EISENBISE-High Energy Piping Presentation

8/10/2019 EISENBISE-High Energy Piping Presentation

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High Energy

Piping



Piping Systems usually

contained/considered within the High

Energy Piping Concept:

Main Steam

Hot Reheat Cold Reheat

Feedwater Discharge

Extraction Steam if an alloy system Auxiliary Steam if an alloy system



Present Materials Of Choice

Main Steam Grade-91 Seamless Alloy Steel

Grade-92 Seamless Alloy Steel (ASME Code Case 2179-3 andB31 Case 183) Grade-92 is currently being Balloted in B31.1 foracceptance into the Code and subsequently the Case annulled

Hot Reheat Grade-91 Seamless Alloy Steel

Grade-92 Seamless Alloy Steel (ASME Code Case 2179-3)

Cold Reheat

Seamless and Welded Carbon Steel Grade B and C Seamless and Welded Alloy Steel - Grade-11



Present Materials Of Choice

Feedwater Seamless Carbon Steel Grade B and C

Extraction Steam

Seamless Carbon Steel Grade B & C

Seamless Alloy Steel – Grade-11 and Grade-22

Auxiliary Steam

Seamless Carbon Steel Grade B

Seamless Alloy Steel - Grade-91 and Grade-22



GRADE-91

Grade-91 is a modified 9% Chrome 1% MolyAlloy Steel that was developed in the USA in the

seventies and eighties and has now reached a stage

of operational qualification for use in piping

systems for both new designs and retrofit actions.



GRADE-92 – ASME Code Case

2179-3 AND B31 CASE 183

Grade-92 is a modification of P-91 with 2%Tungsten being added as a constituent replacingmost of the moly. Grade-92 was primarilydesigned as a piping material for advanced steamconditions and is seen as a major improvement onGrade-91, with a rupture strength advantage(Allowable Stress Values) of approximately 16 to

30% over Grade-91 at the elevated temperatures.



Creep Strength Enhanced Ferritic

Steels

Grade 91 and Grade 92 steels are known as Creep Strength

Enhanced Ferritic Steels.

These steels differ from the “traditional” ASME Code

materials ( Grade 11 and Grade 22 for example) inasmuch

as they gain their exceptional high temperature creep

rupture properties based upon a specific condition of

microstructure, rather than the primary chemical

composition of the materials.

This subsequently means that manufacturing andfabrication processes must be controlled very carefully to

ensure that the appropriate microstructure is achieved,

failing which the material will suffer a significant

reduction in its creep strength properties.



MAIN STEAM WALL THICKNESS COMPARISONS

FOR DIFFERENT MATERIALS



Advantages of P-91 & P-92

High Creep Rupture Strength (Allowable Stress)

Excellent Toughness

Lighter Weight from Wall Thickness Reductions Higher Temperatures

More Flexible Piping Systems

Lower Support Weight

Lower Loads at Terminal Points



Disadvantages of Grade-91

Higher Pipe/Fitting/Valve Cost

Unforgiving if Proper Processing Steps are Omitted or missed

Longer Lead Time Processing during fabrication & erection

Heat Treatment both for bends and welds

Weld Filler Material

Cost Availability



Disadvantages of Grade-92

Higher Pipe/Fitting/Valve Cost than P-91

Unforgiving if Proper Processing Steps are Omitted ormissed

No Real History here in the USA

Longer Lead Time Processing during fabrication & erection

Heat Treatment both for bends and welds

Weld Filler Material

Cost Availability



Material Availability

Material availability is primarily market driven. Present material availability for both alloy Grade 91 and Grade

92 as well as carbon steel is exhibiting relatively short leadtimes.

Example:

Alloy Steel P-91 special (minimum) wall pipe for MainSteam, Hot Reheat, Boiler Components, etc. are four to fivemonths from time of order placement from the pipe supplier.This does not include the fabrication time at the pipe

fabricator. Fabrication is currently running four months forstart of delivery. This gives a start delivery at the jobsite inapproximately eight to nine months from order placement tothe pipe supplier. This compares to over two years fromorder placement to start delivery 3 years ago.



