Belzona Oil Presentation

ADNOC/ADCO/GASO Workshop, 11th Feb. ‘08

1

Identifying the Hidden Threats in Austenitic Stainless Steels and Practical Repair


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Hidden Threats in Austenitic Stainless Steel

SS AISI 321 was extensively used in Gasco

Buhasa NGL Extraction Plant intended to prevent internal CO2 corrosion and brittle fracture at :

• GAS Transmission Lines.• Equipment and Piping at Compression Section.• Cold BD Piping System and KO Vessel.

Key Words : 1. Chloride Stress Corrosion Cracking (CSCC) 2. Stainless Steel (SS)

3. Blow Down (BD)


3

Hidden Threats in Austenitic Stainless Steel

SS AISI 321 is vulnerable to Stress Corrosion Cracking in the presence of Chlorides depending on :

• Stress Levels,• Oxygen Content,• Temperature.

External CSCC phenomenon occurred at Welding Regions of the Reinforcing Pads, Wear Pads and Saddles resulting in Severe Cracking and Leakage.


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Typical Reinforcing Pad and Wear Pad

BRANCH CON.

WEEP HOLE

MAIN PIPE

FULL ENCIRCLEMENT SLEEVE

WEEP HOLE

WEEP HOLE

RAINFORCING PAD

WEAR PAD

TACK WELD

SUPPORT

WEEP HOLE

WEAR PAD

SUPPORTBRANCH CON.


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Reinforcing Pad Cross Section

WEEP HOLE

MAIN PIPE

REINFORCING PAD SECTION VIEW

CSCC AT WELD REGION

GAP BETWEEN MAIN PIPE AND REINFORCING PAD. (ANNULAR SPACE)

REINFORCING PAD


6

Wear Pad Cross Section & Metallographic Examination

MAIN PIPE

Metallographic Examinationof Typical CSCC Initated atthe Weld Region Annular Space.

WELDING

CSCC AT WELD REGION

GAP BETWEEN MAIN PIPE AND (ANNULAR SPACE)WEAR PAD.

WEAR PAD


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Piping Reinforcing Pad – Cracks and Leaks

Leak at Reinforcing Pad Weep Hole

CSCC at Reinforcing Pad Weld


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Vessel Reinforcing Pad & Saddle - Cracks

Cracks at Boot Reinforcing Pad


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Cracks and Leaks at Wear Pads


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Cracks and Leaks at Tack Weld Region after Wear Pad Removal


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Action Taken

To restore the Integrity of the Plant, 8 SS Vessels had to be replaced and the Transmission Gas and Process Lines were also replaced at locations affected by CSCC. The Cold BD Piping System is fitted with 288 Wear Pads and operates at just positive Pressure and ambient Temperature. In spite of the Very Low Operating Pressure cracks and Leaks have been detected in some cases.

With the Objective of restoring the Integrity of the SS Cold BD Piping System, in a planned and cost effective manner a minimum risk with the Plant in Operation some options and non-standard repair methods were considered and evaluated.


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Strategic Options

1. Replacement of the Cold BD Piping System.2. Do-nothing, Monitor Crack Propagation & Leaks. 3. Glass-Fiber Reinforced Protection Wrapping.4. Replace the Original Wear Pads with Cracks and Leaks by Larger Cold Bonded SS Wear Pads.

• Option-4 Was Chosen by Buhasa Plant and Endorsed by the 2003 Shareholders Integrity Review Team.

• The Repair Work was Implemented in accordance with the Gasco Plant Change Request procedure .


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Test Piece

New Wear Pad

BelzonaPrimer

Top Coat


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Practical Repair

Replacement of the 288 original Wear Pads with Cracks and

Leaks by “Larger Cold Bonded SS Wear Pads”.

1. Jack the Pipe Up.2. Removal of Wear Pads by Grinding.3. Assessment of Cracks with Regard to Fitness-For-Purpose

Criteria (Shell Study).4. SS Cold BD Line and Pads Anchor Profile >50 microns.5. Cold Bonding of Larger SS Wear Pads (Belzona 1121).6. Painting.


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Steps to Bond Wear Pads to the Main Line

1 2

3 4


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Cold BD Piping System Completion

Painting of New Wear pad Cold BD Partial View


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Thank you

Francisco Costa,

Buhasa Inspection Head, GASCO

Business

Belzona Oil Presentation