Are you running this for regulatory or R&D purposes? In my experience, ASTM E662 is more repeatable.

Dear Tim, R&D and regulatory too, particularly for Indian market where they use this standard for the classification of FRLS cables (the SDR should be below 60 % in this case). The cross check with other labs is discouraging with huge differences. The gas is forced through a 0.13 mm orifice and if the gas for some reasons passes also elsewhere (clogging, deformation of the burner items etc..) the flame changes shape, becoming longer and so it reaches the sample with its colder zone. So little differences on the flux and on the shape of the flame give huge differences in test results. A colder flame gives its effect is on the ignition time and so the impact on SDR is high (the smoke comes too late at the end of the test, with a minor impact on the area below the curve).

How does ASTM E662 work?

Thank you

Gianluca

E662 uses a radiant heat furnace, so more consistent output.

Found a comparison online between the two tests and shared the link below. One interesting point was that the orientation of the light path is vertical in the E662 and horizontal in the D2843. The author below claims that stratification of the smoke in the chamber can lead to higher smoke measurement variability in the D2843. I suspect the larger sample size of the E662 (I recall using 3 mm thick specimens) would also help with the reproducibility of that test versus the D2843. I gained access to cone calorimeters in the mid 90's and really haven't used anything else in the last 15 years, not everyone has that luxury! https://books.google.com/books?id=Bb0Ea4Q3dHoC&pg=PA59&lpg=PA59&dq=Differences+between+ASTM+D+2843+and+E+662&source=bl&ots=U1g9Od-dIp&sig=ACfU3U0q9kz4q_oAyr3p6NtMGS3fN6XHxA&hl=en&sa=X&ved=2ahUKEwjNnKyRoO7jAhUJm-AKHQ7uA4wQ6AEwA3oECAgQAQ#v=onepage&q=Differences%20between%20ASTM%20D%202843%20and%20E%20662&f=false

The standard ASTM D 2843 does not specify the length of the flame or the temperature of the flame. The only requirement is the pressure of propane. With different flame lengths the results also changes a lot. Air is also getting mixed with propane through the burner by venturi effect. Hence the air intake changes the flame length. Another point is positioning of the sample and the sample behavior under the burning. Some sample foam up and it tends to move away from the vicinity of the flame and the smoke emission is less. The chamber is also not completely closed as in the case of ASTM E 662. Smoke comes out of the chamber across the bottom opening of the chamber during the test itself and the smoke density also does not stay at the peak value and there is a decrease in the value of smoke density after reaching the peak value. In order to get three repeatable results we need to test at least 10 samples.

@ Arunjothy R

1) The decrease of the max value at the end is common but it does not affect so much the SDR as a delay of smoke emission does, due to a flame with less energy. Therefore the shape of the flame is crucial;

2) Depending on the formulations, sometime the sample escapes from the flame and some parts of it remain unburnt and this I guess affect a lot the measurements. But in this case the extent of the phenomenon depends on the kind of ingredients used in the formulation (see pictures: they are different formulations with different extent) ;

3) have your burner ever had a clogged nozzle?;

4) do you have data’s on specific known PVC compounds to share?;

Thank you

Gianluca

Yes sir We have also experienced burner clogging and used to remove and clean the burner. Since we are the testing agency, we will not be knowing about the formulation or any specific compound of PVC. Sorry sir. What kind of standard material you are using for this particular test.

Arunjothi R

we use two internal standards checked with other labs. 1st at SDR 75 % and the second at 50%. Before each set of measurements we check both. What standards do you use?

thank you

Gianluca

Last week we changed the old burner, installing a new one, so I can show more in detail with some pictures what happens when smoke, dirt and tar reach the vents.

The problem is the position of the vents too exposed to smoke, dirt and tar leakage. The burner must turn to ignite the test specimen and to remove the flame for starting new measurements. Therefore, at the base of the burner there is tiny circular opening through which tar, dirt and smoke leak down sucked by vents, causing their partial obstruction. That reduces the airflow and the flame change shape and energy affecting the measurements. With vents free, our reference sample gives SDR 67 %. With the partial obstruction, the reference sample gives SDR 52 %. The concept is simple. Month by month, depending on kind and quantity of processed samples, we have a severe drift of the measurements, and the only way to notice it is repeating periodically the measurement of our reference samples.

Another problem is that the base of the burner must be lubricated to avoid its blocking. Do not use grease or lubricants leaving too much residues making worst the phenomenon.

Any other advice is appreciated.

ASTM D2843 is purely intended for use with light transmitting plastics and should not be used for any other materials, including PVC

Marcelo Hirschler

ASTM D 2843 is used for rating FRLS PVC cables in India in example. When the smokes are intense, the repeatability is less, but with specific PVC formulations we can reach less than 30 % of SDR and there the repeatability is higher. But some stuffs affecting repeatability (smoke coming out from the bottom, or deformation of the test specimens making unburnt some part of it) are present even if you test “light transmitting plastics”. So I guess ASTM D 2843 is “hard” even for “light transmitting plastics”.

Can you suggest some papers claiming ASTM D 2843 suitable for light transmitting plastics?

Thank you for your help

Gianluca

ASTM D2843 was invented in the early 1960's by workers from what was at the time "Rohm and Haas", with the intent to measure smoke from PMMA. The A Method of Measuring Smoke Density,” NFPA Quarterly, NFPA, Vol 57, January 1964, p. 276. Reprint NFPA Q57-9.

Below is a link to the paper. You will notice that all the materials tested are low smoke materials. Fire Testing Technology (FTT) manufactures the equipment because it has been out of use for many years (since those who need it for US code work already tested their materials) but we believe that it is not a very robust test and that ASTM E662 of ISO 5659-2 are much better.

https://www.fire.tc.faa.gov/pdf/fsr-0121.pdf

Another paper by Rarig and Bartosic, the guys who invented it, can be bought at

https://www.astm.org/DIGITAL_LIBRARY/STP/PAGES/STP41308S.htm

Marcelo Hirschler

thank you very much for the interest and for the files you sent. I really appreciated that. The aim of the question is try to receive some suggestions on how we can use ASTM D 2843 at the best. Unfortunately, we are forced to use it with PVC compounds, because some our target markets use this standard for rating FRLS PVC cables. So no chance to use E 662 or Cone. When you use ASTM D 2843 with PVC compounds, you can see very well the impact of smoke suppressants, and making many measurements you can have an idea of the right direction. But their impact must be huge and you must pay attention to what can reduce the repeatability a lot. In your opinion, is there some tricks we can use to improve the repeatability with PVC?

thank you

Gianluca