Surface and Weld Inspection

Inspection protects the connection between design intent, fabrication quality and service performance. A quick glance at the weld face is not enough. The inspector needs a defined item and revision, a safe and representative surface, adequate access and visibility, a repeatable coverage path, suitable measuring tools, an acceptance basis and a record that locates every relevant observation. Visual testing is valuable before, during and after welding, but it cannot establish every internal, subsurface or metallurgical condition. [S240; S241]

Chapter objectives

After this chapter, the reader should be able to:

• identify the weld, surface, drawing revision, inspection stage, extent and acceptance basis;
• distinguish an observation, indication, imperfection, measured result and acceptance decision;
• make the area safe and establish representative access, cleanliness and visibility;
• inspect the weld face, toes, starts, stops, craters, transitions, adjacent base metal and accessible reverse side systematically;
• recognise common visible condition families without claiming hidden depth or cause;
• measure specified profile, alignment and local surface characteristics with suitable gauges;
• map an indication by station, side, orientation, length and relationship to the weld zone;
• select the correct boundary between visual inspection and penetrant, magnetic, ultrasonic or radiographic testing;
• prevent grinding and repair from hiding the original condition or reducing required section;
• record inspection method, extent, result, disposition and re-inspection status clearly; and
• stop when access, surface condition, acceptance basis or inspection competence is inadequate.

Before examining the surface, confirm:

1. part, assembly, weld and joint identity;
2. drawing, weld symbol, fabrication specification and revision;
3. material and joint type;
4. inspection stage: before welding, during production, after welding, after finishing, after repair or in service;
5. required inspection extent and accessible sides;
6. specified method, testing level and personnel requirement;
7. dimensional and surface characteristics to be assessed; and
8. applicable acceptance criteria and disposition route.

Weld symbols can convey geometry, manufacture, quality, testing and surface-finish information. Read the complete symbol system and associated notes; do not interpret one isolated symbol from memory. Where a symbol, finish requirement, testing extent or quality level is unclear, use the controlled drawing and inspection process before proceeding. [S244]

Confusion between description and acceptance creates inconsistent decisions. Use the following sequence:

ISO 6520-1 provides a classification basis for geometrical imperfections in fusion welding. ISO 5817 provides quality levels for covered fusion-welded joints, while ISO 17635 links method selection, testing levels and acceptance levels on a general basis. These documents serve different functions; a classification code or quality-level label must not be converted informally into a universal pass/fail rule. [S241; S242; S243]

Inspection can expose personnel to residual hot-work hazards even when welding has stopped. Confirm the safe system of work before approaching, touching, cleaning, gauging or marking the item.

Control, as applicable:

• movement, stored energy, suspended loads and unstable components;
• hot metal, sharp edges, slag, spatter and recently ground surfaces;
• welding fume, metal dust and residues from coatings or cleaning chemicals;
• sparks, fragments, noise and kickback when preparation or repair grinding is authorised;
• electrical and magnetic equipment;
• penetrant materials, cleaners, developers and ultraviolet sources;
• confined-space entry, atmosphere, access, rescue and communication; and
• radiography exclusion zones and specialist access control.

Do not enter an industrial-radiography controlled area or disturb radiography equipment. Radiography is performed only through the authorised radiation-protection programme, trained personnel and controlled-area arrangements. [S251]

Welding and grinding can involve fumes, UV radiation, fire, sparks, flying fragments and confined-space hazards; use the site's Malaysian risk assessment, permits and control measures. [S252; S253]

The surface must show the condition being inspected without preparation that destroys evidence. Remove loose slag, dust, oil, marker residue or spatter only to the extent authorised by the inspection plan. Do not grind, peen, polish, pickle, wire-brush or blast an area merely to make it look acceptable.

Before inspection:

• confirm the surface state required by the procedure;
• identify coatings, oxides, heat tint, scale, contamination and previous repairs;
• clean using a compatible method that will not smear metal across a crack, fill a recess or round an edge;
• allow wet surfaces and cleaning residues to reach the required condition;
• use suitable direct or aided viewing access;
• position lighting to reveal profile and surface-breaking features without glare or deep shadow; and
• verify mirrors, borescopes, magnifiers, cameras and measuring aids when the method depends on them.

A photograph is useful evidence but not a substitute for controlled inspection. Include scale, orientation and location, avoid perspective distortion, and retain an unmarked original when annotated copies are used.

