Dear All,
Sort of UK-oriented food grade suitability response -
http://www.bssa.org.....php?article=45
Expanded US appraisal of sanitary requirements for food contact/non-contact surfaces -
http://edis.ifas.ufl.edu/fs119
I can think of other specialised factors which may practically dictate also, eg low temperature freezing belts.
Rgds / Charles.C
added - extracts below seem to respectively disagree (No.1) and agree (Nos 2,3,4) regarding the relative 304/316 response characteristics given in JimE's post (I assumed a "comma" after the word "rejects" ). The practical situation may apparently also relate to the source of any to-be-detected fragments since the specific magnetic permeabilities can depend on their fabrication history, (especially can increase for SS304, AFAI could see from the literature).
I suppose it would be interesting to compare the quantitative detector response for wands of each variety. Hopefully 304 will be consistently (and significantly) > 316. Bye-bye BRC ?
Or just add one more, possibly meaningless, validation job, with thks to BRC.
1. The most common types of metal contamination in a broad range of industries include ferrous (iron), copper, aluminum, lead and various types of stainless steel. Of these, ferrous metal is the easiest to detect and relatively simple metal detectors, or even magnetic separators, can perform this task well. Stainless steel alloys are extensively used, particularly in food processing equipment, and they are the most difficult to detect, especially the common non-magnetic grades such as 316 (SN58J) and 304L (EN58E). The non-ferrous metals such as copper and lead fall between these two extremes
…………..>>
Other factors that influence sensitivity include type and shape of metal, orientation, operating frequency and throughput speed. A good indication of a detector’s all-around capability is the sensitivity ratio between ferrous and the most difficult to detect grade of stainless steel 304L (EN58E). This ratio can be as good as 1:1½ and as poor as 1:2½. This has a major effect on the detectors ability to detect contamination such as slivers and screen wire which exhibits an “orientation effect.” Non-spherical metals such as wire are easier to detect when passing in one orientation as opposed to another.
food metal detection and x-ray inspection (2006).pdf 84.56KB
120 downloadsand possibly opposing views -
2. Test your metal detectors at regular intervals, every hour is common practice, use three test samples made from Ferrous (Chrome Steel), Non-Ferrous (Brass) and grade 316 Stainless Steel. Grade 316 Stainless is used as it has Non-Magnetic properties, which means that it is one of the most difficult grades of Stainless Steel for a metal detector to find. So the theory is, if it can find this grade then it will certainly find the others
(note that "others" does not explicitly include SS304, I noted the company does also offer test spheres for 304)
http://www.fastecser...test-standards/3. Stainless Steel 316 has slightly better corrosion resistance than 302 and 304. It also has better non-magnetic properties
http://www.alloywire.com/alloy_stainless_steel_316.html
4. A noteworthy difference between 304L and 316L stainless steel is that while 304L is “low magnetic”, 316L approaches non-magnetic in character.
(The “L” parameter indicates that the material is “low carbon” steel (less than 0.03%). Low carbon improves ability to resist corrosion, particularly in salt environments.)
http://vandalstop.com/index.php?main_page=page&id=4