Stress Analysis Report-US Channel Head-2

ABU DHABI MARINE OPERATING COMPANY Das Island Division

Das Engineering Team

US COLUMNS HEAT EXCHANGER-CHANNEL HEAD DIVIDING

PLATE

Work Request #: DIAD/WR/12/030

NON-LINEAR ANALYSIS OF HEAT EXCHANGER -

CHANNEL HEAD

DOC. NO.: 20/1552/DET/2014/0XXX

0 26/02/2014 For Review JVB DETL EPM(DAS)

Rev. Date Description Prepared

By

Reviewed By Approved By

Das Island Division


Stress Analysis Report-US channel head Page 2 of 39

TABLE OF CONTENTS

1.0 INTRODUCTION .............................................................................................................................3

2.0 REFERENCE ....................................................................................................................................3

2.1 LIST OF APPLICABLE CODES AND STANDARDS .................................................................................3

2.2 DRAWINGS ....................................................................................................................................4

2.3 DESIGN DATA ................................................................................................................................5

2.4 HISTORY OF FAILURES ....................................................................................................................7

2.5 SITE VISIT .......................................................................................................................................8

3.0 ASSUMPTIONS ............................................................................................................................. 12

4.0 FITNESS FOR SERVICE PROCEDURE ............................................................................................... 14

5.0 DISCUSSION ON THE ASSESSMENT ............................................................................................... 19

6.0 CONCLUSIONS ............................................................................................................................. 26

7.0 RECOMMENDATIONS: .................................................................................................................. 27

8.0 APPENDICES ................................................................................................................................ 31

8.1 ORIGINAL WORK REQUEST AND CORRESPONDENCES ................................................................... 31

8.2 INSPECTION REPORT .................................................................................................................... 32

8.3 DAMAGE MECHANISM AS PER API571 .......................................................................................... 33

8.4 LEVEL -1 ASSESSMENT .................................................................................................................. 34

8.5 METALLURGY ASSESSMENT .......................................................................................................... 35

8.6 FEA FOR THE DESIGN BASE CASE .................................................................................................. 36

8.7 NON-LENEAR ANALYSIS RESULTS (10MM PASS PARTITION PLATE) ................................................ 37

8.8 PROPOSED SOLUTION (TO MITIGATE HIGH DIFFERENTIAL PRESSURE ACROSS THE PASS PARTION

PLATE) ................................................................................................................................................... 38

8.9 DRAWINGS .................................................................................................................................. 39

Das Island Division



1.0 INTRODUCTION

The heat exchanger of stripping column 200 at Umm-Shaif plant was under major

Overhaul. Upon the opening of the heat exchanger, the Pass partition plate of the

channel head was found broken in two places and fallen down on the bottom of the

channel. The inspection team suspected the pass partition plate had a fatigue

failure. Similar problems were found in column 100 and 400 heat exchanger and the

plates were replaced with 10mm ASTM A516 Gr.70.

It was observed that the water hammering was high in the steam side.

The objective of this study is to carry out a root cause analysis for the breaking of

the heat exchanger channel pass partition plate at Umm-Shaif plant and put forth

recommendations/solutions.

2.0 REFERENCE

2.1 List of Applicable Codes and Standards

International Standards

API 571: Damage Mechanisms Affecting Fixed Equipment in the

Refining Industry

API579: Fitness-for-Service Second Edition

ASME FFS-1

ASME Sec VIII Div.1 Pressure Vessels

BSI 1501 Steel for pressure purpose

ASTM A516 Standard Specification for Pressure Vessel Plates,

Carbon Steel, for Moderate- and Lower-Temperature

Service

Das Island Division



AVIFF Guidelines for the avoidance of vibration induced

fatigue failure in process pipework

ADMA OPCO Standards

CP-117 Code Of Practice For Evaluation, Repair, and Rerate

Of Heat Exchangers

PRO-154 Procedure For Failure Analysis For Exchangers

2.2 Drawings

Plant Specification

AD41-4.3/8.7-R-0013

P&ID

AD-04.3-D-2980

AD-04.3-D-2981

AD-04.3-D-2982

PFD

ED7-90-D-3252

GAD’s

FAD-4-M-7210

FAD-4-M-7211

FAD-35-M-15714

FAD-4-M-8262

Das Island Division



FAD-4-M-8264

FAD-4-M-8265

FAD-35-M-15715

Misc

AD41-36-R-0076

AD-4.3-M-15719

2.3 Design Data

The heat exchangers were built between 1972 and 1980’s to ASME Section

VIII Div.1 and TEMA ‘C’ (refer name plate detail drawing FAD-4-M-8264).

Channel Head:

Channel type – Front End Stationary Head Type, Removable cover (TEMA

Type A)

The exchanger channel side is fillet welded with flat metal plate which divides

(pass partition plate) the head into separate compartments for the tube side

fluid and to provide the desired flow path. The original thickness of the plate

was 12.7/13mm. The material for the pass partition plate was not clearly

identified in the drawings; however, in the analysis BS 1501-151-Gr28A

(1964) was used. The nearest equivalent as per latest BS 1501 is 151 grade

430. The equivalent grade as per TEMA 2007(ninth edition) in ASME is SA-

515-65

Sour Charge heater details from ED7-90-D-3252 are as follows:

TEMA Size & Type : 26-144/AEU(HORIZ)

Effective Surface per Unit = 810ft2

Design(rated) Heat duty = 29.585 x 106 BTU/Hr

An allowable stress used in the original design calculation is 15700psi

(108MPa) at 204DegC (refer Drawing FAD-4.3-M-15719).

Das Island Division



The thickness of the pass partition plate was checked in accordance with

TEMA and enclosed is the calculation in Appendix.

Therefore,

Maximum allowable stress = 15,700lbf/in2 = 108Mpa

As per BS1501 :Part1 :1980

Yield Strength = 192Mpa @ 250Deg C,

215Mpa @ 200Deg C

222Mpa @ <150DegC

Mass density of steel as per BS4360 = 7850kg/m3

Das Island Division



2.4 History of Failures

The following are the history of failures of the pass partition plate on each heat exchangers for the US stripping columns:

Sl.n

o

Description Commissioni

ng

Failures of Pass partition plate Action during

Investigations

Remarks

1 Heat

exchanger for

US Column

401

(43100344)

Jan 1982 March 2008,

corroded pass

partition plate

replaced

Feb 2013,

Rupture/

broken.

Replaced with

10 mm

thickness plate

with 13 mm

drain hole

Decided to replace

the 10mm plate

with 13 mm hole to

13 mm plate

without hole on

trial basis as per

PMR, but PMR not

approve, partition

plate should be

replaced specified

13mm thickness

plate

Two times

replaced.

Started failure

occur in year

2008

2 Heat

exchanger for

US Column

101

(43100341)

Jan 1981 Dec 2011,

Rupture/

broken pass

partition plate

replaced

April 2013,

Rupture/ broken

pass partition

plate

April 2013,

replaced with 13

mm thickness plate

with 13 mm drain

hole

two time

replaced

3 Heat

exchanger for

US Column

201

(43100342)

Oct 1981 May 2012,

Rupture/broken

pass partition

plate replaced

March 2013,

Rupture/ broken

pass partition

plate

March 2013,

replaced with 13

mm thickness plate

with 13 mm drain

hole

two time

replaced

4 Heat

exchanger for

US Column

301

(43100343)

March 1982 Feb 2008,

Rupture/broken

pass partition

plate replaced

March 2011,

rupture/broken

March 2013,

replaced with 13

mm thickness plate

with 13 mm drain

hole

Three times

replaced.

Started failure

occur in year

2008

Das Island Division



2.5 Site visit

Umm Shaif Process Plant

36" Main Oil Line coming from offshore Umm Shaif Super Complex(USSC)

arrives at Das to Umm Shaif plant, (see Figure below). The US plant at Das

comprises of:

a) 7 HP Separators, 2nd stage, 250 psig operating pressure.

b) 7 LP Separators, 3rd stage, 40 psig operating pressure.

c) 2 Spheroids, 4th stage, Atmospheric pressure.

d) 3 Parallel trains of dehydrators and desalters have now been de-

mothballed and commissioned.

e) 4 Cold stripping towers.

Umm Shaif crude is sweetened via one of four cold stripping units, each with

a nominal capacity of 120,000 BPD. The following description refers to the

operation of just one of these units.

A common 30” sour crude oil header delivers crude via the charge pumps to

the stripping area. The crude is divided into four by parallel 12” inlet lines,

which feed the four cold stripping units.

Crude is preheated, using steam as the heating medium, in the sour crude

charge heater to approximately 43ºC. A flow control valve FV-702, in the inlet

line to the stripping tower also acts as shutdown valve SDV- 702. The

preheated crude flows down through the stripping tower against a counter-

current flow of sweet gas from the gas sweetening unit. Sweet gas enters the

tower below the bottom tray.

The sweet gas, as it passes through the descending oil lowers the partial

pressure of the oil thereby removing H2S and some light hydrocarbons from

the crude. The spent sweet gas passes through a demister pad, before

leaving the tower and entering the 60” atmospheric gas manifold.

The stabilized and stripped crude flows from the bottom of each stripping unit

via a seal loop into the vent drum where further gas separation occurs.

Gas evolved in the vent drum is vented to join the spent sweet gas leaving

the stripping tower, before joining the 60” atmospheric gas manifold.

The sweetened crude from each stripping unit combines in the 24” crude

product header and is pumped to the finished crude STOREX area.

Das Island Division



It is to be noted is that ETPP D&D train heat exchanger are not used and are to be

demolished.

There are four trains of strippers in the Umm Saif i.e. three Running and one stand-

by/maintenance/Dual(ZK/US service).

Das Island Division



Design Parameters

The original design of the heat exchanger was reviewed and the following

observations were made (refer ED7-90-D-3252):

Flow for individual cold stripping units Nominal Design Operation for summer and

winter = 120,000BPSD

The Design minimum temperature of the crude = 50DegF(10Deg C)

The Design maximum temperature of the crude =83.6DegF(28.6Deg C)

Design Maximum Crude flow rate = 150,000BPSD

Design Maximum Steam weight flow rate = 33,590lb/hr.

Design Winter steam flow rate = 26,872lb/hr

Design summer steam flow rate = 6,940lb/hr

Design Differential Pressure across the Pass partition plate was not found in the

records.

Also, to be noted is that D&D train heat exchanger are not used and are to be demolished.

The crude oil was intended to be routed to the D&D plant; however, this plant was never

operated.

Present Operations

During the site visit the following production profile were noted in the Umm Shaif

plant:

- Old production profile – prior to 1992 : 180-200,000MBD

- New Production profile(2012): 250-300,000MBD

- Per train Capacity: 120,000MBD

- Mani/Maximum differential Pressure: 11-18Psig(given at site).

(Across the Pass Partition Plate)

- Nominal Differential pressure: 13Psig(Email Confirmation

Das Island Division



(Across the Pass Partition Plate) dated 3rd Feb 2013)

The Data for USP H/Exchanger steam inlet pressure D/Stream the TCVs:

Stripper Inlet

Pressure

Cond. Outlet Pressure Remarks

Col.100 28 PSIG 17 PSIG {common header to

Utilities}

Existing production = 280/50MBD


Utilities}



Utilities}



Utilities}

Now ZK crude service, Existing ZK

production = 365/0 MBD

The inlet steam pressure depends on the oil production, and the pressure of the

common steam condensate header for all of the Das plants. The common steam

header pressure varies from 12 to 17PSIG.

More over these Data also vary upon ambient temperature which is considerably

different in summer & winter. Accordingly, the steam load is varied to maintain the

crude oil temperature.

Below table shows existing operating temperature

Stripper Existing

Oil Flow

to Strip.

MBD

Inlet TEMP Inlet

TEMP

D/Stream

TCV

Strippers

Oil Outlet

Temp.

Remarks

Col.100 95 14.3 Deg C 44 DegC 37 Deg C Temporary Auto control

Col.200 67 30.2 Deg C 44 Deg C 36 Deg C On cascade control {Operational

Das Island Division



requirement}.

Col.300 95 14.4 Deg C 44 Deg C 36 Deg C Temporary Auto control

Col.400 At the time of taking the reading this

stripper was used for ZK crude service.

There is only one pressure transmitter in the inlet steam header of each heat

exchanger. The steam passes through each exchanger in parallel trains. However,

the differential pressure measurement is not monitored continuously.

During the site visit the broken plate were visually inspected along with the channel

head. Anomalies are reported in the inspection report.(Refer inspection report in

appendix of the findings)

A random instantaneous flow measurement was taken(26 Feb 2014 at 11:45am) at

the steam inlet of the heat exchanger and compared to the design values

FT-741 28,410Lb/hr (High as winter design case is 26,872lb/hr)

FT-791 28,710Lb/hr (High as winter design case is 26,872 lb/hr)

FT-841 38,604Lb/hr (Very high as design max is 33,590lb/hr)

As the D&D trains heat exchangers are not used, the capacity of the heat exchanger

for the increased flow is to be analyzed. There is no record/report which provides

concurrence to the present operating parameters.

3.0 Assumptions

a. It was assumed that there was no thickness loss/variation - as inspection reports

did not reveal any such defect.

b. The original design data and calculation were not available. A finite element

model of the design case (without any flaw/base case) was generated to look at

the maximum stress at the relevant part and compare with the flaw assessment.

