Wednesday, March 25, 2009

Visual Examination Procedure

The Visual examination is a nondestructive examination method used to evaluate surface of material and weld by observation.

Visual Inspection should be the primary evaluation method of any quality control program, generally to determine such as things as the surface condition of the materials, parts, components used in the fabrication & construction; alignment of mating surfaces, shape, or evidence of leaking.

Visual examinations shall be performed in accordance with a written procedure, which shall establish a single value, or range of values, for each requirement.

The below discussion describes applicable sample of Visual Examination Procedure applied for construction project.

1. General

This document is made in general form applicable without adaptation to variety of unlisted products or situations.
This Section provides guidelines for performing Visual inspection of materials, weld fit-up, welding in progress, and complete welds that will be applied of product.

2. References
- Project Quality Assurance plan
- Quality Control Procedure
- Non Destructive Examination Personnel Qualification Procedures
- Inspection and Test Plan

3. Responsibility
3.1. QC Manager
QC Manager responsible for supervision of Quality Control activities and coordinates Quality Control efforts to ensure the intended results according contract requirements.
QC Manager responsible for all release and/or rejected work/ inspection/ testing under ultimate judgment of the OWNER specification and statutory requirement.
QC Manager shall approve the acceptable result of inspection.
3.2. QC Engineer
QC Engineer shall responsible to monitor implementation of inspection procedure in accordance with Owner specifications; Code and Standard; Scheduling, and monitoring their inspection result and reporting to QC Manager.
QC Engineer ensures that certification and validity of adjustment and calibration, inspection, test and measuring equipment.
QC Engineer has to maintain a current file on non-conforming items.
Discipline Inspector
Discipline Inspector has responsibility to report the result of each attend the testing and inspection of their each discipline to the Quality Engineer.
Discipline Inspector has right to inspect at any time according their determined schedule and can give notification that the work is release or rejected.
3.4. Quality Control Administration
QC Administration shall also sets up and verifying the documentation filling system and controls all documents on inspection and quality control in accordance to the contract requirements.

4. Supporting Documents
i) “Issue for Construction” drawings, complete welding symbols.

5. Coordination
i) QC engineer shall develop inspection schedule refer to construction schedule, and inspection & test plan; and instruct the Discipline Inspector to visual examine.
Discipline Inspector examines the construction items/ parts, and publish & signing of the inspection record; and the result of inspection shall be reported to QC Engineer.
QC engineer review the result of inspection, and then QC Manager approve it.
QC administration shall put identification of inspection record, register, and document it.

6. Personnel Qualification
i. Visual examiner shall a Welding Inspector or person that has been trained, refer to Non Destructive Examination Qualification Personnel Procedures.
ii. Personnel physic shall has vision (with correction, if necessary) to be able to read a Jaeger Type 1 standard chart at a distance of not less than 300 mm (12 in.) and color contrast differentiation check. The Visual Examiner shall be checked annually.

7. Technique
i. Direct visual examination may usually be made when access is sufficient to place the eye within 600 mm (24 in.) of the surface to be examined and at an angle not less than 30 deg. to the surface to be examined.
ii. Mirrors may be used to improve the angle of vision, and aids such as a magnifying lens may be used to assist examinations.
iii. Illumination (natural or supplemental white light) for the specific part being examination is required. The minimum light intensity at the examination surface shall be 100 foot-candles.

8. Equipment
i. Visual aids and gages are sometimes used to make detection of discontinuities easier and to measure the size of welds or discontinuities in welds.
ii. Lighting of the welded joint must be sufficient for good visibility. Auxiliary lighting may be needed.
iii. If the area to be inspected is not readily visible, the inspector may use mirrors, bore scopes, flashlights, or other aids.
iv. Low power magnifiers are helpful for detecting minute discontinuities. However, care must be taken with magnifiers to avoid improper judgment of the discontinuity size.

v. Inspection of weld usually includes quantitative as well as qualitative assessment of the joint. Numerous standard measuring tools are available to make various measurements, such as joint geometry and fit-up, weld size, weld reinforcement height, misalignment, and depth of undercut.

vi. Some situations require special inspection gages to assure that specifications are met. Indicators, such as contact pyrometers and crayons should be used to verify that the preheat and inter-pass temperatures called for in the welding procedures are being used.

9. Evaluation
An examination checklist shall be used to plan and to verify that the required visual observations

were performed.

This checklist shall refer to Inspection & Test Plan that it establishes minimum

examination requirements and does not indicate the maximum which the Manufacturer may

perform in process.

9.1. Materials and Base Metal

Examination of the base metal prior to fabrication for detect conditions that tend to cause weld defects, such as: scabs, seams, scale, or other harmful surface conditions; plate laminations may be observed on cut edges.

