API 510- INSERVICE PRESSURE VESSEL INSPECTOR

PREPARATORY COURSE

PART III

CODE WISE PUNCH POINTS

SUMMARY OF ALL CODES AND STANDARDS FOR API 510) EXAMINATION

API 510 CERTIFICATION – PREPARATORY COURSE

API 510 - Pressure Vessel Inspection Code

Note: Figures in parenthesis give the reference number of code paragraphs from where the

punch points are drawn up.

A Section 1 : Scope of API 510

1. API 510 covers in-service inspection, repair, alteration and re-rating activities for pressure

vessels and Pressure Relief Devices protecting the vessel. (1.1.1)

2. API 510 applies to all Refining and chemical process vessels that have been placed in

service.

3. API is applicable to vessels constructed in accordance with applicable construction code,

or constructed without a construction code (1.1.2)

4. API 510 shall not be used in conflict with regulatory requirements. If API 510 code

requirements are more stringent than regulation, then requirements of the code shall

govern (1.1.3)

5. Following are excluded from API 510 (1.2.2)

a. Vessels on movable structures.

b. All exemptions listed in ASME Sec. VIII (Div. 1)

c. Very small vessels with certain limitation of volume and pressure.

B Section 2 : References.

6. Important reference documents which have been referred in API 510:

a. API 571 : Damage Mechanisms

b. API 572 : Recommended Practice for pr. vessel inspection

c. API 576 : Inspection of Pr. Relief Devices.

d. RPI RP 577 : Welding inspection & Metallurgy.

e. API RP 578 : Material Verification program

f. API 579 : Fitness for service ( FFS).

g. API 580 : Risk Based Inspection (RBI).

h. API Publ. 2201 : Procedures for welding or Hot tapping on the equipment in

service.

C Section 3 : Definitions.

This chapter gives definitions.

7. Alteration : A Physical change in any components affecting the design (3.2)

8. Authorised inspection agency : Any one of the following (3.6)

a. Inspection organisation of jurisdiction.

b. Inspection organisation of insurance company

c. Inspection organisation of owner - User.

d. Organisation or individual under the contract with owner user.

9. Examiner : A person who assists the inspector by conducting specific NDE (3.20)

10. Engineer : One or more persons evaluating mechanical and material characteristics (like

strength calculations, corrosion, the vessel integrity etc.) (3.19)

11. Repair : Work necessary to restore a vessel suitable for safe operation at design

conditions. Any work not specifically conditions. Any work not specifically considered as

alteration is considered repair.

12. Repair organisation : Any one of following (3.54)

a. Holder of ASME Stamp (e.g., U Stamp)

b. Holder of R Stamp

c. Owner user who repairs his own equipment.

d. Sub-contractor appointed by owner user for repair jobs.

e. Organisation authorised by jurisdiction.

13. Rerating : A change in either design temperature, the MDMT or MAW rating of vessel.

(3.56)

14. Condition Monitering locations are designates areas on vessel where periodic

examinations are conducted (3.9)

D Section 4 : Organisation and Responsibility.

15. Owner / User holds overall responsibility for all activities under API 510 (4.1).

16. Before implementing API 510, the owner / user organization should prepare quality

assurance manual describing inspection and control activities (4.2.1).

17. Engineer is responsible to owner user for design, engineering review, analysis and

evaluation of pressure vessels. (4.2.2)

18. Inspector is responsible to owner user to assure that NDE testing activities meet API 510

requirements. All NDE results must be evaluated by inspector. (4.2.4)

19. Examiner shall perform NDE in accordance with job requirement (4.2.5)

20. Repair organization is responsible to owner user and shall provide materials, equipment,

quality control and workmanship as required for repair activities. (4.2.3)

E Section 5 : Inspection Examination and Testing.

21. Before taking up any inspection, an inspection plan shall be developed by inspector or

Engineer (5.1.1).

22. A RBI assessment determines Risk by combining the probability and the consequence of

failure (5.2)

23. RBI assessment shall be preformed in accordance with API 580. The detailed RBI

methodology is presented in RBI 581 (5. 2)

24. Before performing any inspection inspector should review the prior inspection results.

(5.3.4)

25. Internal inspection is preformed by inspector. The primary goal of internal inspection is to

find damage that can not be found by regular monitoring of external CMLS. (5.5.2.1)

26. On-stream inspection may be used as alternative to internal inspection under certain

conditions. It shall be conducted by either Inspector or examiner. It may include several

NDE techniques to check for various types of damages. (5.5.3)

27. External Inspection is essentially visual inspection conducted externally to check for

leakage, hot spots, vibration distortion etc. It is normally conducted by inspector but may

also be conducted by other qualified persons. (5.5.4)

28. 28. CUI inspection is required for insulated vessels where moisture ingress is likely and

vessels operate between 100 F to 350

0 F for carbon and alloy steels and 140

0 F to 400

0 F

for Austenitic Stainless Steels (5.5.6)

29. Thickness measurement is usually done by UT techniques. (5.7.2)

30. Ultrasonic Scanning or profile radiography is preferred where corrosion is localized

(5.7.2)

31. Pressure test is conducted if inspector believes it is necessary after the repairs. Pressure

text is normally required after an alteration. (5.8.1)

32. Hydrostatic Test Pressure on vessels is as follows (5.8.2)

a. For vessels constructed prior to 1999 = 1.5. X MAWP X stress ratio.

b. For vessels constructed after 199 = 1.3 X MAWP X stress ratio.

