Pre heat -Press. vessels

[Kumar]

Dear Experts,

I would like to have a discussion regarding "pre- heating & its
mainatances" for aPressure vessel weldings ( ASME SEC. VIII DIV.1,
shell thickness -55mm & dish end -65mm, material SA 516 Gr.70, vessel
length -18mtr & ID-3mtr). WPS is calling for pre-heating of 100 deg.
C.(maintainace required for joints above 25 mm thickness) project
location - GCC.

Welding processes - LS & CS - SAW. Nozzles- SMAW.. since due to the
high ambient temp. of around 35-40 deg. & due to practical
difficulties, the welders could only maintain pre-heating while they
starting welding & not during the welding ( specially on the other
side of joints). the client insisting for continuous heating during
welding.

I want to request for the opinions from members how far pre-heat is
crucial in GCC environment especially in CS materials.

Thanks in advance,
Kumar

[vnb...@gmail.com]

Respected members,

One of site has non PWHT carbon steel and stainless steel pressure vessels. As they are undergoing some repair, overseas engineer suggested PWHT on repaired portion for relieving the stress and to deal with HAZ.
Doing local PWHT imposed a question that during manufacturing the WPS PQR and the welding electrode employed was okay for non PWHT job. Doing the local PWHT would necessitate revised WPS PQR and the electrode this can't be done as circ. seam is covering portion of repair. Thus we are in dilemma as to what is the way out.
Being week off I request welding and code expert to suggest their opinion.

Thank you all.

Kind Regards,

Vinod Bhatt

[Raghuram Bathula]

what is MOC, code of construction, type of repair, service?  pl provide detailed info...

temper bead might be an alternative

[vnb...@gmail.com]

These vessels are designed to ASME Sec VIII Div 1, but not code stamped. 

Regards,

Vinod Bhatt

Sent from my iPhone

On 25-Sep-2016, at 10:16 PM, vnb...@gmail.com wrote:

Dear Sir,

I stated that, the vessels are mix of stainless steel - SS316 and carbon steel - SA 516 Gr 70, handling compressed natural gas. 

We require to add small gussets, to stiffen small bore (below 50 mm) nozzles for drain & vent, as some of these failed due to vibration. 

Regards,

Vinod Bhatt

Sent from my iPhone

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[George Dilintas]

there is a huge misunderstanding regarding the non essential variable "Preheat Maintenance". What is meant by the Code is the keeping of the preheat temperature after the completion of the welding and until the performance of the PWHT.

Preheat maintenance according to the Code is not identical with continuous heating during welding

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Dr. Georgios Dilintas,

Dipl. Ing. In Aeronautic and Space Engineering

Ph.D in Mechanics of Solids - Computational Mechanics

A.I.S, A.N.I, IRCA Lead Auditor

Welding, Stress Analysis, Corrosion, QA/QC, Failure Analysis, Risk Analysis