Farid44,
Assuming your header is for ASME Sec I boiler application, my answers are:
1) Yes, 9mm fillet weld is practical.
2) Per Sec I PW-15.1.6, weld strength calc is not required if your design conforms with certain figures in Fig. PW-16.1. From your description your design matches type (z)...
I worked for boiler OEM companies for many years. The typical D-style boilers cannot run safely and continuously at 10% design capacities but might be possible at some higher loads. There are many possible problems for low-load operations. Not being able to maintain stable combustion, like some...
1. Corrosion - explains the rusts on the outer surface - bad fuel used, avoid. Might also cause creep happening at much lower temperature.
2. Tube material - explains the material appearing brittle. 13Cr-Mo44 looks correct but check,
a. actual material used? b. heat treatment?
3. Frequent...
If failures only happened on a few unique tubes then it could be vortex. The fix is to eliminate irregular tube spacings or arrangements which create gas path channels and allow flue gas to take shortcuts and hit certain tubes at much higher velocities.
If damages including thinnings happened...
I agree with Trottiey, except for very critical items like tubes and pipes for supercritical and ultra-supercritical plants, the majority of the rest of items are all made from Chinese materials and by Chinese manufacturers, especially the pressure vessels such as 100% of the steam drums and...
Like Metengr said, failure from fatigue is the major concern. One famous term is the 'S/N curve'. Fatigue should include mechanical, thermal and, particular to your chemical industry, corrosion fatigue. Here are some quick Wikipedia links:
http://en.wikipedia.org/wiki/Fatigue_(material)...
Notice that first, English and Chinese versions of Wiki have different maps and second, even though neither map shows China to be still a 3rd word country, the leadership still claims 'we always belong to the Third Word' and further more, in the news, 'U.S. Downgraded to Third World Nation'...
RR79,
This might make it easier to understand why change from bottom-supported to top-supported as boilers get larger:
If you imagine making small and large boxes from the same thin wall material, such as paper, and leave them on the ground. Below certain size the box cans still be...
Athomas236,
You contractor is right. High-sulfur fuel oil DOES have big problem of generating sticky ash to the heating surfaces, especially on the superheater elements and thus reduces heat absorption and the steam production of boiler.
The other and bigger concern is, like most others...
I helped my company to buy pressure parts from China in the past. Just need to find the ones with good reputations, not the cheap suppliers plus hire good inspectors/agents. After a few rounds, you will get to know the culture and the tricks and be successful.
If you feel intimidated about...
Make no mistake, MJCronin, according to the question asked this bolt is for the boiler flue gas damper which is a non-pressure part for which application B7 can be used for much higher temperatures plus B7 matches the typical low-alloy damper blade and frame materials used for the 480 deg. C...
It is not the tubes that need welding but the tie bars need to count on the welds to each tube to carry the horizontal loads plus this design has the concern of possible tearing the tubes open through the tiny bits of welds if have localized and concentrated loads. It is also easy to burn holes...
In general, the answer is 'not necessarily'.
For the typical ranges of velocities used in the flue gas systems, the major concern is the natural frequencies of the um-restrained tubes and pipes in the streams. When gas passes a tube it generates a vibration but only if the vibration frequency...
I designed boilers for years. I can safely say that the staggering is for making sure that all tubes get welded to the tie bars, not just ever other ones and the loads get evenly distributed.
There is a slight concern, if not staggered but having two welds on every other tubes, of thermal...
B7 should be good for the 480 deg. C temperature but I would look at the reason why the bolts have failed because even carbon bolts can still have some strengths at this temperature.
The Three Mile Island nuclear accident was also related to closing of cooling line valves for maintenance which violated regulation.
When can people learn?
I want to mention that it is a 'NO, NO' to perform the heat-treatments and try to increase the strengths of the pressure vessels after they are manufactured per the codes and ready for installations. Performing such heats at sites can very possibly mess up shop-manufactured conditions including...
