|
Post by chameleonrob on Jun 12, 2007 18:13:56 GMT
I currently doing some work on a friends loco after the superheater failed and have found some interesting problems with it, not least of which is that it has 1 1/2 piston rings in the RH cylinder and no way they could have come out in service. The biggest problem is the superheaters, they are tube within a tube type and the cover over the end has split at the weld, not unexpected and perfectly fixable. but along with that all along them, apart from the radiant part, there are pin holes and craters. From what I can see they are corrosion of some sort from the outside of the tube (not from condensate and the like from the inside). What I need to know is is this likely to occur no matter what grade of stainless they're made of and as such just patch the worst bits, or if this is a symptom of either a larger problem or the wrong grade of stainless was used to start with. here is a (unfortunately poor) photo of the problem img.photobucket.com/albums/v700/chameleonrob/picture4.jpgAs an aside what is a good grade of stainless to use for superheaters? my research points to 310 but I don't have the experience to make a decision on that alone. BTW do you think the valves need refacing? img.photobucket.com/albums/v700/chameleonrob/picture5.jpgrob
|
|
jackrae
Elder Statesman
Posts: 1,333
|
Post by jackrae on Jun 12, 2007 21:50:14 GMT
It seems strange that all the defects appear to be on the same straight axial line. This might suggest that the tubes from which they are made are perhaps manufactured from rolled and welded sheet rather than drawn from solid and what you have is weld root corrosion. One of the best ways to rot the poorer grades of stainless steel is to put it in hot oxygen-rich water. Jack
|
|
|
Post by chameleonrob on Jun 12, 2007 22:10:12 GMT
thats just one location, the worst, there are several other areas spread in no pattern that I can see and going from the fire side of the tubes to the water side, its tempting to replace the lot but it really hasn't been designed to be taken apart, let alone replaced.
rob
|
|
|
Post by alanstepney on Jun 13, 2007 2:50:33 GMT
I would replace the superheater rather than try to repair it.
As for the valve face, although it isnt as bad as it could be, I would reface them. Much easier while it is partly in pieces than to take to take it apart again later.
|
|
|
Post by Shawki Shlemon on Jun 13, 2007 10:36:19 GMT
My first question is does S/H run into the fire box or just in the fire tubes? I stand corrected but for the end to split it must have cracked may be due to thermal shock . During firing the regulator was fully closed and the S/H was red hot and a sudden contact with water/steam when regulator was opened caused the crack hence split . Stainless steel , household water and heat are not a good combination . This topic has been discussed somewhere on this board . One can make S/H tubes from copper if they do NOT go in the fire box otherwise they should be made of stainless steel .It is advisable to have the regulator slightly cracked open and cylinders drain cocks open during firing . I am not sure but think ss grade 316 is good quality y , I checked the boiler code but there is no information regarding the grade .S/H is an accessory and therefore a leak will not be dangerous .Repairing or replacing tubes or the complete S/h depends on the condition of the parts .If the pitting is not very deep you can fill them with silver solder AFTER WELDING THE SPLIT END . As for the cylinder face , the question is the cylinder removed from the engine ? if yes then face it if no may be clean it up and try to dress it up with wet and dry 600 grade and see how you go it does not look very bad .Best of luck .
|
|