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Filter fhesSurface f¡Éeirs: Surface f i l ters work by direct interception ofp a r t i c l e s l a r g e r t h e n t h e p o r e s i z e o f t h e m e d i a . D i r t i s t r a p p e do n t h e u p s t r e a m s i d e o f t h e m e d i a w i t h t h e h o l d i n g c a p a c i t yl i m i t e d b y t h e n u m b e r o f p o r e s i n t h e m e d i a . W h e n n e w ,m e d i a r e s i s t a n c e t o f l o w i s s m a l l , b u t a s t h e f i l t e r b u i l d s u pd i r t , t he res is tance to f l ow rap id ly inc reases . The capac i t y o fmos t su r face f i f t e r med ía í s usua f f y measured in g rams.

Depth lYpe Fi l terc: This type of f i l ter works by both directin te rcep t ion o f pa r t i c les and absorp t ion (mo lecu la r a t t rac t iono f pa r t i c les ) . These f i l t e rs use severa l t ypes o f med ia toa c h i e v e t h e g o a l o f h o l d i n g p a r t i c l e s . T h e f l u i d m u s t t a k e al o n g e r p a t h t h r o u g h t h e f i l t e r b e f o r e e x i t i n g . N o r m a l l y , t h e s ef i l t e r s h a v e l a r g e h o l d i n g c a p a c i t i e s a n d i n i t i a l l y h a v e a h i g h e rres is tance to f l ow. However , a d rop in p ressure occurs asc o n t a m i n a t i o n b u i l d s u p o r i s t r a p p e d .

The Functions of OilClean: This function is to transport undesirable materíals inoil to the filter or hold in suspension the particles until the oilis changed. This is the characteristic that keeps internal partsclear of varnish and sludge build up.

Cool: An important functíon of oil is to cool the machineparts it comes into contact with. Some systems require thatall cooling be performed by only the oil.

Filters SystemsFull-Ffow FiÉerc: Designed to filter fastf l o w i n g o i l , f u l l - f I o w f i l t e r s p r o t e c tdowns t ream componen ts f rom la rgers ize par t i cu la te mat te r . These f i l t e rstyp ica l l y ho ld par t i c les f rom 20 to 40m i c r o n s i n s i z e . T h e i r a b i l i t y t o p a s s l a r g ev o l u m e s o f f l u i d m a k e s f u l l - f l o w f i l t e r su n s u i t a b l e f o r s m a l l e r p a r t i c l e s ; w i t h o u tb e c o m i n g l a r g e a n d e x p e n s i v e .

Partial-Flow Filterc: Sometimes ca lleda k i d n e y l o o p , t h e s e f i l t e r s a r e d e s i g n e dt o f i l t e r a s m a l l s t r e a m o f f l u i d ;r e t u r n i n g t h e f i l t e r e d f l u i d t o t h e s u m pof the sys tem. These f i l t e rs t yp ica l l y ho ldp a r t i c l e s f r o m 1 - 1 0 m i c r o n s . S m a l l e rq u a n t i t i e s o f f l o w a l l o w t h e f i l t e r s t or e m o v e s l i g h t e r p a r t i c l e s w i t h o u ta f f e c t i n g t h e n o r m a I f u n c t i o n s o fthe sys tem.

Seal: The film of oil that bridges the gap between twosurfaces to keep fluids in while keeping air and dirt out iscalled the seal. An example is the seal that oil provides in ahydraulic ram or spinning shaft, the thin film of oil bridges tlgap and isolates two sides.

Lubricate: Lubrication is the function of oil that allows twmoving parts to slide past each other wíth little friction. Thisfilm of oil is important in reducing wear and providing ease (movement within a machine.

Cleanliness LevelsSince fluids can have such small particles insuspensio n and maintaining good cleanliness iseconomically important, the oil industry hasdeveloped standards to quantify particulatebuild-up. The current standards are ISO 4406c.Ihese standards are used by manufacturers andengineers to determine how clean fluid shouldbe to províde acceptable performance andservice life. A chart is used to show the level ofparticles of a given size in a milliliter of fluíd andthen a grade or number is assigned to indicatewhat /5O c/ass the fluid is. Hydraulic oils that areused with servo valves should have a 1611411 2level or better while in servíce. The first numberrs c/ass code for 4 microns and greater particles,the middle number indicates the class for 6mícrons and greater while the last number isthe class for 14 microns and greater. At thiscleanliness level sticky or binding valves shouldnot be a problem and o i l should be inserviceable condition for an extended time.This method can also be used to evaluatecontamination control systems or filters in asystem.

lUew oils: As surprising as it may seem, mostoil purchased today has not been filtered beforesold. Yes, i t is newly refíned and lookstranslucent, but it has many more particles thenwould be expected from new oil. Typically, newoils being delivered to customers are c/ass22118116 and sometimes worse. This puts the enduser ín a position of having to filter the oilbefore it is put into service to assure it will notcause premature wear on the machinery.

