Monday, January 24, 2011

Purging Tip of the Week: #32

Sometimes, due to excessive contamination or the requirements of a Preventive Maintenance program, you just have to tear down a piece of equipment. Split a die, pull a screw, open up heads…all unpleasant tasks. Often a purging compound, used as a pre-tear-down aid, can make the job easier.

Some resins are tacky and difficult to remove from metal surfaces but purging compounds are designed for removal from the system – they should peel off quite readily. Just run the purge in accordance with the supplier's instructions and when you reach the stage where the system is run empty, cut the heats and begin your tear-down.

Monday, January 10, 2011

Purging Tip of the Week: #31

When purging extruders that normally run with screen packs in place, be sure to discuss with your purging compound supplier whether the purging material will be able to pass through the screen mesh without hanging up.

And even if it will, don’t forget that part of a purging compound’s job is to break loose contaminants. If, for any reason, your screw and barrel is badly contaminated then even a purging compound that, by itself, would clear the screens with no trouble may break loose enough degraded material to clog the screens and rupture the screen pack.

If there probably is a significant amount of degraded material in the screw and barrel then the screens should come out.

Wednesday, January 5, 2011

Is the Giant Pacific Plastic Garbage Patch Imaginary?

Were we to give credence to the media reports describing the purported pollution of the North Pacific Gyre by plastic debris, we'd probably think you could walk from Oregon to Japan on the trash. But now a serious scientist is saying that it ain't necessarily so!
Dr. Angel White
Dr. Angelicque White, an oceanographer at Oregon State University, has been out there, on an actual boat, looking for all the plastic. It turns out that there's not much there. Sort of like those reports of Mark Twain's demise, the tales of catastrophic levels of plastic pollution may have to be relegated to the "Greatly Exaggerated" category.

In an article in Innovations Report, Dr. White debunks, among other things, claims that the plastic debris in the Pacific covers an area twice the size of Texas and that it's been doubling very ten years. She observes:

“There is no doubt that the amount of plastic in the world’s oceans is troubling, but this kind of exaggeration undermines the credibility of scientists. We have data that allow us to make reasonable estimates; we don’t need the hyperbole. Given the observed concentration of plastic in the North Pacific, it is simply inaccurate to state that plastic outweighs plankton, or that we have observed an exponential increase in plastic.”
“The amount of plastic out there isn’t trivial. But using the highest concentrations ever reported by scientists produces a patch that is a small fraction of the state of Texas, not twice the size.”

Dr. White clearly is NOT suggesting that oceanic plastic contamination is a non-problem, in part because the material would be devilishly hard to remove without a raft of unintended consequences. She appears to believe that concern is appropriate but alarm is not. Her conclusion:

“If there is a takeaway message, it’s that we should consider it good news that the ‘garbage patch’ doesn’t seem to be as bad as advertised, but since it would be prohibitively costly to remove the plastic, we need to focus our efforts on preventing more trash from fouling our oceans in the first place.”