33. The pressure test temperature shall be above (5.8.6).

MDMT + 100 F for vessel thickness upto 2" and MDMT + 30

0 F for vessels thicker than

2".

F Section 6 : Inspection Frequency.

34. External Inspection frequency shall not exceed lesser of internal inspection interval or 5

years. (6.4.1)

35. Internal and on-stream inspection frequency shall not exceed lower of one-half the

remaining life or 10 years.

If remaining life is less than 4 years inspection interval may be full remaining life up to a

maximum of two years. (6.5.1)

36. ARBI assessment may be used to establish appropriate inspection interval for internal on

stream and external inspection and 10 years limit may be exceeded. (6.3.1)

37. If service conditions of a vessel are changed inspection intervals shall be established for

new service condition. (6.2.2)

38. If both ownership and location of vessel are changed, Allowable Service Conditions and

inspection interval shall be established. (6.2.2)

39. On stream - inspection may substituted for internal inspection if the inspector approves,

for following conditions. (6.5.2)

a. General corrosion rate is less than 5 mpy as confirmed for at least 5 years.

b. vessel remaining life in at least 10 years.

c. vessel is not operating in creep temperature range.

d. vessel is not subject to SCC.

e. vessel does not have non integral lining inside.

40. For Multi zone vessels each zone shall be inspected based on interval for that zone. (6.5.3)

41. Pressure-Relieving devices shall be tested in accordance with API 576 (6.6)

42. The repair organization for PRDS shall have a documented quality control system. (6.6.1)

43. The repair organization shall have documented training program to ensure that personnel

are adequately qualified required (6.6.1)

44. Testing and inspection interval for PRD s.

a. Five years for typical service.

b. Ten years for clean and non-corrosive service. (6.6.2)

G Section 7 : Inspection data evaluation.

45. Corrosion rate (7.1)

Long term corrosion rate = t initial – t actual

years between t initial & t actual.

Short term corrosion rate = t previous – t actual

years between t previous & tactual.

46. Out of long-term and short-term corrosion rates the inspector in consultation with

corrosion specialist shall select the rate that best reflects current conditions (7.1.1.2)

47. For newly installed vessel or for change or service corrosion rate can be estimated based

on : (7.1.2)

a. Data collected on vessels in same or similar service.

b. corrosion rate may be estimated from published data.

c. If there is not data on any of above on-stream determination after 1000 hours of service

shall be made.

48. Remaining life = t actual – t required

corrosion rate (7.2.1)

49. MAWP determination (7.3.1)

The thickness (t) used for MAWP formula is given by

t = tactual - 2 (corrosion rate X Interval)

50. For evaluation of locally thinned are corrosion averaging may be done over a length (L)

not exceeding following (7.4.2.1)

a. For vessel I.D. upto 60", L=lesser of ID or 20"

2

b. For vessel I.D. above 60", L=lesser of ID or 40"

3

51. Pitting Evaluation (7.4.4)

Widely scattered pits may be ignored if all of the following are true.

a. Remaining thickness below the pit is greater than one-half or required thickness.

b. Total pitted area (i.e. deeper than corrosion allowance) does not exceed 7 sq. in

c. Sum of pit dimension that is deeper than corrosion allowance along any 8 inch straight

live does not faced 2 inches.

52. If a vessel with joint efficiency less than 1 has corroded surface away from the weld, an

independent calculation using weld joint factor = 1 can be made.Surface away from weld

means surface beyond 1 inch on either side or twice the required thickness which ever is

greater, as measured from toe of the weld. (7.4.5)

53. To recalculate required thickness for tori-spherical head use following guideline (7.4.6)

a. For knuckle region use thickness formula in construction code.

b. For central portion use Hemispherical head formula with crown radius equal to O.D. of

shell.

c. Central portion is defined as center of head with diameter equal to 0.8 times shell

diameter.

54. To recalculate the required thickness for 2:1 ellipsoidal head use following guide line .

(7.4.6)

a. For Knucle region use construction code formula.

b. For central portion use Hemispherical head formula with crown radius equal to 0.9

times the inside shell diameter.

c. Central portion is defined as center of head with diameter equal to 0.8 times shell

diameter.

55. If exact material specification for carbon steel unknown, then use allowable stress value

(s) for S.A 2836 Gr. C material (7.7).

56. If extent or radiography done originally is not known (E is unknown) then for butt welds

use E=0.7 (7.7).

57. Typical pressure vessel records consist of 4 types of information.

a. Construction and design information.

b. Inspection History.

c. Repair, Alteration, re-rating information.

d. Fitness for service records.

