Please consult API 510. Are included also information about cladded vessels.

Hope this help

This subject is covered by the following code items: API 510, API 572 and ASME SA264 (or ASTM A264).

♣ A. API 510 "Pressure Vessel Inspection Code: Maintenance Inspection, Rating, Repair, and Alteration". Please refer to Paras.: 5.5 Defect Inspection & 5.6 Inspection of Parts.

Quote 5.5 Defect Inspection Vessels shall be examined for visual indications of distortion. If any distortion of a vessel is suspected or observed, the overall dimensions of the vessel shall be checked to confirm whether or not the vessel is distorted and, if it is distorted, to determine the extent and seriousness of the distortion. The parts of the vessel that should be inspected most carefully depend on the type of vessel and its operating conditions. The authorized pressure vessel inspector should be familiar with the operating conditions of the vessel and with the causes and characteristics of potential defects and deterioration. (For recommended inspection practices for pressure vessels, see API RP 572.) Careful visual examination is the most important and the most universally accepted method of inspection. Other methods that may be used to supplement visual inspection include:

(a) magnetic-particle examination for cracks and other elongated discontinuities in magnetic materials;

(b) fluorescent or dye-penetrant examination for disclosing cracks, porosity, or pin holes that extend to the surface of the material and for outlining other surface imperfections, especially in nonmagnetic materials;

(c) radiographic examination;

(d) ultrasonic thickness measurement and flaw detection;

(e) eddy current examination;

(f) metallographic examination;

(g) acoustic emission testing; hammer testing while not under pressure; and

(h) pressure testing. (Section V of the ASME Code can be used as a guide for many of the nondestructive examination techniques.)

Adequate surface preparation is important for proper visual examination and for the satisfactory application of any auxiliary procedures, such as those mentioned above. The type of surface preparations required depends on the individual circumstances, but surface preparations such as wire brushing, blasting, chipping, grinding, or a combination of these preparations may be required.

If external or internal coverings, such as insulation, refractory protective linings, and corrosion-resistant linings, are in good condition and there is no reason to suspect that an unsafe condition is behind them, it is not necessary to remove them for inspection of the vessel; however, it may be advisable to remove small portions of the coverings to investigate their condition and effectiveness and the condition of the metal underneath them. Where operating deposits, such as coke, are normally permitted to remain on a vessel surface, it is particularly important to determine whether such deposits adequately protect the vessel surface from deterioration. To determine this, spot examinations in which the deposit is thoroughly removed from selected critical areas may be required.

Where vessels are equipped with removable internals, the internals need not be removed completely as long as reasonable assurance exists that deterioration in regions rendered inaccessible by the internals is not occurring to an extent beyond that found in more accessible parts of the vessel.

The owner/user shall specify industry-qualified UT shear wave examiners when the owner/user requires the following: (a) detection of interior surface (ID) breaking planar flaws when inspecting from the external surface (OD); or (b) where detection, characterization, and/or through-wall sizing is required of planar defects. Application examples for the use of such industry-qualified UT shear wave examiners include fitness-for-service and future monitoring of known interior flaws from the external surface. The requirement for use of industry-qualified UT shear wave examiners becomes effective two years after publication in this code or addendum.

5.6 Inspection of Parts The following inspections are not all inclusive for every vessel, but they do include the features that are common to most vessels and that are most important. Authorized pressure vessel inspectors must supplement this list with any additional items necessary for the particular vessel or vessels involved.

a. Examine the surfaces of shells and heads carefully for possible cracks, blisters, bulges, and other signs of deterioration. Pay particular attention to the skirt and to support-attachment and knuckle regions of the heads. If evidence of distortion is found, it may be necessary to make a detailed check of the actual contours or principal dimensions of the vessel and to compare those contours and dimensions with the original design details.

b. Examine welded joints and the adjacent heat-affected zones for service-induced cracks or other defects. On riveted vessels, examine rivet head, butt strap, plate, and caulked edge conditions. If rivet-shank corrosion is suspected, hammer testing or spot radiography at an angle to the shank axis may be useful.

c. Examine the surfaces of all manways, nozzles, and other openings for distortion, cracks, and other defects, paying particular attention to the welding used to attach the parts and their reinforcements. Normally, weep holes in reinforcing plates should remain open to provide visual evidence of leakage as well as to prevent pressure build-up in the cavity. Examine accessible flange faces for distortion and determine the condition of gasket-seating surfaces. Unquote

♣ B. API Recommended Practice 572 "Inspection of Pressure Vessels (Towers, Drums, Reactors, Heat Exchangers, and Condensers)". Also API 574 provides more information on the inspection of piping, valves, and fittings associated with pressure vessels.

See Sections : 6 Maintenance Inspection, 7 Reasons for Inspection, 8 Causes of Deterioration, 10 Inspection Methods and Limitations, 11 Methods of Repair & 12 Records and Reports.

♣ C. The stainless steel clad specification is covered by ASME Code, Section II, Part A, Material ASME SA 264 "Specification for Corrosion-Resisting Chromium Steel-Clad Plate, Sheet, and Strip". The following paragraphs are extracted from the code:

Quote 8.1.4 Bond Strength—As an alternative to the shear strength test provided in 8.1.2 and when required by the purchaser, three bend tests shall be made with the alloy cladding in compression to determine the quality of the bond. These bend tests shall be made in accordance with the specifications for the cladding metal. At least two of the three tests shall show not more than 50% separation on both edges of the bent portion. Greater separation shall be cause for rejection.

8.2 Sheet and Strip:

8.2.1 The bend test specimens of sheet and strip shall stand being bent cold, without cracking on the outside of the bent portion, through an angle of 180°.

8.2.2 The bend test specimens shall be bent over a single piece of flat stock of the same thickness as the material tested, allowing the test material to form its natural curvature. The axis of the bend shall be transverse to the direction of rolling. Note 1. The bend may be made over a diameter equal to the thickness of the test material.

8.2.3 The bond between the alloy cladding and the base metal shall be ascertained by observation of the behavior of the composite sheet or strip when sheared with the alloy side down.

8.3 Methods and practices relating to mechanical testing required by this specification shall be in accordance with Test Methods and Definitions A 370. Unquote

Important Note. Hardness test for all areas of base metal which subjected to overheating is required to be measured and be sure that all measurements are within the allowable limits. May be you need to proceed some destructive tests to find the mechanical and chemical properties.