N u m b e r o f P a r t i c l e s p e r M i l l i l i t e r( C o u n t s / m i l )

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Síze MattersWhat i s a rn i c ron? A mic ron i s one mi l l i on th o fa m e t e r . T o p u t t h i s i n a v i s u a l r e f e r e n c e , at y p i c a l h u m a n h a i r i s a b o u t 7 5 m i c r o n s t h i c ka n d t h e u n a i d e d h u m a n e y e c a n s e e d o w n t oa b o u t 4 0 m i c r o n s . T h e i n d i v i d u a l p a r t i c l e s o fs m o k e f r o m a c i g a r e t t e a r e a b o u t o n e m i c r o n i ns i z e . W e c a n s e e t h e s e o n l y b e c a u s e t h e r e a r es o m a n y o f t h e m t o g e t h e r .

F i l t e r s a r e d e s i g n e d t o r e m o v e p a r t i c l e s t h a tc a n a n d w i l l c a u s e d a m a g e t o m a c h i n e r y . W i t hg r e a t e r p e r f o r m a n c e a n d s o p h i s t i c a t i o n o ft o d a y ' s m a c h i n e r y , h i g h e r c o n t a m i n a t i o nc o n t r o l i s e s s e n t i a l . B u t w h a t s i z e p a r t i c l e s w i l lc a u s e d a m a g e ? W h a t i s t h e t h i c k n e s s o f t h e o i lt h a t s e p a r a t e s t h e m o v i n g p a r t s ?

. T h e f i l m o f o i l t h a t s e p a r a t e s t h ee n g i n e r í n g a n d c y l i n d e r w a l l i s2 - 3 m i c r o n s .

. T h e o i l t h a t i s b e t w e e n a s p o o lv a l v e a n d b o r e i s u s u a l l y3 - 5 m i c r o n s .

. T h e o i l l u b r i c a t i n g a s l e e v e b e a r i n gw i l l p r o v i d e 5 - 8 m i c r o n c l e a r a n c e .

T h e s e n u m b e r s t e l l u s t h a t s t a n d a r d f u l l - f l o wf i l t e r s w i l l n o t t a k e o u t n o r e l i m i n a t e p a r t i c l e st h a t c a u s e a n a b r a s i v e b r i d g e . T h i s b r i d g e o fp a r t i c l e s c o n n e c t i n g t h e t w o s i d e s w i l l a l l o ww e a r t o b o t h s u r f a c e s , c r e a t i n g e v e n m o r ep a r t i c l e s . T h e m a i n r e a s o n w e c h a n g e o i l i nm a c h i n e r y i s t o r e m o v e s m a l l p a r t i c l e s i n t h e o i l

t h a t t h e f i l t e r s d i d n o t r e m o v e a n d h a v e b u i l tu p t o a p o i n t o f c a u s i n g e x c e s s i v e w e a r t o t h ei n t e r n a l p a r t s o f t h e m a c h i n e . T h i s i s w h e r ec o n t a m i n a t i o n c o n t r o l i n r e m o v i n g p a r t i c l e sd o w n t o 1 m i c r o n w i l l m a k e a s i g n i f i c a n tr e d u c t i o n i n t h e w e a r o f t h e m a c h i n e r y a n dl e n g t h e n t h e s e r v i c e l i f e o f t h e o i l .

A l t h o u g h p a r t i c u l a t e s t h a t b r i d g e t h e m o v i n gp a r t s d o c a u s e w e a r , t h i s i s n o t t h e o n l y h a r mt h e s m a l l p a r t i c l e s u n d e r 5 m i c r o n s c a u s e .T h e s e s l i g h t e r p a r t i c f e s , r e f e r r e d t o a s s i l t i n gb u i l d u p i n t h e f l u i d , i n t e r f e r e w i t h p r o p e rf u n c t i o n s o f t h e f l u i d , a n d c r e a t e c o s t l y w e a ro n m a c h i n e r y .

