(04) Erling Ryengen

8/18/2019 (04) Erling Ryengen

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part of Aker

© 2008 Aker Solutions

Materialer / Korrekt Varmebehandling

Ventiler i Olje- og Gassindustrien

Stavanger 3. – 4. mars 2010

Erling Ryengen

Aker Solutions

Oslo


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© 2008 Aker Solutions part of Aker Revision 01.03.2010

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Materials / Correct Heat Treatment

This presentation includes,

● Examples of faulty heat treatments by some case stories

■ Case 1: A DN ¾” valve in duplex SS material, A182 grade F51,fractured after welding.

■ Case 2: Failure of a welding procedure qualification test usinga DN 2” flange in material A694 grade F65 as test material.

■ Case 3: Failure of a production test of a DN 8” weldolet in material A694 grade F65 welded onto a vessel.

■ Case 4: Leakage in a 25Cr duplex SS elbow.

● Summary of the case stories

● Quality assurance/control of heat treatment


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Slide 3

Faulty Heat Treatment

Case 1: DN ¾” valve in duplex SS material, A182 grade F51,fractured after welding.

● Description:

A DN ¾” valve in duplex SS material, A182 grade F51, fractured afterwelding of one end. The fracture was partly in the weld and partly in thebase material.

Subsequent impact testing of the fractured valve body gave extremelylow values, 2J, 3J and 3J, when tested at specified test temperature

– 46 C.

Impact testing of additional valves showed impact values belowminimum specified, 45J/35J at – 46 C, for more than 50 % of the total

number of valves tested. The whole delivery was questioned.

● Material certificate:

The corresponding material certificate showed good results withaverage impact value of 287J at -46 C.


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Slide 4



● Results of investigations:

Further investigations concluded that the low impact values werecaused by improper forging and unsatisfactory (un-qualified) heattreatment.

Test pieces for material certification was taken from special testforgings and not from production forgings.

All delivered valves, 524 off , were replaced.

A general warning was issued to other developments to check valvesfrom this manufacturer.


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Slide 5



● Results of investigations from another project

Due to the general warning being issued also other projects had tocheck valves from the same manufacture.

The results of the original investigation were confirmed.

Inadequate heat treatment and use of unsatisfactory heat treatmentfurnac(es) were considered to be the main reasons for the poor valves.

The problem proved to include valves also in materials■ A182 grade F53 (super duplex SS)■ A350 grade LF2 (low temperature carbon steel)

■ A350 grade LF3 (3½ % Ni-steel)

More than 1000 valves already installed into the lines had to bereplaced at a late stage in the project.


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Slide 6



Microstructure in failed super duplex valves.


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Slide 7

Faulty heat treatment

Case 2: Failure of a welding procedure qualification test usinga DN 2” flange in material A694 grade F65 as test material.

● Description:

A DN 2” flange in material A694 grade F65 was used as material in awelding procedure qualification test.

Impact testing at -40 C of the qualification weld showed lower andlower values from FL to FL+5mm.

In unaffected base materials the results were between 7J and 13J at

-40 C.

● Material certificate:The corresponding material certificate showed good results withaverage impact value of 150J at -40 C.


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Slide 8




After a visit to the manufacturer and the heat treatment shop it wasconcluded that the cause for the low impact values was un-satisfactorystacking of the flanges during the heat treatment.

A test was made by re-heating some flanges with satisfactory stackingresulting in impact values of 215J – 255J at -40 C.

All flanges were returned to the manufacturer for re-heat treatment.


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Slide 9



Stacking of flanges during heat treatment, which failed impact testing.


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Case 3: Failure of a production test of a DN 8” weldolet inmaterial A694 grade F65 welded onto a vessel.

● Description:

During a production test of a weldment between a DN 8” weldolet inmaterial A694 grade F65 welded onto a vessel in material x65 lowimpact test results were experienced when tested at -46 C.

● Subsequent impact testing of the base material of the weldolet gave asresults,

■ Longitudinal direction: 21-35-21 Ave 27J

■ Transverse 20-16-18 Ave 18J

● Material certificate:The corresponding material certificate showed good results with impactvalues between 132J - 240J at -50 C.


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Slide 11




It was concluded that the low impact values were caused by un-satisfactory heat treatment.

The DN 8” weldolets, which already were welded onto the vessel, werescrapped resulting in major repairs (see figures) and delays.


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Slide 12



Welding of weldolets onto the vessel.


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Slide 13



Repair of vessels by removing the defective weldolets.


