Re: Grain Bulk Density
What you measure is poured bulk density and for compaction during filling / transportation you need to measure tapped / tamped density to give maximum weight in container. Measuring it is simple as the name says tap the container, grain will settle down add more grain and tap again. Continue till the level in the container doesn’t fall anymore. Mass / volume will give you tapped density. In your container probably you are not getting full compaction and it will not be difficult to back calculate the actual density in the container from actual min – max densities. ■
Re: Grain Bulk Density
First, what size is the container you used to get 660 kg/m3 ?
The larger the container the greater the accuracy, especially important with granular and lumpy materials (for wheat/barley/maize I used to use a one cubic foot container).
Second, if you are measuring the loose bulk density as is normal for conveying and elevating then you may wish to consider tapping/vibrating the container of material to see if the density increases, or applying a load to the free material surface, to simulate the pressure when stored in a silo, to see if the density increases.
There is also the consideration of what are the exact dimensions of the silo and the "as stored" angle of repose which can significantly affect the stored capacity. ■
Re: Grain Bulk Density
Thank you for your replays. You are both quite right. I have measure poured bulk density and I use only 1L container for density determination which is probably too small for accurate measuring. But we are using ISO 7971 Standard: “Cereals: Determination of bulk density, called ‘mass per hectolitre’” with corresponding and certified equipment, that is also approved as our national standard.
Just read your messages, I went to laboratory and made an experiment as Mantoo describe. I got the next results: poured density of barley/sunflower seeds is 665/403 kg/m3, temped density of barley/sunflower seeds is 678/411 kg/m3.
Also I found that pressure has almost twice greater affect on density of grain in bulk then tamping. The tamped and pressured by 30 kg weight (simulation of 10-13 mtrs pile) density of mentioned cargoes was 685/422 kg/m3.
Anyhow, if I know min and max density of the cargo that probably will appear only in uppermost an lowest layers of cargo, what I have to use in calculations in case with silo and in case with dome? ■
Re: Grain Bulk Density
It may help if can explain what the purpose of the calculation is.
As you have found, bulk density is not a single number for any sample, it is dependent upon the history of the sample (load applied, time, moisture content, etc.)
If you are checking things structurally you need to be conservative (i.e. take a higher density) , if you are checking whether a mass will fit into a volume you will again want to be conservative but in this case conservative will be a lower density.
if you are using it for buying and selling, it is generally better to stick to weight as the basis of sale. ■
Re: Grain Bulk Density
Originally posted by Vladimir
..But we are using ISO 7971 Standard: “Cereals: Determination of bulk density, called ‘mass per hectolitre’” with corresponding and certified equipment, that is also approved as our national standard...
Anyhow, if I know min and max density of the cargo that probably will appear only in uppermost an lowest layers of cargo, what I have to use in calculations in case with silo and in case with dome?
When using any standard check with any limitations on application. Just because it's a standard does not mean it's right for your application.
As to which density to use I'd probably take an average. ■
Re: Grain Bulk Density
Originally posted by designer
Just because it's a standard does not mean it's right for your application.
That is why this thread was started. I'm looking for some standard which is right for my application.
For our internal needs, we can use min, max and average rates, depend on situations RPD discribed. But when we work with our clients (sellers, buyers, shippers etc.) we can't use only our suggestion because apointed independent syreyors must follow standard rules.
Other situation when we need it, is ship loading operations. In case if vessel has to be loaded up to full hold's capasity, we must give accurate stowage factor. If finally it will wrong, and vessel take more ore less quantity of grain, in both cases we have to pay deadfreight.
Any comments are appreciated. ■
Re: Grain Bulk Density
Originally posted by Vladimir
I'm looking for some standard which is right for my application.
Sorry, haven't come across one. ■
Re: Grain Bulk Density
I think I understand the issue a little bit better now.
You appear to be looking for different "standard tests" to suit your different applications for bulk density measurement.
I would approach it slightly differently, I would look for a single test procedure which gives a repeatable consistent result. I would then use a series of factors to adjust the test result to suit each particular application, based on one off or special testing.
Using a standard test and a factor, both of which can be agreed by all parties looks to be a more open and clearer way forward than using a multidude of different tests for different purposes. ■
Grain Bulk Density
Hi all
Working with the grain we have define its density from samples. Then putting grain in storage with known volume, and filling storage up to full capacity, we check grain density again: density=weight/volume. We faced with the next situation: the more capacity of storage (especially its height), the more apparent density differs from laboratory factor. For example if we put barley with measured density 0.66 MT/Cub.Mtrs into volume of 15000 Cub.Mtrs, last one can take 10300 MT of barley and even more instead of pre-calculated 9900 MT.
In fact we have a case of compaction lower layers of cargo under high pressure of upper layer of cargo. I have found some tables with transferring coefficients for grains depend on height of pile but only for typical kinds of silos. I can’t find any approved technique for such density correction.
I’d appreciate if some one help with this or give a reference to source with corresponding information. ■