WE ARE USING 8 MICRONS MILLIPORE FILTER FOR OIL PATCH, CUSTOMER IS COMPLAINING IT IS TOO SMALL
iS THERE A SPECIFIC MICRON SIZE ?
Original Post
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John, what is the purpose of filtering the oil. As youre aware, there are several size patches all used for different purposes.
John
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Hi John
What are the customers reasons for considering the filter is too small?
Regards
Rob S
What are the customers reasons for considering the filter is too small?
Regards
Rob S
The use of the word "Patch" indicates that you are using this to evaluate the cleanliness of the fluid rather than cleaning it up by filtering it through the membrane filter. Incidently, the "Patch Test" was developed by Millipore in the '70 (or even earlier), and evaluated the contamination level by the discolouration that the filtered dirt created. This has spawned the generic term "Patch Test"and is used by many. I thought it used a 5µm membrane not an 8µm. In essence this does not really matter as long as your customers controls are based upon an 8µm patch.
Saying this most people in the hydraulics and lube industry are using an 1.2 or 3.0µm membrane filters and evaluating the cleanliness by comparison th a series of master slides or photographs of known ISO4406 cleanliness levels. As I am currently drafting a British Standard on the Comparative membrane technique I have to disagree with Alan's inference about it's limited usefulness. It is really "horses for courses", if a fluid system has been designed (with good filtration of course!!)and is being managed properly, wear is mimimal and it only requires a regulat quick 'look'to see if conditions have changed for the worse. The "Patch Kit" principle allows this and an assessment can be near the point of use and in about 10 min. About the same time as it takes to walk the sample to the lab!! The kit is simple to use (ie the operartor can do it) and cheap to buy (about $500 for the basic form). This assessment will indentify whether more analytical means like particle counting or even Ferrography needs to be used.
Saying this most people in the hydraulics and lube industry are using an 1.2 or 3.0µm membrane filters and evaluating the cleanliness by comparison th a series of master slides or photographs of known ISO4406 cleanliness levels. As I am currently drafting a British Standard on the Comparative membrane technique I have to disagree with Alan's inference about it's limited usefulness. It is really "horses for courses", if a fluid system has been designed (with good filtration of course!!)and is being managed properly, wear is mimimal and it only requires a regulat quick 'look'to see if conditions have changed for the worse. The "Patch Kit" principle allows this and an assessment can be near the point of use and in about 10 min. About the same time as it takes to walk the sample to the lab!! The kit is simple to use (ie the operartor can do it) and cheap to buy (about $500 for the basic form). This assessment will indentify whether more analytical means like particle counting or even Ferrography needs to be used.
I agree with others here. One needs to know what you want to use the filter patch for, before deciding the micron size filter patch used. On clean oil systems i.e. (systems that are filtered / have filters fitted) like hydraulics, compressors etc. a 5 micron or smaller patch can be used. But for non-filtered systems like drivetrains or gearboxes where "extreme cleanliness" is not a top priority a coarser patch is probably sufficient.(especially if using the patch to screen for abnormal wear). If using as a comparitive tool for estimating particle count make sure you know the micron size of the original patches you are comparing to as this will have an effect on the result. (You should compare apples with apples.)All this said, I agree with Mike, the patch test is a quick on site test that can, if used correctly and interpreted correctly, tell a lot. Even if just to determine if further testing need be done.
I realize the post is a little old, however I'm making an assumption you are preparing the membrane for determination of the ISO code under a microscope. If so the answer is quite simple. ISO 4407 covers this and calls for a membrane with a pore size of 1 micron. 1.2 micron is popular as they are more common. It is logical that if you want to determine the number of 5 micron particles present (Yes, 4406-1999 optical counting is still based on 5/15 micron and not 4/6/14 micron(c)) you need a membrane with a smaller pore size. I use 1.2 micron membranes for everything (including 1200cST oil). I you can't pass the prescribed 100ml through the membrane the oil is either too dirty, or an additive or some other issue exists.
To determine varnish potential use a 47mm diameter by .45 micron patch. For comparative field analysis for particle count use a 5 micron patch. I have an old pall filter patch visual comparator kit, if done correctly, it does a decent job. Both are nitro cellulose base paper.
