1

TFC KAOHSIUNG FACTORY 30

KMT AMMONIA STORAGE TANK

INSPECTION REPORT

By: Jackson Yang (TFC R&D Department)

01 Oct 2016

2

CONTENT

1. Introduction

2. Internal Inspection Planning

3. Applied Inspection Technique

4. Inspection Findings 1) External & internal visual inspection

2) Bottom plates corrosion test & UT measurement

3) Bottom plates weld WFMP test

4) Bottom plates & shell plates joint weld WFMP test

5) Shell plates weld WFMP test

6) Accessories weld WFMP test

7) Mechanical properties test

5. Summary

1. Introduction

T-101 is a flat bed, double wall & double roof anhydrous liquid

ammonia storage tank. The internal wall is constructed with low

temperature resistant steel plate and outer wall is constructed by

steel covered with reinforced concrete wall. Inside of external wall

has 6m/m layer of low temperature resistant steel and a layer of

insulation cotton.

The internal tank dimension is 48 meter diameter and 38 meter

height with 60,000 cubic meter volume. The design storage

capacity is 30,000 MT anhydrous liquid ammonia.

All the tank nozzles and transfer pump connections are located at

the tank roof, there is no any nozzle connection at the side or

bottom of the tank.

The tank was designed and constructed in 1987 by Mitsubishi

Heavy Industries & Chiyoda Tank Engineering Corporation,

Japan. For 27 years (1987-2014), this tank was well maintained

and successfully operated without incurring any incident related to

safety or environmental issues.

Description of Ammonia Storage

Tank T-101

5

Ammonia Tank T-101 Outline

6

Ammonia Tank T-101 General Assembly

T-101 Equipment Name Plate (Design Specification)

8

Ammonia Tank T-101 Annular space

2. INTERNAL INSPECTION

PLANNING

10

Inspection Planning

1. Inspection Party: Taiwan Metal Quality Control Co., LTD

(TMQC)

2. Inspection Date: Inspectors got entry permit to start T-101

internal inspection on 7 Jun 2016. The field inspection,

testing & data collecting were completed on 17 Jun 2016.

3. Inspection Program: Refer to the inspection methodology

& scope in the next slides.

T-101 Inspection Program-1

Inspection area Technique Description 1. Tank internal and

external structure

Visual Inspection Visual inspecting bottom plates, wall plates, ceiling

plates, fittings, nozzles for any deformation, bulging,

dents, corrosion, cracking and localized corrosion.

Keep the photographic record.

2a. Corrosion test of

bottom plates on both

soil side & chemical

side

Floor Mapping test

(Magnetic Flux

Leakage test,

MFL)

Apply Floor Mapping to test all bottom plates for any

corrosion on both soil side & chemical side. Against the

corrosion parts, apply Ultrasonic thickness test to

measure the plate thickness.

2b. Corrosion test of

Annual Ring Plate on

both soil side &

chemical side

Hand Type Floor

Mapping test

Apply Hand Type Floor Mapping to test annular ring

plates and the area that Floor Mapping cannot reach.

Against the abnormal parts, apply Ultrasonic thickness

test to measure the plate thickness.

2c. bottom plates

ultrasonic thickness

measurement

Ultrasonic

thickness

monitoring (UT)

Take 6 samples of each selected plate ( 30 cm from 4

corners and 2 at center region) to do UT measurement

for observing corrosion rate and trend.

2d. bottom plates

welds

Wet fluorescent

magnetic particle

test (WFMP)

Bottom plates are the most loaded and stressed area.

Apply WFMP test to samples of 30 cm from left & right

each for all T and Y welds.

3. Bottom and wall

joint welds

Wet fluorescent

magnetic particle

test (WFMP)

To do WFMP test for 100% bottom and wall joint welds.

11

T-101 Inspection Program-2

Inspection area Technique Description 4. Shell plates welds Wet fluorescent

magnetic particle

test (WFMP)

1. Apply WFMP to vertical welds (50 cm above bottom

plate) in course 1.

2. Apply WFMP to 100% horizontal and vertical welds

in course 1 and 2 (50 cm left & right and 50 cm up &

down).

4a Shell plates thickness

measurement

Ultrasonic

thickness

monitoring (UT)

Take 6 samples of each shell plate from course 1 & 2

(30 cm from 4 corners and 2 at center region) to do UT

measurement.

5. Accessories welds Wet fluorescent

magnetic particle

test (WFMP)

1. Apply WFMP to all manhole welds and fitting welds.

2. Apply WFMP to pump seat casing welds.

3. Apply UT to 2 samples of pump seat casing plates.

6. Pseudo installation

welds

Wet fluorescent

magnetic particle

test (WFMP)

Apply WFMP to 10% samples.