T h e f o u r f u n c t i o n s o f o i l a l s o h e l p u su n d e r s t a n d w h y i t i s i m p o r t a n t t o m a i n t a i nh i g h c l e a n l i n e s s l e v e l s . C o n t a r n i n a t i o ni n t e r f e r e s w i t h t h e s e f u n c t i o n s i n t h ef o l l o w i n g w a y s .

C l e a n : T h e a b i l i t y o f t h e f l u i d t o h o l dp a r t i c l e s i n s u s p e n s i o n i s l i m i t e d . O n c e t h e l i m i ti s r e a c h e d t h e f l u í d w i l l d e p o s i t t h e p a r t i c l e so n t o t h e m a c h i n e r y , l e a v i n g s l u d g e a n d v a r n i s ho n t h e p a r t s . l t w i l l a l s o f u r t h e r r e d u c e t h ef l u i d ' s a b i l i t y t o c o o l .

C o o l : T h e o i l m o v e s h e a t f r o m t h e m a c h i n e ' sh e a t g e n e r a t i n g l o c a t i o n s t o a c o o l e r o r t h eo u t e r c a s e o f t h e m a c h i n e t o b e r a d i a t e d t o t h ea t m o s p h e r e . F l u i d s w i t h c o n t a m i n a t e b u i l d - u ph a v e a r e d u c e d c a p a c i t y t o m o v e h e a t a n d a i di n c o o l i n g t h e m a c h i n e a s i t s h o u l d .

S e a l : T h e f i l m o f o i l t h a t s e a l s t h e g a pb e t w e e n t w o s u r f a c e s w i l l m a i n t a i n t h e s e a l i n gi f t h e r e a r e n o p a r t ¡ c l e s b r i d g i n g t h e s e a l . l fc o n t a m i n a n t s b r i d g e a n d l i f t t h e s e a l i n gs u r f a c e s a p a r t , i t a l l o w s f l u i d o u t a n dc o n t a m i n a n t s i n . T a k e , f o r e x a m p l e , a s e a l i n ah y d r a u l i c r a m . A s t h e r a m m o v e s o u t p a s t t h es e a l , t h e o i l i s s c r a p e d o f f t h e s h a f t . w h e n t h er a m i s v i e w e d u n d e r a m i c r o s c o p e , t h e s u r f a c el o o k s l i k e t h e p e a k s a n d v a l l e y s o f a m o u n t a i nr a n g e . E a c h o n e o f t h e s e v a l l e y s i s a l o c a t i o nw h i c h c a n l o d g e p a r t i c l e s t h a t c a n b e d r a w ni n t o t h e r a m a s i t i s r e t r a c t e d . A s t h e s m a l lc o n t a m i n a n t s b u i l d , . p a r t i c l e s c a n s t a r t t o l i f tt h e s e a l o f f t h e r a m a n d a l l o w l e a k a g e a n df u r t h e r c o n t a m i n a t e b u i l d - u p . T h e i n c r e a s e i nc o n t a m i n a t i o n , i f a l l o w e d t o c o n t i n u e , w i l lw e a r o n t h e s e a l m a t e r i a l a n d c a u s e p r e m a t u r ef a í l u r e .

Lubr i ca te : The b r idg ing ac t ion o f the par t i c lesi n t e r f e r e s w i t h l u b r i c a t i o n , i n c r e a s i n g f r i c t i o nb e t w e e n m o v i n g p a r t s , w h i c h c a n l e a d t oh i g h e r e n e r g y c o n s u m p t i o n . T h e q u a l i t y o fl u b r i c a t i o n i s r e d u c e d a s c o n t a m i n a n t sb u i l d u p i n f l u i d s .

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SummarvHydraulic Syltems: W¡th hydraulic systems,fluid is used to transmitpower to components, such as motors and rams. The fluid passesthrough valves which direct the oil to the working components. Thehigher the system pressure, the closer the tolerances that thecomponents will need to maintain. As a ram is extended and retracted asmall amount of contamination is brought into the system.To the nakedeye the ram looks smooth but if viewed under a microscope it has manypeaks and valleys.