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Slide 14


Case 4: Leakage in a 25Cr duplex SS elbow.

● Description After being welded into a pipe system a DN 2”, sch 10s, elbow inmaterial 25Cr duplex SS, started to leak after the piping system hadbeen tested by means of circulating sea water for approximately 60days.


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Slide 15



● Investigations carried outLaboratory examination of the failed elbow showed a defective

microstructure with intermetallic phases as shown on enclosed pictures.

Subsequent investigations and verifications at the manufacturer

concluded that poor heat treatment due to a combination in first hand ofstacking and short holding times have caused poor metallurgical

properties in the fittings.

The poor heat treatment practice had started after installation of a new

heat treatment furnace and has been ongoing for approximately 2 years.

This means that many thousands of fittings may be affected.

For Aker Solution alone more than 30 different projects have been

affected resulting in replacement of a large number of 22Cr duplex and

25Cr superduplex fittings.


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Slide 16



● Material certificates

■ All material certificates showed acceptable results.

Centre of the bend, mid thickness Adjacent to HAZ

Microstructure of originally failed fittings


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Slide 17



Stacking of components

Original stacking of components. Such

a load was also used for verification of

the holding times by placing

thermocouples in the middle of the load

and in two of the corners.

Satisfactory stacking


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Slide 18



Verification of heat treatment procedure


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Slide 19

Summary of Case Stories

■ The case stories shows that inadequate heat treatment affects,

● All type of components

● All type (grade) of materials

● Properties of the materials in an adverse way

■ Brittleness

● Carbon steel● Low alloyed steel● Ferritic/martensitic stainless steels (eg. 13 % Cr)● Duplex stainless steels

■ Corrosion● Ferritic/martensitic stainless steels (eg. 13 % Cr)● Duplex stainless steels● Austenitic stainless steel

■ Strength● All materials● But especially quenched & tempered steels


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Slide 20


Acknowledgement: Statoil, Trondheim


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■ All material certificates showed good test results well inside theapplicable specifications

■ All cases were detected BY CHANCE

● Can we live with that ?


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Slide 22

Quality Assurance/Control of Heat Treatment

■ Assessment of heat treatment furnaces and facilities

● Condition of heat treatment furnaces

● Temperature uniformity check of heat treatment furnace

Ref. NORSOK standard M650, rev. 3, Annex B● Temperature control and calibration of thermocouples

● Recording of heat treatment cycle

● Capacity and stirring of quenching bath

● Temperature measurement and recording of quenching bath

● Layout of heat treatment facilities. Maximum transfer time ofcomponents from furnace into quenching bath shall be 60s.


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Slide 23


■ Heat treatment procedure

● Heat treatment parameters

■ Loading temperature of furnace

■ Heating rate

■ Holding temperature

■ Holding time

● Stacking of components

■ Free circulation of air and water shall be ensured around each

component

■ Sketch


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Slide 24


Free circulation of air and water shall be ensured around each component


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Slide 25


■ Heat treatment procedure, cont.

● Location of component for production testing within the heattreatment load

■ Normally the component for production testing should be located in

the middle of the load

● Documentation of heat treatment load■ Sketch

■ Photograph

● Traceability

■ Of components within each heat treatment load

■ Of the heat treatment load

■ Of component(s) used for production testing within each load


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Slide 26


■ Verification of heat treatment procedure

● The objective is to check that,■ All components within a load reach specified temperature

■ The start and length of the holding time is sufficient

● To be carried out on,

■ The heaviest load to be heat treated or■ The most densed stacked load to be heat treated

■ To be agreed

● The verification is carried out by fixing mobile thermocouples onto the

components at different locations in the load and compare with thecontrolling thermocouple of the furnace

■ As a minimum thermocouples should be fixed onto a component in

the middle of the load and in the corner of the load closest to the

furnace door.


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Slide 27


Verification of heat treatment procedure


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■ Witnessing of heat treatments

● Heat treatment must be identified as a separate activity in the Inspectionand Test Plans

● Witnessing is probably the most effective activity to ensure correct

heat treatment

● Should be carried out to a larger extent than today

■ Heat treatment has a high focus in the ongoing revision work of

NORSOK standards

● In M630, ”Material Data Sheets”, requirements to stacking of

components will be included

● The planned revision this year of M650, ”Qualification of Manufacturers

of Special Alloys”, will probably include more strict requirements to both

heat treatment equipment and - procedures and require verification of

heat treatment procedures.

(04) Erling Ryengen

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