If hydraulic fluid is the lifeblood of your system, hydraulic fluid contamination is its Achilles heel. That’s because even unseen, microscopic particulate matter in the fluid can bring colossal machines to their knees. In this war against contamination, the hydraulic filter is your first and only line of defence. When in good condition, filters will diligently remove debris and contaminants from the fluid - protecting your valuable machinery and saving you untold thousands in repair costs.
However, your filters are always fighting a losing battle. The more they operate, the more the contamination levels rise and eventually they become too fouled to perform correctly. When this happens, your filter is no longer able to protect the sensitive reciprocating parts in your system such as seals, piston surfaces, pump vanes, and other components. Leading to increased wear.
Thus, replacing your hydraulic fluid filters regularly is an important practice, but it’s also important to optimise the frequency of replacement to maximise the value of your filters and to keep your maintenance costs low. Replace too early and your maintenance costs will increase unnecessarily. Replace too late and you run the risk of damaging your hydraulic machinery. So, how can one maintain a watchful eye over the contamination levels of your hydraulic filters? That’s the job of the clogged filter indicator.
The clogged filter indicator is a device which may be fitted to any hydraulic filter, which provides visual verification of the contamination levels within. It’s a small, clever component that could save you thousands in maintenance costs over the long term. That’s why it’s an important weapon in your fight against fluid contamination.
How clogged hydraulic filter indicators work:
Clogged filter indicators are also known as Differential Pressure Indicators - for a good reason. They measure the pressure on the inlet side of the filter element and compare it to the pressure on the outlet side. This difference between pressures gives an indication of how easily the fluid is able to pass through the filter element.
The more clogged the filter, the more it restricts the fluid flow. Thus, the fluid on the outlet side will become progressively lower in pressure as the contamination levels rise. When the pressure falls below a certain level, it triggers a signal that it is time to change the filter.
There is a wide range of clogged filter indicators available, but here are two of the most common examples.
Mechanical Pop-Up Button Type:
Mechanical filter indicators utilise a magnetic system. A spring-loaded button is held down by a magnet attached to a piston within a tube. As the pressure lowers on the outlet side, it withdraws the piston. Consequentially, the magnet moves progressively further away from the button. As it does so, the magnetic force weakens. At a certain point, the distance becomes too great and the spring pressure exceeds the magnetic force and the button pops up. Providing a simple visual indication to the maintenance engineer that contamination levels have been exceeded. In this system, the button will remain extended even if pressure returns to normal - and must be manually reset.
Electrical Microswitch Type:
Electrical switches operate on the same principle with the magnet-piston arrangement, however, in this case, the magnet performs in such a way as to complete an electrical circuit, which sends a signal to a visual indicator. Depending on the model, this indicator could be as simple as a light. In other cases, it may connect to a computer system, which monitors the device remotely.
The advantage of electronic clogged hydraulic filter indicators is that they are more versatile and have the ability to reset automatically. Thus, they can accommodate for things like pressure differentials created during cold-start situations.
In a cold-start situation, the fluid pressure differential may initially be too low, but will return to normal levels once the fluid reaches operating temperature. In this case, a Single Pole Double Throw Switch features a red and green light. When the pressure differential is within acceptable limits, the green light is illuminated. If the pressure differential is too low, the red light illuminates. In the cold start situation described above, the light would appear as red, but change back to green when pressure normalises as the fluid heats up. Thus, this type of electrical pressure differential switch can also perform the function of a system warm-up indicator.
Save your equipment & save on maintenance costs
As you can tell, the humble clogged filter indicator plays a significant role in the health of your equipment and the state of your maintenance costs. So it pays to select the right type for your application and your situation and to pay attention to what they’re telling you. Berendsen offers a wide range of these components from our principle supplier - Pall Corporation - among other brands. For information and advice on selecting the right indicator for your needs and your machinery, please contact our sales department who will be glad to assist you.
The Importance of Changing Hydraulic Filters
Hydraulic filters aid in trapping dirt, dust and other unwanted particles in hydraulic machinery. This filtration ensures that contaminants are kept out of the fluids, airways and cavities. In the ACES Workshop, we have found the that number one cause for hydraulic system breakdowns is due to contamination. Having a neglected filter in your machine, can be worse than having no filter at all!
When a hydraulic filter clogs, fluid cannot pass freely through, creating a pressure drop in your machine. If the pressure drops so low, and the filter has a bypass valve; fluid will bypass the filter entirely and introduce new contaminants to the system. If there is no bypass valve set up on your filter, the filter element will collapse, and all contaminants will enter the system in any case. If a filter was not to collapse, it would cause cavitation quickly damaging the hydraulic pump before catastrophic failure.
A contaminated hydraulic system will firstly cost you a lot of money. The downtime associated whilst investigating the failure delays productivity, damaged machinery parts such as pumps or motors will need repairing (or replacing), hydraulic fluids will need to be flushed and then re-filled with brand new fluid, hydraulic hoses will need to be blown out, new filters installed… all when you could have just changed that hydraulic filter to begin with, at a fraction of the cost!
It is far more economical and practical to establish a routine preventative maintenance schedule for changing your hydraulic filters. Regular changing of the filter solves the problem of having a clogged filter to begin with! This will enable your machine to run at maximum efficiency, promoting cleanliness of your hydraulic system, retaining its value and stay in service longer.
Which leads us to the ultimate question, when is the right time to change your filter? Some say this is according to the manufacture’s recommendations, and usually then proceeds to give you a time in operating hours. The drawback to this approach is that the filters may or may not need to be changed, just because you’ve had, say 15 hours clocked already. The filter might not require changing yet, and you have just wasted some of its useful filter life. Or it may be well over due and already clogged, thus allowing contaminants into the system. In some cases, it is better getting advice from a hydraulic machinery repairer as their own experience with the equipment sometimes proves useful to develop a schedule for changing the filters that makes better use of overall filter life.
Another way to know when to change filters; is using a hydraulic filter clogging indicator. This measures the pressure drop across the filter, and once it reaches a critical low pressure, will reveal that a filter change is required as well as impending failures down the track. This approach can be very useful, however requires constant monitoring, upfront investment in the actual indicator itself, a reliable data logging system, and a technician who knows just how to extract the information from that data.
In summary, it is best to consult both the manufacturer and service technicians to best work out a routine preventative maintenance schedule of your hydraulic system.