DISSIMILAR METAL WELD(DMW) IN SOUR SERVICE

VESSELS

Khalifa A. Al-Ammari

KGP

Objective

To give an update about the problem of welding of Stainless Steel attachments to

Carbon Steel in sour service vessels

The current status

• KGP has 63 CS equipments with SS welded attachments in areas K-82, K-84 & K-85

48 in non-sour service

15 in sour service

Dissimilar Metal Weld (DMW)

• DMW is susceptible to Sulfide Stress Cracking (SSC) in sour services

• DMW is prohibited in SA standards :

SAES-W-010

32-SAMSS-004

Replacement difficulties

• Vessels are PWHT’d

• Replacement of SS with CS might introduce other problems

• Negative impact on the project schedule

CSD proposal

• Vessels in the non-sour service:1. Low risk of SSC failure

2. Replacement of the attachment is impractical and may introduce other problems with the vessels

CSD proposal

• Vessels in the sour service:1. The severity of the sour environment is mild.

2. A coating system will be applied to the DMW area.

Summary

• 63 vessels contain DMW’s

48 in non-service

15 in sour service

• Violation to two SA standards

• CSD recommended to apply coating on the DMW’s exposed to sour services

• Two waivers will be issued

• Modify and update inspection record documents

Thank you

Questions

Definition of DMW

• Dissimilar Metal Welds can be defined as:

1. Any weld joint between ferritic steel and either austenitic stainless steel, duplex stainless steel or nickel-based alloys. Or

2. Use of stainless steel or nickel-based filler metals on ferritic steels.

Violation to

• SAES-W-010 6.5.2

“DMW’s are not permitted for pressure-containing welds in sour service”

• 32-SAMSS-004 Table#1 note #3

“All internal and external attachment clips on vessels shall be of the same ASME material as the pressure parts”

Sulfide Stress Cracking

Sulfide Stress Cracking (SSC) is defined as cracking of metal under the combined action of tensile stress and corrosion in the presence of water and H2S. SSC is a form of hydrogen stress cracking resulting from absorption of atomic hydrogen that is produced by the sulfide corrosion process on the metal surface.

Sulfide Stress Cracking

List of Equipment

The following Vessels & Exchanger in Non-Sour service:

K84-D-178/278/378 1ST converter

K84-D-180/280/380 2ND converter

K84-D-182/282/382 3RD converter

K82-D-701 AB&C SFG compressor suction scrubbers

K82-D-703 AB&C SFG compressor discharge scrubbers

K82-D-704 AB&C SFG compressor interstage scrubbers

List of Equipment

K82-D-140/240 LP feed gas knock out drum

K84-F-171/271/371 reaction furnace burner

K84-F-172/272/372 reaction furnace combustion chamber

K84-F-173/273/373 reaction furnace steam generation section

K84-F-174/274/374 thermal oxidiser

K82-D-710 A&B DGA storage tanks

K85-D-800 A&B sulfur storage tanks

List of Equipment

K84-E-173/273/373 1ST sulfur condenser

K84-E-175/275/375 2nd sulfur condenser

K84-E-177/277/377 3rd sulfur condenser

K84-E-179/279/379 4th sulfur condenser

List of Equipment

The following Vessels Sour service:

K82-C-340 HP DGA contactor

K82-C-140/240 LP DGA contactor (design temp. 260/300 oF)

K82-C-142/242 LP DGA regenerators (design temp. 410/300 oF)

K82-C-342 HP DGA regenerator

K82-D-142/242 LP hydrocarbon flash drums (design temp. 235/300 oF)

K82-D-342 HP hydrocarbon flash drums

K82-D-143/243/343 LP DGA regenerator reflux drum (design temp. 260/300 oF)

K84-D-172/272/372 acid gas KO drum

Coating

A coating system will be applied to the dissimilar metal weld area for the vessels in sour service. The coating will cover surfaces within 100mm minimum from the dissimilar metal weld on the carbon steel. This is an additional measure to prevent Sulfide stress cracking. The proposed coating system is APCS-27 (SAES-H-001). There are two products that comply with this requirement, BELZONA 1593 and DURAPOL UHT