H Section 8 : Repairs Alteration Re-rating.

58. Approval of repair or alteration procedures : (7.1.2)

For Repairs : Inspector

For Alterations : Inspector and Engineer.

59. Authorization of repair/ alteration work on vessels complying with

a. ASME Sec. VIII Div. 1 : Repairs by Inspector.

b. ASME Sec. VIII Div. 2 : Both Repairs and Alteration to be authorized by Inspector

and Engineer.

60. The inspector shall approve all repair and alteration work at the hold points and after

completion. (8.1.2)

61. Materials used for welded repairs and alterations shall be of known weldable quality.

Carbon or alloy steels with carbon content more than 0.35% shall not be welded.

62. Normally temporally repairs are replaced by permanent repair at next turnaround but may

remain for longer period if approved by engineer and inspector (8.1.5.1).

63. Fillet welded patches may be used for making temporary repairs. (8.1.5.1.2)

64. New fillet patch on existing fillet patch is not permitted when installing a fillet welded

patch adjacent to existing fillet welded patch, distance (d) between toes of fillet weld shall

not be less than

d = 4 RT

d = Toe - to - Toe distance

R = Inside radius of vessel

T = Actual thickness of vessel wall

65. Full encirclement lap band are permitted by code under certain restrictions (8.1.5.1.3)

66. Non-penetrating nozzles (including pipe caps) are permitted as permanent repairs.

(8.1.5.1.4)

67. Insert plates are accepted as permanent repairs if :

a. Full penetration butt welds are used.

b. Welds are radiographed as per construction code.

c. Plates shall have round corner with minimum 1 inch radius. (8.1.5.2.2)

68. For overlay repairs filter material of lower strength than base metal is permitted if :

a. Repair thickness does not exceed 50% of required thickness.

b. Thickness of repair weld is increased by ratio of tensile strength of base metal to

tensile strength of filter.

c. Increased thickness is given 1:3 taper.

d. Repair made with minimum two passes. (8.1.5.3.2)

69. For damaged S.S. cladding with base metal exposed to Hydrogen migration, before repair

degassing should be done. Additionally, for P-3, P-4 and P-5 materials base metal in

repair area should be examined by UT at least 24 hours after completed repair. (8.1.5.4.3)

70. For on-stream welds refer API 2201 for guidance (8.1.6)

71. Welders and procedures used for repairs shall be qualified as per ASME Sec. IX

72. Local PWHT is permitted instead of 3600 banding with certain precautions (8.1.6.4.1).

73. Pre-heat method may be used as alternative to PWHT for P No. 1 and same P No. 3 and P.

No. 5 materials, if impact test was required (8.1.6.4.2)

74. NDE of welds. (8.1.7)

For weld overlay and Fillet welds - PT or MT

For butt - welds - Radiography as per the construction code.

75. Re-rating calculations shall be performed by engineer. Re-rating of old vessel (built prior

to 1999) can be done as per latest code under certain conditions. Re-rated pressure and

temperature shall be shown by additional name plate or stamping on existing name plate.

(8.2)

ASME Sec. VIII Div. 1

(Figures in parenthesis give reference paragraph of ASME Sec. VIII. Div. 1, from where punch

points are)

A. INTRODUCTION :

1. A pressure vessel is a container for the purpose of holding the pressure, either internal or

External (U-1 a2)

2. ASME Sec. VIII. Div. 1 contains requirements and guidance for pressure vessel materials,

design, fabrication, inspection and testing (u-1 A 3).

3. Following are excluded from scope of ASME Sec. VIII. Div. 1 (u- 1c).

a. All piping systems.

b. All fired vessels (i.e. Boilers)

c. Vessels with operating pressure less than or equal to 15 psig.

d. Vessels with inside diameter less than or equal to 6 inches.

B. Weld Category, types, joint Efficiency :

4. "Weld joint category" defines the location of a joint in a vessel but not the type of joint.

They are indicated by letters A, B, C, D (UW-3)

5. There are 4 categories of joints (UW-3)

Category A : All longitudinal welds in shell and nozzles.

: All welds in Heads.

: Circumferential weld joining Hemispherical head to shell.

Category B : All circumferential welds in shell and nozzles.

: Circumferential welds joining shell to any formed head (other than

Hemispherical head)

Category C : All Flange Welds.

Category D : All welds joining nozzle to the vessel shell or head.

6. Longitudinal welds are normally full stress welds, while circumferential welds are half

stress welds.

7. Welds type are indicated by numbers (UW-12)

Type 1 : Typically double welded giving full penetration.

Type 2 : Full penetration weld with backing strip in place.

Type 3 : Joints welded from one side only (May or may not be full penetration

weld).

8. Table UW-12 gives weld joint efficiency to be used in thickness formulas depending on

full, spot or Nil radiography.

9. Extent of radiography is indicated, on name plate (UG-116).

RT 1 : Full Radiography (with all butt welds fully radio graphed)

RT 2 : Full Radiography (Category a welds full length and category B spot

radio graphed).