The construction code ASME Section VIII Div.1 year 1977and TEMA ‘C’ year

Das Island Division



1978 as per the name plate details were used for the calculation of the base

case. The year of manufacture was Nov 1980.

c. For the purpose of this calculation, it is assumed that the Heat Exchangers have

a suitable monitoring / inspection program and that the Exchangers will be

operated in future under its present operating conditions. Also noted, is the fact

that, the Exchangers have been operated safely for more than 31years and these

are recent occurrences i.e. it is assumed that no pervious failure exists as no

similar records were found.

d. The applicability and limitation of the fitness for service assessment is as per API

579.

e. The original design data was taken from the FAD-35-M-30847 / 30848 / 30849.

It is to be noted that the original material for the Pass partition plate is not mentioned

in the drawings/manufacturing records and is assumed as BS 1501-151-28A. This was

considered in all the calculations.

f. As per the site visit report the weld procedure followed was requested and the

weld procedure was check with the manufacturing records FAD-35-M-30847 /

30848 / 30849. The welding procedure used does not exist in the records for he

pass partition plate.

g. As the temperature variation in the channel head (only 2 pass) are very minor

during operation and the channel head is free to expand, the effect of

temperature was not considered. Only during cold start up the thermal variations

are experienced. This effect is known to all and it is assumed that proper

procedures are practiced during start up and shutdowns. If this effect has to be

investigated, it will be based on site team’s advice.

h. The result of vacuum case for channel is not included in this report as no

concerns have been reported. It is assumed that a proper procedure is followed

during shutdown and no rapid cooling is envisaged.

Das Island Division



i. It is assumed that a detailed metallurgical study report was done by the site team

and all defects related to metallurgical aspect were covered and no anomalies

are reported.

4.0 Fitness for service Procedure

The following Procedure was followed:

STEP 1 – Flaw and Damage Mechanism Identification:

The damage mechanism (as per API 571) was analysed and enclosed is the

discussion in Appendix.

The following case scenarios were considered for further evaluations: (serial number

maintained as per Appendix on Damage mechanisms as per API 571)

SLNO

DAMAGE MECHANISM

DESCRIPTION OF THE DAMAGE

MECHANISM

REMARKS

12 Thermal Fatigue

Thermal fatigue is the result of cyclic

stresses caused by variations in

temperature. Damage is in the form of

cracking that may occur anywhere in a

metallic component where relative

movement or differential expansion is

constrained, particularly under repeated

thermal cycling.

The startup and shutdown of

equipment increases the

susceptibility to thermal fatigue. The

number of start-up and shutdown

cycles needs to be controlled. The

magnitude of temperature swing

needs to be controlled.

This damage mechanism is a

credible case, however, this can

easily be controlled by procedures of

slow start up and shutdowns.

18 Caustic Cracking

Caustic embrittlement is a form of stress

corrosion cracking characterized by

surface-initiated cracks that occur in

piping and equipment exposed to caustic,

primarily adjacent to non-PWHT’d welds.

Affected Materials-Carbon steel, low alloy

steels and 300 Series SS are susceptible.

Caustic stress corrosion cracking typically

propagates parallel to the weld in

adjacent base metal but can also occur in

the weld deposit or heat-affected zones.

PWHT is recommended to be

carried out on the channel head. A

heat treatment at 1150°F (621°C) is

considered as an effective stress

relieving heat treatment for carbon

steel

To rule this out, analysis of steam

and metallographic examination

needs to be carried out.

Das Island Division



22 Amine Cracking

Amine cracking is a common term applied

to the cracking of steels under the

combined action of tensile stress and

corrosion in aqueous alkanolamine

systems used to remove/absorb H2S

and/or CO2 and their mixtures from

various gas and liquid hydrocarbon

streams. Amine cracking is a form of

alkaline stress corrosion cracking. It is

most often found at or adjacent to non-

PWHT’d carbon steel weldments or in

highly cold worked parts.

A metallurgical analysis report on

the plate needs to be carried out to

rule it out.

This damage mechanism can be

ruled out on the basis that similar

materials are existing in other plant

in similar service.

PWHT of the Channel head is

recommended.

23 Chloride Stress Corrosion

Cracking

Surface initiated cracks caused by

environmental cracking of 300 Series SS

and some nickel base alloys under the

combined action of tensile stress,

temperature and an aqueous chloride

environment. The presence of dissolved

oxygen increases propensity for cracking



rule it out.




in similar service.

24 Carburization

Carbon is absorbed into a material at

elevated temperature while in contact

with a carbonaceous material or

carburizing environment. Three

conditions must be satisfied:

1) Exposure to a carburizing environment

or carbonaceous material -

(hydrocarbons, coke,

gases rich in CO, CO2, methane, ethane)

and low oxygen potential (minimal O2 or

steam)..

2) Temperature high enough to allow

diffusion of carbon into the metal [typically

above 1100°F

(593°C)].

3) Susceptible material



rule it out.

This is steam service and maximum

temperature is only 204Deg C.




in similar service.

31 Brittle Fracture

Brittle fracture is the sudden rapid

fracture under stress (residual or applied)

where the material exhibits little or no

evidence of ductility or plastic

deformation.

Affected Materials:

Carbon steels and low alloy steels are of

prime concern, particularly older steels.

400 Series SS are also

The hydrotest case needs to be

carefully analyzed and would require

a FEA analysis looking at the stress

on the components. This damage

mechanism is a credible and will

need to be further analyzed.

Das Island Division



susceptible.

39 Dissimilar Metal Weld

(DMW) Cracking

Cracking of dissimilar metal welds occurs

in the ferritic carbon steel or low alloy

steel) side of a weld between an

austenitic (300 Series SS or Nickel base

alloy) and a erritic material operating at

high. Cracking can result from creep

damage, from fatigue cracking, from

sulfide stress cracking or hydrogen

disbonding

This is a credible case and will be

studied further.

40 Hydrogen Stress Cracking

in HF

Hydrogen Stress Cracking is a form

of environmental cracking that can

initiate on the surface of high strength

low alloy steels and carbon steels

with highly localized zones of high

hardness in the weld metal and HAZ

as a result of exposure to aqueous

HF acid environments.



rule it out.




in similar service.

43 Corrosion Fatigue A form of fatigue cracking in which cracks

develop under the combined effects of

cyclic loading and corrosion. Cracking

often initiates at a stress concentration

such as a pit in the surface. Cracking can

initiate at multiple sites.

Contrary to a pure mechanical fatigue,

there is no fatigue limit load in corrosion-

assisted fatigue.

Corrosion promotes failure at a lower

stress and number of cycles than the

materials’ normal endurance limit in the

absence of corrosion and often results in

propagation of multiple parallel cracks.

Crack initiation sites include

concentrators such as pits, notches,

surface defects, changes in section or

fillet welds.

This is a credible case as multiple

site cracks are observed and will be

studied further. However, only minor

corrosion was observed during the

site visit and reported in the

inspection reports.

48 Ammonia Stress Corrosion

Cracking

Aqueous streams containing ammonia

may cause Stress Corrosion Cracking

(SCC) in some copper alloys. Carbon

steel is susceptible to SCC in anhydrous

ammonia. Anhydrous ammonia with

<0.2% water may cause cracking in

carbon steel.

PWHT eliminates susceptibility of

most common steels. To rule this

out, analysis of steam and

metallographic examination needs to

be carried out.

56 Vibration-Induced Fatigue

A form of mechanical fatigue in which

cracks are produced as the result of

dynamic loading due to vibration, water

hammer, or unstable fluid flow.

The plate is rigidly supported all

around. There is report of

vibration/water hammer, or unstable

fluid flow from site. This damage

mechanism is likely. However, if this

Das Island Division



is to be ruled out completely, then a

complete vibration study of the

system needs to be carried out. In

the interim period a DP across the

heat exchanger is recommended.

STEP 2 – Applicability and Limitations of the FFS Assessment Procedures:

The widely used API 579 fitness for service procedure was used for the evaluation of

the crack on the heat exchanger plate. As the heat exchanger partition plate is not

covered in the standards, a modified approach was used inline with the principle of

the FFS study.

As no original design information was available, a base model was made and all

parameter were check to the name plate codes ASME VIII and TEMA.

STEP 3 – Data Requirements:

The available data required for a FFS assessment depend on the flaw type was

identified. Data requirements included: original equipment design data, information

pertaining to maintenance and operations, and material properties.

The available original design information on the heat exchanger was gathered.

However, only some dimensional drawings were available in the ADMA document

system along with name plate details. No design data or calculations were available.

Therefore a based case finite element model to look at the conformance to ASME

Section VIII Div.1 and TEMA ‘C’ was required. The relevant drawings are referenced

in section 2.2. The design data as per the P&ID and vendor drawings referenced

was used for the calculation.

The WPS was reviewed with the original manufacturer. However, there was no

record of the procedure used for the pass partition plate. The fillet weld design used

at site was not found in the records.

Das Island Division



The material of construction was not available on the General arrangement

drawings.

STEP 4 – Assessment Techniques and Acceptance Criteria:

As the damage was crack in the pass partition plate, assessment techniques and

acceptance criteria are not provided in API 579.

As multiple damages are present for the various thickness of the pass partition plate

used, the individual model of the damage was made and analysis was carried out

separately.

This was then compared to the base model. It was found that the pass partition plate

was initially design to withstand a differential pressure of only 12psig.

STEP 5 – Remaining Life Evaluation:

An estimate of the remaining life or analysis for lowering of MAWP was not required.

Therefore, this was not carried out.

STEP 6 – Remediation:

Based on the damage mechanism, the possible cause of crack failures was

established. It was due to high stress on the pass partition plate due to high

differential pressure leading to brittle fracture and/or vibration induced fatigue failure.

The recommendations for the above are given in section 7.0

STEP 7 – In-Service Monitoring:

As, the heat exchanger was under major overhaul and it was clearly established that

the flaw will be repaired (if found unacceptable) before put the heat exchanger is

back to service - there is no requirement of in-service monitoring of the flaw.

However, as highlighted in section 7.0 regular inspection of the heat exchanger are

recommended along with lowering of the steam load.

STEP 8 – Documentation:

Das Island Division



This report aims to document the record of all information and decisions made in

each of the previous steps and to qualify the heat exchanger for continued

operation.

5.0 Discussion on the assessment

There are three level of assessment as per API579 and below is brief of the

assessment carried out:

5.1 Level 1 Assessment:

The assessment procedures included in this level are intended to provide

conservative screening criteria that can be utilized with a minimum amount of

inspection or component information.

The steam sample revealed no anomalies as per the passports for the heat

exchangers and the boilers. Therefore, the following modes of failure were

rules out:

The following design code were used to check the minimum thickness of the

pass partition plate

1. ASME Section VIII Div.1 and

2. TEMA ‘C’

Refer Appendix – 8.2 for details, of the calculations.

Das Island Division



For Shell & Tube heat exchangers employed in refineries & petrochemical

complexes, the applicability of API 660 (ISO 16812) in addition to TEMA has

becoming mandatory by most end users and consultants. API 660 lays down

most requirements based on practical considerations & past experience. At

the same time, incorporating such requirements does have an impact on cost

and efforts during fabrication of S&T Heat exchangers. The table below

compares critical requirements of API 660 with relative TEMA requirements

for the channel head only. It does not include API 660 Supplementary

Requirements and Recommended Practices.

Sl

no

Subject API 660 Requirement API 660 Requirement Remarks

1. Pass Partition

Plate Weld

(9.2)

Pass-partition plates for

forged or welded channels

and floating heads shall be

welded full length, either

from both sides or with full-

No specific guideline is

given in TEMA for full

penetration weld

requirement for pass

API 660

recommendation is

applicable and shall

be considered. It is

recommended to

Das Island Division



penetration welds, except

for special designs approved

by the purchaser. If welded

from both sides, the first 50

mm (2 in) from the gasket

face shall be full-penetration

welds.

partition plate. carry out full

penetration welding of

the full length.

2. PWHT

requirement of

Channel(9.6.4)

• CS and LAS Channels with

6 or more pass

• Nozzle to channel ID ratio

> 0.5.

No specific guideline is

given in TEMA.

• In our case the heat

exchanger is 2 pass

and therefore not

applicable.

• Nozzle to channel ID

ratio=220mm /660mm

=0.33. Therefore, not

applicable

The following damage mechanisms as per API 571 were reviewed and the findings are as

follows: (serial number maintained as per Appendix on Damage mechanisms as per API 571)

SLNO

DAMAGE MECHANISM

FINDINGS

12 Thermal Fatigue

From the site visits there were no findings of abnormal start up and

shutdowns. However, considered for further analysis.

18 Caustic Cracking

Steam analysis was carried out recently on the boiler and reviles no

concerns. Therefore, this ruled out. However, PWHT is recommended.

22 Amine Cracking



23 Chloride Stress Corrosion

Cracking



24 Carburization

This was ruled out. However, PWHT is recommended.

31 Brittle Fracture

Further analysis is required to rule this out.

Das Island Division



39 Dissimilar Metal Weld

(DMW) Cracking

This was ruled out after review of the weld records, metallurgy report and

the site visits.

40 Hydrogen Stress Cracking

in HF

This was ruled out after review of the steam analysis, weld records,

metallurgy report and the site visits.

43 Corrosion Fatigue No major corrosion/errosion was reported in the inspection findings,

metallurgy report. This was ruled out.

48 Ammonia Stress Corrosion

Cracking

This was ruled out after review of the steam analysis, weld records,

metallurgy report and the site visits. However, PWHT is recommended.


