Pressure Vessel Inspection Procedure Rev.2 [PDF]

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CTEP - AIT-P-I-003: Inspection of Pressure Vessel

Chevron Thailand Exploration and Production Requirements and Procedures For:

AIT-P-I-003 Inspection of Pressure Vessel

Revision

Approval Date

Description

Prepared by

0

Initial release for comment

ITNN

1

Revised per Anuchai’s comments

ATOH

2

Revised per Abie’s comments

APZH

Version 0. Revised 26 October 2012

Reviewed by

Approved by

CTEP - AIT-P-I-003: Inspection of Pressure Vessel

Contents 1. 2. 3. 4. 5. 6.

PURPOSE …………………………………………………………………………………. SCOPE …………………………………………………………………………………….. REFERENCE ……………………………………………………………………………… DEFINITIONS …………………………………………………………………………….. RESPONSIBILITIES ……………………………………………………………................. INSPECTION PERSONNEL ……………………………………………………………...

1 1 1 2 3 4

7. PROCEDURES …………………………………………………………………………….

4 4 4 4

7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9

Safety ………………………………………………………………………………... Preparation and Planning …………………………………………………………... External inspection ………………………………………...………………………... Internal inspection ……………………...……………………...……………………... Inspection of removed and replacement of vessel components ……...…………….. 4 Inspection and non-destructive testing……...……………...…………………............... Pressure vessel repair and alternation……...…...………...……………………………... Hydrostatic Pressure Testing……...……...………...…………………………... Final inspection ……...………...………...………...……………………….....................

8. RECORDS AND DOCUMENTATION ………………………………………………….. 9. APPENDIX 8.1 APPENDIX A CORROSION RATE AND REMAINING LIFE CALCULATION……13 8.2 APPENDIX B MINIMUM RETIRED THICKNESS …………………………………15

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CTEP - AIT-P-I-003: Inspection of Pressure Vessel

1. PURPOSE

This procedure provides guidelines for both in-service and out-of-service inspection of various types of pressure vessels such as separators, drum, columns, towers, and reactors etc. These can vary greatly in design, fabrication complexity, working conditions and accessibility. However, inspection frequency is based on risk-based inspection (RBI) criteria included several factors such as service conditions, operational criticality and availability. The objective of inspection is to confirm the mechanical integrity of the pressure vessel in order to ensure safe and reliable operation. 2. SCOPE

This procedure defines inspection requirements and specific responsibilities for internal and external inspection of existing pressure vessels including separators, drums, columns, towers, and reactors etc. It applied for all pressure vessel of any metallic material which have been constructed in accordance with a pressure vessel design code at Chevron Thailand Exploration and Production Co., Ltd (CTEP) area of operations. The scope of this procedure applies for existing pressure vessel installed and serviced in operation (Brown field); however, it does not apply for the new construction (Green field). The inspection frequency of in-service and out-of-service inspection is also outside the scope of this procedure. This procedure is not a detailed inspection manual, specific location selective may change on case-by-case basis. 3. REFERENCES

1. API STD 510 Pressure Vessel Inspection 2. API RP 571 Deterioration Mechanisms 3. API RP 572 Inspection of Pressure Vessels 4. API RP 579 Fit For Services 5. ASME Section V Non-destructive Testing 6. ASME Section VIII Div. 1 & 2 Unfired Pressure Vessels 7. Corrosion Prevention and Metallurgy Manual Volume I, II, III, ChevronTexaco Energy Technology Co. 8. Pressure Vessel Manual, Section-700 In-Service Inspection, ChevronTexaco Energy Technology Co. 9. Procedure of Asset Integrity Management (AIM) in SERIP document

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CTEP - AIT-P-I-003: Inspection of Pressure Vessel