7. Against crack or

corrosion on welds

ultrasonic

phased-array

detector test

When observing weld cracks or corrosion, apply

advanced ultrasonic phased-array detector for further 3-

D imaging detection.

8. Mechanical

properties test

1. Take 2 samples each of bottom plates from center,

half radius and near wall to do pull test.

2. Take 2 samples each of wall plates from course 1 & 2

to do pull test. . 12

3. APPLIED INSPECTION

TECHNIQUE

Applied Inspection Technique

Technique Inspection Area Remarks

Visual Testing Tank bottom/shell/roof View deformation, bulging,

dents, corrosion, cracking,

localized corrosion.

Magnetic Flux

Leakage test

(MFL)

Tank bottom plates/Annual Ring Plate Corrosion test of bottom plates

on both soil side & chemical

side

Ultrasonic

gauging (UT)

Bottom/shell plate (including vapor-

liquid phase interface)/roof

Measure steel plates thickness

Wet Fluorescent

Magnetic

Particle Testing

(WFMP)

(A) the base plate bead comprising an

annular plate, (B) the bottom wall

bead, (C) wall weld: horizontal and

vertical bead, (D) the top wall groove

weld, (E ) tank top bead, (F) on the

tank nozzle (or cannula) bead

Inspect orientation: Vertical &

horizontal bead, wall covering

at least a gas and liquid phase

region.

Refer to the next slide for

sampling location.

Mechanical

Properties

Testing

Sampling: chassis / shell plate / roof of

the weld and the base material, each

three pieces

Test items:

(A) Tensile test: room temp.

(B) Impact test: -33 ℃

(C) Hardness test: room temp.

14

WFMP Sampling Area & Location

Course 1

Course 2

Course n

Course n+1

Scope of Internal Inspection

Step 1: Initial inspection

Step 2: The 2nd inspection if any defect found during initial inspection.

Step 3: The 3rd inspection if any defect found during the 2nd inspection.

4. INSPECTION FINDINGS

18

1A: External visual inspection

findings • Tank external ladder was corroded at some parts and tank

top platform and handrail were found corroded and deformed.

Roof platform corroded Roof handrail corroded

and deformed

19

1B: Internal visual inspection findings

• During visual inspection, found 2 bolts of internal pipe

flange connection were missing and an impact dent of 1.5

mm depth at bottom plate. No other abnormality was

observed at internal tank.

2 bolts missing Impact dent (A16)

20

2A: Bottom plates corrosion test and UT

measurement

• Applied UT to measure the corrosion rate. The design

bottom edge plate thickness was 19.0 mm, UT test result

was 19.2~19.6 mm, no soil side corrosion found. The

design other bottom plate thickness was 4.8 mm, UT test

result was 4.9~5.2 mm, no soil side corrosion found.

Bottom plates MFL test

Bottom plates UT

measurement

21

2B: Bottom plates corrosion test and UT

measurement

Impact dent (A1)

Bottom plates numbering (A1~A139)

• The bottom plates were numbered from A1to A139.

• Applied MFL(Magnetic Flux Leakage test) to do floor mapping,

found 6 defects. After visual confirmation, 1 defect at ring plate

was impact dent (A1) and the other 5 defects were chemical

side corrosion.

22

2C: Bottom plates corrosion test and UT

measurement

• Applied MFL to do floor mapping, found 6 defects. After visual

confirmation, 1 defect at ring plate was impact dent and the other 5

defects were chemical side corrosion (A20*2/A22/A30/A68).

corrosion defect (A68)

corrosion defect (A20)

corrosion defect (A30)

corrosion defect (A22)

23

3: Bottom plates T & Y welds WFMP test

• For T & Y welds of bottom plates, applied WFMP test at 30

cm left and right areas. No crack at first or second layer

was found.

Bottom plates T welds WFMP test Bottom plates Y welds WFMP test

24

4: Bottom and shell plates joint welds

WFMP test

• The joint welds of bottom and shell plates are the most

loaded and stressed area, applied WFMP to do 100% test,

no crack at first or second layer was found.

Bottom & shell plates joint

welds WFMP test Bottom & shell plates joint

welds WFMP test

25

5A: Shell plates welds WFMP test and UT

measurement

• Apply WFMP to vertical welds at 50 cm above bottom plate

in course 1 and horizontal and vertical welds in course 1

and 2 at 50 cm left & right and 50 cm up & down for 100%

test. No crack at first or second layer was found.

Shell plates welds WFMP test Shell plates welds WFMP test

26

5B: Shell plates welds WFMP test and UT

measurement

• Take 6 samples for each shell plate from course 1 & 2 (30 cm from

4 corners and 2 at center region) to do UT measurement. The

design plate thickness of course 1 was 30.3 mm, the UT test result

was 29.9~30.2 mm, no shell plate corrosion in course 1 found. The

design plate thickness of course 2 was 27.4 mm, the UT test result

was 27.2 mm, no shell plate corrosion in course 2 found.

