Hankison Air Dryer Problem

[rmonks]

I have a friend who bought a used Hankison Air dryer/chiller which has a water seperator that catches the water, he was using the auto last week and the plastic bowl on the seperator exploded into hundreds of pieces. We have been trying to figure out why it would do this, has anyone ever experienced this. First thought was the valve on the bottom of the bowl was shut off but no we found it and it was open.

[mk162]

used?  that plastic could be old and saturated with oil.  they will do that over time.

[rmonks]

Never thought of oil saturating the plastic but that sounds logical.

[mk162]

the plastic canister that holds the filter on our parts washer broke apart a few months back, it was just brittle from the solvents.

[Baron265]

Was he playing opera in the shop? Maybe they hit one of those high notes and it shattered the bowl. 

[ScreenFoo]

I think PTFE is the only somewhat common plastic that is actually really solvent resistant. 

If you need it to last, get a filter with a metal bowl--they aren't much more money.

[Baron265]

Okay fine, it probably wasn't the Opera.

I would say it's because they used regrind when they molded it. Using reground plastic in your process without adding more plasticizer makes a product that's more brittle than if you use virgin plastic. Many materials can accept 10% regrind and still hold many of their engineered specifications. However, regrind is cheaper than virgin material and when nobody's watching, a molder will add a higher percentage of regrind to save money. The pulses of compressed air that the compressor sends through the system, require the part to have a certain yield strength. That means it can bend without breaking, to an extent. If it doesn't have the required yield strength, the constant pulsing could weaken the bowl and pow.