RT 3 : Spot Radiography (For both category A & B)

RT 4 : No radiography.

10. Joint Efficiency for reamers for dished heads depends on radiography of shell to head

weld (UW-12d).

11. Joint Efficiency for welded pipes and tubes is always taken as 1 (UW-12e).

C. Thickness of vessel components :

12. Various thick nesses for vessel are defined as below (Mandatory Appendix 3)

a. Required Thickness : Thickness required for holding pressure.

b. Design thickness : Required thickness plus corrosion allowance.

c. Nominal thickness : Commercially available thickness as used for vessel

fabrication.

13. Required thickness of cylindrical shell having internal design pressure (P), Internal radius

(R) Allowable stress (S), Joint efficiency (E) is given by (UW-27).

Required thickness = PR

SE - 0.6 P

MAWP for cylindrical shell = SE t

R +0.6t.

14. Head thickness and depths (UW - 32)

a. 2:1 Ellip head : depth = ¼ D, Thk = nearly same as shell.

b. Hemispherical head : depth = ½ D, Thk = nearly half of shell.

c. Torispherical head thickness= 1.77 times shell thk approx.

D. MAWP Analysis :

15. Water causes a static head pressure given by

1 ft water column = 0.433 psi.

16. Total pressure is given by = vessel MAWP plus static head.

17. Total at any point can not exceed vessel part MAWP for that location.

18. Vessel MAWP is measured at top of the vessel. It is least value of all part MAWPS after

deducting the static head on that part (UG-98a)

E. External Pressure :

19. Allowable external pressure on cylindrical shell is given by (UG-28).

Pa = 4B (Use this formula if B is given)

3 (Do/t)

Pa = 2AE (Use this formula if A is given)

3 (Do/t)

F. Pressure Testing :

20. ASME code prefers Hydrostatic pressure test as standard test. Pneumatic Test may be

used only if Hydrostatic Test can not be performed due to Design reasons or process

reasons. (UG-99, UG-100)

21. Standard Hydrostatic Test (UG-99)

a. The test is applied after all fabrication inspection is completed.

b. Hydrostatic test pressure = 1.3 X MAWP X stress at test pr.

stress at Design pr.

c. Inspection pressure shall be not less than test pressure divided by 1.3

d. Test temperature = MDMT + 300 F

e. Relief value Pressure = 1.1/3 times test pr.

22. Pneumatic Test (UG-100)

a. Performed only if Hydro test is not possible due to design or process reason

b. Prior to test PT or MT examination of nozzle welds is mandatory to identify cracks if

any as per UW-50.

c. Pneumatic test pr = 1.1 X MAWP X Stress test temp.

Stress at Design temp.

d. Test Temperature = MDMT + 300 F (shall)

e. Pressurization in 6 steps. first step 50% of test pr subsequent steps 10% of test pr.

f. Inspection pressure shall be at test pressure divided by 1.1.

23. Test gage range (UG-102) Ideal range 0 to twice the test pr.

Min. range 0 to 1.5 times test pr.

Max. range 0 to 4 times test pr.

G. Impact Testing :

24. For carbon and low ally steel vessels operating at low temperature, impact testing

requirements of materials is decided by figure UCS-66. (UCS-66)

25. Steps in deciding impact test requirements. (UCS-66)

a. First decide curve for given material.

b. Go to Fig. UCS-66, If MDMT-Thickness combination point is on or above the

curve from (a), Impact testing not required if below, Impact test is required.

c. If the point is close to curve, Table UCS-66 is helpful in deciding exactly whether

the point is above, on, or below the curve.

d. All base metals above 6 inch thickness and all welds above 4 inch thickness always

require impact tests.

26. If impact tests are required as per above steps, there are further exemptions possible if

thickness for curve 'A' materials is less than or equal to 0.5" and for curve B, C, D

thickness is less than or equal to 1 inch [UG-20(f)]

27. For carbon steels (P No. 1) further reduction of 300 F from temperature on UCS - 66 curve

can be given if PWHT was performed when it was not mandatory by code.

H. Nozzle welds and Re-inforcements:

28. The nozzle welds shall be checked for code conformance by comparing with suitable

diagrams given in code (UW-16)

29. Throat of filled weld = 0.707 X leg of weld.

30. Nozzle shall be adequately reinforced by providing the reinforcement pad if required (UG

36 C 3)

31. Reinforcement area must be within limits of reinforcements given by : (UG - 37)

a. Limit along vessel wall = 2 d

b. Limit perpendicular to wall = 2.5 tn.

c. Diameter of finished opening.

d. tn = nozzle thickness.

32. Reinforcement Area required = d X tr

(tr = Required thickness of shell).

33. Extra available in vessel wall = d (t - tr.)

(t = vessel shell thickness as provided.)

34. Extra available in nozzle = 5 tn (tn - trn.)

(trn = Required thickness of nozzle.)

35. Reinforcement pad is not required if :

a. nozzle opening is less than or equal to 23/8 inch. for shell thickness above 3/8 inch.

b. For nozzle opening up to 3.5 inch. for shell thickness 3/8 inch. or less. (UG - 36 C 3).