This was credible and will be studied further.

The review of the operation of the heat exchanger reveled the following:

a. There was no record for the design limits for the differential pressure.

b. The steam flow was maintained higher than the design maximum

c. The heat exchanger was used to heat the crude from 10 deg C to 44 Deg

C, while the design intent was to heat till 28 deg C.

Due to this, a high differential pressure was observed across the pass

partition plate.

The calculation showed that the minimum thickness required was 13mm plate

for meeting the required differential pressure of 18psig across the plate. Also,

the welding used was not as per the recommendations made by the codes.

Therefore a further assessment was carried out.

5.2 Level-2 assessment:

For the pass partition plate, a level 2 assessment criteria does not exist and

the existing design calculation were also missing from ADMA documentation.

Therefore, a level 3 assessment was carried out.

5.3 Level-3 assessment:

Das Island Division



Initially, as the design calculations of the heat exchanger were not available,

the base case model (model without any distortion) was created, using the

design parameters.

Limit-Load Analysis Method (refer B1.2.3 of API579) was used in determining

the maximum pressure required to reach the minimum yield stress i.e. to

determine the load required to reach the plastic deformation. The base case

established that a differential pressure of 18psig (0.1241Mpa) was required to

be applied uniformly on the pass partition plate at 204degC.

Along with linear analysis, a non-linear analysis and even Riks non-linear

method was used when convergence was not achieved.

The equivalent stress equal to the von Mises equivalent stress was used.

Allowable Equivalent Stress

To determine the acceptability of a component, the computed equivalent

stresses shall not exceed specified allowable values.

It is to be noted that the allowable stress for this analysis at 204 deg C for the

steel was 15,700lbf/in2 or 108Mpa.

The assessment procedure as per API579 was followed.

The following cases were analyzed:

10mm plate without hole:

1. Hydrotest case at 263psig(1.8133MPa) at 37 deg C

2. Normal Operating case with following parameter

a. Internal Pressure = 35psig

b. Differential pressure across the Pass partition=18Psig

c. Temperature = 204Deg C

3. Operating case with following parameter

Das Island Division





c. Temperature = 204Deg

4. Design case with following parameter




5. Failure/Max Design case with following parameter




13mm plate without hole:






8. Operating case with following parameter




9. Design case with following parameter




Das Island Division



10. Failure/Max Design case with following parameter




13mm plate with 13mm hole:






13. Design case with following parameter(Base Case)




From the above analysis it was concluded that if the present scenario of

operation is continued, the failure of pass partition plate is possible.

Therefore, stiffeners on the plate are required. After analyzing more than 33

possible design improvement/cases, the most optimum is presented which

required the least amount of modifications.

For example the following cases were analyzed:

1. Change in Pass plate thickness to 15mm

2. Change in channel head wall thickness to 12.5mm

3. Change in both channel head to 12.5mm and pass partition plate

thickness to 15mm

4. Various type and profile of stiffeners on 13mm plate, 15mm plate

Das Island Division



This is presented as the proposed solution in the appendix.

6.0 Conclusions

From the finite element analysis carried out on the pass partition plate the

stresses were found to be high. The following are the findings of the stress

analysis:

1. The design of the pass partition plate was to handle a differential pressure

of only 12psig.

2. The four corners of the pass partition plate are found to be heavily

stressed when the differential pressures across the pass partition plate

exceed 12psig.

3. A proper weld WPS needs to be developed for the pass partition plate.

Design of the weld shall consider full penetration weld along the full length

of the pass partition plate.

4. The result of the stress analysis is enclosed in the appendix in three

section

a. Base case (13mm pass partition plate)

b. 10mm pass partition plate

c. Proposed Solution (to mitigate high differential pressure)

5. The hole in the pass partition plate did not contribute to any additional

stress and can be retained. However, it is suggest to move it from the

center to low stress region (see 13mm proposed solution case results)

offset from the center.

6. A vibration study has to be carried out on the entire steam header with

specialist contractor. As the high differential pressures are maintained and

reports of vibration exist, it is believed that the initial failure of the 13mm

Das Island Division



plates were due to vibration induced fatigue. However, the 10mm plate

failure is believed to be due to the fact that the design thickness of the

plate not maintained resulting in high stress causing brittle facture.

7. It should be noted that the differential pressure across the heat exchanger

are high and has to be brought down to below 12psig. There is always a

trade-off between the pressure-drop in the channel with the thermal rating.

With recommendation to lower the pressure drop, maintaining the

temperature of the crude would be difficult. If the pressure cannot be

maintained below 12psig, stiffeners are recommended to be installed with

full penetration welds of the pass partition plate as soon as possible.

8. Operating parameters are exceeding the design parameters and these

have to be controlled.

9. D&D train heat exchanger are not used and are to be demolished. The

D&D heat exchangers were supposed to have operated in serial with the

US column heat exchangers, lowering the steam load on these

exchangers.

Root Cause: of the 10mm plate failure is due to high differential pressure

causing a Brittle fracture. Also, the improper welding have compounded/

attributed to the failure.

Root Cause: of the 13mm plate failure is due to high differential pressure

causing a Brittle fracture and /or vibration induced fatigue failure.

7.0 Recommendations:

The following recommendations are made based on the study:

a) For new exchangers, the pressure differential used to calculate the pass-

partition plate thickness shall be in accordance with TEMA (8th edition), RCB-

9.132, shall be the allowable tube-side pressure drop of the entire exchanger

Das Island Division



unit. Also, the estimate differential pressure across the new heat exchanger/s

shall be provided by the vendor and the differential pressure across the pass

partition plate design shall withstand the estimated differential pressure or

30psig minimum (whichever is greater). In future all new heat exchanger pass

partition plate shall be design to withstand a differential pressure of 30Psig as

a minimum in ADMA OPCO. A review of ADMA OPCO standard is requested.

b) The operating parameter is to be maintained well within the design limits of

the system. It is observed that steam inlet flow measurements are maintained

high during winter.

c) Differential pressure gauge shall be installed across the heat exchanger with

alarm setting and trip setting for all the heat exchangers, even in new built.

d) The differential pressure across the heat exchanger has to be brought down.

This can be brought down by

i. Common spare stripper to be made online always

(If this does not reduce the differential pressure then)

ii. Replacement of heat exchanger / Additional train to be considered to

carter to the recent Production increases.

e) In some Das facilities, the heat exchangers in crude service are TEMA “R”

and in some place TEMA “C”. This should be standardized in ADMA OPCO. It

is recommended to develop a standard in ADMA OPCO for heat exchangers.

Note: The general descriptions of the three major TEMA classes are:

TEMA C - General Service

TEMA B - Chemical Service

TEMA R - Refinery Service

**TEMA R is the most restrictive and TEMA C is the least stringent.

f) At the time of writing this report, the pass partition plates are replaced with

13mm plate as per original manufacturer material & design recommendations.

Das Island Division



In the next major overhaul the pass partition plate and the weld shall be

checked with MPI for crack or any discontinuity. PWHT is also recommended

even if no anomalies are found.

g) If any anomalies are found the pass partition plate shall be replaced with

13mm plate, as per the original design. However, with the drain hole offset

from the centre to a lower stress region.

i. For the welding of the pass partition plate it is recommended to have

full length penetration weld V-type. A proper design of the weld is

suggested and to be adopted in ADMA OPCO as a standard.

ii. The stiffener as per enclosed design is recommended to be welded to

allow for any pressure surge of up to 30psig.

iii. Welding shall be carried out as per the Approved ADMA OPCO

procedure.

iv. PWHT is recommended to be carried out after welding of the pass

partition plate. Obtain hardness reading at weld vicinity to ensure

effective treatment.

v. After hydrotest the pass partition plate shall be examined and

inspected with report issued.

vi. MPI shall be carried out on the pass partition weld upon completion of

the repair.

vii. Hydrotest for the shell side and tube side to carried out after the

completion of the repair and NDT.

h) A complete review of the steam trap efficiency for the entire steam headers

shall be carried out by a specialist contractor. The steam traps functional test

to be carried out to ensure no steam condensate on the steam line upstream

and downstream of the Heat exchanger.

i) Vibration study is suggested to be carried out for the steam headers.

Das Island Division



j) Steam analysis is to be carried out on a regular basis and reports to be

available.

k) Number of cycles of start-up and shutdown are to be reduced or minimized.

Ideally the units should be in operation always until the next major overhaul.

Proper procedure should be in place to the start-up and shutdown with logs

maintained to avoid Thermal fatigue failure.

Das Island Division



8.0 APPENDICES

8.1 Original Work request and correspondences

Das Island Division



APPENDICES

8.2 Inspection report

1 of 3

Endorsed by VPI

Risk Mitigation Recommendations

Short Term: None.

Long Term. Perform shellside internal pitting inspection to confirm depth and pitting corrosion rate. This is required before Dec-2018.

Strip insulation and perform 100% visual external inspection followed by UT thickness readings of any suspected damaged areas. This is required before Dec-2018.

Prepared by E2G Reviewed by E2G Approved by SISL Approved by TIM

POF(Failures/yr)COF($)

Risk($/yr)

3.06E-52.8479E+6

87.1457


Risk($/yr)

3.06E-52.8524E+6

87.2823

4 0.01 < POF <= 0.1 D 1000000 < COF <= 10000000

5 POF > 0.1 E COF > 10000000

2 0.0001 < POF <= 0.001 B 10000 < COF <= 100000

3 0.001 < POF <= 0.01 C 100000 < COF <= 1000000

Probability of Failure Consequence of Failure1 POF <= 0.0001 A COF <= 10000

X

4

3

2

1

A B C D E

5

X

4

3

2

1

A B C D E

5

Fluid PhaseC17-C25

Liquid

Risk ResultsLong Term Predicted Risk Risk After Mitigation

Process InformationOp Pressure (MPag) 0.586 Temp (C) 29/42 Fluid Name

InsulationLiner Type

Corr. Allow. (mm)Weight (kg)

CALCIUM SILICATENA3.2NA

PWHTDesign Temp. (C)

Joint EfficiencyT-min (mm)

NO66

0.8507.1173

Length (m)Design Press. (MPag)Base Thickness (mm)Clad Thickness (mm)

4.82.4119NA

Diameter (mm)Design Code

Base MaterialClad Material

660S8-DIV1

SA516 - 70NA

Location/Unit Das Island/Umm Al Shaif Description Sour Crude Heat Exchanger - Shell Side

Mechanical InformationExchanger Type Shell & Tube Component Start Date 02-Jan-1980

HEAT EXCHANGER PASSPORT43100341

(Shellside Pressure Boundary)

Revision #Analysis DateLocation Tag

201-Dec-2012

04.3-HSR4-C101-SS

2 of 3

Inspection History Summary

July-06 - Isolated areas of light wastage and pitting were reported along the bottom less than 1mm deep on shell internal surface.Mar-08 - The heat exchanger was taken out of service due to a water leak from the area between the channel head & the tube sheet. Inspection revealed a small groove on both the channel head face & the tube sheet. Repairs were carried out with Belzona compound followed by a hydrotest.Dec-11 - A crack was noted along the partition plate weld, and the partition plate was replaced. Repair coating was applied on internal surfaces at affected (pitted )areas at the shell and dished end.

Equipment Sketch

Process Summary

This exchanger is used to exchange heat between superheater steam and crude oil, which purpose is to heat up the crude oil entering the cold stripping tower / vent drum to strip H2S from the system before transporting the crude to crude oil storage tanks. The Sour Crude Oil pumped from Umm Shaif Charge Pumps (J184, J185, J186, J187) and distributed using a common distribution header is then preheated by Superheated Steam from Steam Header before entering the Cold Stripping Tower / Vent Drum (HSR4-E-101/F-101).Commissioned in 1981, monitoring the service efficiency and fouling resistance are recommended as it affects the heat transfer capacity over time.

HTHA Susceptibility NONE

Threats

The major threat to the carbon steel shell is pitting of the shell bottom due to underdeposit corrosion from crude BS&W collecting in shells of these crude preheat exchangers. A corrosion pitting rate for the Umm Shaif plant shells is estimated at 0.12 mm/yr.

CUI damage is also a threat, the calculated rate is 0.22 mm/yr.

External Ext. Corr. Rate (mm/yr) 0.1987 Ext. Cracking NACracking Susceptibility NA Type NA

13.117.77

BM Corrosion Rate (mm/yr)CM Corrosion Rate (mm/yr)

0.12NA

ThinningType

Last Insp. DateLOCAL

01-Dec-2011Thickness (mm)

Remaining Life(yrs)


Risk Mitigation

Material ReviewComments

All carbon steel construction shell and tube crude preheat exchanger. Heats wet crude on the shellside with superheated steam on the tubeside prior to sending to H2S stripping. tower. A thorough review of the materials and process shows the shell is fit for continued service subject to pitting monitoring of shell.




201-Dec-2012

04.3-HSR4-C101-SS

1 of 3


(Tubeside Pressure Boundary)


201-Dec-2012

04.3-HSR4-C101-TSLocation/Unit Das Island/Umm Al Shaif Description Sour Crude Heat Exchanger - Tube Side

Mechanical InformationExchanger Type Shell & Tube Component Start Date 02-Jan-1980Diameter (mm)

Design CodeBase MaterialClad Material

660S8-DIV1

SA516 - 70NA


0.52.4119NA



NO66

0.8503.5585





Fluid PhaseSTEAM

Two Phase


A B C D E

5

4

3

2

1

X

A B C D E

5

4

3

2

1

X


2 0.0001 < POF <= 0.001 B 10000 < COF <= 100000

3 0.001 < POF <= 0.01 C 100000 < COF <= 1000000

4 0.01 < POF <= 0.1 D 1000000 < COF <= 10000000

5 POF > 0.1 E COF > 10000000


Risk($/yr)

0.1534.2056E+46434.5039


Risk($/yr)

0.06024.2056E+42530.3474


Short Term: None.

