UHMWPE question... two tubes of same material in exact same use/wash conditions etc

[ben_armstrong]

Hi,


We have two UHMWPE tubes... both supposedly made from PE1000 (but i don't have raw material supplier info other than that)


Both undergo the same use and washing cycles etc

One started out at 130.8mm... this is a pure white colour, described as 'natural'

One started out at 130.6mm... this is a yellow-ish colour, described at 'natural'

(when we asked supplier, the colour range of 'natural' was said to range from white to yellow-ish)



Problem is the white item's diameter has drifted out to 131.5, and we observed the internal pig's o-ring fit get gradually worse and worse over time to the point that it started out fine, now the pig just drops through

...

and over a longer time period, but the same (concurrent) use-conditions the yellow-ish one is still definitely 130.6mm, and the seal fit is perfect and has not changed



Any ideas as to what is going on? Any ideas as to the actual differences in material, so we can tighten our spec when we reorder to replace the loose tube?

Thanks

Ben

[Kelly_Bramble]

The materials composition or chemistry is different. Without trace-ability, you don't know what your getting. Regardless, your end item specifications should be reviewed and clarified to ensure you get what you need.