J. Misc. Requirements :

36. Weld misalignment and weld reinforcements must be within code requirements (UW-33

and UW - 35).

37. Ovality tolerance shall not exceed one percent of Nominal diameter. (UG-80)

38. Maximum under tolerance on plates is lesser of 6% ordered thickness or 0.01 inch i.e.

0.25 mm (UG-16 C).

39. For welding unequal thickness, a taper transition of 1:3 must be provided i.e. taper length

= 3 times plate offset (UW -9).

40. PWHT requirement depends on P No. of material and thickness. The minimum holding

temperature and holding time shall be as per tables UCS-56 for various P. Nos. (UCS-56).

ASME - Sec. IX - welding Qualification Code

Note : Figures in parenthesis give reference cause in the code.

1. ASME Sec. IX gives requirement for Qualifying Procedures and welders (QW 100).

2. For Procedure Qualifications a test coupon is welded and then tested for strength (tension

tests) and ductility (Bend tests) to ensure that the weld has required properties (QW- 141).

3. In performance qualification we determine welder's ability to produce sound welds by

conducting either Bend tests or Radiography. (QW 141, 142)

4. Tension test is passed if either of the following is satisfied.

a. If break is in weld metal is must be at strength above the specified minimum tensile

strength of Base metal.

b. If break is in base metal it must meet at least 95% of minimum tensile strength of Base

metal. (QW 153).

5. Bend test (It may be Face bend, root bend or side bend) is passed if test specimen does not

show open discontinuity more than 1/8 inch. (3 mm.) (QW 163).

6. Radiography for welder qualification shall meet acceptance criteria of ASME Sec. IX

(QW 191.2).

7. A PQR is a record of welding data used to weld test coupon. It also contains test results on

backside it can not be revised. (QW 202.2)

8. A WPS is used to provide direction for making production welds. It shall be within ranges

qualified by P & R (QW 200.1)

9. A P & R support WPS as long as essential variables on both are same.

10. For P & R test to pass it shall pars 2 tension tests and 4 bend tests (QW 202).

11. Bend tests are 2 face Bend and 2 Root bends for coupon thickness less than 3/4" (19 mm)

and 4 side bend tests if thickness is equal to greater than 3/4" (QW 451)

12. P Q R should also list P. No. (for parent metal) F.No. (for filler metal) and A-No. (for

weld metal) [QW-422, QW-432, QW-442].

13. For procedure qualification test coupon may be a plate or pipe. plate qualities for pipe and

vice versa (QW 211)

14. A procedure qualification in any position qualities the procedure in all positions. (QW-

203)

15. For welder qualification 2 bend tests or Radiography can be used (Except for GMAW - 5

process) [QW - 452] and QW 304

16. for welder qualification position is important (QW - 461.9)

Qualification Test Position Qualified

1 G (flat) 1 G

2 G (Horizontal) 1G, 2 G

3 G (Vertical) 1 G, 3 G

4 G (Overhead) 1 G, 4 G

5 G (Pipe fixed) 1 G, 3 G, 4 G, 5 G

6 G (Pipe at 450) All.

2 G and 5 G All.

17. For pipe positions 5 G and 6 G qualification 4 bend tests are required and all must pass.

(QW-452).

18. If a welder passes procedure qualification test, be is also qualified for performance in that

position. (QW -301.2)

19. When welder is qualified by radiography for plate test coupon, at least 6" length

shall be examined by radiography and for pipe, entire weld circumference shall be

examined. (QW - 302.2)

20. Performance qualification of a welder is affected if he does not weld with a process for 6

months or more. If there is specific reason to question his ability to make acceptable welds

his qualification for the welding he is doing shall be revoked. (QW-322)

ASME Sec. V - Non destructive Examinations.

A. General :

1. ASME Sec. V. gives methods and requirements for conducting NDT. It becomes

applicable only if referred by the other referencing codes.

2. The user of Sec. V. Code is responsible for following.

a. Getting NDT personnel properly certified.

b. All NDT examinations require written procedures.

c. All NDT equipments shall be as per Sec. V.

d. Equipments shall be calibrated as required by Sec.V.

e. Records retention.

B. RT Examination :

3. For RT Examination, either hole type or wire type IQI shall be used.

4. A radiograph is considered satisfactory, if it is within the density limits and has required

IQI image. For hole type 2 T hole and for wire type the designated wire image shall be

seen.

5. Density limitation :

2 to 4 for Gamma Rays.

18 to 4 for X rays.

Density variation permitted = +30% to - 15%

6. Selection of IQI is based on weld thickness plus the weld reinforcement. Thickness of

backing strip is excluded.

7. IQI is normally placed on Source side unless inaccessibility prevents it. They IQI may be

placed on Film side and a Lead letter F shall be put adjacent to it.

8. Hole IQI may be placed on or near the weld. Wire IQI is placed on the weld with wires

perpendicular to the weld axis.