Long Term: By Dec 2018, perform visual internal tubeside inspection followed by UT measurements as necessary for corrosion at condensate liquid level and outlet nozzle. Perform crack inspection at pass partition plate to channel cylinder welds.

Prepared by E2G Reviewed by E2G Approved by SISL Approved by TIM Endorsed by VPI

2 of 3




201-Dec-2012


Risk Mitigation


All carbon steel construction shell and tube crude preheat exchanger. Heats wet crude on the shellside with superheated steam on the tubeside prior to sending to H2S stripping. tower. A thorough review of the materials and process shows the channel is fit for continued service.

ThinningType

Last Insp. DateGENERAL

01-Dec-2011Thickness (mm)

Remaining Life(yrs)13

50.00BM Corrosion Rate (mm/yr)CM Corrosion Rate (mm/yr)

0.05NA

External Ext. Corr. Rate (mm/yr) 0 Ext. Cracking NACracking Susceptibility HIGH Type OTHER


Threats

There is a minor threat to the channel due to steam condensate corrosion. There have been little corrosion problems reported for the steam side. A corrosion rate of 0.05 mm/yr is estimated for steam condensate corrosion. In 2011, the channel pass partition plate weld to shell was cracked and a new head was installed. This should be considered an on-going threat until the root cause is established.


July-06 - Isolated areas of light wastage and pitting were reported along the bottom less than 1mm deep on shell internal surface.Mar-08 - The heat exchanger was taken out of service due to a water leak from the area between the channel head & the tube sheet. Inspection revealed a small groove on both the channel head face & the tube sheet. Repairs were carried out with Belzona compound followed by a hydrotest .Dec-11 - A crack was noted along the partition plate weld, and the partition plate was replaced. Repair coating was applied on internal surfaces at affected (pitted )areas at the shell and dished end.This is an insulated horizontal “U” tube heat exchanger of all welded carbon steel construction, mounted on two integral steel saddle supports bolted to steel support structures approx. 2.0m high.Dimensions - Vessel 4838 mm long x 660mm i/d x 13mm thick.Design Pressure - 360 psig @ 66ºC. Test Pressure - 525 psig. Design Code - ASME VIII Div.1.

Equipment Sketch

Process Summary


1 of 3

Endorsed by VPI


Short Term: None.

Long Term. Perform shellside internal pitting inspection to confirm depth and pitting corrosion rate. This is required before May-2019.

Strip insulation and perform 100% visual external inspection followed by UT thickness readings of any suspected damaged areas. This is required before May-2019.



Risk($/yr)

3.06E-52.8479E+6

87.1458


Risk($/yr)

3.06E-52.8527E+6

87.2923

4 0.01 < POF <= 0.1 D 1000000 < COF <= 10000000

5 POF > 0.1 E COF > 10000000

2 0.0001 < POF <= 0.001 B 10000 < COF <= 100000

3 0.001 < POF <= 0.01 C 100000 < COF <= 1000000


X

4

3

2

1

A B C D E

5

X

4

3

2

1

A B C D E

5

Fluid PhaseC17-C25

Liquid








NO66

0.8506.995


4.82.4113NA



660S8-DIV1

SA516 - 70NA


Mechanical InformationExchanger Type Shell & Tube Component Start Date 02-Jan-1980




201-Dec-2012

04.3-HSR4-C201-SS

2 of 3


July-06 - Isolated areas of light wastage and pitting along the bottom less than 1mm deep on shell internal surface. Mar-08 - Heat exchanger taken out of service due to water leak from the area between the channel head & the tube sheet. Inspection revealed small groove on both the channel head face & the tube sheet. Repairs were carried out by Belzona compound followed by a hydrotest. Dec-11 - Crack noted along the partition plate weld, partition plate was replaced. Repair coating applied on internal surface at affected (pitted) areas at shell and dished end.

Equipment Sketch

Process Summary



Threats




1318.26


0.12NA

ThinningType


01-May-2012Thickness (mm)

Remaining Life(yrs)


Risk Mitigation






201-Dec-2012

04.3-HSR4-C201-SS

1 of 3




301-Dec-2012


Mechanical InformationExchanger Type Shell & Tube Component Start Date 02-May-2012Diameter (mm)


660S8-DIV1

SA516 - 70NA


0.552.4110NA



NO66

0.8503.4667





Fluid PhaseSTEAM

Two Phase


A B C D E

5

4

3

2

1

X

A B C D E

5

4

3

2

1

X


2 0.0001 < POF <= 0.001 B 10000 < COF <= 100000

3 0.001 < POF <= 0.01 C 100000 < COF <= 1000000

4 0.01 < POF <= 0.1 D 1000000 < COF <= 10000000

5 POF > 0.1 E COF > 10000000


Risk($/yr)

0.1534.4192E+46761.3133


Risk($/yr)

0.04994.4192E+42204.5408


Short Term: None.

Long Term: By June 2017, perform visual internal tubeside inspection followed by UT measurements as necessary for corrosion at condensate liquid level and outlet nozzle. Perform crack inspection at pass partition plate to channel cylinder welds.


2 of 3




301-Dec-2012


Risk Mitigation



ThinningType


01-May-2012Thickness (mm)

Remaining Life(yrs)NA


0.05NA



Threats



July-06 - Isolated areas of light wastage and pitting along the bottom less than 1mm deep on shell internal surface.Mar-08 - Heat exchanger taken out of service due to water leak from the area between the channel head & the tube sheet. Inspection revealed small groove on both the channel head face & the tube sheet. Repairs were carried out by Belzona compound followed by a hydrotest .Dec-11 - Crack noted along the partition plate weld, partition plate was replaced. Repair coating applied on internal surface at affected (pitted )areas at shell and dished end.

Equipment Sketch

Process Summary


1 of 3

Endorsed by VPI


Short Term: None.

Long Term. Perform shellside internal pitting inspection to confirm depth and pitting corrosion rate. This is required before Mar-2018.

Strip insulation and perform 100% visual external inspection followed by UT thickness readings of any suspected damaged area and required before Mar-2018.



Risk($/yr)

3.06E-52.8479E+6

87.1457


Risk($/yr)

3.06E-52.8524E+6

87.2823

4 0.01 < POF <= 0.1 D 1000000 < COF <= 10000000

5 POF > 0.1 E COF > 10000000

2 0.0001 < POF <= 0.001 B 10000 < COF <= 100000

3 0.001 < POF <= 0.01 C 100000 < COF <= 1000000


X

4

3

2

1

A B C D E

5

X

4

3

2

1

A B C D E

5

Fluid PhaseC17-C25

Liquid








NO66

0.8507.1173


4.82.4119NA



660S8-DIV1

SA516 - 70NA


Mechanical InformationExchanger Type Shell & Tube Component Start Date 02-Oct-1993




301-Dec-2012

04.3-HSR4-C301-SS

2 of 3


The shell of this crude charge heater was opened due to high vibration and noise in the unit. The partition plate of the channel was found to have cracked in HAZ of weld joint, probably due to process hammering. It was replaced with a new one. MPI was conducted after welding and found acceptable.

Equipment Sketch

Process Summary



Threats




19.835.05


0.12NA

ThinningType


01-Mar-2011Thickness (mm)

Remaining Life(yrs)


Risk Mitigation






301-Dec-2012

04.3-HSR4-C301-SS

1 of 3




301-Dec-2012


Mechanical InformationExchanger Type Shell & Tube Component Start Date 02-Oct-1993Diameter (mm)


660S8-DIV1

SA516 - 70NA


0.52.4119NA



NO66

0.8503.5585





Fluid PhaseSTEAM

Two Phase


A B C D E

5

4

3

2

1

X

A B C D E

5

4

3

2

1

X


2 0.0001 < POF <= 0.001 B 10000 < COF <= 100000

3 0.001 < POF <= 0.01 C 100000 < COF <= 1000000

4 0.01 < POF <= 0.1 D 1000000 < COF <= 10000000

5 POF > 0.1 E COF > 10000000


Risk($/yr)

0.1534.2056E+46434.5039


Risk($/yr)

0.06024.2056E+42530.3474


Short Term: None.

Long Term: By Mar-2018, perform visual internal tubeside inspection followed by UT measurements as necessary for corrosion at condensate liquid level and outlet nozzle. Perform crack inspection at pass partition plate to channel cylinder welds.


2 of 3




301-Dec-2012


Risk Mitigation



ThinningType


01-Mar-2011Thickness (mm)



0.05NA



Threats



In March 2011, the shell of this crude charge heater was opened due to high vibration and noise in the unit. The partition plate of the channel was found to have cracked in HAZ of weld joint, probably due to process hammering. A crack in this weld also occurred in 2008. The plate was replaced with a new one. MPI was conducted after welding and found acceptable

Equipment Sketch

Process Summary


1 of 2

Endorsed by VPI


Short Term: None.

Long Term. Perform shellside internal pitting inspection to confirm depth and pitting corrosion rate. This is required before Feb-2019.

Strip insulation and perform 100% visual external inspection followed by UT thickness readings of any suspected damaged areas before Feb-2019.



Risk($/yr)

3.06E-52.8479E+6

87.1457


Risk($/yr)

3.06E-52.8524E+6

87.2823

4 0.01 < POF <= 0.1 D 1000000 < COF <= 10000000

5 POF > 0.1 E COF > 10000000

2 0.0001 < POF <= 0.001 B 10000 < COF <= 100000

3 0.001 < POF <= 0.01 C 100000 < COF <= 1000000


X

4

3

2

1

A B C D E

5

X

4

3

2

1

A B C D E

5

Fluid PhaseC17-C25

Liquid





CALCIUM SILICATENA3

NA



NO66

0.8507.1173


4.82.4119NA



660S8-DIV1

SA516 - 70NA


Mechanical InformationExchanger Type Shell & Tube Component Start Date 02-Nov-1980




301-Dec-2012

04.3-HSR4-C401-SS

2 of 2


The internal shell surface was found in good condition except isolated pitting in the range of 0.2 to 1.5 mm depth at the 4.0 to 8.0 o’clock position. Belzona compound was previously applied on three pitted locations, and it was found intact. The Crude oil heater is considered suitable for continued service on 48 months endorsement.

Equipment Sketch

Process Summary

This exchanger is used to exchange heat between superheater steam and crude oil, which purpose is to heat up the crude oil entering the cold stripping tower / vent drum to strip H2S from the system before transporting the crude to crude oil storage tanks. The Sour Crude Oil pumped from Umm Shaif Charge Pumps (J184, J185, J186, J187) and distributed using a common distribution header is then preheated by Superheated Steam from Steam Header before entering the Cold Stripping Tower / Vent Drum (HSR4-E-401/F-401). The stripped crude then transported to Crude Oil Storage Tanks 13,14,17,18,19,20&21.Commissioned in 1981, monitoring the service efficiency and fouling resistance are recommended as it affects the heat transfer capacity over time.


Threats




1317.63


0.12NA

ThinningType


01-Feb-2012Thickness (mm)

Remaining Life(yrs)


Risk Mitigation






301-Dec-2012

04.3-HSR4-C401-SS

1 of 3




301-Dec-2012


Mechanical InformationExchanger Type Shell & Tube Component Start Date 02-Nov-1980Diameter (mm)


660S8-DIV1

SA516 - 70NA


0.52.4119NA



NO66

0.8503.5585



CALCIUM SILICATENA3

NA


Fluid PhaseSTEAM

Two Phase


A B C D E

5

4

3

2

1 X

A B C D E

5

4

3

2

1 X


2 0.0001 < POF <= 0.001 B 10000 < COF <= 100000

3 0.001 < POF <= 0.01 C 100000 < COF <= 1000000

4 0.01 < POF <= 0.1 D 1000000 < COF <= 10000000

5 POF > 0.1 E COF > 10000000


Risk($/yr)

3.06E-54.2056E+4

1.2869


Risk($/yr)

3.06E-54.2056E+4

1.2869


Short Term: None.

Long Term: Perform visual internal tubeside inspection followed by UT measurements, as necessary, for corrosion at condensate liquid level and outlet nozzle before Feb-2019.


2 of 3




301-Dec-2012


Risk Mitigation



ThinningType


01-Feb-2012Thickness (mm)



0.05NA

External Ext. Corr. Rate (mm/yr) 0 Ext. Cracking NACracking Susceptibility NA Type NA


ThreatsThere is a minor threat to the channel due to steam condensate corrosion. There have been little corrosion problems reported for the steam side. A corrosion rate of 0.05 mm/yr is estimated for steam condensate corrosion.


The internal shell surface was found in good condition except isolated pitting in the range of 0.2 to 1.5 mm depth at the 4.0 to 8.0 o’clock position. Belzona compound was previously applied on three pitted locations, and it was found intact. The Crude oil heater is considered suitable for continued service on 48 months endorsement.

