The modern hydraulic systems put more emphasis on precise lubrication and contamination control.
As a result, there is always a need to have the right knowledge on how to select the right filter cart.
With this, you can easily avoid catastrophic mistakes that can lead to component failures.
Furthermore, this can lead to unnecessary expenses.
In this article, you’re going to learn about 5 things you must consider when choosing a filter cart.
1. Have an In-depth Understanding of the System Parameters
Well, this is the first step to choosing a suitable filter cart for your industrial system.
By knowing the system pressure and temperature, you’ll choose a filter cart that will optimize filtration efficiency.
Remember, the design of a hydraulic filter cart, especially at the pump and filter section depends on the viscosity and temperature.
That is, high viscosity that meets the ISO VG 220 oil will basically require a low flow rate to limit the higher differential pressure across the filter.
On the other hand, temperature may affect the viscosity of oil.
At low temperature, a slow flow rate that prevents high differential pressure will increase the filtration time.
As a matter of fact, choosing either very high or low flow rate may be costly.
This is because in most cases it can lead to machine failure or damage.
Under normal circumstances, you should pump about 10% of reservoir volume per minute.
You can calculate flow rate by determining the time it takes for all oil to pass through a filter to reach the set target.
You can use this simple formula:
In short, you need to have a clear understanding of how the system behaves whenever there is a change in viscosity, pressure, flow rate and temperature.
With this, you’ll choose a filter cart that will be efficient.
2. Which Application (s) Do You Intend to Use Filter Cart For?
Filter carts are mainly designed for routine filtration.
That is, a cart can be used to clean oil externally as the machine operates.
However, this is not the only application of oil filter carts.
You may use it to change oil or take samples during the process.
In such circumstances, filter carts should be uniquely designed with a bypass valve, drum and even explosion-proof options.
With an attachable and secured drum, you can conveniently recirculating or transferring fluids.
Moreover, while considering the specific applications of oil filtration units, it is important to analyze other features such as its weight, design and shape.
It should be one you can carry and install easily.
You should choose one with an appropriate power source depending on the environmental condition.
That is, even though most of them use electricity, in areas with explosive gases or dust, air driven motors will be a perfect choice.
Apart from the standard designs, there are stripped down versions.
Even with these versions, ensure they have the right fittings, efficiency, safety or sample valves (where necessary).
In short, you must assess the type of application and the exact location where you intend to install a cart.
3. Consider Type of Filter Elements
The type of filter elements will determine the efficiency of a cart.
Normally, it is the desired cleanliness level that determines the choice of various filter elements.
You can choose:
- Unique filter element pore size
- Several filters in parallel to balance between filter rating and flow rate
- Double length of the element to halve the differential pressure
- Filter with an appropriate capture efficiency or Beta rating
- Filter with better dirt holding capacity
These filters come with a wide range of Beta rating and pore size depending on the unique applications as indicated below:
- 6μ βx ≥ 200 for gearboxes
- 3μ βx ≥ 200 for hydraulics
- 3μ βx ≥ 200 for bearings and circulating systems
As you go through this evaluation process to get the best oil filter cart element, it is worth focusing on how costly the contamination will be in the system as opposed to the cost of filter element itself.
Another critical element to consider here is the right pump for a filtration system.
You should ensure that the type of pump for any filter cart suits its unique application.
There are many factors that determine the choice of a specific type of pump:
- Type of oil filtration units
- Viscosity of fluid; the ISO VG 68 and ISO VG 460 fluid will definitely require different types of pumps
- Desired flow rate; to increase efficiency and guarantee safety, it should pump up to 10% of reservoir volume per minute. Therefore, it’s unrealistic to have a pump with a 2 gpm capacity in a system with over 6000 gallon reservoir.
- How do you power the pump? The modern filter carts can be powered using electricity, air motors, single or 3 phase motors.
When you consider all these, obviously you’ll choose a pump that will increase efficiency.
4. Consider the Desired Cleanliness Level
The level of cleanliness will determine the type of filter rating.
This implies, whenever you think of buying a hydraulic oil filter cart, you need to know the type of hydraulic systems.
With this knowledge, you’ll definitely choose the right pore size.
Furthermore, you’ll use this knowledge to ensure filter cart are arranged to guarantee optimal performance.
As a general rule, the pore size of the finest filter should be smaller than the size of particles you’re trying to eliminate.
In most cases, you’ll use 6 microns for gear oils and 3 microns for hydraulic fluid.
Remember, all these cleanliness processes should conform to the ISO standards.
For example, when your cleanliness target is ISO 15/13/10 then a filter element rated 10 micron can achieve better results.
However, if the desired cleanliness level is below this, then you may consider a 6 micron filter.
In short, it is the cleanliness level that determines the type of filter element.
In most cases, these carts are such that they have two filter elements.
That is, the oil passes through the coarse filter before it reaches the small-pore filter.
Let’s look at some possible scenarios you may encounter while choosing filter carts:
- One filter element is suitable for systems that are sealed and a possibility of being contaminated by large particles or water is unlikely during oil filtration process.
- Use cellulose filters to remove soft particles, which may be as a result of oxidation.
- For situation where moisture is a problem, the first element should be a water filter that doubles up as a course filter.
When you pay attention to these, I am quite sure you’ll get an efficient filter cart.
5. Know the Type of Oil You Wish to Filter
Here, you need to be clear about the viscosity level, contamination degree of the oil you intend to filter.
Remember, oil viscosity and particulate & water contamination will determine the type of pump mechanism, flow rate and overall efficiency of the system.
Take for example highly viscous oil has a low flow rate.
However, when you pump it at a high speed, air bubble may form in the machine and this may damage the pump and cause oxidation.
Filter elements for highly contaminated industrial fluids should adopt special filter materials with reliable separation characteristics and high deep-level filtering capacity.
High solid filter carts are widely used in the waste oil regeneration and depth filtration.
In short, you need to specify the ISO VG, water and particle content of hydraulic fluids.
Conclusion
As you can see, buying a filter cart involves a lot of analysis.
Failure to consider these 5 aspects will come at a high cost.
Generally, you have to choose the right filter carts, decide on the level of cleanliness based on ISO standards, specify the application of your systems and state the ISO VG.
Remember, consulting widely with professionals in this industry will help you eliminate all contaminants, thus improving efficiency and reliability of your system.
Further Reading
- Design, Construction and Evaluation of Hydraulic Oil Filtration Cart– By Eric Steiger.
- How to Define and Achieve Hydraulic Fluid Cleanliness– By Brendan Casey