PART 3: FACTS NOT FICTION 6
PART 4: SUSCEPTABILITIES TO FAILURE 7
PART 5: CONSEQUENCE OF FAILURE 11
PART 6: CRITICALITY 14
PART 7: REMNANT LIFE CALCULATIONS 17
PART 8: INSPECTION PLAN 22
2
3. MODULE 31
V-3010
VT-30002-9341X
4-VF-42057-1341X 4-VF-42057-9341X
10-VF-42056-1341X
10-PG-30002-AA02
6" 4" 10"
HIGH High Level Trip
10-PO-30018-9145X 10"
24"
1743 mm
1660 mm
Low Low Level Trip
558 mm
3" 3" 3" 3" 8"
3-OW-40013-9143X 3-OW-40013-9341X 6-PO-30019-9341X 6-PO-30019-3145X
6-CD-40007-9341X
PART 1: GENERAL INFORMATION
Unit Name: High Pressure Oil Production Separator
Unit Description: Horizontal cigar shape gravity separator, with one bottom weir.
Process Description: 3 phase (oil, gas, water) mix from high pressure oil producing
wells enters the vessel via 10” inlet nozzle, inside the vessel the product separates with
the assistance of the spreader, gas occupies the upper half of the vessel while oil and
water goes to the lower half of the vessel while oil and water goes to the lower half
behind the weir. By gravity (density difference). Oil passes over the weir when reaches
the desired level to the front compartment.
Unit Design Parameters:
Design Pressure 100 BARG
Design Temperature 90/-50 DEGC
3
4. Unit Operating Parameters:
Maximum Operating Pressure 89 BARG
Maximum Operating Temperature 78 DEGC
Unit Construction Parameters:
Volume: 53m3
Material: Carbon Steel
Shell Thickness: 71mm
Head Thickness: 38 mm
Corrosion Allowance: 6 mm
Inner Surface Area: 135 m2
Inner Surface Coating: Amine Adduct Crude Epoxy 75 mic, + 300 Glass
flake Epoxy 300 mic
Outer Surface Area: 150 m2
Outer Surface Coating: Zinc Silicate 100 mic.
Year Built: 1989
Attached Piping:
10-PO-30018-9145X 3 PHAZE PRODUCT INLET LINE
10-PG-30002-AA02 GAS TO GAS TRAINS
4-VF-42057-9341X GAS TO FLARE HEADER
4-VF-42058-1341X GAS TO FLARE HEADER
10-VF-42056-1341X GAS TO FLARE HEADER
6-CD-40007-9341X WATER TO CLOSED DRAIN
3-OW-40013-9341X WATER TO OILY WATER NET
3-OW-40013-9143X WATER TO OILY WATER NET
6-PO-30019-3145X OIL TO V-3020
6-PO-30019-9341X OIL TO V-3020
4
5. PART 2: THREATS AND RISKS:
Vessel Threats:
External Corrosion:
External corrosion is caused by surrounding environment impact on the vessel material.
External corrosion forms as general, pitting and crevice corrosion.
Internal Corrosion:
Internal corrosion is caused by processed product impact on the vessel material,
exacerbated by elevated pressure and temperature.
Internal corrosion forms as general, pitting, galvanic, crevice and stress corrosion.
Associated Piping Threats:
External Corrosion:
External corrosion is caused by surrounding environment impact on the piping material.
External corrosion forms as general, pitting and crevice corrosion.
Internal Corrosion:
Internal corrosion is caused by processed product impact on the vessel material,
exacerbated by elevated pressure and temperature.
Internal corrosion forms as general, pitting, galvanic, erosion, crevice and stress
corrosion.
Saddles, Supports, Walkways and Concrete Foundation Threats:
Saddles, supports and concrete foundation reinforcing steel suffer from general and
crevice corrosion. Walkways, platforms and ladders are more susceptible to mechanical
damage and bolting looseness.
5
6. PART 3: FACTS NOT FICTION
Date Ref Description
26.09.94 94-398 • Coating problems exist since the beginning of the vessel
• Coating failure reported since September 1992
14.03.95 POC/0282/95 • Recommendations for wall thickness survey on water outlet line after
the level control valve on 3-OW-40013-9341X line.