4. DEFINITIONS

Vessel: A container designed to withstand internal or external pressure which is built to a pressure vessel construction code (e.g. ASME, BS, JIS). Column: Any vertical vessel containing trays, packing or other internals which is used to separate product fractions. Reactor: Any vessel containing beds of catalysts used to crack or improve the quality of the feed product. CMMS: Computerized Maintenance Management System. External Thickness Monitoring: External thickness measurements normally performed with, but not limited to, the NDE ultrasonic gauging instrument which may be performed while the vessel either is in service or out of service. This definition coincides with the term "On-Stream Inspection" used in API 510 External Inspection: An assessment of the conditions of the vessel's external surfaces, such as: insulation, fire proofing, painting and structures associated with the pressure vessel. Internal Inspection: This normally refers to, but is not limited to, an assessment of the condition of the vessel's internal surfaces and components, i.e. shells, heads, welds, internal parts, coating & linings, cladding, anodes etc. Condition Monitoring Location (CML): An area of a pressure vessel boundary surface which has been selected and identified by monitoring shell, head and nozzles thicknesses. Previously, they were normally referred to as “thickness monitoring location (CML).” Corrosion Circuit (CC): A term used to describe a zone of a pressure vessel within which the corrosive conditions are approximately equal, taking into account the corrosive environment (internally and externally), temperature, pressure, and the constructed material. The Visions4 software also specifies corrosion circuits for inspection and monitoring. Risk: A combination of the probability of occurrence of pressure vessel failure and magnitude of the consequence of the failure. Inspector: Pressure vessel inspectors shall be API 510 certified or authorized by company. NDT Technician: NDE Technicians who are performing and interpreting non-destructive examinations must be certified in the method(s) used by one of the following: • ANST Level I, II or III • ISO 9712 level I, II or III • NDT techs pass a CVX test from Practice of NDT Personnel Qualification Restricted interval (RI): A factor in company computerized inspection records system used to shorten the length of the thickness measurement inspection interval when there is a potential for uneven corrosion rates in the circuit/loops.

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CTEP - AIT-P-I-003: Inspection of Pressure Vessel

5. RESPONSIBILITIES

5.1 Asset integrity program owner 5.1.1

Responsible to implement of the Owner User Program and ensure that resources are adequate.

5.1.2

Provide necessary qualified people and tools to execute inspection work to follow the RBI programs.

5.1.3

Responsible for assuring the Authorized Inspector maintains the required qualifications/certifications. Inspection and nondestructive examination personnel who perform inspection tasks do not have to be company personnel.

5.2 Asset integrity SME team shall be responsible for: 5.1.1

Providing technical support and fit for purpose solutions to the corrosion, inspection, repair method and integrity challenges.

5.1.2

Evaluating inspection findings and providing evaluation of potential repairs and replacement.

5.1.3

Preparing required inspection, replacement, and repair scopes

5.3 Asset integrity offshore execution team shall be responsible for: 5.3.1

Performing external and internal inspection of the piping and components in accordance with this procedure.

5.3.2

Determining if cleaning is needed to achieve a satisfactory thorough inspection.

5.3.3

Establishing circuits and CMLs on-site.

5.3.4

Obtaining ultrasonic thickness readings of piping, valves, and fittings.

5.3.5

Physically identifying CMLs and providing a sketch of the piping marked to indicate inspection findings and the location of findings.

5.3.6

Identifying the locations of repairs and replacements.

5.3.7

Providing an inspection report and anomaly report to meeting all requirements in this procedure.

5.4 Asset integrity program shall be responsible for: 5.4.1

Maintaining static data, historical data and repair records in Visions4.

5.4.2

Running Visions4 for planning and scheduling of piping system. This will include generate work order of both inspection and repair scope in CMMS.

5.4.3

Being focal point to conduct Risk Assessment with the RBI group and ETC

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5.5 FE Construction Team shall be responsible for: 5.5.1

Replacing or repairing the deteriorated piping or components

5.5.2

Conducting Radiographic Examination.

5.6 Field operation and maintenance (O&M), and Asset team shall be responsible for: 5.6.1

Providing preparation work for pressure vessel inspection such as vessel cleaning, vessel isolation

5.6.2

Removing insulation for inspection and repairs and re-installing insulation after inspection and repairs are completed.

5.6.3

Facilitating and Coordinating with all related parties to achieve repair work efficiently.

6. INSPECTION PERSONNEL

Personnel performing inspection of pressure vessel and vessel components shall be certified in accordance with Chevron’s written Practice of NDT Personnel Qualification in the SERIP Document. They should also have at least 3 years of experience in design, construction, repair, operation or inspection of vessel system and qualify at least level I or higher for UT and level II or higher for other NDT techniques. API 510 Certified inspectors shall hold valid certificates and recognized by the Company. 7. PROCEDURE

7.1 Safety 7.1.1

All necessary permits/clearances in accordance with CTEP Safety Regulations shall be obtained before commencement of inspection activities.

