I find
this micron and mesh issue confusing….I found this today…. Don’t confuse MESH
with MICRON
What is mesh? It refers to the number of openings in a
lineal inch measured from the center of one wire to a point 1” distant. It has nothing to do with the size of the hole
and this is where confusion reigns. Someone gives you a mesh size (and this
happens all the time) and through some hocus–pocus, a size in microns is given. How it ever evolved
is beyond me and has caused more problems than people realize. A simple example: A 40 mesh filter screen has 40 holes per
lineal inch – so what? Depending on which manufacturers catalog you use, you
can end up with, and I hate doing this as a comparison, a micron retention
ranging from 307 microns to 435 microns. For some applications, the difference
is minimal, but for most companies, it can mean rejection of product or
contamination. What determines the
disparity when you convert to microns? That’s a good question, and I will answer
it as simply as I can. The reason is this: manufacturers use different wire
diameters. Why? My guess is due to the structural integrity of the screen, and
a need to please everyone (you know what happens when you try that!). Using our 40-mesh example, a manufacturer
will use a wire diameter of 0.013", which results in smaller holes per
linear inch. This calculates to a width
opening of 0.012". The same manufacturer will then use a
0.008" wire diameter, which produces bigger holes and corresponds to a
width opening of 0.017". Remember, we still have 40 holes per linear inch
but our micron size has changed
from 307microns to
435 microns. What
can a company do? Well, the first thing you need to do
is think in terms of microns. I know, your thinking what is a micron? For those
who are not sure or forgot, a micron is 0.000039". How is it applied? In
an ideal world, a particle distribution count would be taken – this breaks down
the size and quantity of suspended particles in a sample liquid. Unfortunately,
most companies do not have the budget or time to do this (the cost can run
anywhere from $300 to over a $1000). So the next best thing is to evaluate
(guess) or contact a filter specialist.
To help, use the mesh /micron chart provided – the most common are listed. It isn’t complete
by any means, but it will get you pointed in the right direction. As a general rule of thumb, anything
below 40 microns cannot be seen with the eye. Keep in mind that a mesh screen
you're presently using, may not correspond to our chart. If this occurs, you
will need to look at the nearest mesh/micron size and evaluate which is better
(above or below). Better yet, determine which
micron size is needed for particle removal.
Tom Jaszewski www.livesoil.com 702-595-7012 -----Original
Message----- 100 Microns sounds too small.....400 , I think, is the order.... To unsubscribe from this group, send an email to: compost_tea-unsubscribe@yahoogroups.com Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. |