23.03.95 TI95-111 • Wall thickness survey carried out, no thickness degradation revealed.
21.01.95 TI95-024 • External wall thickness survey on the vessel showed no thickness
degradation.
24.02.96 TI96-024 • External wall thickness survey on the vessel and attached piping
showed no thickness degradation.
15.07.96 TI96-117 • Internal visual inspection reported internal coating deterioration, and
2mm pitting corrosion distributed allover the vessel surface.
27.02.98 TI98-047 • External wall thickness survey showed no significant degradation
• Low readings obtained on 10-VF-42056-1341X.
13.08.2K TI2K-196 • Clusters of sound blistered areas along the vessel coating with no
corrosion or rusting beneath.
• Cracks in the internal paint reported.
• Paint flecking in the nozzles reported.
• Internal painting condition considered acceptable until the next
recoating activity on July 2002.
26.05.2K TI2K-126 • External wall thickness survey showed no significant degradation.
22.04.02 TI02-120 • External wall thickness survey showed no significant degradation.
29.08.03 Painting Report • Vessel internally painted with 75 mic TankGuard primer and 300 mic
Marathon top coat system.
6
7. PART 4: SUSCEPTABILITIES TO FAILURE
Extreme High Medium Low Negligible
5 4 3 2 1
Vessel Failure
Failure due to External General corrosion:
External general corrosion is eliminated by the external coating, in addition, the absence
of severe environmental conditions due to the lack of pollution and desert dry weather
eliminates the probability of general external corrosion to occur or propagate rapidly.
Rating 1
Failure due to External Pitting corrosion:
External pitting corrosion is associated with insulation that can be damped with water. It
is unlikely to be found within the vessel as it is not insulated by any means.
Rating 1
Failure due to External Crevice corrosion:
External crevice corrosion is formed due to moisture and dirt coalition at dead points
within the unit construction, especially platform supports and attached nameplates.
The cylindrical shape of the vessel is eliminating the existence of the dead points, as well
as the nameplate is not directly attached to the vessel body but to a special holder.
The attached platforms supporting may be collecting dirt and moisture, the moisture is
not likely found for long times in desert environment, but there is a low possibility of
generating corrosion cells there.
Rating 2
Failure due to Internal General corrosion:
Internal general corrosion is being controlled and eliminated by internal coating system
applied. 6 mm corrosion allowance is also added to the designed wall thickness. Taking
into consideration the design lifetime of 25 years, this gives 0.24 mm for lose per year.
Internal coating has been re-applied in several occasions according to painting material
manufacturer’s recommendations. During that, internal visual inspections had been
carried out revealed with a confidence that no general corrosion mechanism is taking
place.
7
8. There is always a possibility of changing the operation conditions what may lead to the
appearance of general corrosion, although it is very rare.
Rating 2
Failure due to Internal Pitting corrosion:
Internal pitting corrosion is also controlled by the internal painting; the corrosion spices
may consume the corrosion allowance throughout the lifetime. It had been recorded the
occurrence of spreaded pitting with a depth of 2 mm but no propagation was reported
afterwards.
Partial deterioration of internal coating has been reported, what may increase the
possibility of pitting occurrence
Rating 3
Failure due to Internal Galvanic corrosion:
Galvanic corrosion may occur between the vessel stainless steel internals and the carbon
steel vessel, but the internal coating and the insulation installed between them make it
unlikely to be found.
Rating 1
Failure due to Internal Crevice corrosion:
Crevice corrosion is most likely to happen in the vertical attached nozzles and their
flanges. Adequate painting is being applied internally what may reduce the probability of
the occurrence, but previous experience with painting deterioration inside the attached
nozzles increases the possibility of such mechanism to take place.
Rating 3
Failure due to Internal Stress corrosion:
Stress corrosion cracking occurs mainly within the welds heat affected zones, but the
possibility of happening within the main vessel body exists. The vessel is mainly
designed to withstand the stresses caused by the internal pressure, although the
overpressurising conditions may occur from time to time. The existence of internal
coating reduces the possibility of such mechanism, in addition it has not been reported
before within the area.
Rating 2
8
9. Associated Piping Failure:
Failure due to External General corrosion:
External general corrosion on associated piping is controlled by the application of
protective painting system, the absence of severe environment conditions and pollution
eliminates the possibilities of occurrence or propagation.