Current Cost of Grade 91 and Grade

92 Material

Present cost of Grade 91 pipe is approximately $3.17 to $3.68

per pound.

Present cost of Grade 92 pipe is approximately $4.10 per pound.



Hangers and Supports

Shop fabrication should be set up such that all hanger/support

attachments are welded to the pipe in the fabrication shop and not

in the field. The majority of these types of attachment welds will

require post weld treatment and some form of NDE.

It is considerably more economical to have the welding, post

weld heat treatment, and NDE done in a fabricating shop under a

controlled environment than in the field. This includes all

trunnions, lugs for riser clamps or snubber assemblies, and otherattachments such as insulation lugs particularly on alloy steel.



PROCUREMENT OF WELD

FILLER METAL

For High Energy Piping the weld filler metal needs to be purchased

requiring Actual Test Reports in lieu of Typical Test Reports.

For Grades 91 and 92.

The Nickel plus Manganese content of the filler metal needs to be

less than or equal to 1.5 percent (Ni + Mn ≤ 1.5 percent). Thiscombination affects the Lower Critical Temperature of the filler

material. The lower the nickel manganese content the higher the

Lower Critical Temperature.

The Nickel content of the filler metal should not exceed 0.4

percent. The Manganese to Sulfur ratio should be greater than 50 (Mn/S >

50).

Nitrogen needs to be controlled to 0.02 percent minimum.

After post weld heat treatment the filler metal needs to have a

minimum toughness of 20 ft. lbs. @ 70° F.



Welding of High Energy Systems:

Field or Shop Welding

Shop welding utilizes GTAW (Gas Tungsten Arc Welding),

SMAW (Shielded Metal Arc Welding), GMAW (Gas Metal Arc

Welding), FCAW (Flux Cored Arc Welding) and SAW

(Submerged Arc Welding) processes. The field can primarily only use GTAW (Gas Tungsten Arc

Welding) and SMAW (shielded Metal Arc Welding) process.





The important aspects/points to remember andfollow be it shop or field welding: Proper application of preheat and the maintenance of

this preheat. Maintain a maximum inter-pass temperature.

For Grades 91 & 92 this temperature is 600° Fmaximum. For other alloys the welding procedurewill specify the maximum inter pass temperature.





For Grades 91 and 92, at the completion of welding orfor interruption of welding, comply with theintermediate PWHT/Bake out followed by wrappingthe weld with insulating material.

Bake Out is an intermediate post weld heattreatment wherein the weld is heated to atemperature of 500° F to 600° F and held for a

period of time dependent upon the weld thicknessfollowed by slow cooling.

Maintain good control of welding electrodes. Makesure bare wire (GTAW) electrodes are clean beforewelding. Ensure proper storage and handling ofSMAW electrodes takes place.




Weld End Preparation

Weld end preparations for field welds should be for the

GTAW welding process for the root pass with an inert

gas purge and utilize Figure 4, 5b or 6b of ASMEB16.25.






Terminal Point Welds

Terminal Point welds at equipment such as the boiler and turbine

require close attention.

The size, the minimum wall thickness, the weld end preparation

and, most importantly, the material of each equipment terminal point must be totally understood and evaluated for the pipe to

equipment weld.

It is entirely possible that transition type pieces may be required

between the Main Steam and Hot Reheat pipes and the turbine

connections.

Transitions pieces are basically reducers that permit the

change in diameter and wall thickness between the equipment

terminal point and the main pipe run.






Terminal Point Welds (cont)

The need for these transition pieces is the result of the

main pipe run being of one material (i.e. P-91 or P-92

for example) and the equipment connection being of

some other material composition which does not

possess the identical physical characteristics (i.e.

tensile, yield strength, allowable stress value, etc.) asthe main run pipe.





It is very common that the equipment terminal point material is a

proprietary type material, particularly on the turbine end and will

be noted as “SIMILAR TO” a material designation such as

“SIMILAR TO P-11 or P-22”.

