[MW:4021] material procurement for liquid gas storage tank

Dear Mr Asghari,

What is the lowest design temperature for the tanks ?

Usually the procurement specification for steels should indicate the impact test requirement, that is at the design temperature. One may ask for impact at lower temperature (i.e for minus 50⁰C design one may specify minus-55⁰C in the specification), however impact values can be erratic, because the ductile to brittle transition for a specific steel at some temperatures can be drastic. I have access to API-620 but not to BS-7777, hence I could not verify the LOWERMOST DESIGN temperature requirements for this steel as per BS -7777.

However based on the information supplied below on the basis of the attached data sheet it looks to me that the lowest guaranteed impact temperature for this steel as per EN-10028-2/3 is -50⁰C (minus 50 deg C) for guaranteed 42J lateral and 27 J transverse impact energy as supplied by various mills.

Requirements for impact energy on weld and HAZ at the impact test temperature should also be specified by the design code. Usually the impact values after welding + PWHT(if applicable) should be less than that specified for base metal (to take into account , the effects of thermal cycles.)

As a thumb rule if one gets the impact values in the base metal (during procurement), which is 2-3 times more than the values after fabrication, then there should not be much concern.

Feel free to ask me if you have any concern, if I have a copy of BS-7777, I may clarify your query fully.

Thanks

Pradip Goswami,P.Eng

Senior Engineer/Specialist(Welding-Metallurgy)

Machine Dynamics & Component Integrity Dept.

Engineering & Training Services Division

ONTARIO POWER GENERATION Inc.

PO Box-2000, RR-55(South)

Nanticoke, Ontario,N0A1L0

Tel:-(519) 587-2201, Ext 3107--in Nanticoke

(416) 231-4111, Ext 5925--in Kipling,Toronto

Fax: (519) 587-6814

Email-pradip.goswami@opg.com.

From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of ali asghari
Sent: Sunday, January 10, 2010 11:57 PM
To: materials-welding@googlegroups.com
Subject: [Norton AntiSpam] [MW:4009] material procurement for liquid gas storage tank

Dear all

I have a question about procurement & preparation of material specification that related to construction of storage tank for cryogenic liquid gas according, API620 & BS7777. The specified steel for this project is P355NL2,THAT according BS7777-PART2 the impact testing is carried out in -50-(delta T).(delta T is acquired according ANNEX A) now manufacture of steel said that due to time consuming of producing (delta T),he tested in lower temperature of -50, for preparing of order & material specification , what additional requirement or testing is given to ensure haz &base metal have adequate impact value?

regard advances.

THIS MESSAGE IS ONLY INTENDED FOR THE USE OF THE INTENDED RECIPIENT(S) AND MAY CONTAIN INFORMATION THAT IS PRIVILEGED, PROPRIETARY AND/OR CONFIDENTIAL. If you are not the intended recipient, you are hereby notified that any review, retransmission, dissemination, distribution, copying, conversion to hard copy or other use of this communication is strictly prohibited. If you are not the intended recipient and have received this message in error, please notify me by return e-mail and delete this message from your system. Ontario Power Generation Inc.

Re: [MW:34105] SA266 GR4N 4 Cycle SPWHT

Hi, You are correct, Minimum refers to the one cycle for which this part will expose until final work shop PWHT. hence mill test certificate shall include this. Max. SPWHT, refers to additional cycles of heat treatment that are reserved for future repairs during equipment lifetime. Again, these simulated no. Of cycles shall be specified in MTC. The idea is we need to make sure that steel mechanical properties are not compromised upon exposure to multiple repairs (i e 4 cycles in your case). One could say, if steel is subjected to 4 cycles and is ok, then it should by defacto be good for one cycle, yet, this is wrong assumption cause mechanical problems and microstructure of materials varies accordingly based on no. Of cycles for which material will expose. This is apparent in alloy steel and especially for impact test values as an example. In your case, this forged CS with properties before PWHT can be understood to be " as forged" condition (i.e. Wit...

Materails FAQs

Q: What are equivalents for standard Q 235 B (and Q 235 A) for U-channels? (asked by: boris.vielhaber@vait.com) A: DIN Nr. = 2393 T.2, 2394 T.2, EN 10025 W. Nr. DIN 17007 = 1.0038 Design DIN 17006 = RSt 37-2, S235JRG2 (Fe 360 B) Q: What is St DIN 2391 BK material? (asked by: dmcandrews@automaticstamp.com) A: Precision steel tubes, cold-finished/hard. Q: What is C.D.W. Boiler Tube? (asked by: montydude123@yahoo.com) A: Cold Drawn Welded Boiler Tube. Q: WHAT IS W.Nr. 1.4301? PLS TELL US IN EASY LANGUAGUE (asked...

Heat tint (temper) colours on stainless steel surfaces heated in air // Heat tint

Introduction The colour formed when stainless steel is heated, either in a furnace application or in the heat affected zone of welds, is dependent on several factors that are related to the oxidation resistance of the steel. The heat tint or temper colour formed is caused by the progressive thickening of the surface oxide layer and so, as temperature is increased, the colours change. Oxidation resistance of stainless steels However, there are several factors that affect the degree of colour change and so there is no a single table of colour and temperature that represents all cases. The colours formed can only be used as an indication of the temperature to which the steel has been heated. Factors affecting the heat tint colours formed Steel composition The chromium content is the most important single factor affecting oxidation resistance. The higher the chromium, the more heat resistant the steel and so the development of the heat tint colou...

Materials & Welding

Search This Blog