Rating 1
Failure due to External Pitting corrosion:
External pitting corrosion is associated with insulation existence, and the existence of
chlorides for stainless steel piping. Associated piping of the vessel is not insulated, and
the stainless steel piping is painted, in addition to lack of chlorides existence.
Rating 1
Failure due to External Crevice corrosion:
External crevice corrosion for piping occurs mainly at supporting points and within the
external side of flange connections due to moisture and dirt trap. There is a fair chance to
occur although the general environment conditions are not so helpful.
Rating 2
Failure due to Internal General corrosion:
Internal general corrosion is a result of the flowing media reaction with the pipe metal. It
is most likely to happen within the carbon steel portions rather than the stainless steel.
The routine wall thickness survey carried out on the attached piping throughout the last
few years did not show any significant wall thickness loss.
Rating 1
Failure due to Internal Pitting corrosion:
Internal pitting corrosion is mainly happening due to the presence of particular agents,
like chlorides and sulfides. No history of such failure within the vessel piping, but threat
exists.
Rating 2
Failure due to Internal Galvanic corrosion:
Internal galvanic corrosion occurs between dissimilar metal connections with the
existence of suitable electrolyte. There are causes of galvanic corrosion between carbon
9
10. steel and stainless steel connections within BED area, but none of them within the vessel
skid.
Rating 1
Failure due to Internal Erosion corrosion:
Internal erosion corrosion occurs at or after flow restrictions and direction changes. In
general it shows up within carbon steel piping, with a possibility of occurrence within
stainless steel piping.
Rating 2
Failure due to Internal Crevice corrosion:
Internal crevice corrosion is more combined with slow flow piping. It is unlikely to
happen within the vessel piping due to high pressure and flow rate.
Rating 1
Failure due to Internal Stress corrosion:
Internal stress corrosion within piping system is usually combined with excess vibration
rather than over pressurizing.
Rating 2
10
11. PART 5: CONSEQUENCE OF FAILURE
Extreme High Medium Low Negligible
5 4 3 2 1
Vessel Failure Consequence:
Consequence of failure due to External General corrosion:
External general corrosion leads to general wall thickness loss exposing the vessel to be a
subject to collapse or fracture under internal pressure, what will lead to a large amount of
oil and gas release, massive production loss and cost of new vessel.
Rating 5
Consequence of failure due to External Pitting corrosion:
External pitting corrosion leads to low amount of oil or gas release, low production loss
and low cost of vessel repair.
Rating 2
Consequence of failure due to External Crevice corrosion:
External crevice corrosion leads to low amount of oil or gas release, low production loss
and low cost of vessel repair.
Rating 2
Consequence of failure due to Internal General corrosion:
Internal general corrosion leads to general wall thickness loss exposing the vessel to be a
subject to collapse or fracture under internal pressure, what will lead to a large amount of
oil and gas release, massive production loss and cost of new vessel.
Rating 5
Consequence of failure due to Internal Pitting corrosion:
Internal pitting corrosion leads to low amount of oil or gas release, low production loss
and low cost of vessel repair.
Rating 2
11
12. Consequence of failure due to Internal Galvanic corrosion:
Internal galvanic corrosion leads to no oil or gas release, low production loss and low
cost of vessel repair.
Rating 1
Consequence of failure due to Internal Crevice corrosion:
Internal crevice corrosion leads to low oil or gas release, medium production loss and
medium cost of vessel repair.
Rating 3
Consequence of failure due to Internal Stress corrosion:
Internal stress corrosion cracking leads to high oil or gas release, high production loss
and high cost of vessel repair.
Rating 4
Associated Piping Failure Consequence:
Consequence of failure due to External General corrosion:
External general corrosion on associated piping leads to medium oil or gas release,
medium production loss and low repair cost.
Rating 3
Consequence of failure due to External Pitting corrosion:
External pitting corrosion on associated piping leads to low oil or gas release, negligible
production loss and low repair cost.
Rating 2
Consequence of failure due to External Crevice corrosion:
External crevice corrosion on associated piping leads to low oil or gas release, negligible
production loss and low repair cost.