“SIMILAR TO” is not “IDENTICAL TO” and will usually

result in a complete new welding procedure and procedure

qualifications having to be generated and qualified since the

equipment material is not a ASME P-Number as defined inASME Section IX.





It is very important that this be addressed with the

equipment supplier as the qualifications of the WPS

will require that the material used be identical inchemistry to the equipment connection to be welded.

Weld coupons need to be supplied by the equipment

supplier for the qualification.



Post Weld Heat Treatment

There are no exemptions for Grade 91 and Grade 92 weldsfor post weld heat treatment. Post weld heat treatment

temperature for these two Grades of material should be

1400° F ± 25° F.

Grade 91 and Grade 92 completed welds are susceptible to

stress corrosion cracking between the time the weld is

completed and it undergoes post weld heat treatment if the

weld is exposed to moisture such as rain, snow,

condensation, lubricants, etc.

If the weld cannot be immediately subjected to post weldheat treatment, the weld needs to be kept at a temperature

above the dew point to prevent condensation and further

protected from the elements such as rain, snow, etc.



Non Destructive Examination (NDE)

The minimum NDE required for piping under ASME

B31.1 is stated in Table 136.4 with the acceptance

standards for each type of NDE addressed also in the

B31.1 Code.

Types of NDE

Radiography (RT)

Ultrasonic – Flaw Detection (UT) Ultrasonic – Thickness Verification (UT)

Magnetic Particle (MT)

Liquid Penetrant (PT)

Visual (VT)




Non Destructive examination of the Grades 91 and 92(Creep Strength Enhanced Ferritic) steels is no differentthan the traditional steels (i.e. Grade 11 and 22). Therequirements of the applicable Code are sufficient with oneexception.

If welds are exposed to moisture between the time theweld/welds are completed and post weld heat treatmenttakes place the possibility of stress corrosion cracking canoccur, further non destructive examination needs be

performed.

Wet fluorescent magnetic particle examination on allaccessible surfaces.

Ultrasonic examination for inside surfaces that are notaccessible.




Cold Reheat pipe over 24” OD typically becomes longitudinal seam

welded pipe. Material is usually carbon steel (ASTM A 672 Grade

B70, Class 22)

A 672 is the ASTM Specification for electric fusion welded steel pipe where filler metal is added at the longitudinal joint.

B70 is the designation for the pipe grade and the plate material

where the 70 designation indicates a tensile strength of 70 KSI.

Class 22 requires the pipe to be stress relieved, the longitudinalweld seam subjected to 100 percent radiography and the pipe

hydrostatic tested.




Cold Reheat design conditions normally require only a

visual examination by Table 136.4 of ASME B31.1 (Ex.

730° F @ 770 psig for the Cross 3 & 4 Units). Cold

Reheat piping is considered a high energy system andalthough the B31.1 Code may require only a visual

examination it should be specified to require radiography

of both the longitudinal weld seam (Class 22) and the

circumferential welds.



Present Usage of Grade 91 and Grade

92

Grade 91 material is being used extensively for

Main Steam and Hot Reheat piping systems and

boiler headers and boiler tubing here in the UnitedStates and world wide. There has been a “lessons

learned” with this material in understanding what

to do and what not to do. It continues to be a work

in progress.



Present Usage of Grade 91 and Grade

92

Grade 92 material has not been used here in theUnited States for Main Steam or Hot Reheatsystems with two (2) exceptions. One is theWestin Unit 4 for Wisconsin Public Service which

has a grade 92 Main Steam and went commercialin June 2008. The other is the John W. Turk Plantin Arkansas which also has a Grade 92 MainSteam with a design temperature of 1115° F and is

currently under construction. The Grade 92 material has and is being used in

Europe, Japan, and China. There has been someinformation come forward concerning cracking of

welds and “soft areas” in the piping.

