Welding Thick S500QL & S690QL plates for Hydro Power

[Erhan Turgut]

Hi,
We're working on 2700 mm dia. pipes with a thickness range of 26 - 40 mm
for S500QL and 30 - 48 mm for S690QL.
These penstocks will be used in hydro power plant with a pressure of
aprx. 140 bar
We have two methods for welding: SAW on GTAW (root GTAW, fill & cap SAW)
and SMAW on GTAW. We will try to achieve max. 12 kJ/cm heat input.
So shall we apply PWHT (Stress relief)? If yes what is the thickness
limits for PWHT.
We planned to apply Soaking (Hydrogen Releasing) with a temperature of
aprx 250 oC for 2.5 - 3 hours. So if we apply Stress relief
heat-treatment with a temp. of 550 oC for 1 hour do we have to apply
soaking anyway?

Thanks in advance
Regards,

Erhan TURGUT

[sanjay]

PWHT is generally not recommended on Q&T steels. There is no mention
of PWHT for P No. 11B material in the code also.

Post heating (Soaking) is anyways required. This is irrrespective of
PWHT.

You should meticulously monitor Preheat and Interpass temperatures for
successful welding of this material.

Regards.

Sanjay

[Tansu Ozcelebi (KREA)]

Hello Erhan;

I think PWHT method is necessary for that pressure.

Regards,

Tansu Ozcelebi
Manager
KREA Makina Muh. Ltd.Sti.
ta...@kreamakina.com
Tel : +90.232.478 59 78 Ext : 14
Mobile : +90.533.489 55 22
Fax : +90.232.478 60 32
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Bornova-IZMIR-TURKIYE

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[piepe...@kpnmail.nl]

Dear Erhan,

I agree fully with Sanjay that it is not advisable to execute PWHT on
QT materials in order to avoid changes in materials microstrucre by
which it's loosen the original mechanical properties.
Most manufactures have datasheet available which give recommandations
and/or guidelines for welding such materials, I would advise to take a
look at the website of your supplier to see if you can find this
information, if not than take a look at the site of SSAB Sweden
(S690QL is similar to Weldox 700) and see what they advise for welding
these materials.
Always use heat imput as low as possible for same reason as why
omitting PWHT, especially in case where fatigue also can become a
problem.

Best Regards,

Herman Pieper

[piepe...@kpnmail.nl]

Hello Erhan,

Forgot to mention in my previous mail that in my opinion you only need
to apply Soaking when using welding proces / filler metal / flux with
Hydrogen content > 5 ml. When using processes with low hydrogen
containing filler metals and controlled parameters during welding it
is not obligatory. Be aware of storage of filler metals under
controlled conditions as well for this reason.

Regards,

Herman Pieper

On 3 apr, 16:17, Erhan Turgut <ertur...@gmail.com> wrote:

[babu k]

Hi,

 

S690QL is Equivalent to A517 Gr.Q ; Since this is Q&T , in general PWHT is not recommended, but Post heating as shall be applied as you stated.

 

But as per as concern PWHT , if it is beneficial to your service conditions you can do;

 

 

It seems to Hydropowerplant application(Penstock) , the vibration factor, & what Codes/Standards your following should decide your main requirement for the PWHT

 

Thanks & Regards,

K.Babu

Singapore.

 

2009/4/3 Erhan Turgut <ertu...@gmail.com>