Rating 2
Consequence of failure due to Internal General corrosion:
External general corrosion on associated piping leads to medium oil or gas release,
medium production loss and low repair cost.
Rating 3
12
13. Consequence of failure due to Internal Pitting corrosion:
Internal pitting corrosion on associated piping leads to low oil or gas release, negligible
production loss and low repair cost.
Rating 2
Consequence of failure due to Internal Galvanic corrosion:
Internal galvanic corrosion leads to low oil or gas release, negligible production loss and
low repair cost.
Rating 2
Consequence of failure due to Internal Erosion corrosion:
Internal erosion corrosion leads to low oil or gas release, negligible production loss and
low repair cost.
Rating 2
Consequence of failure due to internal Crevice corrosion:
Internal crevice corrosion leads to negligible oil or gas release, negligible production loss
and negligible repair cost.
Rating 1
Consequence of failure due to Internal Stress corrosion:
Internal stress corrosion leads to high oil or gas release, medium production loss and
medium repair cost.
Rating 4
13
14. PART 6: CRITICALITY
Extreme High Medium Low Negligible
5 4 3 2 1
Vessel Failure Criticality
Criticality of failure due to External General corrosion:
Susceptibility Rating 1
Consequence Rating 5
Criticality Rating 4
Criticality of failure due to External Pitting corrosion:
Susceptibility Rating 1
Consequence Rating 2
Criticality Rating 1
Criticality of failure due to External Crevice corrosion:
Susceptibility Rating 2
Consequence Rating 2
Criticality Rating 2
Criticality of failure due to Internal General corrosion:
Susceptibility Rating 2
Consequence Rating 5
Criticality Rating 5
14
15. Criticality of failure due to Internal Pitting corrosion:
Susceptibility Rating 3
Consequence Rating 2
Criticality Rating 3
Criticality of failure due to Internal Galvanic corrosion:
Susceptibility Rating 1
Consequence Rating 1
Criticality Rating 1
Criticality of failure due to Internal Crevice corrosion:
Susceptibility Rating 3
Consequence Rating 3
Criticality Rating 4
Criticality of failure due to Internal Stress corrosion:
Susceptibility Rating 2
Consequence Rating 4
Criticality Rating 4
Associated Piping Failure Criticality:
Criticality of failure due to External General corrosion:
Susceptibility Rating 1
Consequence Rating 3
Criticality Rating 2
Criticality of failure due to External Pitting corrosion:
Susceptibility Rating 1
Consequence Rating 2
Criticality Rating 1
Criticality of failure due to External Crevice corrosion:
Susceptibility Rating 2
Consequence Rating 2
Criticality Rating 2
Criticality of failure due to Internal General corrosion:
Susceptibility Rating 1
Consequence Rating 3
Criticality Rating 2
15
16. Criticality of failure due to Internal Pitting corrosion:
Susceptibility Rating 2
Consequence Rating 2
Criticality Rating 2
Criticality of failure due to Internal Galvanic corrosion:
Susceptibility Rating 1
Consequence Rating 2
Criticality Rating 1
Criticality of failure due to Internal Erosion corrosion:
Susceptibility Rating 2
Consequence Rating 2
Criticality Rating 2
Criticality of failure due to internal Crevice corrosion:
Susceptibility Rating 1
Consequence Rating 1
Criticality Rating 1
Criticality of failure due to Internal Stress corrosion:
Susceptibility Rating 2
Consequence Rating 4
Criticality Rating 4
16
17. PART 7: REMNANT LIFE CALCULATIONS
Vessel Remnant Life Calculations:
1- Shell Remnant Life
Calculation: Shell Thickness Degradation Chart
Year Built: 1989 75
Year Start in Service: 1990
Thickness
70
Corrosion allowance: 6 mm 65
Original wall thickness: 71 mm 60
1990
1995
2000
2005
2010
2015
2020
2025
2030
2035
2040
Minimum accepted wall Service Years
thickness: 71 – 6 = 65 mm Min Design Actual
Design Corrosion Rate: 6mm/25years = 0.24 mm/year
Actual up to date Corrosion Rate (based on internal inspection reports): 2mm/15years
= 0.133 mm/year
2- Heads Remnant Life
Calculation: Heads Thickness Degradation Chart
Year Built: 1989 40
Year Start in Service: 1990
Thickness
35
Corrosion allowance: 6 mm
Original wall thickness: 38 mm 30
1990
1995
2000
2005
2010
2015
2020
2025
2030
2035
2040
Minimum accepted wall Service Years
thickness: 38 – 6 = 32 mm Min Design Actual
Design Corrosion Rate:
6mm/25years = 0.24 mm/year
Assumed up to date Corrosion Rate (no corrosion reported on heads): 2mm/15years =
0.1 mm/year
17
18. Piping Remnant Life Calculation:
A- 10-PO-30018-9145X
10-PO-30018-9145X
Year Start in Service: 1990
18.5
Corrosion allowance: 1 mm 18
Thickness
17.5
Original wall thickness: 18.24mm 17
16.5
Minimum accepted wall thickness: 16
1990
1995
2000
2005
2010
2015
2020
2025
2030
2035
2040
17.24mm Years
Min Design
Design Corrosion Rate: 1mm/25years
= 0.04 mm/year
Assumed up to date Corrosion Rate (no corrosion reported on this piping): 0.04
mm/year
B- 10-PG-30002-AA02
Year Start in Service: 1990 10-PG-30002-AA02
10
Corrosion allowance: 0 mm 8
Thickness
6
Original wall thickness: 9.27mm 4
2
Minimum accepted wall thickness: 0
1990
1995
2000
2005
2010
2015
2020
2025
2030
2035
2040
9.27mm Years
Min Design
Design Corrosion Rate: 0
Assumed up to date Corrosion Rate (no corrosion reported on this piping): 0
C- 4-VF-42057-9341X
Year Start in Service: 1990 4-VF-42057-9341X
9
Corrosion allowance: 0 mm 8
7
6
Thickness
Original wall thickness: 8.56mm 5
4
3
2
Minimum accepted wall thickness: 1
0
1990
1995
2000
2005
2010
2015
2020
2025
2030
2035
2040
8.56mm Years
Min Design
Design Corrosion Rate: 0mm/year
Assumed up to date Corrosion Rate (no corrosion reported on this piping): 0 mm/year
18
19. D- 4-VF-42058-1341X
Year Start in Service: 1990 4-VF-42058-1341X
3.5
Corrosion allowance: 0 mm 3
2.5
Thickness
Original wall thickness: 3.05mm 1.5
2
1
Minimum accepted wall thickness: 0.5
0
1990
1995
2000
2005
2010
2015
2020
2025
2030
2035
2040
3.05mm
Years
Design Corrosion Rate: 0mm/year Min Design
Assumed up to date Corrosion Rate (no corrosion reported on this piping): 0mm/year
E- 10-VF-42056-1341X
Year Start in Service: 1990 10-VF-42056-1341X
4.5
Corrosion allowance: 0 mm 4
3.5
3
Thickness
Original wall thickness: 4.19mm 2.5
2
1.5
1
Minimum accepted wall thickness: 0.5
0
1990
1995
2000
2005
2010
2015
2020
2025
2030
2035
2040
4.19mm Years
Design Corrosion Rate: 3mm/25years = Min Design
0.12 mm/year
Assumed up to date Corrosion Rate (no corrosion reported on this piping): 0.12
mm/year
F- 6-CD-40007-9341X
Year Start in Service: 1990 6-CD-40007-9341X
12
Corrosion allowance: 0 mm 10
8
Thickness
Original wall thickness: 10.79mm 6
4
2
Minimum accepted wall thickness: 0
1990
1995
2000
2005
2010
2015
2020
2025
2030
2035
2040
10.79mm Years
Min Design
Design Corrosion Rate: 0mm/year
Assumed up to date Corrosion Rate (no corrosion reported on this piping): 0mm/year
19
20. G- 3-OW-40013-9341X
Year Start in Service: 1990 3-OW-40013-9341X
9
Corrosion allowance: 0 mm 8
7
6
Thickness
Original wall thickness: 7.62mm 5
4
3
