Alexa wrote:Awill42d.
When you deposited weld metal for the large 'cracks', did you butter (build of the sides of the joint) before welding the center of the joint?
Tanks for your patience.
Alexa
No Alexa, I filled the large cracks with 6mm diameter rods bent to shape and tacked either side of the rod on the outside of the casing.
I then used a die grinder to cut a groove on one side of the rod and welded that side and then did the same to one of the other cracks.
I then returned to the 1st crack and grooved out the other side of the rod and welded that side until all the cracks were close to filled and I then capped the weld area to tie it all together.
I was very careful to ensure good penetration and try to control the heat so the casing was evenly heated while welding.
I did consider buttering either side but decided to use rod to fill the cracks instead.
Regards Andrew.
We are Tig welders, gravity doesn't worry us. Miller Dynasty 350 OTC hybrid wave 300 amp inverter Tig at work (Now retired) Kemppi MLS 2300 inverter, 230 amps of welding brilliance for home use
AKmud, nice rack! Curious, do those extensions, protruding out from under the shell, create a gap along the bed rail, or is there a plate there as well?
Nils wrote:AKmud, nice rack! Curious, do those extensions, protruding out from under the shell, create a gap along the bed rail, or is there a plate there as well?
Thanks,
Nils
The owner routed out some 1" trex material (full bed rail length) around the plate and mounting bolts to have a smooth surface to mate to. Worked out pretty slick. He will have to adjust the rubber flap on the back window to shut tight though.
Markus wrote:Great work pictures buddy and a interesting thread Spokesy
Great to find another Kemppi fan
Have you awill4wd liked MINILOG-function?
MarKus, I use MiniLog as my default setting and use it all the time.
It was worth buying the MLS 2300 just to get the MiniLog function.
I refuse to pay Kemppi's inflated price on their foot pedal which I like also as my friend where I work after hours has the foot pedal arrangement on his MLS 2300.
Regards Andrew from Oz.
We are Tig welders, gravity doesn't worry us. Miller Dynasty 350 OTC hybrid wave 300 amp inverter Tig at work (Now retired) Kemppi MLS 2300 inverter, 230 amps of welding brilliance for home use
Markus wrote:Great work pictures buddy and a interesting thread Spokesy
Great to find another Kemppi fan
Have you awill4wd liked MINILOG-function?
MarKus, I use MiniLog as my default setting and use it all the time.
It was worth buying the MLS 2300 just to get the MiniLog function.
I refuse to pay Kemppi's inflated price on their foot pedal which I like also as my friend where I work after hours has the foot pedal arrangement on his MLS 2300.
Regards Andrew from Oz.
Like most countries worldwide there's been a slowing down in employment.
We here certainly haven't been hit as hard as the USA and Europe but over the last 18 months or so there's been a noticeable decrease in the jobs advertised.
I work in a 2 person shop and we tend to complement each other, the boss looks after the sprintcar chassis repair side of things and I tend to do everything else. We've been pretty lucky and had enough work to keep us both going (just enough at times) with a couple of quiet weeks but at least we're still ticking over and I'm able to put a wage on the table every week.
The slowing down of China's minerals demand has hit the Oz mining sector that has basically held the Oz economy up.
The contraction in the mining sector means workers moving back into the manufacturing side which is slow anyway and often they have unrealistic expectations about wages potential compared to what they were being payed in the mines.
Luckily we own our house and don't live a expensive lifestyle so we make ends meet and save a bit which more than some other unfortunates.
Cheers Andrew from Oz.
We are Tig welders, gravity doesn't worry us. Miller Dynasty 350 OTC hybrid wave 300 amp inverter Tig at work (Now retired) Kemppi MLS 2300 inverter, 230 amps of welding brilliance for home use
Not actually today, but a project i did a while ago.
Stainless 316L frames for UV-lights. The units have 4 or 6 pcs. 130W UV tubes! They make a hell of alot ozon when test running them, and they will burn your eyes (like welding) in relative few seconds. Really nasty stuff.
Migatronic Automig 233 MPS
Migatronic Sigma² 400 Pulse CW
Migatronic Pilot 2400 HP
The first time that I saw UV water sterilization was in a portable water purifier. http://www.steripen.com/ (Sterilizes water in seconds.)
This device was also tested by the National Research Council of Canada.
Citroën wrote:You guessed right
It is for water purification in a fish farm.