7.1.2

Appropriate Personal Protection Equipment shall be worn in accordance with guidelines in the CTEP Safety Regulations or according to Permit to work requirements.

7.1.3

Adequate and proper ventilation, lighting and scaffolding should be provided.

7.1.4

Proper safe access should be provided for inspection to be conducted.

7.1.5

The inspector and NDT examiner shall review the situation of vessel entry, and follow the safety requirements for all necessary aspects related to the circumstances of the inspection, including working in confined spaces, working at height, precautions for H2S, etc.

7.1.6

For an internal inspection, positive isolation (blinds) from all sources of liquids, gases or vapours shall isolate the vessel. The vessel should be cleaned, ventilated and gas tested before it is entered. Particular attention should be given to areas

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CTEP - AIT-P-I-003: Inspection of Pressure Vessel

behind weir plates and inside drains and nozzles to ensure they are also thoroughly drained prior to entry and inspection. 7.2 Preparation and Planning 7.2.1

Prior to conducting inspection of pressure vessel, inspector should familiarize with vessel design, service condition, operating experience and inspection history.

7.2.2

Prior to conducting internal inspection, inspector need to be ensure that proper cleanliness needs to be carried out.

7.2.3

Besides the need for adequate cleaning of the metal surface, sufficient internal lighting of the vessel is essential for proper and thorough visual inspection.

7.2.4

Examination/inspection must not take place when the preparation which provided by Asset team is found to be inadequate.

7.2.5

Internal inspection of large vessels may be constrained by accessibility. Prior to inspection, Asset Integrity team should inform with maintenance and operations department, the need for removal of trays and fittings or construction of internal scaffolding and ladders to enable the necessary extent of inspection to be carried out.

7.2.6

Safe and adequate means of access to and into the equipment must be provided

7.2.7

It is the responsibility of the inspector to ensure that the vessel has been suitably prepared for inspection. Particular attention should be given to vessel cleanliness, access to all necessary locations, and insulation removal where required.

7.3 External inspection of pressure vessel 7.3.1

Overview of external inspection

Assessing the condition of the vessel's external surfaces, such as fitting, protective devices, protective painting, insulation, fire proofing, bolting, sign of leakage, bulging or excessive dent and structures associated with the pressure by visual inspection An external inspection of vessels should be carried out periodically whilst the vessel is in service, preferably preceding a planned shutdown. External corrosion can be a significant problem, particularly in any local areas where the protective coating has broken down on uninsulated vessels or where water can accumulate. Insulated vessels operating in the range -50 deg. C to 150 deg. C or in intermittent service are particularly prone to external corrosion. For insulated vessels, damaged or loose fitting insulation cladding will allow the ingress of water so that corrosion may occur. Corrosion can also be experienced at locations where adequate draining of any accumulated water in the insulation may not be possible. A thorough visual inspection of all external surfaces shall be carried out as far as access and insulation permits. Insulation should be removed in areas selected by the Inspector, where accelerated corrosion can be anticipated. Known problem areas are at the junction Version 0. Revised 17 July 2012

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of supporting structures and cowling, insulation or vacuum rings, manholes and nozzles. In determining the possible susceptibility of insulated vessels, columns and reactors to external corrosion the Inspector shall take account of the actual operating temperature and any temperature gradients which may exist over the equipment such as dead-legs 7.3.2 o

Guideline of external inspection Perform external visual inspection on all external surface of vessel and piping in the skid as following below 1. Location of inspection : Entire external vessel Inspection for : • Distortion, bulging, blistering, cracking. • Any sign of leakage. • General and Pitting Corrosion. 2. Location of inspection : Protective coatings Inspection for : • Evidence of deterioration. 3. Location of inspection : Steel supports and skirts of vessel Inspection for : • Sign of corrosion, distortion, vibration and cracking for further proper functioning. 4. Location of inspection

: Ladder, walkways, platforms, grating and stairways

Inspection for : • Corroded, bent, broken, or missing structural parts. • Loose or missing bolting. • Worn stair treads and rungs. 5. Location of inspection : Insulated vessels Inspection for : • External evidence of corrosion under insulation (CUI). • Loose, corroded, or deteriorated insulation support systems. • Insulation jacket damage which would permit water to penetrate • Check areas, particularly at joints or skirts where moisture can penetrate and lead to corrosion of unprotected surfaces. • Cold insulation should be checked for flaws in the vapour barrier. 6. Location of inspection : Level gauge legs and other appurtenances Inspection for : • External evidence of corrosion under insulation (CUI). • Loose, corroded, or deteriorated insulation support systems. • Insulation jacket damage which would permit water to penetrate • UT is recommended ; however, RT maybe considered for small bore or pitting type services. Version 0. Revised 17 July 2012

