Michael asks,
Recently, we have been discussing ECT test methods with one of our partners plants. They are utilizing ‘X Brand’ testing equipment and using the Neckdown method (T 838 cm-12), which was revised as a ‘classic method’ in 2012. We have been using the ‘short column test’ (TAPPI/ANSI T 839 om-12), which has been an official test method since 2002.
The problem is that we have recently been getting different ECT values, where ours have better numbers than our partner plant. Assuming there is nothing happening to the material during transit, our feeling is that our different test methods could be the source of our conflicting data values.
I have heard that there are not many who still use the Neckdown method of testing. I have also been informed that supposedly there have been studies that indicate that ‘X Brand’ of equipment may not be giving consistent data.
Is there any information or perspective you can share regarding all of this? Specifically, how probable is it that any significant difference in our data is because of our different testing methods or equipment?
As I recall from my last visit, you are also using ‘X Brand’. All testing machines and tools can get out of calibration and need regular and often costly maintenance.
There should not be a significant difference between test methods. The quality of the cutting knives is critical. Are you using gloves? You might consider preconditioning and then conditioning the samples before testing until you discover the root cause of the differences. What is the two sigma range for the two testing methodologies? Have you exchanged samples? How about considering a third party testing facility to validate your tests? Perhaps you would want to send samples directly from your partner plant and then equivalent samples, from the same batch, that you have received from the partner plant.
Please don’t assume that there is no damage in transit! One study shows an ECT loss of 7% depending on the roads.
Sometimes operator variability and preference comes into the picture.
These are a few things you can look at and if you have any additional information, or follow up results to share, please do.
If anyone else ahs any comments, we’ll be happy to listen.
— Ralph
askralph 
February 21, 2015 at 3:22 pm
I see this type of thing often and I believe Ralph’s got it with operator variability. Sample preparation for the neck-down is a big one but a big advantage with 839 over 811 and 838 is that it does not involve those blocks you’ve got to position and move. If you’re a bit of a fumbler with your hands, the sample gets knocked a bit off dead-vertical and your ECT result suffers.
If I’m not mistaken, Tappi T-811 is still considered to be the “referee” method for exactly when this kind of debate comes up.