Equipment Sketch

Process Summary

This exchanger is used to exchange heat between superheater steam and crude oil, which purpose is to heat up the crude oil entering the cold stripping tower / vent drum to strip H2S from the system before transporting the crude to crude oil storage tanks. The Sour Crude Oil pumped from Umm Shaif Charge Pumps (J184, J185, J186, J187) and distributed using a common distribution header is then preheated by Superheated Steam from Steam Header before entering the Cold Stripping Tower / Vent Drum (HSR4-E-401/F-401). The stripped crude then transported to Crude Oil Storage Tanks 13,14,17,18,19,20&21.Commissioned in 1981, monitoring the service efficiency and fouling resistance are recommended as it affects the heat transfer capacity over time.

0 08 - 09 Issued for Implementation

Rev. Date Description / Text Affected

Manual For Welding Procedure Specification(in-House Use)

ADMA-OPCO MNL-02 PAGE

21

SF / General / 002 Rev.0 sheet 1 of 1

QW – 482 WELDING PROCEDURE SPECIFICATION (WPS)

(See QW- 200.1, Section IX, ASME Boiler and Pressure Vessel Code)

Company Name ADMA-OPCO By: Mustafa A. Jarebi

Welding Procedure Specification No. ADMA-OPCO-3 Rev. 0 Date Supporting PQR No. ADMA-OPCO-1-1

Revision No. 0 Date /

Welding Process (es) SMAW Type(s) Manual

(Automatic, Manual, Machine, or Semi-Auto)

JOINTS (QW-402) DETAILS

Joint Design Groove or (Refer to the attached weld joint

configurations)

Backing (Yes) With (No) No

Backing Material (Type) /

(Refer to both backing and retainers)

Metal Nonfusing Metal

Nonmetallic Other

Sketches, Production Drawings, Weld Symbols or Written Description

Should show the general arrangement of the parts to be welded. Where

Applicable, the root spacing and the details of weld groove may be

Specified.

(At the option of the Mfgr., sketches may be attached to illustrate joint design, weld

layers and bead sequence, e.g. for notch toughness procedures, for multiple process

Procedures, etc.)

* BASE METALS (QW-403)

P-No. 1 Group No. 1 or 2 to P-No. 1 Group No. 1 or 2

OR

Specification type and grade ASTM A 106 Gr. B or Equivalent (i.e. A 105…) (Sweet or Sour)

To Specification type and grade Same

OR

Chem. Analysis and Mech. Prop.

to Chem. Analysis and Mech. Prop.

Thickness Range:

Base Metal: Groove 5 mm to 16 mm Filet ALL

Other

* FILLER METALS (QW-404) SMAW

Spec. No. (SFA) 5.1

AWS No. (Class) E 7018-1

F-No. 4

A-No. 1

Size of Filler Metals 2.5, 3.25, 4.0 mm

Weld Metal

Thickness Range:

Groove Up to 16mm max.

Fillet ALL

Electrode – Flux (Class)

Consumable Insert

Other

* Each base metal- filler metal combination should be recorded individually.





22


QW – 482 (Back)

WPS No. ADMA-OPCO-3 Rev. 0

POSITIONS (QW – 405) POSTWELD HEAT TREATMENT (QW – 407)

Position(s) of Groove ALL Temperature Range N/A

Welding Progression: Up Uphill Down Time Range

Position(s) of Fillet All

PREHEAT (QW – 406) GAS (QW – 408)

Preheat Temp. Min 300C Percent Composition

Inter-pass Temp. Max. 2500C Gas(es) Mixture Flow Rate

Preheat Maintenance / Shielding N/A N/A N/A

Trailing N/A

Backing N/A

(Continuous of special heating, where applicable, should be

recorded)

ELECTRICAL CHARACTERISTICS (QW – 409)

Current AC or DC DC Polarity EP (SMAW)

Amps (Range) As Shown Below Volts (Range) As Shown Below

(Amps and volts range should be recorded for each electrode size,

Position, and thickness, etc. This information may be listed in a

Tabular form similar to that shown below. )

Tungsten Electrode Size and Type N/A

(Pure Tungsten, 2% Thoriated, etc.)

Mode of Metal Transfer for GMAW N/A

(Spray arc, short circuiting arc, etc.)

Electrode Wire feed speed range

TECHNIQUE (QW – 410)

String or Weave Bead String bead (Root), Weave Bead (Fill & Cap)

Orifice or Gas Cup Size N/A

Initial and Inter-pass Cleaning (Brushing, Grinding, etc.) Grinding and brushing using C.S Material

Method of Back Gouging N/A

Oscillation N/A

Contact Tube to Work Distance N/A

Multiple or Single Pass (per side) Multiple

Multiple or Single Electrodes Single

Travel Speed (Range) See Below

Peening N/A

Other N/A

Filler Metal Current

Weld Layer(s) ProcessClass Dia.

Type

Polar

Amp Range

(A)

Volt

Range

(V)

Travel Speed

Range

Other (eg.

Remarks,

Comments, Hot

Wire Addition,

Technique, Torch

Angle etc.)

Root SMAW E 7018-1 2.5 mm +ve 95 -110 22-24

Fill and Cap SMAW E 7018-1 3.25, 4.0 mm +ve 100-140 22-2470-80mm/min





23


3.3 to 6

t

0 to 2.3 mm

5t

t

450

(G) Double-

bevel-groove T-joint

(H) Lap joint

t t

450 to 600

t1.5 to 3.0

0 to 2.3 mm

0 to 2.3 mm

(D) Fillet corner joint (E) Single-bevel-groove corner joint

(F) Square-grooveT-joint, single weld

600

600

(typ)

1.5 + 0.5 mm

0 to 2.3t

tt

1.5 to 3.0 1.5 to 2.3(A) Square- 1.5 to 3.0 1.0 to 1.5

groove butt joint

(B) Single V-groove butt joint

© Double V-groove

butt joint

1

Jose Bijoy (ADMA DID)

From: Das Mechanical Maint. Section Leader (ADMA DAS)

Sent: Saturday, March 23, 2013 9:12 AM

To: Jose Bijoy (ADMA DID)

Cc: Rabindra K. Singh DETL (ADMA DID); Das Maintenance TL (ADMA DAS); Das Mech. Engineer P&V (Bala/Rashid) (ADMA DAS); Das Process

Operations TL (ADMA DAS); Das Facility Integrity SL (ADMA DAS); Das Integrity Svs. Eng. (A1) (ADMA DAS); Gamal Saeed Bazara (ADMA

DID)

Subject: FW: Channel head for the US column-300 Heat exchanger - 43100343 - Worl Request DIAD/WR/12/030

Attachments: Work Request DIAD/WR/12/030: Repeated Failure of Umm Shaif Heat Exchangers Channel Pass Partition Plate

Mr. Bijoy,

Please note that failure was observed on US Column 300 Exchanger Channel Partition Plate also when we opened the Channel cover on 22/03/2013 to check

the condition.

Appreciate if you can expedite the deliverables of the work request raised in June-2012 regarding this type of failure.

Regards,

Sunil Kumar

From: Das Integrity Svs. Eng. (A1) (ADMA DAS) Sent: 23 March 2013 8:58 AM

To: Das Mech. Supervisor P&V Crew #2 (Andre/ Kassim) (ADMA DAS)

Cc: Das Facility Integrity SL (ADMA DAS); Das Mechanical Maint. Section Leader (ADMA DAS); Das Process SL (ADMA DAS); Das Process Supervisors (ADMA DAS); Das Process Operations TL (ADMA DAS); Ali Saleh Khorooh FITL (ADMA ID); Junior Das Integrity Svc. Eng. (AlHammadi) (ADMA-DAS); Das Mech. Engineer P&V (Bala/Rashid)

(ADMA DAS) Subject: Channel head for the US column-300 Heat exchanger - 43100343

Gents, Visual inspection was carried out on Channel head for the US column-300 Heat exchanger after removing from service. It was observed that the pass partition plate was found rupture, the crack propagate from the HAZ area of the pass partition plate on both side and on the center of the pass partition plate. The thickness of the existing pass partition plate is noted to be 10.0mm. Recommendation

2

1) The rupture pass partition plate shall be replaced with 13mm plate, as per the original design. 2) After removing the cracked pass partition plate the area on the channel shall be checked with MPI for crack or any discontinuity. 3) It is recommended to have full penetration weld at least 50mm on both side from gasket area and then continuous fillet weld as per the original

construction drawing. 4) Welding shall be carried out as per the Approved ADMA OPCO procedure. 5) MPI shall be carried out on the pass partition weld upon completion of the repair 6) Hydrotest for the shell side and tube side to carried out after the completion of the repair and NDT. 7) The steam traps functional test to be carried out to ensure no steam condensate on the steam line upstream of the HE.

Since the failure of the pass partition plate have been occurred on the same heat exchanger during Feb 2008 and Mar 2011, it is required to expedite the engineering review /root cause analysis(refer the attached mail) for all the US Sour crude heat exchangers which are having the pass partition plate rupture history.

Regards, Ashraf kassim Das Integrity Service Engineer-A1 68036 16911

Das Island Division



APPENDICES

8.3 Damage Mechanism as per API571

From API 571 Table 5-4 – Key to Damage Mechanisms Damage Mechanism

SLNO

DAMAGE MECHANISM

DESCRIPTION OF THE DAMAGE MECHANISM

REMARKS

1 Sulfidation Corrosion of carbon steel and other alloys resulting from

their reaction with sulfur compounds in high temperature environments. The presence of hydrogen accelerates corrosion. This mechanisms is also known as sulfidic corrosion.

As this is steam service, this damage mechanism can be ruled out.

2 Wet H2S Damage(Blistering/HIC/SOHIC/SSC)

This result in blistering and/or cracking of carbon steel and low alloy steels in wet H2S environments

As this is steam service, this damage mechanism can be ruled out.

3 Creep / Stress Rupture At high temperatures, metal components can slowly and continuously deform under load below the yield stress. This time dependent deformation of stressed components is known as creep. Also, deformation leads to damage that may eventually lead to a rupture.

As the threshold temperature of carbon steel is 353Deg C, this damage mechanism can be ruled out.

4 High temp H2/H2S Corrosion The presence of hydrogen in H2S-containing hydrocarbon streams increases the severity of high temperature sulfide corrosion at temperatures above about 500°F (260°C). This form of sulfidation usually results in a uniform loss in thickness associated with hot circuits in hydroprocessing units.

This damage mechanism is crack and not corrosion – therefore this can be ruled out.

5 Polythionic Acid Cracking

A form of stress corrosion cracking normally occurring during shutdowns, startups or during operation when air and moisture are present. Cracking is due to sulfur acids forming from sulfide scale, air and moisture acting on sensitized austenitic stainless steels. Usually adjacent to welds or high stress areas. Cracking may propagate rapidly through the wall thickness of piping and components in a matter of minutes or hours. Affected Materials- 300 Series SS, Alloy 600/600H and Alloy 800/800H.

This damage mechanism can be ruled out.

6 Naphthenic Acid Corrosion

A form of high temperature corrosion that occurs primarily in crude and vacuum units, and


downstream units that process certain fractions or cuts that contain naphthenic acids.

7 Ammonium Bisulfide Corrosion

Aggressive corrosion occurring in hydroprocessing reactor effluent streams and in units handling alkaline sour water. Several major failures have occurred in hydroprocessing reactor effluent systems due to localized corrosion.


8 Ammonium Chloride Corrosion

General or localized corrosion, often pitting, normally occurring under ammonium chloride or amine salt deposits, often in the absence of a free water phase


9 HCl Corrosion

Hydrochloric acid (aqueous HCl) causes both general and localized corrosion and is very aggressive to most common materials of construction across a wide range of concentrations. Damage in refineries is most often associated with dew point corrosion in which vapors containing water and hydrogen chloride condense from the overhead stream of a distillation, fractionation or stripping tower. The first water droplets that condense can be highly acidic (low pH) and promote high corrosion rates.


10 High Temperature Hydrogen Attack

High temperature hydrogen attack results from exposure to hydrogen at elevated temperatures and pressures. The hydrogen reacts with carbides in steel to form methane (CH4) which cannot diffuse through the steel. The loss of carbide causes an overall loss in strength.

A metallurgical report on the plate and steam analysis needs to be carried out. However, as this is steam service and this steam is supplied throughout the plant. There is no reported failures in other plants. This damage mechanism can be ruled out.

11 Oxidation

Oxygen reacts with carbon steel and other alloys at high temperature converting the metal to oxide scale. It is most often present as oxygen is in the surrounding air (approximately 20%) used for combustion in fired heaters and boilers. Oxidation of carbon steel begins to become significant above about 1000°F (538°C). Rates of metal loss increase with increasing temperature.

A metallurgical report on the plate and steam analysis needs to be carried out. However, as this is steam service and this steam is supplied throughout the plant. There is no reported failures in other plants. This damage mechanism can be ruled out.

12 Thermal Fatigue

Thermal fatigue is the result of cyclic stresses caused by variations in temperature. Damage is in the form of

On our case the startup and shutdown of equipment increase the susceptibility to thermal fatigue. The

cracking that may occur anywhere in a metallic component where relative movement or differential expansion is constrained, particularly under repeated thermal cycling.

number of start up and shutdown cycles needs to be controlled. Also the magnitude of temperature swing needs to be controlled also. This damage mechanism is a credible case however, can easily controlled by procedures for slow start up and shutdowns.