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CTEP - AIT-P-I-003: Inspection of Pressure Vessel

7. Location of inspection : Small Branch Connections Inspection for : • PT is recommended if vibration is observe o

Perform external thickness monitoring inspection on located CML 1. Vessels constructed with corrosion resistant materials, including all internal cladding may not require external thickness monitoring. 2. Insulated vessel shall be installed inspection ports (IP) to prevent the ingress of moisture under the insulation. The access port shall be defined as CML. 3. Within the area of CML vessel thickness shall be scanned to obtain the minimum reading thickness. This reading shall then be recorded as the thickness value for the CML in VISIONS4. 4. If a large scatter in the thickness readings at a CML is experienced, additional areas adjacent to the CML may need to be scanned until the nature of the condition can be assessed. The verified minimum wall thickness reading shall be recorded. • Such conditions may require engineering evaluations or fitness for service. • All conditions of this sort shall be noted in the vessel inspection file. • Thickness readings greater than previous readings for the CML which are considered to be outside the acceptable instrument and/or operator error shall be evaluated to determine the reason for the error. The incorrect value shall be corrected and noted in the vessel inspection file.

7.4 Internal inspection of pressure vessel 7.4.1

Overview of internal inspection

Vessels may be subjected to a range of service conditions, including regular changes of contents, or unexpected traces of corrosive impurities and they may be constructed from a range of materials to suit these service conditions. The defects to be inspected for will; therefore, vary significantly according to the conditions that the vessels are exposed to and the materials of construction. All internal surfaces, welded seams and heat affected zones including nozzle openings, should be examined for any signs of discoloration, corrosion, erosion, pitting, cracking, grooving, scale deposits, sludge accumulation or other defects. The general condition must be recorded and any areas showing damage, leakage or deterioration must be investigated and remedial action proposed where applicable. The inspection should particularly include a re-check of any defects or repairs made previously, as documented in previous inspection reports. Any indication of a reduction in wall thickness of the pressure containing part of the vessel shall be verified by ultrasonic or radiographic testing. The use of photography as a means of permanently recording areas of interest is recommended. Samples of scale or Version 0. Revised 17 July 2012

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deposits should be obtained for analysis as and when judged necessary by the Inspector or advised by the Corrosion Engineer. 5.3.2

Local Deformation Any local deformation of the vessel wall is most probably due to overstressing or overloading of nozzles by connecting pipe work etc. Internals can be deformed for a number of reasons, which may be related to the operating conditions. In H2S-containing service, blistering of the vessel wall may be present. Accessible surfaces should be checked for deformation or blistering. The primary method for locating suspected deformation is to direct a flashlight beam parallel to the surface. Shadows will appear in depressions and on the unlighted side of internal bulges. Placing a straight edge parallel with the vessel axis against the vessel wall, and using a steel rule to measure the extent of bulging can also measure local deformation.

5.3.3

Signs of Thermal Shock The stress resulting from the sudden unequal expansion or contraction of the different parts of a vessel may cause distortion that can result in cracking. This type of damage is more likely to occur in austenitic materials such as stainless steel than in ferritic materials like carbon steel or low alloy steel. If located, the extent and depth of cracking should be established by NDT methods.

5.3.4

Corrosion Damage The location and form of any corrosion observed in the vessels should be clearly identified. Corrosion damage can be classified as:a) Those, which can be distinguished by visual examination. • general or pitting corrosion • localised corrosion • galvanic corrosion • velocity-related corrosion (e.g. erosion) b) Those, which can usually be positively identified only with the assistance of supplementary methods of inspection or through microscopic examination. • Cracking due to fatigue, creep or environment induced stress corrosion cracking. These types of cracking are often associated with the weld heat-affected zone. • Intergranular corrosion, commonly experienced in stainless steels and high nickel alloys, and often observed in the heat affected zones of welds. • Dealloying (graphite corrosion, dezincification of brass). In particular, the type and appearance of any scale in the vessel should be noted, as a possible indication of the type of corrosion damage that has occurred.

