Need some insight...

[MrMarley]

I work for a company that has been manufacturing irrigation equipment since the early 60's. Recently we have noticed a number of parts start to leak. When the parts are created and tested they do not leak, it's only after some months that we start to notice some begin to leak, and in time nearly all start to leak. Needless to say it's not good for business. Wondering if anyone has any insight as to what may be causing this issue. What could cause something to leak after 3 months of sitting on a shelf. The material is a toyolac 100-322 by the way. I am not the most knowledgable when it comes to injection molding, my skills are more computer related, but I told the owners I would see what I could dig up... Any assistance is greatly appreciated.

Bob

 

[aspearin1]

The little bit I was able to come up with on Toyolac (and ABS plastic), on google suggest that UV degradation and oxidation resistance are not great. Storage will likely cause embrittlement and a color change. Since it is an outdoor application, ABS may not be the best choice of material.

ChemE, M.E. EIT
"The only constant in life is change." -Bruce Lee

 

[patprimmer]

Where do they leak. through a seal, through a crack or hole or through a joint.

As a result of almost no relevant information, some rough guesses at the possible explanations are:-
Post moulding shrinkage causing warping.
Hardening of seals.
Thermoplastic creep of seal or gasket areas.
Environmental stress cracks.
Chemical attack, from seemingly benign or common chemicals.

ABS would not be my first choice for most irrigation applications because of it's sensitivity to solvent stress crack, UV light and fatigue.

Regards

eng-tips, by professional engineers for professional engineers
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[btrueblood]

Also would add to Pat's list - brittle failures due to shipping/handling while parts are at temperatures below 0 deg. C. (Unless you are using an impact-modified grade).

 

[MacGyverS2000]

For the UV sensitivity alone I would question who spec'd ABS in the first place...

Regardless, I can't imagine ABS failing by simply sitting on the shelf for several months. If there was such a mistake made in selection of plastics, any chance a similar mistake was made on the choice of glues used to assemble the components? Another poor choice here could certainly account for month-long shelf life.


Dan
Owner

http://www.Hi-TecDesigns.com