Minimum accepted wall thickness: 2
1
0
7.62mm
1990
1995
2000
2005
2010
2015
2020
2025
2030
2035
2040
Years
Design Corrosion Rate: 0mm/year Min Design
Assumed up to date Corrosion Rate
(no corrosion reported on this piping): 0mm/year
H- 3-OW-40013-9143X
Year Start in Service: 1990 3-OW-40013-9143X
9
Corrosion allowance: 1 mm 8
7
Original wall thickness: 7.62mm 6
Thickness
5
4
3
Minimum accepted wall thickness: 2
1
0
6.62mm
1990
1995
2000
2005
2010
2015
2020
2025
2030
2035
2040
Years
Design Corrosion Rate:
Min Design
1mm/25years = 0.04 mm/year
Assumed up to date Corrosion Rate (no corrosion reported on this piping):
0.04mm/year
I- 6-PO-30019-3145X
Year Start in Service: 1990 6-PO-30019-3145X
8
Corrosion allowance: 1 mm 7
6
Original wall thickness: 7.11mm
Thickness
5
4
3
Minimum accepted wall thickness: 2
1
6.11mm 0
1990
1995
2000
2005
2010
2015
2020
2025
2030
2035
2040
Design Corrosion Rate: Years
Min Design
1mm/25years = 0.04 mm/year
Assumed up to date Corrosion Rate (no corrosion reported on this piping): 0.04
mm/year
20
21. J- 6-PO-30019-9341X
Year Start in Service: 1990 6-PO-30019-9341X
12
Corrosion allowance: 0 mm 10
8
Thickness
Original wall thickness: 10.97mm 6
4
Minimum accepted wall thickness: 2
0
10.97mm
1990
1995
2000
2005
2010
2015
2020
2025
2030
2035
2040
Years
Design Corrosion Rate: 0mm/year Min Design
Assumed up to date Corrosion Rate
(no corrosion reported on this piping): 0mm/year
21
22. PART 8: INSPECTION PLAN
A- Vessel Inspection:
1- Internal Inspection:
Vessel Highest Criticality rating: 5 (Extreme)
Inspection Confidence Rating: High
Inspection Interval Factor: 0.3
Maximum Internal Inspection Interval = Remnant Life X Inspection Interval Factor
= 240 months X 0.3
= 72 months (6 years)
(Last Internal Inspection was in 2002, next to be in 2008)
2- External Inspection:
Technique Application Area Interval Failure to be monitored
X-Ray Shooting Attached Horizontal nozzles and bottom Yearly Wall thinning
vertical nozzles
Ultrasonic Wall Bottom area of the vessel with height up 2 Yearly Wall thinning
Thickness to 1660mm, covering the water phase
Measurements area, with a 150mm grid
Visual Inspection All flange connections Yearly Flange Leakage
22
23. B- Associated Piping Inspection:
External Inspection:
Piping Highest Criticality rating: 4 (High)
Inspection Confidence Rating: High
Inspection Interval Factor: 0.4
Maximum External Inspection Interval = Remnant Life X Inspection Interval Factor
= 120 months X 0.4
= 48 months (2 years)
(Last Inspection was in 2004, next to be in 2006)
Application Area Material Corrosion Inspection Technique Interval Failure to be monitored
Allowance
10-PO-30018-9145X Carbon Steel 1mm UT wall thickness measure 2 Yearly Wall thinning
10-PG-30002-AA02 Duplex Stainless Steel 0mm Visual Inspection Yearly Flange leakage
4-VF-42057-9341X 316L Stainless Steel 0mm Visual Inspection Yearly Flange Leakage
4-VF-42058-1341X 316L Stainless Steel 0mm Visual Inspection Yearly Flange Leakage
10-VF-42056-1341X 316L Stainless Steel 0mm Visual Inspection Yearly Flange Leakage
6-CD-40007-9341X 316L Stainless Steel 0mm Visual Inspection Yearly Flange Leakage
3-OW-40013-9341X 316L Stainless Steel 0mm Visual Inspection Yearly Flange Leakage
3-OW-40013-9143X Carbon Steel 1mm UT wall thickness measure 2 Yearly Wall thinning
6-PO-30019-3145X Carbon Steel 1mm UT wall thickness measure 2 Yearly Wall thinning
6-PO-30019-9341X 316L Stainless Steel 0mm Visual Inspection Yearly Flange Leakage
23