9. Double wall double image technique is suitable for pipes up to 3.5" OD.

10. Back scatter shall be avoided. If light image of Lead Letter - B is seen on dark background

then the backscatter is excessive and radiograph shall be rejected.

C. PT Examination.

11. For conducting PT on certain materials, the contaminants shall be controlled as follows.

a. For Nickel and its alloy : Sulpher content not to exceed 1% of residue.

b. For Austenitic S.S. Duplex S.S. and Titanium content of chlorine plus Florien shall

not exceed 1% of residue.

12. Two type of penetrates (visible and Fluorescent) can be used. For excess penetrate

removal 3 methods are used for visible and fluorescent.

- Water washable

- Post Emulsifying.

- Solvent Removable.

This results in total 6 techniques.

13. PT is normally conducted between temperatures 500 to 125

0 F (10

0 to 52

0 C). For below or

above this range special penitents shall be used and the dwell time should be worked at

using quenched Aluminum blocks.

14. After applying the developer, interpretation shall be done within 10 to 60 minutes.

15. Intermixing of penetrate material from different families (i.e. visible & fluorescent) or

penetrate materials from different manufacturers are not permitted.

D. MT Examination : 16. The Magnetic Particle Examination can be performed on

Ferromagnetic materials for finding surface and near surface defects.

Drug or wet Iron powder and visible, or fluorescent powder is used.

17. Prod Technique used Direct current. The distance between prods shall be 3 inches to 8

inches. This is suitable for finding surface and near surface defects.

18. Yoke technique is suitable for surface defects only and can use A.C., D.C. or permanent

magnet.

19. Ammeter on instrument shall be calibrated annually by comparing 3 current readings with

a standard Ammeter, and permitted tolerance is + 10% of full scale.

20. For yoke, the electromagnetic yokes shall be calibrated annually by checking lifting

power.

A.C. yoke shall lift 10 pounds (4.5 kg.)

D.C. yoke shall lift 40 pounds (18 kg.)

21. Lifting power of permanent magnet yoke shall be checked daily prior to use by lifting 40

pounds (18 kg) weight.

22. Examination is performed in two perpendicular directions.

E. UT Examination :

23. Pulse - Echo contact method is used for finding thickness and laminations.

24 In Direct contact (single element) method is not suitable for smaller thickness hence delay

line method is used which uses a delay block to delay the echo.

25. In delay line, end of delay is made to coincide with Zero thickness on CRT.

26. Dual Search units are also used using two crystals one for sending pulse and other for

receiving echo. On smaller thickness this method results in vee-error which needs

correction.

27. For thick section measurement use of multiple echo technique is made. The calibration

block chosen is smaller thickness which will permit standardizing the full-sweep distance

to adequate accuracy on CRT.

28. For measurement at high temperatures thickness correction is needed. A positive error of

1% per 1000 F increase in results.

API RP 572 - Inspection of Pressure Vessels.

1. API 572 covers guide lines for conducting detailed inspection of pressure vessels.

2. Basic reasons for inspection are to determine the physical condition of the vessel and to

determine type rate, and causes of degradation and damage. A good timely inspection

results is safety, continuity and reliability of the plants equipments.

3. Creep damage depends on time, temperature & applied stress.

4. Graphitization may take please due to long exposure in range of 825o

f to 1400o f (

440oC to 760

o f in which carbide decomposes to produce ferrite ( pure iron ) and

Graphite noodles ( pure carton ). This causes loss of strength steel . In-situ

metallography is useful in detecting Graphitization .

5. De alloying is selective leaching or loss of one or more alloy components example.

Dezincification of copper-zinc (brass) alloy.

6. Hydriding of titanium alloys is that Titanium alloys may become brittle (lose ductility)

due to absorption of Hydrogen.

7. External inspection starts with platform and ladders, which is mostly visual and

supplemented by hammer test.

8. Anchor bolts may be checked by sideway blow with hammer.

9. Grounding connection should be checked for good electrical contracts and the resistance.

Recommended resistance is 5 ohms or less but shall not exceed 25 ohms in any case.

10. Vibrations of auxiliary equipments (pressure gauges, right glass etc.) should be arrested by

adding support or vibration analysis should be done to make sure that fatigue failure will

not occur.

11. External distortion may be measured by taking measurements from a parallel line

(typically a stretched wire) to vessel wall.

12. During internal inspection cracks are likely to be found in weld and HAZ particularly at

nozzle welds if following factors are present (more factors present means more

susceptibility.)

a. Heavy wall vessel.

b. Hydrogen or Hydrocarbon service.

c. Wet H2S service,

d. Caustic or Amine service.

e. material with coarse grain structure.

f. High strength materials.

g. Low-chrome materials.

Best method to check internal cracks is WEMT.

13. Areas directly above and below the liquid level in vessels containing acidic corrodants are

subject to Hydrogen Blistering.

14. Laminations appear similar to cracks. Laminations run slant to surface while cracks run at

right angles.

15. Corrosion of Metallic lining can be monitored using corrosion tabs made from lining

material and welded at right angles.