Shell plates

numbering (S1 & S2)

Shell plates UT measurement

27

6: Accessories welds WFMP test

• Apply WFMP to 2 sets of manhole welds and submerged

transfer pump fitting welds. No crack at first or second

layer was found.

Northern manhole

WFMP test Southern manhole

WFMP test

28

7: Mechanical properties test

• The sample tank plate pieces were subjected to three

kinds of mechanical properties tests: the tensile test,

positive bending & back bending test, low temperature

impact test.

Photo of sample tank plate test pieces

29

7A: The tensile test result:

• Compared with the ASTM standard values, all test pieces are in line

with the standard, only No. 8 bottom plate yield strength less than

the standard value 1N /mm2. Observed 3 groups of test pieces, the

fracture points are also fall in the base metal, showing the bead

strength is higher than the base metal required strength.

S# Test Pieces Description Cross

area

(mm2)

Ultimate

strength

(N/mm2)

Yield

strength

(N/mm2)

Elongation

% (G.L=

200mm)

Fracture

point

STD ASTM A537-CL1 - 485-620 345 18 -

No.1 Sidewall bead test piece 1S-12 578.3 603 - - Base metal

No.2 Sidewall bead test piece 2S-10 519.7 595 - - Base metal

No.3 Outer ring plate bead A11 353.4 586 - - Base metal

No.4 Sidewall metal test piece 1S-12 154.7 552 464 33 -

No.5 Outer ring plate metal A11 153.0 536 450 32 -

No.6 Sidewall metal test piece 2S-10 152.8 560 448 32 -

No.7 Bottom plate metal A76 224.0 525 366 23 -

No.8 Bottom plate metal A81 220.0 526 344 20 -

30

7B: Positive & back bending test result:

• The presence of crack of No.4 ~ No.8 test pieces in the

positive bending and back bending test are not found,

indicating that the material anti-bending ability is still quite

adequate after 29 years of use.

S# Test Pieces Description Positive

bending test

Back

bending test

No.4 Sidewall metal test piece 1S-12 No crack No crack

No.5 Outer ring plate metal A11 No crack No crack

No.6 Sidewall metal test piece 2S-10 No crack No crack

No.7 Bottom plate metal A76 No crack No crack

No.8 Bottom plate metal A81 No crack No crack

31

7C: Low temperature impact test result:

• No.4 to 6 test pieces were made to a V-notch of 10x10x55 size. The

three test pieces had high absorption energy of 260J, 112J &182J.

It indicates that the side wall and bottom plates in the low-

temperature area still has a very good toughness, did not change

into brittle material and still meet the standard requirements after

long-term service.

S# Test Pieces Description V-notch

(mm)

Test Temp.

(oC)

Absorption

Energy (J)

No.4 Sidewall metal test piece

1S-12

10*10*55 -35 260

No.5 Outer ring plate metal

A11

10*10*55 -35 112

No.6 Sidewall metal test piece

2S-10

10*10*55 -35 182

5. SUMMARY

33

T-101 Inspection report summary

• The UT measurement had been done for T-101 shell

plates in course 1 & 2 (S1 & S2) and bottom plates:

The design and actual thickness difference for shell

plates S1 is 0.1~0.4 mm and for S2 is 0.1~0.3 mm.

The bottom plates thickness measurement showing

the actual is higher than design value.

• T-101 was operating in the condition of -33 oC and there

was no corrosion mechanism available. Therefore, it is

reasonable to conclude that the thickness difference

between design and actual is resulting from

manufacturing tolerances of the plates during

construction.

34

T-101 corrosion rate & remaining life

assessment

• Based on thickness measurement data, the corrosion rate

and the tank remaining life are calculated:

T-101 corrosion rate is 0.0034-0.0138mm/year.

T-101 remaining life is 43.5 years at minimum.

35

Conclusion of T-101 inspection report

• The factors that will affect the integrity of ammonia storage

tank are: construction defect, corrosion, SCC crack and fatigue.

Taking the opportunity of T-101 decommission, this ammonia

storage tank had gone through thorough internal inspection by

non-destructive technique.

• There is only minor corrosion spots observed on bottom plates

and no defect found on all shell plates and welds. All welds

were inspected without SCC cracking as observed. Based on

this inspection result, we can conclude that ammonia storage

tank under cryogenic operating condition, there is no sign of

corrosion or SCC crack/fatigue even after near 30 years of

service.

• Therefore, it is concluded that if we are able to strictly control

the construction quality, eliminate construction defects, follow

proper commission procedure and normal operating procedure,

the risk of tank failure can be considered as zero.

36

End of Presentation

&

Thank You!