13 Sour Water Corrosion (acidic)

Corrosion of steel due to acidic sour water containing H2S at a pH between 4.5 and 7.0. Carbon dioxide (CO2) may also be present. Sour waters containing significant amounts of ammonia, chlorides or cyanides may significantly affect pH but are outside the scope of this section


14 Refractory Degradation

Both thermal insulating and erosion resistant refractories are susceptible to various forms of mechanical damage (cracking, spalling and erosion) as well as corrosion due to oxidation, sulfidation and other high temperature mechanisms.


15 Graphitization

Graphitization is a change in the microstructure of certain carbon steels and 0.5Mo steels after longterm operation in the 800°F to 1100°F (427°C to 593°C) range that may cause a loss in strength, ductility, and/or creep resistance. At elevated temperatures, the carbide phases in these steels are unstable and may decompose into graphite nodules. This decomposition is known as graphitization.

The design temperature are much lower and therefore this damage mechanism is ruled out

16 Temper Embrittlement

Temper embrittlement is the reduction in toughness due to a metallurgical change that can occur in some low alloy steels as a result of long term exposure in the temperature range of about 650°F to 1070°F (343°C to 577°C). This change causes an upward shift in the ductile-to-brittle transition temperature as measured by Charpy impact testing. Although the loss of toughness is not evident at operating temperature, equipment that is temper embrittled may be susceptible to brittle fracture during start-up and shutdown.


17 Decarburization

A condition where steel loses strength due the removal of carbon and carbides leaving only an iron matrix. Decarburization occurs during exposure to high temperatures, during heat treatment, from exposure to fires, or from high temperature service in a gaseous environment.

This damage mechanism can be ruled out due to the temperatures (204deg C only)and similar materials are existing in other plant in similar service

18 Caustic Cracking

Caustic embrittlement is a form of stress corrosion cracking characterized by surface-initiated cracks that

PWHT is recommended to be carried out on the channel head. A heat treatment at 1150°F (621°C) is

occur in piping and equipment exposed to caustic, primarily adjacent to non-PWHT’d welds. Affected Materials-Carbon steel, low alloy steels and 300 Series SS are susceptible. Caustic stress corrosion cracking typically propagates parallel to the weld in adjacent base metal but can also occur in the weld deposit or heat-affected zones.

considered an effective stress relieving heat treatment for carbon steel To rule this out, analysis of steam and metallographic examination needs to be carried out.

19 Caustic Corrosion

Localized corrosion due to the concentration of caustic or alkaline salts that usually occurs under evaporative or high heat transfer conditions. However, general corrosion can also occur depending on alkali or caustic solution strength.

As this is steam service and this steam is supplied throughout the plant. There is no reported failures in other plants. This damage mechanism can be ruled out.

20 Erosion / Erosion-Corrosion

Erosion is the accelerated mechanical removal of surface material as a result of relative movement between, or impact from solids, liquids, vapor or any combination thereof. Erosion-corrosion is a description for the damage that occurs when corrosion contributes to erosion by removing protective films or scales, or by exposing the metal surface to further corrosion under the combined action of erosion and corrosion.

Slight erosion related damage was observed on the plate. However, the thinning was very minor and was not attributed to the crack on the plate. Therefore this damage mechanism is ruled out

21 Carbonate SCC

Carbonate stress corrosion cracking (often referred to as carbonate cracking) is the term applied to surface breaking cracks that occur adjacent to carbon steel welds under the combined action of tensile stress in systems containing a free water phase with carbonate, where some amount of H2S is also present. It is a form of Alkaline Stress Corrosion Cracking (ACSCC).

A metallurgical analysis report on the plate needs to be carried out to rule it out. This damage mechanism can be ruled out on the basis that similar materials are existing in other plant in similar service.

22 Amine Cracking

Amine cracking is a common term applied to the cracking of steels under the combined action of tensile stress and corrosion in aqueous alkanolamine systems used to remove/absorb H2S and/or CO2 and their mixtures from various gas and liquid hydrocarbon streams. Amine cracking is a form of alkaline stress corrosion cracking. It is most often found at or adjacent to non-PWHT’d carbon steel weldments or in highly cold worked parts.

A metallurgical analysis report on the plate needs to be carried out to rule it out. This damage mechanism can be ruled out on the basis that similar materials are existing in other plant in similar service. PWHT of the Channel head is recommended.

23 Chloride Stress Corrosion Cracking

Surface initiated cracks caused by environmental cracking of 300 Series SS and some nickel base alloys under the combined action of tensile stress, temperature and an aqueous chloride environment. The presence of dissolved oxygen increases propensity for cracking


24 Carburization

Carbon is absorbed into a material at elevated temperature while in contact with a carbonaceous material or carburizing environment. Three conditions

A metallurgical analysis report on the plate needs to be carried out to rule it out. This is steam service and maximum temperature is

must be satisfied: 1) Exposure to a carburizing environment or carbonaceous material - (hydrocarbons, coke, gases rich in CO, CO2, methane, ethane) and low oxygen potential (minimal O2 or steam).. 2) Temperature high enough to allow diffusion of carbon into the metal [typically above 1100°F (593°C)]. 3) Susceptible material

only 204Deg C. This damage mechanism can be ruled out on the basis that similar materials are existing in other plant in similar service.

25 Hydrogen Embrittlement

A loss in ductility of high strength steels due to the penetration of atomic hydrogen can lead to brittle cracking. Hydrogen Embrittlement (HE) can occur during manufacturing, welding, or from services that can charge hydrogen into the steel in an aqueous, corrosive, or a gaseous environment

This is not a credible, this damage mechanism is ruled out.

26 Steam Blanketing

The operation of steam generating equipment is a balance between the heat flow from the combustion of the fuel and the generation of steam within the waterwall or generating tube. The flow of heat energy through the wall of the tube results in the formation of discrete steam bubbles (nucleate boiling) on the ID surface. The moving fluid sweeps the bubbles away. When the heat flow balance is disturbed, individual bubbles join to form a steam blanket, a condition known as Departure From Nucleate Boiling (DNB). Once a steam blanket forms, tube rupture can occur rapidly, as a result of short term overheating, usually within a few minutes.

This is not a credible case, this damage mechanism is ruled out.

27 Thermal Shock

A form of thermal fatigue cracking – thermal shock – can occur when high and non-uniform thermal stresses develop over a relatively short time in a piece of equipment due to differential expansion or contraction. If the thermal expansion/contraction is restrained, stresses above the yield strength of the material can result. Thermal shock usually occurs when a colder liquid contacts a warmer metal surface.

There is no evidence of a large thermal shock and therefore, this damage mechanism is ruled out.

28 Cavitation

Cavitation is a form of erosion caused by the formation and instantaneous collapse of innumerable tiny vapor

bubbles. Inadequate NPSH in pumps can result in cavitation


29 Graphitic Corrosion (see Dealloying)

a) Cast irons are comprised of graphite particles embedded in an iron matrix. Graphitic corrosion is a form of dealloying in which the iron matrix is corroded, leaving corrosion products and porous graphite.


b) Attack results in a porous structure with a loss of strength, ductility and density. It usually occurs under low pH and stagnant conditions, especially in contact with soils or waters high in sulfates.

30 Short term Overheating – Stress Rupture

Permanent deformation occurring at relatively low stress levels as a result of localized overheating. This usually results in bulging and eventually failure by stress rupture.

As no heat is exists and no bulging is observed - this is not a credible case, this damage mechanism is ruled out.

31 Brittle Fracture

Brittle fracture is the sudden rapid fracture under stress (residual or applied) where the material exhibits little or no evidence of ductility or plastic deformation. Affected Materials: Carbon steels and low alloy steels are of prime concern, particularly older steels. 400 Series SS are also susceptible.

The hydrotest case needs to be carefully analyzed and would require a FEA analysis looking at the stress on the components. This damage mechanism is a credible and will need to be further analyzed.

32 Sigma Phase/ Chi Embrittlement

Formation of a metallurgical phase known as sigma phase can result in a loss of fracture toughness in some stainless steels as a result of high temperature exposure. Affected Materials a) 300 Series SS wrought metals, weld metal, and astings. Cast 300 Series SS including the HK and HP alloys are especially susceptible to sigma formation because of their high (10% to 40%) ferritecontent. b) The 400 Series SS and other ferritic and martensitic SS with 17% Cr or more are also susceptible (e.g., Types 430 and 440). c) Duplex stainless steels.

The material is carbon steel and this damage mechanism can be ruled out.

33 885oF (475oC) Embrittlement

885°F (475°C) embrittlement is a loss in toughness due to a metallurgical change that can occur in alloys containing a ferrite phase, as a result of exposure in the temperature range 600°F to1000°F (316°C to 540°C).


34 Softening (Spheroidization)

Spheroidization is a change in the microstructure of steels after exposure in the 850°F to 1400°F (440°C to 760°C) range, where the carbide phases in carbon steels are unstable and may agglomerate from their normal plate-like form to a spheroidal form, or from small, finely dispersed carbides in low alloy steels like 1Cr-0.5Mo to large agglomerated carbides. Spheroidization may cause a loss in strength and/or creep resistance.


35 Reheat Cracking Cracking of a metal due to stress relaxation during Post Weld Heat Treatment (PWHT) or in service at elevated temperatures above 750°F (399°C). It is most often observed in heavy wall sections.


36 Sulfuric Acid Corrosion Sulfuric acid promotes general and localized corrosion of carbon steel and other alloys. Carbon


steel heat affected zones may experience severe corrosion.

37 Hydrofluoric Acid Corrosion

Corrosion by HF acid can result in high rates of general or localized corrosion and may be accompanied by hydrogen cracking, blistering and/or HIC/SOHIC


38 Flue Gas Dew Point Corrosion

Sulfur and chlorine species in fuel will form sulfur dioxide, sulfur trioxide and hydrogen chloride within the combustion products. At low enough temperatures, these gases and the water vapor in the flue gas will condense to form sulfurous acid, sulfuric acid and hydrochloric acid which can lead to severe corrosion.


39 Dissimilar Metal Weld (DMW) Cracking

Cracking of dissimilar metal welds occurs in the ferritic carbon steel or low alloy steel) side of a weld between an austenitic (300 Series SS or Nickel base alloy) and a erritic material operating at high. Cracking can result from creep damage, from fatigue cracking, from sulfide stress cracking or hydrogen disbonding

This is a credible case and will be studied further.

40 Hydrogen Stress Cracking in HF

Hydrogen Stress Cracking is a form of environmental cracking that can initiate on the surface of high strength low alloy steels and carbon steels with highly localized zones of high hardness in the weld metal and HAZ as a result of exposure to aqueous HF acid environments.


41 Dealloying (Dezincification/ Denickelification)

Dealloying is a selective corrosion mechanism in which one or more constituents of an alloy are preferentially attacked leaving a lower density (dealloyed) often porous structure. Component failure may occur suddenly and unexpectedly because mechanical properties of the dealloyed material are significantly degraded. This affect primarily copper alloys (brass, bronze, tin) as well as Alloy 400 and cast iron.


42 CO2 Corrosion

Carbon dioxide (CO2) corrosion results when CO2 dissolves in water to form carbonic acid (H2CO3). The acid may lower the pH and sufficient quantities may promote general corrosion and/or pitting corrosion of carbon steel.

As this is steam service and this steam is supplied throughout the plant. There is no reported failures in other plants. This damage mechanism can be ruled out.

43 Corrosion Fatigue A form of fatigue cracking in which cracks develop under the combined effects of cyclic loading and corrosion. Cracking often initiates at a stress concentration such as a pit in the surface. Cracking can initiate at multiple sites.

This is a credible case as multiple site cracks are observed and will be studied further. However, only minor corrosion was observed in the site visit.

Contrary to a pure mechanical fatigue, there is no fatigue limit load in corrosion-assisted fatigue. Corrosion promotes failure at a lower stress and number of cycles than the materials’ normal endurance limit in the absence of corrosion and often results in propagation of multiple parallel cracks. Crack initiation sites include concentrators such as pits, notches, surface defects, changes in section or fillet welds.

44 Fuel Ash Corrosion

Fuel ash corrosion is accelerated high temperature wastage of materials that occurs when contaminants in the fuel form deposits and melt on the metal surfaces of fired heaters, boilers and gas turbines. Corrosion typically occurs with fuel oil or coal that is contaminated with a combination of sulfur, sodium, potassium and/or vanadium. The resulting molten salts (slags) dissolve the surface oxide and enhance the transport of oxygen to the surface to re-form the iron oxide at the expense of the tube wall or component.


45 Amine Corrosion

Amine corrosion refers to the general and/or localized corrosion that occurs principally on carbon steel in amine treating processes. Corrosion is not caused by the amine itself, but results from dissolved acid gases (CO2 and H2S), amine degradation products, Heat Stable Amine Salts (HSAS) and other contaminants.


46 Corrosion Under Insulation (CUI)

Corrosion of piping, pressure vessels and structural components resulting from water trapped under insulation or fireproofing.


47 Atmospheric Corrosion

A form of corrosion that occurs from moisture associated with atmospheric conditions. Marine environments and moist polluted industrial environments with airborne contaminants are most severe. Dry rural environments cause very little corrosion.


48 Ammonia Stress Corrosion Cracking

Aqueous streams containing ammonia may cause Stress Corrosion Cracking (SCC) in some copper alloys. Carbon steel is susceptible to SCC in anhydrous ammonia. Anhydrous ammonia with <0.2% water may cause cracking in carbon steel.

PWHT eliminates susceptibility of most common steels. To rule this out, analysis of steam and metallographic examination needs to be carried out.