Recommended Practice for Operation



Recommended Practice for Operation,

Maintenance, and Modification of

Power Piping Systems

CRITICAL PIPING SYSTEMS (CPS) are

typically defined as those piping systems that are

part of the feedwater-steam circuit (main steam,hot reheat, cold reheat, feed water are the main

systems).

Inspections should be carried out by experienced

personnel while walking down the systemslooking for possible problems with the plant

operating or in an outage.







Excessively corroded support components.

Broken springs or any damaged hardware that is

part of a complete support assembly. Excessive piping vibration, valve operator

shaking, or movements.

Piping interferences.

Excessive piping deflection.

Pipe sagging.







Spring supports riding at either the top or the

bottom of the available travel.

Need for adjustment of spring support load-carrying capacity.

Need for adjustment of support rods and

turnbuckles.

Loose or broken anchors.

Inadequate clearance at guides or limit stops.

Inadequate clearance between safety valve vent

pipes, discharge elbows, and drip pans.




Recommended Practice for Operation,Maintenance, and Modification of


Any failed or deformed support or support

component such as a hanger, a guide, U-bolt,

anchor, snubber, or supporting steel. Unacceptable movement in expansion joints.



Additional Material

(not part of the presentation)





Grade -122 – ASME Code Case

2180-2

Grade -122 is a 12% Chrome, ½% Molybdenum, 2% Tungstenmaterial developed by Sumitomo Metals. Its rupture strength(Allowable Stress Values) is between Grade-91 and Grade-92. Anadvantage of Grade-122 is that the higher Chrome content offers better

resistance to oxidation/exfoliation than the Grade-91 and Grade-92material.

Grade 122 material has not been used here in the United States for aMain Steam or Hot Reheat piping system to date. There is very littleexperience with Grade 122 among US manufacturers.

There have been reported failures of Grade 122 boiler components(tubing) in Japan but very little information has come forward on thespecifics

Chemical Analysis of



Chemical Analysis of

Grade-91, Grade-92 & Grade-122

ELEMENT Grade-91 Grade-92 Grade-122

Carbon 0.08 to 0.12 0.07 to 0.13 0.07 to 0.14

Silicon 0.20 to 0.50 0.50 Max 0.50 Max

Manganese 0.30 to 0.60 0.30 to 0.60 0.70 Max

Phosphorus 0.020 Max 0.020 Max 0.020 Max

Sulfur 0.010 Max 0.010 Max 0.010 Max

Chrome 8.00 to 9.50 8.50 to 9.50 10.00 to 11.50

Moly 0.85 to 1.05 0.30 to 0.60 0.25 to 0.60

Tungsten - 1.50 to 2.00 1.50 to 2.50

Nickel 0.40 Max 0.40 Max 0.50 Max Vanadium 0.18 to 0.25 0.15 to 0.25 0.15 to 0.30

Niobium 0.06 to 0.10 0.04 to 0.09 -

Nitrogen 0.030 to 0.070 0.030 to 0.070 0.040 to 0.100

Aluminum 0.04 Max 0.040 Max 0.02 Max

Boron - 0.001 to 0.006 0.005 Max



Creep Fatigue

Creep is the time-dependent deformation of materials, which

generally takes place in a material subjected to sufficient stress at a

temperature above half of its melting temperature.

Fatigue (thermal fatigue) results from start/stop operation



HOT REHEAT STEAM WALL THICKNESS

COMPARISONS FOR DIFFERENT MATERIALS



Material Specifications

Pipe: A/SA 335 P-91, P-92,

Fittings: A/SA 234 WP91, WP92

Forgings: A/SA 182 F-91, F-92

At present there is no casting specification for valves for Grade-92(i.e., A/SA 217 Grade C12?)

The ASTM has recently approved P-91 under the ASTM A-672and A-691 material specification for Welded Pipe Specification.



Pipe and Fittings

For special (minimum) wall pipe and fittings in piping

systems, the decision to go with ID Controlled or OD

Controlled pipe and fittings needs to be determined.