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CTEP - AIT-P-I-003: Inspection of Pressure Vessel

Where visual inspection has highlighted areas requiring a more thorough examination by ultrasonic testing, these should be clearly marked up and reported. 5.3.6

Internal Fittings, Trays and Attachments All internal trays, support rings, support lugs, baffles, side sumps and nozzles welded to the draw-off trays should be inspected for excessive bulges, depression, or any wear and tear which may need repair. However, at the discretion of the Inspector, only a representative number of each type of fittings can be selected for a more detailed inspection. Complex internal fittings designed for specific purposes should be looked at more critically for cracks and metal loss so that their strength is adequate for their designated function.

5.3.7

Nozzles The nozzles, flanged connections and bolting should be inspected for damage/corrosion. The gasket faces of the flanges that are opened should be inspected to check that they are in good condition. Visual inspection of small nozzles may be supplemented by use of a boroscope. Several methods for the internal examination are also available using ultrasonic techniques, radiography or internal calipers. Nozzles should be visually examined for bulging, excessive scaling and corrosion, internal blockages and in particular, plugging in relief valve and instrument nozzles, where present. Blind flanged nozzles (e.g. utility connection, vent nozzle etc) should be included in the check for internal corrosion. Note that nozzles attached to the equipment and water boots may be inspected on-stream by means of radiography or ultrasonic thickness check, and should be included in the onstream inspection programme where appropriate.

5.3.8

Internal Coatings, Lining or Cladding Non-metallic coatings are applied to prevent internal corrosion of the vessel, but are limited in their use by temperature and compatibility with some process fluids. Metallic linings, in the form of integral cladding, strip lining or weld overlay with a more corrosion resistant material may also be applied internally to protect the pressure vessel from aggressive service conditions. In the event of a coating or lining failure, the pressure vessel may be exposed to conditions that it was not designed to withstand. The coating or lining should therefore be carefully checked for any damage, particularly due to thermal shock or temperature excursion, or separation from the parent metal, particularly around nozzles and areas where there is a cross-section change. Metallic corrosion-resistant linings should be examined using PT to check for cracking. Internal refractory should be inspected for excessive erosion, wear, cracks and damage. If

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CTEP - AIT-P-I-003: Inspection of Pressure Vessel

required, the condition of the refractory-anchoring studs should also be checked. 7.4.2 o

Guideline of internal inspection Clean internal vessel surfaces and vessel internal parts as needed prior to inspection 1) Scale, dirt, hydrocarbon deposits etc. shall be removed so that a thorough and satisfactory inspection can be achieved. 2) Removal of internal coating, lining, obstructed parts may be required as necessary

o

Perform internal visual inspection on all internal surface of vessel and piping in the skid which includes an examination of all accessible surfaces of the vessel and all internal parts. 1. Location of inspection : Vessel shell, head, nozzles, and weld seams Inspection for : • General and localized corrosion, pitting, erosion, and impingement damage • Blistering, bulging, buckling, or distortion • Cracking • Pin-holes 2. Location of inspection : Internal part of vessel Inspection for : • Deterioration or cracking of trays, baffles, mist extractor, vane, piping supports, internal stiffeners, and welds. • Erosion of impingement plates. • Distortion, bulging, blistering, or buckling of weirs, bucket, baffles, trays, supports, and impingement plates. • Missing, loose, or deteriorated bubble caps, weirs, chimney etc. • Missing loose or deteriorated internal piping. • Deteriorated, cracked, or damaged internal piping. • Loose or missing bolting. • damage, sagging, deflection, cracks or corrosion wastage. • Any evidence of cracking at highly stressed areas such as stays and braces on the column wall, support beams or rings damaged due to effect of vibration or internal dynamic upset should be noted. 3. Location of inspection

: Internal linings (both metallic and nonmetallic)

Inspection for : • Sign of corrosion, pitting, cracking, spalling, and leakage 4. Location of inspection : Internal coating vessel Inspection for : • Evidence of deterioration

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7.5 Hydrostatic Pressure Testing 7.5.1

General A hydrostatic test shall be used to prove the integrity of pressure vessel after repairs, provided the design of the vessel and supports can accommodate the test. Hydrostatic testing should be applied carefully and with the knowledge of all parties involved, since the vessel may be subjected to a stress exceeding its normal operating stress. Approval shall be obtained from Reliability Manager (add in role and responsibility) if any requirement for hydrostatic pressure testing is to be waived.