16. Where a lining leaks, whether corrosion has taken place behind it can be determined by

taking VT thickness measurement from outside.

17. Non metallic lining are typically inspected visually or by High voltage spark testing also

known as Holiday detection.

API RP 576 - Inspection of Pressure Relieving devices

1. API 576 describes inspection and repair practices for Pressure Relieving Devices (PRDs).

It does not cover training requirements for mechanics involved in inspection & repair of

PRDs.

2. Difference between Release Pressure and set pressure is known as Overpressure and

difference between set pressure and closing pressure is called Blow down.

3. Cold differential test pressure (CDTP) is the test bench set pressure. It includes correction

for back pressure & temperature.

4. Safety valves are used on compressible fluids (Gases, Vapors) and Relief valves are used

an incompressible fluids (liquids).

5. Safety Relief valve works as Safety valve if installed on gases and vapors. I works as

Relief valve if installed on liquids.

6. Conventional Safety Relief valve operation is directly affected by changes in back

pressure.

7. Balanced Safety Relief valve incorporates a bellow or other devices to minimize effect of

back pressure on operation. This valve is suitable when the discharge from valves must be

piped to remote location.

8. Pilot operated valves are PRDs in which the main valve is combined with and controlled

by a auxiliary valve (pilot).

9. Rupture discs are used to protect the PRD against corrosion or plugging due to system

fluid.

10. Conventional Rupture Disk is designed to burst when it is overpressured on concave side.

It provides satisfactory service for operating conditions withe 70% or less of the rated

burst pressure.

11. Reverse acting rupture disc is designed to burst when it is overpressure on convex side.

They use bursting device like knife blade or shear rings. They can be used for operat ing

conditions up to 90% of rated burst pressure.

12. Transportation of pressure Relief valves (PRV) should be in upright position.

13. The PRV should be installed directly on the vessel and it should not be connected by

lengthy piping to avoid chattering of valve.

14. As soon as the valve is received in shop and mounted on test block "as received" pop

pressure shall be noted.

15. After "as received" pop test valve is visually inspected, decision on dismantling the valve

is taken. If pop test and visual are ok, normally there is no need to dismantle the valve.

16. After re-assembly the valve pop pressure is checked. The deviation of pop pressure from

set pressure shall not exceed.

a + 2 psi for pressures up to 70 psi.

b. + 3% for pressures above 70 psi.

17. Valve is also tested for leak tightness at a pressure equal to 90% of CDTP, by bubble test

method.

18. The Maximum inspection and testing interval is 10 years.

19. Visual on-stream inspection which is like a survey (to check that correct valve is at correct

location, correct tag is at correct valve, valve is not leaking, valve operation is not

obstructed etc). This survey shall be conducted at a interval not more than 5 years.

API RP 571 - Damage Mechanisms.

1. Temper embrittlement is reduction in toughness in low alloy chromium steels due to long

exposure in high temperature range (6500 F to 1100

0 F).

2. Common way to minimize temper embrittlement is to limit "J" factor for base metal and

"X" factor for weld metal.

3. Brittle fracture is sudden fracture under stress due to loss of ductility at low temperature,

cracks are typically, sharp straight, non-branching.

4. Some reduction in possibility of brittle fracture may be achieved by performing PWHT.

5. Fatigue is typically caused due to surface notch and cyclic stresses. If cyclic stress are due

to mechanical reasons (rotating shaft, rapid change of pressure) it is Mechanical Fatigue.

If cyclic stresses are due to changes of temperature, it is thermal fatigue. If surface notch

is due to corrosion and cyclic stresses are present it is corrosion Fatigue.

6. Thermal Fatigue cracks are dagger shaped and oxide filled.

7. Thermal fatigue is prevented by preventing stress concentration and controlling thermal

cycling.

8. Mechanical fatigue failure typically shows "Beach-mark" or "clam shell" type concentric

rings. Mechanical fatigue can be prevented by avoiding stress concentration at surface.

9. Corrosion Fatigue can be prevented by using coatings or inhibitors or by using more

corrosion resistant materials.

10. Erosion-corrosion is damage that occurs when corrosion contributes to erosion by

removing protective scale due to the combined action.

11. Erosion Corrosion increases with velocity, turbulence, concentration of impacting medium

size and hardness of impacting particles.

12. Some methods to reduce Erosion-corrosion are increasing pipe diameter to reduce

velocity, using large radius bends, increasing surface hardness, using corrosion-resistant

materials.

13. Atmospheric corrosion increases with high humidity (marine environment) and

atmospheric pollution (industrial environment) and is best prevented by providing coating

/ painting.

14. CUJ is caused due to water trapped under insulation, for carbon steel it may show scale

formation and for S.S. it may show pitting and cracking due to chloride stress corrosion

cracking.

15. CVI may be prevented by providing protective painting and maintaining insulation is good

condition to prevent the moisture entry.

16. Cooling water corrosion is caused by dissolved salts, gases (typically oxygen) or microbes

(which may be present in stagnant or low velocity water).