Use a repeatable path rather than looking only at visually prominent areas. Start from a defined end or datum and move along the weld in overlapping inspection fields.

Cover, as required:

• weld face and full length;
• both weld toes and transitions;
• starts, stops, craters, restarts and tie-ins;
• attachment ends, corners, branches and changes in section;
• adjacent heat-affected zones and base metal;
• arc strikes, temporary-attachment locations and ground areas;
• accessible root, penetration surface or reverse side; and
• surrounding surface affected by distortion, handling or finishing.

Mark the station direction and side convention before recording. On circular welds, define a clock position or angular datum. On long welds, use station distances from a fixed reference. Avoid descriptions such as “near the left end” when the item can be rotated or installed differently.

Describe what can be supported by the visible surface. Do not infer internal penetration, fusion, toughness, hardness or crack depth from surface appearance alone.

Use neutral wording: “linear surface indication at the upper toe from station 420 to 437 mm” is more useful than “bad crack near the end.” If an authorised classification is required, apply it after the observation is located and described. [S243]

No single NDT method answers every question. ISO 17635 selects methods in relation to quality requirements, material, weld thickness, welding process and testing extent. [S241]

The exact method, equipment, consumables, sensitivity, technique, testing level and acceptance level are controlled by the applicable procedure. Refer to the product label, Technical Data Sheet, or MKTECH representative.

Pre-weld inspection can prevent later conditions that are difficult to correct. ISO 17637 may be applied to visual testing of the joint before welding. [S240]

Check, as specified:

• correct material and joint identity;
• joint preparation, root face, root gap and included angle;
• alignment, mismatch, fit-up and restraint;
• cleanliness, moisture, coatings and contamination;
• tack weld location, condition and integration plan;
• backing, inserts, purge arrangements or consumable supports;
• accessibility for welding and later inspection;
• weld sequence, distortion controls and temporary attachments; and
• traceability marks that must remain visible.

During production, inspect hold points defined by the fabrication plan. Do not disturb hot work or enter the welder's controlled area merely to observe. Record the stage at which an observation was made because later passes can cover earlier surfaces.

View the weld from more than one angle. Low-angle lighting can reveal profile changes; more direct lighting can reveal surface texture and colour differences. Change position rather than relying on glare.

Follow this sequence:

1. survey overall continuity, alignment and distortion;
2. examine the full face for profile, cavities, inclusions open to the surface and irregular stops;
3. trace each toe continuously;
4. examine starts, stops, craters, restarts and tie-ins;
5. inspect adjacent base metal for arc strikes, gouges, spatter, damage and grinding;
6. inspect the accessible reverse side or root condition; and
7. revisit mapped indications with the specified gauge or follow-up method.

Do not accept a smooth face as proof of sound fusion. Conversely, do not reject an irregular but permitted profile without comparing it with the actual requirement.

Use a suitable verified gauge and a defined reference. Chapter 041 covers basic dimensional principles; this chapter applies them to weld inspection.

Record the gauge identity, location, orientation, unit and observed value. Do not use an unverified multipurpose gauge merely because it produces a number.

An inspection record must allow another competent person to return to the same feature. Use:

• weld or joint identifier;
• station measured from a fixed datum;
• arrow side/other side, face/root or a documented side convention;
• clock position for circumferential joints;
• distance from weld centreline or toe;
• indication length, direction and distribution;
• relationship to start, stop, crater, attachment or repair;
• surface condition and inspection method; and
• image or sketch reference.

Marking paint, chalk or metal stamps can interfere with later NDT or damage the part. Use the authorised marking method and preserve traceability through cleaning, repair and finishing.

Grinding can expose a condition, remove it, smear metal across it, reduce section, change toe geometry or erase the original location. Treat repair preparation as a controlled manufacturing step, not as cosmetic tidying.

Before grinding:

• record and map the original condition;
• confirm repair authorisation and permitted extent;
• identify minimum thickness, profile and transition requirements;
• control sparks, fragments, dust, heat and contamination;
• select an abrasive and tool suitable for the material and access; and
• define the re-inspection method and extent.

During grinding, use light progressive removal and inspect frequently. Avoid deep grooves, sharp notches, overheating, excessive pressure and uncontrolled widening. After grinding, clean the area, verify remaining profile or thickness as required, and re-inspect the repaired zone plus affected transitions. A visually smooth repair is not evidence that a crack or internal condition has been removed.

