WE ARE USING 8 MICRONS MILLIPORE FILTER FOR OIL PATCH, CUSTOMER IS COMPLAINING IT IS TOO SMALL
iS THERE A SPECIFIC MICRON SIZE ?

John, what is the purpose of filtering the oil. As youre aware, there are several size patches all used for different purposes.

John

let me know your e mail

Hi John, it's a difficult question to rationalise however here are a few thoughts for your consideration.
You are trying to harvest the information in the oil sample to better supply the customer with valuable information so that they can better manage thier equipment. So with that in mind you want to look at the particles that cause the most damage. These are typically the hard particles around the size range of the dynamic clearance. So 8 micron is probably too course for most applications. If however your client is only looking to a filter patch for root cause failure antidotal evidence then a >8 micron filter might be usefull to him. So if your customer is able to justify to you why he/she wants a coarser filter then it might make sence otherwise I'd consider tightening up your filters to gather additional information regarding the sample. Sometimes you need to educate your customers and protect them from themselves. Remember a filter patch is a poor mans analytical ferrography analysis but it doesn't need to be minimised to a screening test. A filter patch is a reasonable and data rich knowledge source. Have a discussion with the customer and you will probably both learn from each other.

Hi John

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.

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.

What kind of vacuum pump you guys are using for filtering oil thru patch; a bench type or a field type, and what brand?

We use a simple electric diaphram vacuum pump (Gast or Western Scientific etc - do a google). Nothing flash or expensive. We gave up on hand operated mitty vacs or using a vampire sample pump to achieve the same purpose 20 years ago.

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.