There can also be airborne contamination that can drop onto the cylinderand be drawn into the oil past the seal. This small particulate material issuspended in the oil until removed by the filter or drained at the nextservicing. As the small contaminat¡on (si l t ing) bui lds up i t can bind orstick valves. Servo valves are particularly sensitive to silting, the patentedHarvard Filter System is a cost effective way to eliminate failure due tothis. Vane pumps and piston pumps are both components that have anelevated degree of sensitivity to contamination. A 3-5 micron clearanceof the vane tip to housing puts particles under pressure, eroding themetal l ike a sand blaster. The small clearances in these pumpsnecessitates a need for very clean fluid, which needs to be cleaner thenmost new oils with ISO cleanliness codes of 20 or greater. Components inthe system should have codes of 17 or less.

System Component Typ ica l C lean l iness Spec i f i ca t ion

Servo Valve o o oPropo r t i ona l Va l ve o o o

Var ia b l e -d i sp lacemen tP u m n o o o

Cart r idge Valve o o oF ixed -d i sp lacemen t

P i s ton Pump o o oVane Pump o o o

Dressure or F low Contro lVa l ve o o o

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G e a r S y s t e m s : G e a r o i l s p r o v i d e l u b r i c a t i o n w h i c h a l l o w sg e a r t e e t h t o s l i d e p a s t e a c h o t h e r . T h e f l u i d a l s o k e e p s t h es l i d i n g s u r f a c e s c o o l . C o n t a m i n a t i o n i n t h e o i l w i l l c a u s ea b r a s i v e b r i d g i n g a n d w e a r o n t h e t e e t h s u r f a c e s ,g e n e r a t i n g m o r e p a r t i c l e s . O x i d a t i o n ( t h i c k e n i n g ) o f t h e o i ld u e t o e l e v a t e d t e m p e r a t u r e s i n t h e p r e s e n c e o f o x y g e n i sa n i s s u e t h a t m u s t b e c o n t r o l l e d t o k e e p g e a r o i l ss e r v i c e a b l e . C o n d e n s a t i o n o r m o i s t u r e i n t h e o i l , e v e n i ns m a l l a m o u n t s , a c t s a s a c a t a l y s t i n o x i d a t i o n a n d t h ef o r m a t i o n o f a c i d s i n t h e o i l . B y f i l t e r i n g t h e o i l d o w n t o1 m i c r o n a n d r e m o v i n g w a t e r i n t h e o i l , t h e l u b r i c a n t c a np e r f o r m i t s f u n c t i o n b e t t e r a n d l o n g e r .

l lutomatic l?ansmissions: The function of this f luid ist h r e e f o l d : a g e a r l u b r i c a n t , a h y d r a u l i c f l u i d i n t h e t o r q u ec o n v e r t e r , a n d a c o o l a n t . W h i l e e a c h f u n c t i o n i s b e s tp e r f o r m e d a s a c l e a n f l u i d , t h e c l u t c h p a c k s i n t h e s y s t e mc o n t r i b u t e w e a r - p a r t i c l e s c o n t i n u a l l y . E a c h t i m e t h ec l u t c h e s e n g a g e , t h e r e i s a s l i d i n g m o t i o n w h i l e t h ep r e s s u r e i n c r e a s e s t o f i n a l e n g a g e m e n t . W h e n t h e c l u t c hp a c k i s r e l e a s e d a g a i n , i t w i l l d e p o s i t p a r t i c l e s i n t o t h ef l u i d . l f t h i s c o n t a m i n a t i o n i s a l l o w e d t o b u i l d u p i n t h ef l u i d , i t w i l l w e a r o n t h e g e a r s , e r o d e t h e v a n e s o f t h et o r q u e c o n v e r t e r , a n d a c c e l e r a t e t h e w e a r o f t h e c l u t c hp a c k s . A l l t h i s i n a d d i t ¡ o n t o g e n e r a t i n g e l e v a t e d h e a t .A d d i n g a k i d n e y l o o p f i l t r a t i o n s y s t e m t o r e m o v e p a r t i c l e sw h i l e s t i l l s m a l l , h a s b e e n s h o w n t o s i g n i f i c a n t l y i n c r e a s et h e l i f e o f t h e s e t r a n s m i s s i o n s .