Here's my Friday project... A new vacuum penetration in a liquid oxygen trailer. The old had cracked, through the inner pipe, allowing air and LOX to get into the vacuum jacket. The fun part was coping a piece of 6" sch.40 to the radius of the rear head.
GEDC0745.JPG (173.35 KiB) Viewed 7751 times
Naw... the fun part was standing on my head to weld the bottom of this...
I'll weld this mess tomorrow. One of these visible cracks is leaking! (The topmost right.) I'll spend the afternoon grinding this out.
GEDC0753.JPG
=====
Otto Nobedder.
From the photo, it invites me to think that a section of the plate, that had been welded in a tee-joint, was cut out.
Was the welded tee-joint The part cut out seems to had also been welded. What was the original bevel configuration of the tee-joint? Full penetration? Welded from both sides? Base material? In short ... how had it been welded?
The red indications from the dye penetrant testing seem to coincide with the locations of the tee-joint weld, but also with the grinding that was used to remove the remaining weld after cutting out the plate.
Keep us informed as to what type of crack and if possible, what path it took through the base metal.
I am curious to find out if other cracks will be discovered.
Here's a better pic to answer a part of your question:
GEDC0754.JPG (189 KiB) Viewed 7678 times
The section removed is 1/4 X 3", 304 flatbar rolled to a 24" radius. Fillet weld, both sides, no bevel.
As you surmised, the cracks are between the (MIG) fillets, generally perpendicular to the tangent of the "ring".
This is not the first time I've encountered this on this design. My suspicion is these vessel heads (also 304 SS) were cold-formed without annealing, inducing natural stresses. The fillet welds add stresses of their own. The purpose of the ring is to distribute forces from the sole "front-to-back" support for the inner vessel, meaning the entire weight of the inner vessel and it's cargo are pushing and pulling on this structure every time the driver hits the throttle or brake.
I see it as a design flaw, that has taken about 25 years to rear it's ugly head, and I expect to see more like this in the near future as all the trailers in this design series are near the same age.
Here's the evidence proving the leak... At 1 PSIG pressure in the annular space!
GEDC0755.JPG (181.82 KiB) Viewed 7563 times
Here's what it took to eliminate the cracking... The head is nearly 1/2" thick (formed originally from 1/2" 304 sheet). Note the one that leaked was ground through completely. There's an 18 ga. "backing strip" inserted and held firmly in that one.
If the cold working during the forming of 304 plate is great enough, this increases the probability of stress corrosion cracking. It seems like the equipment operates with repetitive stresses. The equipment might have an corrosive environment internally (example: chlorinated water, or salt water.).
If the cracking occurred only at the location of the welds or very close to the welds, then it invites to think that during the welding of the fillets, the microstructure might of been made even more susceptible to stress corrosion cracking.
So we have accumulated risks possibly from:
- the choice of 304 instead of 304L (L = low carbon)
- the cold working during forming without annealing
- the heat input during welding may of been excessive
- the stresses during the operation of the equipment
- the corrosive fluids (if any) circulating within the equipment during its operations
I am curious to know if the metal located under and next to the rest the welds has cracks also, even if the cracks may have not yet 'grown' to reach through-wall thickness lengths.
What is the fluid that circulates internally?
How hot does the equipment reach during operation?
There is NO working fluid behind this metal; It is evacuated equivalent to deep space.
These are like huge Thermos bottles... An inner vessel full of coffee, an outer vessel with a handle, and vacuum in the middle.
It's a bit more complicated than that... There are many layers of Mylar/tissue as a radiant barrier, as well.
Short form, the "backside" of those cracks sees nothing but extreme vacuuum. That's the leak-detection method; Helium mass-spectrometry. The front side of these cracks haven't seen the light of day since the trailer was built.
The cracking always seems to begin directly between the fillet welds, but has extended to just beyond the weld zone. (Loss of vacuum and inherent loss of insulation bring these problems to our attention before they could progress farther, so how far they COULD extend over time is open to speculation.
Of the five cracks visible in the photo with the dye-penetrant, only one was leaking. There could be many smaller cracks around the structure that have simply not shown themselves through leakage yet.
In answer to your last question, the outer vessel in the pictures reacts solely to ambient temperature. 110 degrees in the sun in July, 22 below in Iowa in the winter.
The inner vessel operates at -423*F, but with minimal influence on the outer.
