Cracks in Elevator door-Stainless Steel 1

[Shankarmoorthy]

My client has a Stainless steel cladded Elevator door in his building.The door is exposed to the west sun.The door develops cracks and bows after a period of time.The contractor changed the door twice.What could be the reason for this to happen??Is the Packaging material between the steel door and Stainless steel cladding not of a good quality?As far as I know,SS 304 cannot bow to low surface temperature levels.Can someone explain this phenomenon to me?

 

[metengr]

Several questions;

1. How is the elevator door constructed because you mention stainless steel cladding, is this thin gage stainless steel sheet that is bonded or fastened to a steel frame underneath or steel plate or ???

2. Are the cracks confined to the door frame or only in the stainless steel cladding?

3. Are the interior surfaces of the elevator clad with stainless steel sheet? How is it attached?

 

[Shankarmoorthy]

Yes the door is Mild steel and there is a top Stainless steel sheet cladded on the surface.It is open to sun and only the SS Cladding has developed cracks and probably getting a Popcorn effect.

 

[EdStainless]

When you say clad what do you mean?
How is the SS fastend to the CS door pannel?
Are the cracks related to where the pannel is fastened?
What are the doors washed with?

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[robsalv]

Could thermal cycling "cold work" the stainless at attachment points?

 

[EdStainless]

I suspect that the stainless is heavily cold worked. The trouble may be with the way that it is mounted. Are there welded clips on the stainless? Is it held so tightly that as it expands it distorts? Is it glued down? Are there chlorides in the glue?

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[Shankarmoorthy]

Yes,the SS is cladded on the top of the MS Door for the full width and height.The end of it is spot welded on to the MS Surface on all sides and is pressed totegether mechanically.No glue is being used in this case.My real question is...will the SS Distort if there is direct sunlight on to it??Will the surface temperature rise so much due to the west sun??

 

[Shankarmoorthy]

The cracks develop on the surface and the whole sheet bows outward...The cracks dont develop where the sheet is fastened.The sheet is cleaned only by plain cloth.No chemicals used here.It is in a residential building.

 

[EdStainless]

Well, let's look at some numbers.
The doors are what, 10' tall. And the surface gets how hot, say 160F (uncomfortable to touch).
If the tce is 9.6x10-6 then we will have 120" x 90F x 9.6 = 0.100" of total expansion. Yes, the SS will expand enough to bow outward from heating.
I have seen polished SS get so hot in the sun that it would burn you.
When the sheet boows out the outer srface is in tension. You need to have a sample looked at by a metallurgical lab. This may be choride stress cracking, or it may be thermal fatigue, or something else.

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[Shankarmoorthy]

You mean to say that,even if glued by appropriate glue,I cant have a solution to this Problem??

 

[EdStainless]

No, I don't mean that there is no answer. After all, this is done all of the time. My hunch is that the root of your problem is that all of the edges of the SS are fastended tightly. You may need to make sure that the SS can 'float' some. This would reduce distortion.

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Rust never sleeps
Neither should your protection

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[Shankarmoorthy]

The contractor comes back to me telling that it is due to oil canning.I have 2 questions here
1 . Does Oil canning create bowing of the doors?
2 . Oil canning occurs due to Manufacturing defects and not due to exposure to sun.Then how can the SS Panel bow to the extent that the doors rub against the jamb and creates scratches on the SS??



Shank Kris

http://www.elevatorinspection.org

 

[EdStainless]

It sounds like you have a combination of problems. Oil canning is the generic term for sheet mateiral that has flat edges, but humps up in the middle. (named after the old style oil cans with the domed bottoms that you flexed in and out to deliver oil).
If they took sheet that wasn't flattened properly and forced it flat on the door, then the heating would cause it want to 'pop'. The combination of the two effects would cause huge stresses.

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Rust never sleeps
Neither should your protection

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[Shankarmoorthy]

In esscence,it is a defect of Manufacturing.If thesheet were flattened properly and a proper adhesive were used,I believe this would not happen.The sunlight doesnot hit the door directly.It is a glass building and the heat is not high at all.

Shank Kris

http://www.elevatorinspection.org