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I know people get tired of hearing me ask, "When is the last time you cleaned that breather cap," or "When is the last time you changed that breather cap?"  I'm admittedly a bit of a stickler about them.  And I sometimes get frustrated when I find a very carefully compiled filter schedule on a machine with a ten-year old breather cap.  Oh, don't get me wrong - scheduled filter changes are crucial to keeping oil clean.  But system filters are primarily intended to trap wear contaminants in the oil, not trash that has found its way in from the outside.  Outside contaminants can get into your machine by:

• New Oil - it isn't clean enough to go in your machine.  Actually, when it is first refined, it probably is.  But it has to get to you somehow.  It goes through pipes, hoses and tanker trucks.  It is packaged, and by the time you get it, there are probably visible contaminants.  New oil must be filtered before going in.
• Reservoir Access Plates - whenever the reservoir is cleaned or internal parts are serviced, the oil is drained and the access plates are removed.  There is a reusable gasket, but be sure it is not cracked or brittle.  If it is, replace it.  Keep them stocked, they're cheap - a bead of caulk is not an advisable replacement.
• Cylinder Seals - we get accustomed to seeing them leak, but remember that if oil has a way out, trash has a way in.
• Hose and Component Replacement - these fail while the machine is in operation.  When production gets interrupted, we tend to take shortcuts to get back on line.  But remember, if we don't take the time to do it right, we may have to make time to do it over!

But the number one culprit is the breather cap.  It's regularly removed and replaced for adding oil and taking samples.  Its efficiency is directly related to the seal it makes.  Since it takes more oil to extend a cylinder than it does to retract it, the oil level changes every time a cylinder moves.  And each time it extends, outside air comes in the breather.  How often does this happen each day on your machine?

Does your reservoir have the best breather cap for its machine and environment?  If it still uses the same type that came with the machine, probably not.  Most machines are built by the low bidder.  Shipping with the best breather money can buy is not the best way to win a contract.  Seldom is a particular cap, or even a particular type of cap specified.  Upgrading the breather is usually left to the customer.

How should you go about choosing a breather?  There are actually two factors to consider -  your machine requirements and its environment.  The breather cap should filter intake air to at least the level of the return filters.  How effective can a 5-micron return filter be if the breather cap only filters air to 15 microns?  What type of environment is the machine in - dusty, dry, humid?  Perhaps a cap with a dehumidifying feature should be used.  If so, there are essentially two technologies to consider - a desiccant filter or one with a thermal moisture barrier.  The desiccant filter should be replaced when the crystals turn from blue to pink.  A cap with a thermal moisture barrier typically has a red light that illuminates when it needs to be changed.

The OEM should have a specification for airflow requirements, typically measured in Cubic Feet per Minute (CFM).  If not, your vendor can calculate it.  There are also several choices for filter media - steel mesh, paper and foam.

Standard filler breathers are the most common.  They can be used in applications where moisture is not a problem and the oil need not be filtered below 10 micron.  They should be checked and cleaned at least once a month.  Since their efficiency is directly related to the spring seal, they should be replaced at least once a year.  Don't worry - they only cost a few dollars.  These few dollars will be well spent.

If dust is a problem, the breather cap can be replaced with a filler cap that makes a full seal and a breather filter can be installed.  This type of breather is not unlike the air filter on your car.  It has a removable cover and a replaceable element.  The housing is available in different sizes to accommodate any amount of airflow.  The element can be chosen based on the filtration needs of your machine and can have moisture removal abilities.

A good compromise between a filler breather cap and a breather filter can be a filler breather filter.  This type looks similar to the spin-on filter you replace periodically in your car.  It can filter air as clean as 3 microns and is available with water removal technology.  Some types have indicators that pop up when they need to be replaced.

Whatever type you choose, be sure to maintain it as it needs to be.  There will be instructions - read and follow them.  But take your breather caps seriously.  The fact is, if something can't get in the breather cap, it will have a much harder time getting in anywhere else.  And please, don't allow any of your machines to look like this:

Nothing is more expensive than unscheduled down time.  GPM’s customers know they can call whenever they have a troubleshooting issue they simply can’t resolve.  With over 50 years experience dealing with hydraulic failures, our consultants have the resources to help troubleshoot whatever hydraulic problem you encounter.  Whether you’re experiencing a total system outage, repeated component failure or just need a professionally designed preventive maintenance schedule, the consultants at GPM can help.  Call GPM for 

            In-plant  Troubleshooting                                                

            Leakage Problems                                                         

            Pressure Settings

            Shock Problems

            Preventive Maintenance Scheduling

            Hydraulic Troubleshooting Manual Development

            Startup Consulting and Recommendations

            Heat Problems

            Repeated Component Failures  

            Speed Problems

Do you want to learn more about how GPM can help you? Go to http://gpmhydraulic.com/troubleshooting.htm

I've never done a study of just how much cylinder seals are costing people, but I bet the results would be astounding.  I have literally seen cheap little cylinder seals cost a plant several thousand dollars in down time and hydraulic leaks.  A surprising number of people think that cylinder seals are supposed to leak in order to provide lubrication to the cylinder rod!  No, they're not.  And if you are replacing them often, chances are good that you are using the wrong ones.

The next time you replace seals, pay attention while disassembling the cylinder.  Is there any scoring on the rod?  This is a big red flag.  If you see scoring, look for contaminants.  A particle count of your oil can tell you if the contamination is coming from the machine itself.  If not, it must be coming from the outside.  When the cylinder retracts is when your machine is vulnerable.  Check the rod wiper.  If it wasn't installed properly, trash can imbed itself in either the wiper or the seal.  Make sure the seals are not upside down.

If you're having to change seals often, what is the condition of the old seals in when you remove them?  If they are cracked or brittle, your cylinders are probably overheating.  If there is a chemical breakdown, the problem may not be the seals themselves - it could be your oil.  There could be some incompatibility with certain oil additives.  Your vendor can help with this.

The most common problem?  Improper installation.  Even when the cylinder is brand new.  Learn how to repair cylinders the right way with our Cylinder Replacement CD, available in the GPM Store.

Hydraulic Reliability and Troubleshooting 2011

3 Day Workshop

Registration Fee Only $895.00 Per Person
Three for the Price of TWO! Every Third Registrant Attends for FREE!
Early Registration - $845.00 For Confirmed Reservations Booked 21 Days Prior to the Start of the Workshop

We still have limited availability for registration -  Call (770) 267-3787 To Register

Learn More About Our Hydraulic Reliability and Troubleshooting Course 

2011 Hydraulic Reliability and Troubleshooting Schedule

*Call If You Would Like To See A Workshop Scheduled In Your Area!

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A step-by-step guide for changing cylinder seals and carrying out minor repair. The manual contains disassembly, inspection of parts, minor repair, assembly, examples of seal failures and their causes, hydraulic cylinder speeds, metric/inch conversion table, fluid power formulas, rod and piston groove diameters. 

$24.99 + Shipping & Handling

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GPM Hydraulic Consulting, Inc.
Box 1376
Monroe, GA 30655
(770) 267-3787

gpm@gpmhydraulic.com