17. Cooling water corrosion can be prevented by chemical treatment, maintaining flow

velocity and monitoring oxygen contact in water.

18. Boiler water corrosion is result of dissolved gases namely oxygen and carbon di oxide.

19. Best method to reduce Boiler water corrosion is to use de-aerator for Boiler feed water,

monitoring presence of oxygen and using oxygen scavangers like Hydrazine.

20. Chloride stress cracking corrosion is typically takes place on Austenitic Stainless steel

between 1500 to 400

0 F in chloride environment.

21. Austenitic S.S. (300 Series) are most suceptible duplex stainless steels are somewhat

resistant and Nickel Alloys (more than 40% Nickel) and almost immune.

22. For Hydro-testing of Austenitic S.S. Vessels and pipes use water with low or free of

chlorides (typically less than 50 ppm,)

23. Caustic Stress corrosion cracking typically takes place on carbon steel adjacent to welds

which are not stress relieved.

24. Higher temperature and higher caustic concentration increases suceptibility.

25. Best method to prevent caustic stress corrosion cracking is conducting PWHT of

completed weld or use of Nickel alloys should be considered.

26. Sulphidation of carbon and alloy steels typically takes place above 5000 F and increases

with and sulpher concentration increasing temperature.

27. Best method to prevent sulphidation is upgrading to higher chromium alloys.

28. High temperature Hydrogen attack (HTHA) takes place at temperature above 4000 F due

to migration of atomic Hydrogen which combines with carbide in carbon steels forming

methane gas, which can not diffuse out, collects at grain boundaries and causes cracking.

29. Best method to avoid use of HTMA is select materials using API RP 941 curves (Nelson

curves). HTHA can be detected by metallography.

30. Wet H2S exposure causes 4 types of damages namely Hydrogen blistering, Hydrogen

induced cracking (HIC), Stress Oriented Hydrogen induced cracking (SOHIC) and

sulphide stress corrosion cracking (SSC).

31. Hydrogen blistering takes place due to migration of atomic hydrogen in steel and

combining to term hydrogen molecules which typically collect at voids, slags, porosity

causing Hydrogen pressure to build up and producing Hydrogen Blister.

32. The Hydrogen blisters formed within steel at different levels will grow and combine to

form Hydrogen induced cracking which typically has stepwise appearance.

33. The HIC cracks formed within HAZ will propagate rapidly in perpendicular to surface due

to loss of ductility to HAZ and due to stress this is called SOHIC.

34. The Sulphide formed during the wet H2S exposure (Fe+ H2S - FeS →2H) causes cracking

under combined action of Sulphide and stress (which is caused due to internal pressure in

vessel) leading to SSC.

35. Best method to prevent wet H2S damage is use of controlled Hardness Steel (typically less

than 22 HRC) and steel with low percentage of Sulpher and Phosphorous impurities

(which reduces voids and porosity in steel).

36. SOHIC and SSC can also be reduced by performing stress relieving of welds.

API RP 577 - Welding Inspection and Metallurgy.

1. Recordable indications means the indications recorded on data sheet which need not

exceed the rejection criteria.

2. Reportable indications means the indications which exceed the rejection criteria. They

should be recorded on data sheet and also reported to appropriate authorities to get them

rectified.

3. Any electrodes or fluxes that have become wet should be discarded.

4. For visual examination the personnel are required to demonstrate jagger J-1 eye test

annually.

5. Direct Visual examination requires access to bring the eye within 6" to 24" from the

surface at an angle not less than 300.

6- Radiographic Film density is quantitative measure of film blackening. Clear film has zero

density. Exposed film that allows 10% of light to pass has density =1. A

film density of 2, 3, 4 allows 1%, 0.1 % and 0.01% of light to pars through the film

respectively.

7. Straight beam techniques are used for thickness evaluation or to check laminations. Shear

wave (Angle beam) techniques are employed for finding discontinuities in welds.

8. In UT, A-scan typically given pulse-echo display. B-scan shows a cross-sectional view of

the object and C-scan shows plan view of object.

9. The HAZ is that portion of the base metal (adjacent to the weld) that has not been melted

but whose mechanical properties or microstructure is altered due to heat of welding. For

carbon steels HAZ includes the regions heated to greater than 13500 F (700

0 C).

10. The hardness values in HAZ for steels in Refinery service is given in Table 11 (For

Carbon steels it is 200 BHN) Hardness in

11. "Weldability" is defined as capacity of the metal to be welded under under the fabrication

conditions imposed.

12. Weldability is measured by Carbon Equivalent (CE) formula.

CE= C + Mn + Cr + Mo + V + Si + Ni + Cu

6 5 15

13. Typically steels with CE less than 0.35% requires no preheating. CE will CE of 0.35% to

0.55% requires preheating and CE greater than 0.55% require both pre-heating and

PWHT.

14. Simplest welability tests are the strength and ductility test of weld.

15. For qualifying welder on "GMAW - S" process bend tests shall be used instead of

Radiography.