Crack Invest( D1)

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Crack investigation and repair procedure Report No. VI-013 Client Zfod Procedure RCC-PV-01 Date 9 March 2015

Location : Zaubair Field Tag No. : V-102 Design Code : ASME VIII Div.1 Applicable Code : ASME VIII Div 1/ API 510 Reference Code : API 510 Equipment : DESALTOR VESSEL ( D1 ) Last Inspection Date : N/A Manufacturer : N/A Manufacturing Date : N/A Service : Dehydrator Material

Shell : SA 516 Gr 70 Bolts / Nuts : A563 Gr A/A325/Brass Nozzles : SA 106 Gr A Internals : CARBON STEEL Heads : SA 516 Gr 70 Flanges : SA 105

Orig.W.T. as per Drawing : 25 mm Shell : 25 mm Heads : 26 mm C.A : 3 mm

Equipment drawing No. : CG- 2403

Sketch:

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Crack Investigation Report

Zubair Mishrif Desalter (D1)

Prepared by:

Ratbaa Co. API 510 Authorized Inspector

Esmat Deif Alla Abdel malek

Introduction:

During magnetic test for Dehydrator ( ZA- V- 102 ) ( D1 ) we observed some kind of cracks distributed through weld Heat- Affected Zone ( HAZ) and adjacent to ( HAZ ) as shown in our pictures below no. (1.2.3.3.4.5.6.7.8) after our investigation we found that Cracks is likely to be Stress Oriented Hydrogen Induced Cracking (SOHIC).

Stress Oriented Hydrogen Induced Cracking (SOHIC).

SOHIC Is generally observed in the base metal adjacent to the heat- Affected Zone ( HAZ ) of the welds oriented on the through thickness direction where any initiate from Hydrogen Induced Crack ( HIC ) or other cracks or defects including sulfide Stress Crack .

( Ph. 1)

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(Ph.2 )

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( Ph.4 )

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( Ph.6)

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( Ph.8)

Reason of Stress Oriented Hydrogen Induced Crack (SOHIC)

In many situations Hydrogen Induced Crack (HIC) is relatively non-damaging, as the cracks lie parallel to the plane of the plate, so there is little stress at right angles to the cracks. However, if the cracking is sufficiently severe and the applied stresses high, the cracks may join up to produce a fracture, known as ‘Stress-Oriented Hydrogen-Induced Cracking’ or SOHIC.

SOHIC has been found occur between ambient and 300 °F (150 °C) or higher. High local stress or notch-like discontinuities can serve as initiation sites for SOHIC. SOHIC is driven by localized stresses so that PWHT is somewhat effective in reducing SOHIC

Affected Materials

Carbon Steel and Low Alloy steel

Appearance of SOHIC

In pressure- containing equipment, and most often associated with weldments and beside of Heat-Affected Zone (HAZ) of the weld. And also be found at any location where zones of high hardness are found in vessels.

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Stress Orientation Hydrogen Induced Crack (SOHIC) Repair Procedure:

1- First, Vessel shall be full scanned by magnetic particles testing specially areas surrounding to weld joints.

2- After completion of inspection and defining the value , locations and configuration of the crack , there are two methods to repair the crack : a- Hole drilling :

Hole drilling is perhaps the most widely used repair method for cracks. The hole drilling method requires placing hole at the tip of the crack, removing the sharp notch at the crack tip. However, the hole needs to be of sufficient diameter to be successful in arresting the crack. As a rule of thumb, larger holes are better as long as strength and stiffness of the structure or connection is not compromised. Sufficient hole diameters depending on application.

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Drilling procedure:

Identify the tip of the crack using a recommended Magnetic particle testing. Position the drill/coring bit such that trailing edge of the bit removes the crack tip. This ensures

the tip has been removed to avoid leaving a small crack, which would continue to grow. If cross-section loss is a major consideration, the bit can be centered over the crack tip but it increases the likelihood of missing the crack tip.

Select proper diameter of drill bit. After drilling, it is imperative that the surfaces around the hole be ground smooth. The drill bit typically leaves burrs in the metal as the bit exits the hole, and these burrs can lead to new crack initiation sites. . A small abrasive drum works well for finishing the inside of a hole. Grind or air arc gouge the length of the crack. Welding : ( use approved WPS and qualified welders )

B- INSERT PATCH (Flush patch)

If hole drilling technique is not applicable for repairing crack, and then INSERT PATCH (Flush patch) may be used if the following requirements are met:

Full penetration groove welding are provided. The welds are radiographed accordance with the applicable construction code. Ultrasonic

examination by an industry-qualified UT shear weave examiner may be substituted for the radiographic.

All insert plate corners that do not extend to an existing longitudinal or horizontal weld shall be rounded having a 1 in. (25) minimum radius.

Material : Insert plates and welds should be of the same material as the existing pressure component, or of another material that has at least equal notch toughness and allowable Stress, conforms to the requirements of the applicable code of construction, and is suitable for the intended service. Where ASME materials are used, the replacement material should

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have the same ASME P-Number designation as the pressure component material into which the insert is being installed.

Insert Plate Thickness : The insert plate thickness should be not less than the nominal thickness of the material it welds into. If a thinner insert plate than the nominal thickness of the material it welds into must be used, it shall be evaluated for the intended service (such as fatigue due to cyclic loading) using the rules in the applicable code of construction for the pressure component.

Edge Beveling : Edge bevels in the insert plate and in the pressure component may be prepared by Thermal cutting, arc gouging, machining, or grinding. The method should be appropriate for the material and welding process used. All edges prepared for welding shall be examined to the requirements of the applicable code of construction or post-construction code for the pressure component being repaired. All unacceptable indications shall be repaired to the requirements of the applicable code of construction or post-construction code .

Welding : - The weld between the insert plate and the existing pressure component shall be a full

penetration butt weld. Where possible, double-welded butt joints should be used. - Welding procedures, welders, and welding operators shall be qualified in accordance

with the requirements of the applicable code of construction. Examination :

100% RT or UT examination is required

Prepared By

Esmat Deif alla Abdel malek

Ratbaa Co. Authorized API Inspector

[email protected]

07829971382

References:

API 510 (Pressure vessel Inspection Code: in service Inspection, Rating, Repair, and Alteration

API RP 571 (Damage Mechanisms Affecting Fixed Equipment in the refining Industry )

ASME PCC-2 (Repair of Pressure Equipment and Piping) ASME VIII Div. I (Rules for construction of pressure vessels)

ASME V (Nondestructive Testing)