Dimensions should be confirmed by measurements, Base metal should be identified by type and grade. Corrections should be made before work proceeds.

9.2. Prior to Welding

After the parts are assembled for welding, the inspection should check the weld point for
conformity to the approved construction drawings and specifications as following condition:
i. Joint preparation, such as: type of joint, root opening, edge preparation, other features
that might affect the quality of the weld.
The surface cleanliness of weld bevels shall be free of scale rust, oil, grease, paint and other deleterious foreign material for a distance of at least 25.4 mm
(1 in.) from the welding joint.

The surface shall be reasonably smooth and free from deep notches, and irregularities.

ii. Clearance dimension of backing strips, rings, or consumable insert.
iii. Alignment tolerances and fit-up of butt welded shall refer to relevant codes & standards and technical specifications.
iv. Welding process and consumables.
v. Welding procedures and machine settings.
vi. Specified preheat temperature.
vii. Tack welds quality.

9.3. Inspection during Welding
Some of the aspects of fabrication or erection that can be checked include the following:
i. Treatment of tack welds.
Tack welds shall be carried out by qualified welders.

ii. Quality of the root pass and succeeding welds layers.
ii.a) The most critical part of any weld is the root pass because many weld
discontinuities are associated with the root area.
ii.b) Competent visual inspection of the root pass may detect a condition that would
result in a discontinuity in the completed weld.
ii.c) The root opening should be monitored as welding of the root pass progresses.
Special emphasis should be placed on the adequacy of tack welds, clamps, or
bracer designed to maintain the specified root opening to assure proper joint
penetration and alignment.

iii. Proper preheat and inter pass temperatures.
iii.a) The preheat and inter pass temperatures shall be monitored at the proper times
with a suitable temperature measuring device (i.e., a temperature indicating
crayon or pyrometer).
iii.b) The amount of heat input and also the sequence and placement of each weld
pass may be specified to maintain mechanical properties or limit distortion, or

iv. Sequence of weld passes.

v. Inter pass cleaning.
v.a) Inspection of successive layers of weld metal usually concentrates on bead
shape and inter pass cleaning.
v.b) To ensure the weld quality as work progresses, each weld layer should be
checked by the welder, for surface irregularities and adequate inter pass
cleaning to avoid subsequent slag inclusions or porosity.

vi. Root condition prior to welding a second side.
vi.a) Another critical root condition exists when second side treatment is required of a
double welded joint, this includes removal of slag and other irregularities by
chipping, arc gouging, or grinding to sound metal.

vii. Distortion.
viii. Conformance with the applicable procedure.

9.4. After Welding.
Items that are checked after welding include the following:
i. Final weld appearance.
The weld surface shall be thoroughly cleaned for detection and accurate evaluation of
discontinuities.The cleaning may be carried out by a chipping hammer, brushing, chisel,
or suitable means so as to prevent inclusion of impurities in the weld metal.
ii. Final weld size.
The conformity of weld size and contour may be determined by the use of a suitable weld
gage. The size of a fillet weld in joints whose members are at right angles, or nearly so,
is defined in terms of the length of the legs.

iii. Extent of welding.
iv. Dimensional accuracy.
v. Amount of distortion.
vi. Post weld heat treatment.
When a post weld heat treatment is specified, the operation should monitored and
documented by an examiner. items of importance in heat treatment shall refer to Heat
treatment Procedure.

10. Acceptance Criteria.
The following discontinuities on the surface of a completed weld can be found by visual
i. Cracks.
ii. Undercuts.
iii. Overlap.
iv. Exposed porosity and slag inclusions.
v. Unacceptable weld profile.
vi. Reinforcement weld profile.

The acceptance standards of finish weld shall refer to governing code, engineering standards,
and owner technical specifications.

Unacceptable weld profile
Tack welds used during the assembly shall be removed and shall not remain in the finished
joints when the joints are welded manually.
When such joints are welded by the submerge arc process, the tack welds shall be thoroughly
cleaned of all welding slag but need not be removed if they are sound and thoroughly fused into
the subsequently applied weld beads.

11. Repair to welds.
i. All defects in seam weld shall be repaired by grinding or melting out the defects as required
and applying an additional weld bead over the defective area.
ii. Mechanical caulking is not permitted.

12. Documentation
12.1. Report of examination.
A written report of the examination shall contain the following information:
- The date of examination.
- Procedure identification and revision used.
- Technique used.
- Result of the examination.
- Examination personnel identity, and when required by the referencing code section.
- Identification of the part or component examined.

Even though dimensions were recorded in the process of visual examination to aid in the
evaluation, there need not be documentation of each viewing or each dimensional check.

The inspection record shall be maintained and documented of Mechanical Acceptance Report, that it will be sent to OWNER of the end of project.

13. Attachments.
Attachment - 1 Visual Inspection record form.

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