E n g i n e s : E n g i n e o í l p r o v i d e s l u b r i c a t i o n t o a l l t h e s l i d i n gp a r t s o f t h e e n g i n e ; s e a l i n g b e t w e e n t h e r i n g a n d t h ec y l i n d e r w a l l , c o o l i n g t h e p i s t o n s , a n d k e e p i n g t h ec o m p o n e n t s c l e a n . T h i s i s a d e m a n d i n g s e r v i c e f o r e n g i n eo i l . T h e 2 - 3 m i c r o n g a p b e t w e e n r i n g a n d c y l i n d e r w a l lp r o v i d e s a s e a l t o k e e p c o m b u s t i o n g a s e s f r o m t h ec r a n k c a s e . A s t h e c o n t a m i n a t i o n b u i l d s , p a r t i c l e s w i l l w e d g eb e t w e e n t h e t w o s u r f a c e s a n d b r e a k t h e o i l s e a l a l l o w i n gc o m b u s t i o n p r o d u c t b l o w - b y a n d i n c r e a s i n g o i l u s a g e . T h i sa l s o w i l l i n c r e a s e t h e w e a r t o t h e s u r f a c e s d u e t o t h ea b r a s i v e b r i d g i n g . T h e c o n t a m i n a t i o n b r i d g e a l s o c r e a t e sw e a r o n t h e b e a r i n g s u r f a c e s , c a m s h a f t , a n d g e a r s .T h e a d d i t ¡ o n o f a s e c o n d f i l t e r l o o p , c a p a b l e o f r e m o v i n gm o i s t u r e a n d p a r t i c u l a t e m a t t e r u n d e r 1 m i c r o n i n s i z e , h a sp r o v e n t o i n c r e a s e o i l s e r v i c e l i f e a n d r u n n i n g t i m eo f a n e n g i n e .

D iese l Fue ls : As d iese l eng ines a re fo rcedt o r e d u c e p o l l u t i o n e m i s s i o n s , p r e s s u r e i nt h e f u e l d e l i v e r y s y s t e m h a s g o n e u ps u b s t a n t i a l l y . S o m e e n g i n e s a r e p r o d u c i n g3 0 , 0 0 0 p o u n d s o f p r e s s u r e a t t h e i n j e c t o rt i p t o d e l i v e r c l e a n e r c o m b u s t i o n i n t h ec y l i n d e r s a n d b e t t e r f u e l e c o n o m y . A t t h es a m e t i m e , t h e f u e l m u s t h a v e s u l f u rr e m o v e d w h i c h l o w e r s t h e l e v e l o fl u b r i c a t i o n t o t h e m o v i n g p a r t s . M o s t f u e l st o d a y a r e d e l i v e r e d t o t h e t a n k w i t h I S Og r a d e s 1 9 / 1 8 1 1 6 o r a b o v e . A d d i t i o n a l l y ,w a t e r i n t h e f u e l w i l l p r o m o t e a l g a eg r o w t h i n t h e t a n k s a n d i f a l l o w e d t o b ep u m p e d i n t o t h e i n j e c t o r c a n c a u s ec a t a s t r o p h i c f a i l u r e .

T h e c o m b i n a t i o n o f h i g h p r e s s u r e s , r e d u c e dl u b r i c a t i o n , a n d c o n t a m i n a t i o n i s f o r c i n gc o m p a n i e s t o r e a l i z e t h e i r n e e d f o rc o n t a m i n a t i o n c o n t r o l o f t h e f u e l b e f o r ed e l i v e r i n g f u e l t o t h e e n g i n e . S i m i l a r t ohydrau l i c sys tems, the need fo r con tamina t ionc o n t r o l i n f u e l s y s t e m s i s j u s t a s c r i t i c a l .C l e a n e r f u e l r e d u c e s w e a r o n t h e e x p e n s i v ea n d s e n s i t i v e f u e l i n j e c t o r p a r t sm a i n t a i n i n g p e a k p e r f o r m a n c e a n dd e l i v e r i n g b e t t e r f u e l e c o n o m y . I n a d d i t i o n ,u s i n g a c o n t a m i n a t i o n c o n t r o l s y s t e m p r i o rt o p u m p i n g f u e l i n t o t h e e n g i n e t a n kr e d u c e s f i l t e r p l u g g i n g , i m p r o v e s f u e ls y s t e m l o n g e v i t y , a n d d e c r e a s e s d o w n t i m e .