7.5.2

Test Procedure Details of the requirements for hydrostatic testing shall be followed hydrotest procedure AIT-X-X-002. In case, any deviation from procedure require approval by Reliability Manager (add in role and responsibility)

8. Final Inspection

8.1 Upon completion of all required repair work, the vessel shall receive a re-inspection to ensure the completeness and adequacy of repair and to verify vessel cleanliness prior to closing. 8.2 API Certified Inspector ensure all required inspection activities have been completed as per inspection test plan (ITP) 9. Records and documentation

The Inspector who has inspected the equipment shall record the findings in VISIONS4. In this record, the following are required: • Component history • Corrosion rate (CR) and remaining life (RL) • Highlights • Recommendations, if any • Thickness measurement, if any. • All sketches, photographs results and reports of NDT and other inspection activities Attachments

a. Appendix I – CML for wall thickness gauging b. Appendix II – Inspection checklist for pressure vessel c. Appendix III – Corrosion Rate (CR) and Remaining Life (RL) Calculation d.

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Appendix IV - Wall Thickness Calculation

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Appendix I – CML for wall thickness gauging

Note: 1. UT all nozzle 2” and above 2. Nozzle size 4” & below - 1 Test point 3. Nozzle size above 4” - 2 Test points 4. UT should include level gauge and other appurtenances Version 0. Revised 17 July 2012

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Refer sheet 1 of 4 Note on nozzles

Appendix II – Inspection checklist for pressure vessel Examination Checklists Pressure Vessels: (Including Columns, Reactors, Accumulators, Strippers, Filters, Pots, etc.) 1. Fouling Version 0. Revised 17 July 2012

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2. 3. 4. 5. 6. 7.

Dished heads Shell Boot Nozzles (blockages) Level gauge legs and other appurtenances. Internals (Baffles, Coating, Cladding, Scallops Expansion rings, Centre screen, Support rings, Trays, Tray support beams, Packing rings, demister pads, ) 8. Welds (internal/external) 9. Vortex breaker (thickness) 10. Insulation 11. Insulation supports 12. Supporting structure 13. Skirts/saddles 14. Hold-down bolts 15. Earthing 16. Heating coils/elements 17. Gasket faces 18. Bolting 19. Ladders/Platforms/handrails 20. Welds (internal/external) Note: Delete what components are not applicable to Pressure Vessel being inspected. Note for Columns: It is not unusual for the inspection of columns to be concentrated on part of the equipment only. In that case, the boundaries of the examination must be clearly referenced and the justification for the partial examination explained.

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Appendix II – Inspection checklist for pressure vessel

EXTERNAL INSPECTION GUIDE for VESSELS/COLUMNS/REACTORS Note: This checklist is an additional guide to external inspection covering items that should be considered during inspection of pressure equipment. The list is not exhaustive, and the inspector should apply knowledge and experience in the interpretation and application of the inspection requirements. External condition (painting, lagging, fire-proofing, etc) Support structure, skirt, ladders Nozzles, water boots, (condition, UT/RT/??) Flanges – free of leaks, bolt condition Supports and saddles Earthing Sight glasses/fittings Instrumentation Small bore fittings (condition/design/vibration) Relief valves Bolt/nut condition (inc. hold-down bolts) Clamps on lines On-stream thickness gauging

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Appendix II – Inspection checklist for pressure vessel

INTERNAL INSPECTION GUIDE for VESSELS/COLUMNS/REACTORS Note: This checklist is an additional guide to internal inspection covering items that should be considered during inspection of pressure equipment. The list is not exhaustive, and the inspector should apply knowledge and experience in the interpretation and application of the inspection requirements. Internal Fouling? Before cleaning:

type Location

After cleaning Unlined shell and heads: General corrosion observed/measured - C.R. & R.L. Pitting observed/measured H2 blistering observed Localised corrosion - downcomers, trays, welds, opposite nozzles, liquid levels, etc MPI checks in wet H2S, amines, deaerators, etc Clad shell/heads: General corrosion/pitting observed/measured DP inspected

-C.R.

Nozzles/manways: All inspected General corrosion/pitting observed/measured Gasket face condition Internals: Trays and supports corroded/damaged Tray caps corroded, damaged, in place Demister pads displaced/corroded/fouled Vessel appurtenances corroded/loose Vessel packing intact/fouled Impingement plates corroded/eroded – check welds for cracking Internal lines hammer tested Pressure test: Statutory?? After repairs/modifications

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Appendix III – Corrosion Rate (CR) and Remaining Life (RL) Calculation

CORROSION RATE AND REMAINING LIFE CALCULATION 1.

