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ECT

Box Compression

MEMBER'S QUESTION;

I noticed your question & answer section on the AICC website and I was hoping you couldhelp me.  I’m trying to learn as much as I can about box strength for shipping purposes. I work for a global snowboard company and I’m trying to figure out shipping specifications that we can send to our shipping partners around the world.

We’re using large coffin boxes to ship the snowboards. The boxes have a top and a bottom that measure below:

Tele Top- 66-1/2 x 40 x 12 ECT 86 Kraft
Tele Bottom- 66-1/2 x 40 x 12 ECT 86 Kraft

I’m trying to figure out how much weight is ok in each box, as well as how much weight can be stacked on top. I’ve seen the charts for ECT and Burst Testing, but I’m not sure if I’m reading them correctly. I was hoping you could help.

I appreciate your time.

ASK!RALPH RESPONDS:

One of the critical elements in determining compression is flexural stiffness which
is best predicted by the caliper of the combined board.  Can you provide me with the board combinations, flutes and final caliper of the construction.  Thank you.  You can have your provider/member contact me directly.

MEMBER'S UPDATE MORE INFORMATION:

I appreciate your help. Here’s the additional information I was able to find
about the Board Coffin Box that we use to ship our Snowboards.

Medium as Liner

MEMBER'S QUESTION:

We use the calculations for BCT and ECT that are in the Fibre Box Handbook.  Do you know if those calculations are fairly accurate or do you have another way of calculating that information?

Also, we just tested 33/23/33med/23/33 for ECT and BCT.  The ECT result is 54 and the BCT result is 1,222 lbs.  Do you have any advice that would deter us from running 33 lb medium as the middle liner? The dimension of the box is 21.5 x 12 x 10 1/8.  The boxes are stacked 5 above the bottom box and hold 43 lbs. of material in each box.

ASKRALPH! RESPONDS:

The formulas in the FBA Handbook are the way to go!  I used a simplified version of the same formulas myself.  If you tell me the dimension of the box I can tell you if you were with the theoretical range of predicted BCT based on the components  and the ECT that you obtained after the press.

Medium as a facing is fine.  You could possibly loose a little stiffness in the side walls and a little more compression in the entire structure since moisture pickup in high RH condituions may be greater with the medium.  There are other AICC members that use three plies of medium in certain application and others that use three plies of linerboard, but for very different applications.  It’s all about the wonderful engineered design of the corrugated structure.

The theoretical range in ECT given the variation of the ring crush of the components is 40 to 58.  You were in the top quartile in ECT.  Compression potentials with that given range in ECT start at 980# top-to-bottom and goes up to 1420#.  This assumes that the board caliper was 0.260 inches. You were in the middle range in cox compression and your safety factor was 5.

ECT Comparisons

MEMBER'S QUESTION:

We have the opportunity to secure a substantial piece of business.  The customer's specifications reference box dimensions, ECT, and basis weight combinations.  I will submitt selected box samples to a third party lab for evaluation so that you will be able to offer suggestions as to alternative containerboard combinations that will give us both an environmental and economic sustainability advantage.

ASKRalph! Responds:

Below is an assessment of the five different samples you submitted for testing verses what the ECT potentials that could have been developed given the basis weights of the board combinations discovered during the evaluation.

Basis Weight

Combinations

all C Flute

Converted ECTs

Actual Results by Testing

Potential

ECT Ranges

Degradation Study

MEMBER'S QUESTION:

What do you know about ECT 24 replacing ECT 32 ? How would that be possible and what liners? Maybe replacing 150 mullen? What liner weights are used? Were the liner weights 35#. Doesn't 35# liners gets us to 32# now ??

ASKRALPH! RESPONDS:

In the Degradation Study started during the summer of 2008, and has continued to remain open, we  found several converters that have actually shipped boxes with ECTs below the 32# . These were  post press samples that were sent  that may or may not have been above a 32# ECT as incoming sheets. Since these "boxes" did not fail in the field (that we know of) one could assume that  these combined boards in the low twenties have actually substituted for what was described as 32# ECT. It all goes back to knowing your customers' needs.

Using 35# liners does not quaratee combined board performance.  Basis weights are not a good indicator of box performance! If one doesn't bond the components properlyt on the corrugator, flute the medium properly and crush the combined sheet in the converting operation ECT and box performance suffer.  There is a big difference between the potential in the roll stock and the finished product. 

ECT Potentials From Basis Weight Combinations




MEMBER'S QUESTION:


I am ready to quote on a substantial new piece of business.  The potential customer's specs include both basis weights combinations and minimum top-to-bottom compression.  I will send you my competitors boxes so that they can be evaluated.  Please get back to me with your recommendations.

ASKRALPH! RESPONDS:

As promised here the range in ECT values based on the AF&PA Continuous Containerboard Data Report.  I have taken the CD ring crush values for the grades listed in the spec sheet and calculated the ECTs based on the high and low ring crushes for each grade.  These have not been reviewed by another set of eyes, so tell me if these values do not seem correct to you.  I was also very impressed by the packer’s specification for minimum compression values and not just board combinations with a reference to basis weights.

 

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