49 Cooling Water Corrosion

General or localized corrosion of carbon steels and other metals caused by dissolved salts, gases,

This type of damage mechanism can be ruled out in this case

organic compounds or microbiological activity.

50 Boiler Water / Condensate Corrosion

General corrosion and pitting in the boiler system and condensate return piping.


51 Microbiologically Induced Corrosion (MIC)

A form of corrosion caused by living organisms such as bacteria, algae or fungi. It is often associated with the presence of tubercles or slimy organic substances.


52 Liquid Metal Embrittlement

Liquid Metal Embrittlement (LME) is a form of cracking that results when certain molten metals come in contact with specific alloys. Cracking can be very sudden and brittle in nature.


53 Galvanic Corrosion

A form of corrosion that can occur at the junction of dissimilar metals when they are joined together in a suitable electrolyte, such as a moist or aqueous environment, or soils containing moisture.


54 Mechanical Fatigue

Fatigue cracking is a mechanical form of degradation that occurs when a component is exposed to cyclical stresses for an extended period, often resulting in sudden, unexpected failure. These stresses can arise from either mechanical loading or thermal cycling and are typically well below the yield strength of the material.

The only mechanical loading /thermal cycles loading are during start up and shutdown was reported. These are relative low and therefore this damage mechanism was ruled out.

55 Nitriding

A hard, brittle surface layer will develop on some alloys due to exposure to high temperature process streams containing high levels of nitrogen compounds such ammonia or cyanides, particularly under reducing conditions



A form of mechanical fatigue in which cracks are produced as the result of dynamic loading due to vibration, water hammer, or unstable fluid flow.

The plate is rigidly supported all around. There is report of vibration/water hammer, or unstable fluid flow from site. This damage mechanism is likely. However, if this is to be ruled out completely, then a complete vibration study of the system needs to be carried out. In the interim period a DP across the heat exchanger is recommended.

57 Titanium Hydriding

Hydriding of titanium is a metallurgical phenomenon in which hydrogen diffuses into the titanium and reacts to form an embrittling hydride phase. This can result in a complete loss of ductility with no noticeable sign of corrosion or loss in thickness


58 Soil Corrosion

The deterioration of metals exposed to soils is referred to as soil corrosion


59 Metal Dusting

Metal dusting is form of carburization resulting in accelerated localized pitting which occurs in carburizing

This type of damage mechanism can be ruled out in this case as the damage is cracks and service is

gases and/or process streams containing carbon and hydrogen. Pits usually form on the surface and may contain soot or graphite dust.

steam which does not have carbon or hydrogen.

60 Strain Aging

Strain aging is a form of damage found mostly in older vintage carbon steels and C-0.5 Mo low alloy steels under the combined effects of deformation and aging at an intermediate temperature. This results in an increase in hardness and strength with a reduction in ductility and toughness


61 Sulfate Stress Corrosion Cracking

Surface initiated cracks caused by environmental cracking of copper alloys in sulfate solutions over many years. Most commonly found in heat exchanger tubes, primarily in cooling water services

This type of damage mechanism can be ruled out in this case.

62 Phosphoric Acid Corrosion

Phosphoric acid is most often used as a catalyst in polymerization units. It can cause both pitting corrosion and localized corrosion of carbon steels depending on water content.


63 Phenol (carbolic acid) Corrosion

Corrosion of carbon steel can occur in plants using phenol as a solvent to remove aromatic compounds from lubricating oil feedstocks.


64 Ethanol Stress Corrosion Cracking

Surface-initiated cracks caused by environmental cracking of carbon steel under the combined action of tensile stress and a fuel grade ethanol (FGE, ASTM D 4806) or FGE / gasoline blend environment. Dissolved oxygen and the presence of variable stresses such as cyclic stress or component flexing, increase the propensity for cracking.


65 Oxygen-Enhanced Ignition and Combustion

Many metals are flammable in oxygen and enriched air (>25% oxygen) services even at low pressures, whereas they are non-flammable in air. The spontaneous ignition or combustion of metallic and nonmetallic components can result in fires and explosions in certain oxygen-enriched gaseous environments if not properly designed, operated and maintained. Once ignited, metals and non-metals burn more vigorously with higher oxygen purity, pressure and temperature


66 Organic Acid Corrosion Of Distillation Tower Overhead Systems

Organic compounds present in some crude oils decompose in the crude furnace to form low molecular weight organic acids which condense in distillation tower overhead systems. They may also result from additives


used in upstream operations or desalting. These naturally occurring acids may contribute significantly to aqueous corrosion depending on the type and quantity of acids, and the presence of other contaminants.

Das Island Division



APPENDICES

8.4 Level -1 assessment

Check the Thickness of Pass Partition Plate as per TEMA Ninth Edition -2007 and

ASME Sec VIII

The fillet weld size as per latest TEMA is 3/4t = 9.75mm on both sides. Looking at the

manufacturer’s drawings, the fillet weld size was found to be 6 CFW-continuous fillet weld.

Also, the ADMA OPCO Inspection Division recommendation of API-660 of full penetration

weld 50mm/2inch if welded on both sides is endorsed.

Also, enclosed is the Process Industry Practices (PIP) standard reference

PWHT also is to be reviewed due to the proximity of the two welds.

A review of the fillet weld design is required. A closer examination of the recommendation

of Process Industry Practices, API660 and TEMA is required. Enclosed is the hand

calculations done.

065656

Typewritten Text

065656

Typewritten Text

065656

Typewritten Text

065656

Typewritten Text

8.4

065656

Text Box

8.4

065656

Text Box

8.4

065656

Text Box

8.4

Das Island Division



APPENDICES

8.5 Metallurgy assessment

ADMA-OPCO Repetitive rupture of Channel head pass partition plate of US Heat Exchanger – Das Island Investigation Report

2013 Failure of US Heat Exchangers

Root Cause Analysis (RCA)

Prepared By Tarek A. Hassan (DFISL) Das Integrity Svs. Eng. (A1)

Page 1 of 10


TABLE OF CONTENTS

1.0 EXECUTIVE SUMMARY....................................................................................................................... 3

2.0 DESCRIPTION ....................................................................................................................................... 3

3.0 BRIEF HISTORY ................................................................................................................................... 4

4.0 INVESTIGATION TEAM MEMBER ..................................................................................................... 5

5.0 TOR FOR TASK FORCE ...................................................................................................................... 5

6.0 TF KICKOFF MEETING ........................................................................................................................ 5

7.0 INSPECTION ......................................................................................................................................... 6

8.0 ROOT CAUSE ANALYSIS ................................................................................................................... 8

9.0 CONCLUSIONS ..................................................................................................................................... 9

10.0 RECOMMENDATIONS ....................................................................................................................... 10

11.0 LESSONS LEARNT ................................................................................... Error! Bookmark not defined.

12.0 APPENDIX .................................................................................................. Error! Bookmark not defined.

Page 2 of 10


1.0 EXECUTIVE SUMMARY It was reported that repetitive ruptures occurred on channel head pass partition plate of Heat exchanger for US columns. After the reported failure of Crude Oil Charge heaters for US column 400, visual inspection revealed that the ruptured partition plate (broken into pieces) was resulted of crack propagation on the weld toe on both side of welding at inlet steam side. There was no evidence of ductility or plastic deformation (brittle), this rupture have occurred due to fatigue/cyclic over stress (possible steam hammering effect at inlet side due to suspected steam condensate trapped on steam flow due to insufficient steam traps performance) During the course of repairs after the reported failures, partition plates were replaced by inadequate material with low thickness plate (10mm) and incorrect size of drain hole (22mm) against the original plate thickness of 13 mm with 13 mm drain hole as per manufacture construction drawing. The existing 10.0 mm thickness pass partition plate is not in compliance with TEMA requirement of 12.0 mm minimum thickness plate if it is constructed from carbon steel material for Channel head with the size of 660 mm diameter. (TEMA - Tube Exchangers Manufacturing Association). The 22 mm diameter drain hole on pass partition plate possibly caused vibration & induces stress on the plate due to Nozzle effect (significant steam pressure difference between inlet and outlet) Modification/changes from original design thickness were implemented without following the ADMA OPCO’s PMR procedure.

2.0 DESCRIPTION

A cylindrical carbon steel pressure vessel with one dished end and one flanged end (U-tube type), externally insulated and horizontally mounted on two steel saddles located on two concrete plinths.

Manufacturer - Robert Jenkins & Co. Ltd., Rotherham, England. Design Pressure - 175 psig (tube side) , Test pressure : 263 psi Design Pressure - 350 psig (shell-side), Test pressure : 525 psi Fluid Service - Steam (tube side/channel head), Crude oil (shell side) Dimensions - Vessel 4838mm long x 660mm i/d x 13mm thick.

Commissioned - 20/01/82

Page 3 of 10


3.0 BRIEF HISTORY We experienced the reoccurrence of frequent failures on pass partition plate of the heat exchangers channel heads since 2008, US heat exchangers have been operational since 1981 (32years). The following are the history of failures of pass partition plate on each heat exchanger for US columns. A Task Force was formed under the sponsorship of MDO to investigate the repetitive failure of channel head pass partition plate and to develop Rout Cause Analysis Report. The objectives of the investigation are to examine and identify root causes for this failure and make appropriate recommendations to prevent reoccurrence. Several meetings were conducted on Das Island to align the task force members on the objectives and deliverables.

Sl.no Description Commissioning Failures of Pass partition plate Action during Investigations

Remarks

1 Heat exchanger for US Column 401 (43100344)

Jan 1982 March 2008, corroded pass partition plate replaced

Feb 2013, Rupture/ broken. Replaced with 10 mm thickness plate with 13 mm drain hole

Decided to replace the 10mm plate with 13 mm hole to 13 mm plate withoit hole on trial basis as per PMR, but PMR not approve, partition plate should be replaced specified 13mm thickness plate

Two times replaced. Started failure occur in year 2008


Jan 1981 Dec 2011, Rupture/ broken pass partition plate replaced

April 2013, Rupture/ broken pass partition plate

April 2013, replaced with 13 mm thickness plate with 13 mm drain hole

two time replaced


Oct 1981 May 2012, Rupture/broken pass partition plate replaced

March 2013, Rupture/ broken pass partition plate

March 2013, replaced with 13 mm thickness plate with 13 mm drain hole

two time replaced


March 1982 Feb 2008, Rupture/broken pass partition plate replaced

March 2011, rupture/broken

March 2013, replaced with 13 mm thickness plate with 13 mm drain hole

Three times replaced. Started failure occur in year 2008

Page 4 of 10


4.0 INVESTIGATION TEAM MEMBER

INVESTIGATION TEAM

Tarek A. Hassan / Mohamed Al Ansari Taskforce T/L ID

Aref A. Ahmed / Soud DPOTL DIAU

Moustafa Dawoud /Dheya Al Afeefi DMTL DIAU

Abdallah Alhouig

DMMSL DIAU

Ali Al Hosani / Lione HSESL HSED

5.0 TOR FOR TASK FORCE 5.1 Review the design drawings, inspection report, Process parameters, Functional

checking of instrument upstream and down steam, advice the adequacy of the present procedures, methodologies and advise areas of improvement.

5.2 Identify any acts of omissions/sub–standard practices that could lead to unfavorite consequences.

5.3 To carry out gap analysis and identify gaps. 5.4 To identify the root causes of the incident. 5.5 To recommend the remedial measures. 5.6 To develop lesson learnt.

6.0 TF KICKOFF MEETING The Task force member’s conducted a kickoff meeting on February 23rd, 2013 to address the failure process, to be familiar with the TF objectives and to agree on the way forward.

The Task force members visited the site to inspect the ruptured pass partition plates, to discuss the failure with DED, inspection, operation and maintenance, to address the outcome and propose root causes along with the recommendations.

Page 5 of 10


7.0 INSPECTION Preliminary inspection revealed that the rupture could have occurred on pass partition plated due to low thickness plate used and inadequate drain hole size against the original manufacture construction drawings as indicated in the attached initial file note.

Initial Inspection.docx

7.1 FINDINGS: • The pass partition plate was found ruptured (broken into two pieces). It appears that

the crack propagated from the weld toe of pass partition plate on both side of welding at inlet steam side.

• There was no evidence of ductility or plastic deformation (brittle) at the breaking surfaces.

• 22 mm diameter drain hole was noticed on pass partition plate. • Erosion-corrosion was evident over the surface of the partition plate, cover plate

and drain hole. • The thickness of the existing pass partition plate was found to be 10.0mm

The followings were identified as the main contributing factors lead to failures:

The first factor is the steam/condensate hammering effect on pass partition plate due to increase in steam flow due to increase in Oil production since 2008. We need to ensure the condensate removal (Knock out) prior to interring the HE. The second factor contributing to the problem was low thickness plate 10 mm with 22 mm holes used against the original design thickness of 13.0 mm with 13 mm holes as per original construction drawings. NOTE: The original Pass partition plate was installed in accordance with BS 1501-151-28A in year 1980, Original thickness: 13mm, 6 mm continuous fillet weld on both sides as per drawing. However, the new replacement plate material is ASTM SA 516 grade 70 and thickness 13.0 mm. (Assumed the grade is A 516 Gr 70 as per Maximo Cat. ID:99563).