The long-term (LT) corrosion rate shall be calculated from LT corrosion rate

2.

tinitial −tlast

time (year)between tlast and tinitial

The short-term (ST) corrosion rate shall be calculated from: ST Corrosion rate

3.

=

=

tprevious −tlast

time (year)between tlast and tprevious

The remaining life of piping shall be calculated from: Remaining life

=

tlast −trequire

Selected corrosion rate

The selected corrosion rate shall be determined from the maximum value whether LT or ST, that best reflects the current process. Where: t initial

=

The piping original wall thickness before service.

t last

=

The piping wall thickness at time of last inspection.

t previous =

The piping wall thickness at time of previous inspection.

t required =

the greater value of the pressure design thickness (MAWP) or the structural minimum thickness.

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Appendix IV - Wall Thickness Calculation WALL THICKNESS CALCULATION

In case calculation sheet from manufacture is not available, simple formulas for calculation of wall thicknesses of pressure vessel: Refer to construction codes Formulas in Terms of Inside Diameter: Cylindrical Shell

t

=

2:1 Ellipsoidal Head

t

=

Formulas in Terms of Outside Diameter : Cylindrical Shell

t

=

2:1 Ellipsoidal Head

t

=

Where: P Ri Di Ro Do S

E

= = = = = = = = = = = = =

PRi

SE−0.6P PDi

2SE−0.2P PR0

SE−0.4P PD0

2SE+1.8P

Design Pressure or Maximum Allowable Operating Pressure, psig. Inside Radius of Cylindrical Shell, inch. Plus corrosion allowance CA (if any) Inside Radius of 2:1 Ellipsoidal Head, inch. Outside Radius of Cylindrical Shell, inch. Outside Radius of 2:1 Ellipsoidal Head, inch. Maximum Allowable Stress, psi. 17,500 psi for A516 Gr. 70 Steel for year 1998 downward 20,000 psi for A516 Gr.70 steel for year 1999 upward 15,000 psi for A516 Gr. 60 Steel Joint Efficiency. 1.00 for full radiographic tested weld vessels. 0.85 for spot radiographic tested weld vessels. 0.70 for non radiographic tested weld vessels.

Weight of service fluid, weight vessel itself, and external load are not included in this calculation. When calculate the wall thickness for any rejection of vessel, the inspector shall ensure that the applicable code is correct to the year of construction and edition. Many factors have been revised for each edition. NOTE If any suggestions from offshore inspectors and Asset Integrity Supervisors, let contact Asset Integrity Team, Reliability Group, Facilities Engineering Department, Bangkok, Thailand

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CML for pressure vessel

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CTEP - AIT-P-I-003: Inspection of Pressure Vessel

Vessel dia < 8 ( Typical Cleaning Standards Class A – Special Inspection Clean. The object is super cleaning for UT, ECT or MPI inspection. It will be accepted if all the process fouling and all of the scale is 100% removed only at the position where the UT / ECT / MPI is being conducted. Inspection planner to specify these locations in ITP according to the following grades: Power brush at area required for Inspection A1 Grit blasting at area required for Inspection A2 Ultra-High Pressure Water jetting at area required for Inspection A3 Mill scale removal by Chemical Cleaning at area required for Inspection A4

Class B – Visual Inspection Clean. The object is cleaning for visual inspection. It will be accepted if the process fouling and the scale is approximately 80 % removed Inspection planner to identify locations required for visual inspection in ITP according to the following grades: Hand Brush clean at area required for Visual Inspection B1 Selective Hydro jetting at area required for Visual Inspection B2

Class C - Production Clean The object is light cleaning for production to either clear a blockage or increase the available flow area. It will be accepted if some mill scale (rust) or some hydrocarbon (coke) and process fouling can still remain Operations to specify cleaning requirements according to the following grades: Hand Brush clean C1 Rag cleaning C2 Vacuum Cleaning C3 Volume water wash (using Fire Hose) C4 Mechanical scrapers, hand tools C5 Hydro jetting C6

Version 0. Revised 17 July 2012

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CTEP - AIT-P-I-003: Inspection of Pressure Vessel

General Cleanliness Examples:

A1, A2, A3

B1, B2

C6

Version 0. Revised 17 July 2012

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