ID Controlled Pipe

Lighter wall thickness required than OD Controlled Velocity and Pressure Drop can be easily calculated and

predicted

Can be less weight, which can result in smaller loads forhangers/supports and other structural members

Possible reduced loads at equipment connections such as boilerand turbine

Disadvantage: the pipe OD is not necessarily known as each pipemanufacturer has different tolerances which can producedifferent outside diameters. Problems can be encountered with

pipe clamps and riser type clamps fitting the pipe OD.



OD Controlled Pipe

Outside diameter is controlled by ASME/ASTM specifications,therefore OD values are known for hanger/support clamps

Majority of pipe manufacturers are set up and produce pipe to the

OD controlled method

Must exercise care on special wall pipe to ensure that a minimumID is not infringed upon so as not to affect system pressure drop.



Bending of High Energy Systems:

Induction Bending

The preferred method for pipe bending, particularly on the High

Energy special wall pipe such as P-91 and P-92 is the induction

bending method.

Pipe thinning on the extrados of the pipe bend is minimized andvery predictable with this bending method.

Buckling of pipe walls is virtually eliminated.

Ovality is controlled more closely.

3, 4, and 5 diameter bends are very achievable.








Post Bending Heat Treatment

After bending it is critical to have pipe bends heat treated, where

required, prior to continuing on with fabrication, such as cutting

and welding, especially on P-91 and P-92 pipe.

After bending P-91 or P-92 pipe, it is imperative that the pipe be

normalized and tempered prior to any subsequent fabrication

operations. The normalize and temper heat treatment restores the

pipe to its condition prior to bending by refining the grainstructure, which also helps improve the welding of P-91 and P-

92.




Post Bending Heat Treatment

P-91 and P-92 after bending and prior to post bending heat

treatment are very susceptible to cracking if exposed to

moisture and vibration therefore it is important that the

heat treating facilities are located on the premises of thefacility that performs the bending.

Transportation of Grade 91 bends from one facility to

another after bending has caused cracking in the bends due

to vibration transferred to the pipe from the carrier.



PROCUREMENT OF GRADE 91

AND GRADE 92 PIPE AND

FITTINGS

Grade 91 and Grade 92 pipe, fittings and castings need to

have a Brinell Hardness range of values as noted below

prior to the start of fabrication taking place.

For Grade 91 (85 KSI Tensile Strength)

Pipe – 200 to 250 Brinell

Fittings, Forgings & Castings – 200 to 248 Brinell

For Grade 92 (90 KSI Tensile Strength)

Pipe – 210 to 250 Brinell

Fittings, Forgings & Castings – 210 to 248 Brinell









Safety Valve Nozzle





Hardness Testing

There is a direct relationship between the hardness valuesof a material and its tensile strength.

For the Creep Strength Enhanced Ferritic steels (Grade 91

and Grade 92) it is important that after post weld heat

treatment that welds have hardness values that correlatewith the minimum tensile strength of the base metal.

An acceptable Hardness range for Grade 91 welds is

190 to 275 Brinell.

An acceptable Hardness range for Grade 92 welds is200 to 275 Brinell.



Looking To The Future Ultra Super



oo g o e utu e U t a Supe

Critical & Advanced Ultra Super Critical

Units

Ultra Super Critical & Advanced Ultra Super Critical Units

Research is currently ongoing in both Europe and the United

States with the development of materials, forming, fabrication,

welding and heat treatment that will permit units to achieve

steam conditions of 1300° F to 1400° F with pressures in the

range of 5500 psig.

The United States program is aiming to achieve higher steam

temperatures than the European program (1400 ° F versus

1290 ° F )

With this research steamside oxidation, fireside corrosion and

changes to the design codes are being investigated.



Looking To The Future Ultra Super Critical &

Advanced Ultra Super Critical Units

Materials being investigated:

Creep Strength Enhanced Ferritic Steels (Grade 91

and Grade 92)

Advanced Austenitic Alloys (Super 304H)

Nickel-Based Alloys (Inconel 617 and Inconel 740,

Haynes 230 and Haynes 282)



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