Page 6 of 10


Pass partition plate

Cover plate with groove Channel head

Crack on pass partition propagate on toe of weld

Page 7 of 10


7.2 REVIEW OF HISTORICAL FILE, ORIGINAL CONSTRUCTION DRAWINGS AND TEMA STANDARD:

All relevant original construction drawings are reviewed and confirm the following:-

The original construction drawing revealed that the thickness of pass partition is 13 mm with 13 mm diameter condensate drain hole. As per TEMA, the minimum required thickness of pass partition plate is 12.0 mm if it is carbon steel material for diameter 660 mm Channel head.

7.3 SITE VERIFICATION:

The steam/condensate traps provided at down stream Heat Exchanger was brought to workshop and functional test was carried by maintenance and it was found to be satisfactory. Condensate pumps are provided at the D/S of the heat exchangers and considered as a backup for condensate traps.

The functions of all steam/condensate traps provided at upstream Heat Exchangers were verified and it was found to be satisfactory, as per the energy conservation task force most of the traps were replaced, and some of them yet to be replaced.

PCV for steam at upstream Heat exchanger functional tests were carried out and found to be satisfactory 7.4 PLANT MODIFICATION REQUEST:

A PMR was raised to replace the existing 10 mm pass partition plate of Heat Exchanger for column 400 with 13mm thick plate without hole on trial basis to verify the drain hole as a contributing factor for failure. DED reject the PMR and recommend to replace the ruptured plate with 13mm plate thickness and 13mm condensate drain hole. Also they recommend applying a post weld heat treatment to relieve residual stresses.

8.0 ROOT CAUSE ANALYSIS Inspection report and file note revealed that the following; • The correct size plate 13.0 mm was not used due to non-availability of adequate

material at that time of 1st failure and replacement of pass partition plate . • They did not provide correct size drain hole 13mm due to not verifying the original

construction drawings. • Not followed the Company’s PMR procedure when there is design

changes/modification taking place. • However, the 1st failure could be the steam hammering effect due to the increase in

steam flow in 2008 in addition to the age of the equipment nearly 28 years. Page 8 of 10


8.1 REVIEW OF ISSTL MEMO’s FOR ROOT CAUSE ANALYSIS

8.1.1 Initial report from ISSTL for repetitive failure of pass partition plate revealed that the observed values may be attributable to fatigue vibration acting on the reduced plate thickness of the pass partition plate which has exacerbated by the increasing of the steam flow rate causing hammering on the partition plate.

8.1.2 The ruptured pass partition plates were sent for lab analysis through ID in Abu

Dhabi and report received from ISSTL revealed that the cause of failure is due to the pre-existing plate manufacturing defects (i.e. voids, laminations and inclusions).

It’s also noted that the tensile strength of the plate material does not meet the requirements of the specified grade ASTM A 516 Gr. 70.

9.0 CONCLUSIONS The repetitive failure have occurred on the channel head pass partition plate of US Heat exchanges are mainly due to the followings:-

9.1 Due to the unavailability of design 13mm thickness plate, low thickness 10 mm plate

was used with 22 mm drain holes against the original design thickness of 13 mm with 13 mm drain hole as per original construction drawing when 1st failure occurred.

9.2 The use of unspecified material with pre-existing manufacturing defects (i.e. voids, laminations and inclusions).

9.3 The fracture has simultaneously at multiple sites along the length on tube side where cyclic stress condition due to steam pressure can be expected and has propagated through the thickness connecting the voids, finally rupturing the plate in ductile manner.

9.4 Modification/change from original design thickness was implemented without following the ADMA OPCO’s PMR procedure.

Page 9 of 10


10.0 RECOMMENDATIONS To minimize any further incident of failure, the following recommendations are made:

10.1 Pass partition plate of US Heat Exchanger 401 needs to be replaced with the specified material acc. to ASTM SA 516 Gr. 70, 13mm plate thickness and 13mm condensate drain hole (currently is 10mm thickness)

10.2 Use original specified material (BS 1401-151 Gr 28A) or equivalent 10.3 Use 13.0 mm thickness plate with 13 mm condensate drain hole as per original

construction drawings. 10.4 Welding of new partition plate shall be by complete fillet weld from both sides. Carry

out full penetration at 50 mm from the gasket face (double V joints) as per API 660. 10.5 Apply a post weld heat treatment to relieve residual stresses and to obtain hardness

reading at weld vicinity to ensure effective treatment.

11.0 LESSONS LEARNT 11.1 Maintenance and Inspection to ensure that any repair/replacement is carried out as per

original construction drawings and relevant international code and standards.

11.2 Maintenance to ensure that sufficient material are made available for repair/replacement with relevant test certificate to avoid using unidentified material on urgent basis.

11.3 Any Modification/changes shall be carried out through PMR.

12.0 APPENDIX Construction Drawings for Heat Exchanger and Welding Procedure

US Heat Exchangers 1.pdf






Page 10 of 10

Das Island Division



APPENDICES

8.6 FEA for the design base case

a) With drain Hole

b) Without drain Hole

Page 1 of 12 10mm Plate With a 13mm Hole - Stress Analyses Report

Stress Analysis Results

13mm Plate With a 13mm Drain hole

A stress analysis was carried out on the 13mm pass partition plate with a 13mm dia hole at the center of the plate. The following cases were

analyzed:

1. Hydro test case at hydrotest pressure of 263psig

2. Operating Cases – 35psig operating pressure with 18psig differential pressure across the plate

3. Max design Case – 175psig Design Pressure with 12psig differential pressure across the plate

CASE DESCRIPTION OUTCOME RECOMMENDATION

Hydrotest case

The channel head was subjected to hydrotest pressure of 263psig. Pass partition plate had no differential pressure across the plate.

A linear static analysis was carried out. The maximum stress in the channel head were found to be 107.2Mpa and was found to be within the allowable limits(120Mpa). Max Stress=107.2Mpa < allowable Stress 120Mpa at 37 deg C Therefore Acceptable.

None.


Hydrotest Case

13mm pass partition plate with 13mm

drain hole

Internal Pressure=263psig


Hydrotest Case

13mm pass partition plate with 13mm

drain hole




Operating Cases 35psig operating pressure with 18psig differential pressure across the plate

A linear static analysis was carried out. The maximum Stress of 160.3Mpa was found at the four corners of the plate. At 204Deg C the metal allowable stress is 108Mpa. Max Stress=160.3Mpa > allowable Stress 108Mpa. Therefore Not Acceptable.

A lower differential pressure was to be maintained. The welding the corners to be full penetration. PWHT shall be carried out to relieve stress at the joints.


Operating Case

13mm plate thick Dividing plate with 13mm hole


Differential pressure across the plate =18psig


Operating Cases





Operating Case





Operating Case






Design Base Case 175psig Design Pressure with 12psig differential pressure across the plate

A nonlinear static analysis was carried out to achieve the convergence. The maximum stress was found to be 117.6Mpa. At 204Deg C the metal allowable stress is 108Mpa. Max Stress=117.6Mpa just above the allowable Stress 108Mpa. Due to this, this case is considered as the Base case. Therefore Acceptable.

Same as above The differential pressure shall be maintained Below the design value of 12psig in all cases. A DP is required to be installed across the heat exchanger and monitored the differential pressure. Further it is suggested to install alarm and trip setting of 12psig.


Base Case

13mm plate thick Dividing plate




Base Case





Base Case




Page 1 of 28 10mm Plate Without Hole Stress Analyses Report


13mm Plate Without drain hole

A stress analysis was carried out on the 13mm plate pas partition plate. The following cases were analyzed:



3. Operating case – 35Psig operating Pressure with 30psig differential pressure across the plate

4. Max design Case – 175psig Design Pressure with 12/18/24/30psig differential pressure across the plate


Hydrotest case


A linear static analysis was carried out. The maximum stress in the channel head were found to be 110.7Mpa and was found to be within the allowable limits(120Mpa). Max Stress=110.7Mpa < allowable Stress 120Mpa at 37 deg C Therefore Acceptable.

None.


Hydrotest Case




Hydrotest Case




Hydrotest Case




Hydrotest Case






A linear static analysis was carried out. The maximum Stress of 138.1Mpa was found at the four corners of the plate. At 204Deg C the metal allowable stress is 108Mpa. Max Stress=138.1Mpa > allowable Stress 108Mpa. Therefore Not Acceptable.

A lower differential pressure was to be maintained. The welding the corners to be full penetration. PWHT shall be carried out to relieve stress at the joints.


Operating Case





Operating Case





Operating Cases





Operating Case






Operating case 35Psig operating Pressure with 30psig differential pressure across the plate

A nonlinear static analysis was carried out to achieve the convergence. The maximum stress was found to be 226.3Mpa. At 204Deg C the metal allowable stress is 108Mpa. Max Stress=226.3Mpa > allowable Stress 108Mpa. Therefore Not Acceptable.

Same as above


Operating Case





Operating Case





Operating Case





Operating Case





Operating Case







A nonlinear static analysis was carried out to achieve the convergence. The maximum stress was found to be 111Mpa. At 204Deg C the metal allowable stress is 108Mpa. Max Stress=111Mpa just above the allowable Stress 108Mpa. Due to this, this case is considered as the Base case. Therefore Acceptable.

Same as above The differential pressure shall be maintained Below the design value of 12psig in all cases. A DP is required to be installed across the heat exchanger and monitored the differential pressure. Further it is suggested to install alarm and trip setting of 12psig.


Base Case





Base Case





Base Case





Base Case





Base Case





Base Case






Max design Case 175psig Design Pressure with 30psig differential pressure across the plate

A nonlinear static analysis was carried out to achieve the convergence. The maximum stress was found to be 244Mpa. At 204Deg C the metal allowable stress is 108Mpa. Max Stress=244Mpa > allowable Stress 108Mpa. Therefore Not Acceptable.

Same as above


Design Case





Design Case





Design Case





Design Case




Das Island Division



APPENDICES

8.7 Non-lenear Analysis Results (10mm pass partition Plate)



10mm Plate Without drain hole

A stress analysis was carried out on the 10mm plate pas partition plate. The following cases were analyzed:



3. Operating case – 35Psig operating Pressure with 30psig differential pressure across the plate

4. Design Case – 175psig Design Pressure with 12 psig differential pressure across the plate

5. Max design Case 175psig Design Pressure with 18psig differential pressure across the plate


Hydrotest case


The maximum stress in the channel head were found to be 90.1Mpa and was found to be within the allowable limits(108Mpa). Max Stress=90.1Mpa < allowable Stress 108Mpa. Therefore Acceptable.

None.


Hydrotest Case

10mm plate



Hydrotest Case

10mm plate



Hydrotest Case

10mm plate



Hydrotest Case

10mm plate



Hydrotest Case

10mm plate



Hydrotest Case

10mm plate





A non-linear analysis was carried out as the convergence was not achieved during linear analysis. The maximum Stress of 196.1Mpa was found at the four corners of the plate. At 204Deg C the metal allowable stress is 108Mpa. Max Stress=196.1Mpa > allowable Stress 108Mpa. Mini Specified Yield = 211Mpa @204Deg C Therefore Not Acceptable.

To increase the thickness of the plate to 13mm minimum. The welding the corners to be full penetration. PWHT shall be carried out to relieve stress at the joints.


Operating Cases

10mm plate




Operating Cases

10mm plate




Operating Cases

10mm plate




Operating Cases

10mm plate




Operating Cases

10mm plate





Operating case 35Psig operating Pressure with 30psig differential pressure across the plate

A nonlinear analysis was carried out using the Riks method to achieve the convergence due to plastic deformation. The maximum stress was found to be 327Mpa. At 204Deg C the metal allowable stress is 108Mpa. Max Stress=327Mpa > allowable Stress 108Mpa. Mini Specified Yield = 211Mpa @ 204 Deg C The stress has exceeded the yield strength. Therefore failure of the plate is expected. Therefore Not Acceptable.

Same as above Proper measures are to be in place to ensure that the deferential pressure across the pass partition plate is not exceeded. The Differential pressure gauge to be installed across the Heat exchanger with alarm settings.


Operating Cases

10mm plate




Operating Cases

10mm plate




Operating Cases

10mm plate




Operating Cases

10mm plate






A nonlinear analysis was carried out to achieve the convergence as plastic deformation. The maximum stress was found to be 139.7Mpa. At 204Deg C the metal allowable stress is 108Mpa. Max Stress=139.7Mpa > allowable Stress 108Mpa. Therefore Not Acceptable.

Same as above


Design Case

10mm plate




Design Case

10mm plate




Design Case

10mm plate




Design Case

10mm plate





Max design Case 175psig Design Pressure with 18psig differential pressure across the plate

A nonlinear analysis was carried out to achieve the convergence as plastic deformation. The maximum stress was found to be 204.2Mpa. At 204Deg C the metal allowable stress is 108Mpa. Max Stress=204.2Mpa > allowable Stress 108Mpa. Mini Specified Yield = 211Mpa @ 204 Deg C The stresses are very close to the yield strength. Therefore plastic deformation of the plate is expected. Therefore Not Acceptable.

Same as above


Design Cases

10mm plate




Design Cases

10mm plate




Design Cases

10mm plate




Design Cases

10mm plate



Das Island Division



APPENDICES

8.8 Proposed Solution (to mitigate high differential pressure Across

the pass partion Plate)

Proposed Solution –Stress Analysis (Boundary Condition)

Support

Proposed Solution –Stress Analysis (Load)

Design Pressure = 175psig

Proposed Solution –Stress Analysis (Load)

Differential Pressure = 30psig

Proposed Solution –Stress Analysis




Das Island Division



APPENDICES

8.9 Drawings

Documents

Stress Analysis Report-US Channel Head-2