Penetrant testing detects discontinuities open to the surface on suitable materials using visible or fluorescent systems. It can reveal cracks, laps, folds, porosity and lack-of-fusion conditions only where they communicate with the surface. The term discontinuity does not by itself state acceptability. [S245]

The controlled procedure governs:

• material and product compatibility;
• cleaning and drying;
• penetrant family and sensitivity;
• application, dwell, removal and development;
• viewing conditions and timing;
• control checks and reference materials;
• interpretation and acceptance criteria;
• post-cleaning and corrosion/contamination control; and
• operator qualification.

Do not mix products from different systems casually, substitute household cleaners, guess dwell times or apply penetrant to an excessively rough, porous, contaminated or hot surface outside the procedure. Penetrant acceptance levels for welds are addressed separately from the general method principles. [S248]

Magnetic particle testing is for ferromagnetic materials. It is primarily used for surface-breaking discontinuities, particularly cracks, and may detect some shallow subsurface discontinuities; sensitivity reduces rapidly with depth. [S246]

Weld testing can cover the weld and heat-affected zones using techniques suited to the joint and likely discontinuity orientation. Magnetisation direction, field strength, surface condition, detection medium, lighting, demagnetisation and recording are controlled by the procedure. ISO 17638 does not itself specify acceptance levels; those are addressed separately or by the product/application standard. [S247; S249]

Do not apply magnetic testing to non-ferromagnetic alloys, infer depth from indication intensity, or accept one field direction when the procedure requires coverage of different orientations. Keep sensitive equipment, electronic devices and magnetically affected parts within site controls.

Visual, penetrant and magnetic methods do not provide universal assurance of internal weld soundness. Possible internal lack of fusion, incomplete penetration, inclusions, volumetric porosity or cracking may require ultrasonic or radiographic testing selected through the applicable code, material, thickness, geometry and quality requirement. [S241]

Specialist NDT requires an approved written procedure, suitable equipment and calibration/reference arrangements, defined testing and acceptance levels, and competent personnel. ISO 9712 provides a qualification and certification framework for industrial NDT personnel but the required scheme and authorisation remain contract and jurisdiction dependent. [S250]

Do not:

• request “an X-ray” as a universal answer;
• enter radiography barriers or rely on warning signs alone;
• interpret an ultrasonic screen or radiograph without the required competence;
• convert an NDT indication into a fabrication cause without evaluation; or
• assume a result from one method closes questions outside that method's capability.

Include, as applicable:

• job, part, assembly and weld identity;
• drawing, specification, inspection-plan revision and acceptance basis;
• material, joint type and welding/repair stage;
• inspection date, operator and competence/authorisation reference;
• method, technique, extent and accessible sides;
• surface condition, access and viewing aids;
• measuring or NDT equipment identity and status;
• station convention and indication map;
• observation, classification and measured result with units;
• image, sketch or report references;
• decision and authorised disposition;
• repair reference and re-inspection method/extent; and
• final release, hold or escalation status.

Keep the original observation separate from later annotations and disposition. If an indication changes after cleaning or grinding, retain the before-and-after record rather than replacing the original description.

Before releasing the inspection result, confirm:

• the correct item, weld, drawing and revision were used;
• the inspection stage, required extent, accessible sides and acceptance basis were clear;
• the area was safe to access and specialist exclusion zones were respected;
• the surface condition and visibility were suitable for the method;
• the complete weld face, toes, starts, stops, transitions and required adjacent areas were covered;
• the accessible root or reverse side was inspected where required;
• observations were factual, located and kept separate from acceptance decisions;
• specified dimensions were measured with suitable verified tools and recorded with units;
• indication station, side, orientation, length and relationship to the weld zone were mapped;
• visual inspection was not used to claim hidden depth, internal soundness or metallurgy;
• penetrant, magnetic, ultrasonic or radiographic work followed the approved qualified-person route;
• original conditions were recorded before grinding or repair;
• remaining profile or thickness was checked where material was removed;
• repaired areas and affected transitions were re-inspected to the specified extent;
• the applicable acceptance criteria and authorised disposition were applied; and
• the final record supports traceability, review and release.

This next-chapter title appears on the following page of the printed handbook (page 364), outside this chapter extract.