Skip to main content

[MW:3854] Stress Corrosion Cracking in expansion joints

By Materials & Welding
Dear Forum Members,
 
 
We have consructed a high temperature hot water disrict heating system early in the year 2000,the initial insallation of the system was not so good -there were some axial and lateral deflection in  the system- .The expansion  joints are made fromS.S304,after 3 to 4 years of operation ,we noticed cracks in the bellows ,starting from inside to outside the layers(9 layers).When refering this prblem to some experts in our country, they called it stress corrosion cracking related to chloride content in the sarrounding envr..W e asked an expert to ckeck the presence of chloride in the envr., he found no traces of this gas.As we have no budget to replace all the expansion joints in the future,we are obliged to replace the defected exp.joint  when the joint  starts to leak.In order to vercome this problem we are thinking to paint these joints with a high temp. resisiting paint up to 200degree c,as the max.operating temp. is 150degree.(the operating pressure is around 20 bar).
Plase advise whether this idea is right,if not please give us another solution.
 
Thank you in advance
ENG.RIYAD ALZOUBI

Comments

Anonymous said…
This comment has been removed by the author.
June 28, 2012 at 11:26 AM
Anonymous said…
This comment has been removed by the author.
July 2, 2012 at 4:19 PM
Post a Comment

Popular posts from this blog

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

By Materials & Welding
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...
Post a Comment
Read more

Materails FAQs

By Materials & Welding
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...
21 comments
Read more

The Schaeffler and Delong diagrams for predicting ferrite levels in austenitic stainless steel welds

By Materials & Welding
Introduction Ferrite is important in avoiding hot cracking in during cooling from welding of austenitic stainless steels. 'Constitution diagrams' are used to predict ferrite levels from the composition by comparing the effects of austenite and ferrite stabilising elements. The Schaeffler and Delong diagrams are the original methods of predicting the phase balances in austenitic stainless steel welds. Nickel and chromium equivalents A 'nickel equivalent' is calculated for the austenite stabilising elements and a 'chromium equivalent' ferrite stabilising elements. These are used as the axes for the diagrams, which show the compositional equivalent areas where the phases austenite, ferrite, martensite (and mixtures of these) should be present. Although intended to show the phase balance of weld fillers, these diagrams can also be used to illustrate the phase balance of the 'parent' material. There are different diagrams for dif...
Post a Comment
Read more