How Do You Choose the Right High Flow Filter for Your Application?
Choose the wrong filter and you're gong to know it. Pressure reads skyrocket, flow drops and it's time for someone to get up and swap elements at 2 a.m. on a Sunday. Choose the right one and you'll hardly think about it for months.
High flow filters are designed to pass high volumes of liquid through small-size housings with minimal pressure drop. This unique characteristic makes them useful in several sectors such as chemical processing, machining, and water treatment, just to mention a few. However, when someone mentions high flow, it does not mean that is the only one available. This guide takes you through the relevant options to consider, so you can limit your options before contacting a supplier.
What Is a High Flow Filter?
A high flow filter provides much more surface area than a standard filter by increasing the diameter of the pleated element, commonly to 40 – 60 inches or longer. By providing surface area, the liquid is distributed over it, decreasing the velocity with which it flows through the media. This means higher flow rates with less housings and smaller footprint.
For a plant with thousands of gallons a minute throughput, that can be replacing a bank of old filters with one or two vessels. Less vessels means less seal leaks and less elements to change.
Begin With Your Liquid
What Are You Filtering?
Water, oil, solvents, coolants, chemical solutions – there are many different types. And they behave in quite different ways. In these cases, viscosity is a key factor. If the fluid is thicker then it will be slow and exert a larger pressure drop, requiring more filter area to achieve the same flow.
Chemical Compatibility
This is where errors are costly. The filter media, end caps, seals and housing all need to come through exposure to the fluid. Polypropylene is resistant to many acids and bases; nylon, PTFE and stainless steel are good for other applications. Consult the compatibility chart and make sure the P-A-R-T-S that come in contact with the fluid are compatible (O-rings too!).
Temperature and Pressure
Be aware of your regular operating range and your maximum potential spikes. It might be okay to use a filter that is rated for 70F, but it may disintegrate or become waterlogged at 180F. Make sure your housing has a pressure rating exceeding any pressure the system is capable of generating.
Choose What to Get Rid Of
Micron Rating
The micron size tells you how big the particle is that the filter is capable of catching. Don't go too fine. Going too fine causes the filter element to clog faster and increases the costs of changing it. Use the coarsest rating that will still meet your need or quality standard.
Nominal vs. Absolute Ratings
A nominal filter catches so many particles of that size. Typically that is around 90 percent. An absolute filters almost everything of that size.
Generally that is around 99.9% or more.
When one stray particle can ruin your product or destroy a pump, always go for the absolute. For general use, nominal works fine and is less costly.
Dirt-Holding Capacity
How long two same micron rated filters will last can be very different. Capacity is a function of media depth and media surface area. Even if taking longer to change saves on labour, you will save on downtime, so it is worth the comparison.
Determine Your Flow Needs
Get to know the maximum flow rate, not just average. When sizing a filter, aim for a comfortable load well below rated flow rate. You'll be glad you did - a filter pushed to its limits will not last long and won't perform well.
This rough rule of thumb: select a filter that can flow about 20 to 30 percent higher than your maximum flow. This allows for peak surges and a slow increase in pressure as the element gets dirty.
Also, consider the initial pressure drop. If a system is clean, the differential pressure should be low and the plant should be comfortable with the rise as the system fills. Many plants switch elements when the differential pressure hits somewhere in the 15-to-25-psi range depending on the suppliers' instructions.
Match the Filter to the Application
Industrial Water and Process Water
Pre-filtration prior to reverse osmosis, cooling tower makeup and boiler feed. This application can use pleated polypropylene or polyester elements as they can be cost effective.
Machining & Metalworking
Fines, tramp oil and bacteria are captured by coolants. The success of any coolant recycling system is heavily dependent on clean filtration, which promotes longer fluid life, tooling protection, and reduction in disposal costs. When the filter is undersized or micron rating is incorrect, the recycled coolant delivers abrasive particles back to your machines, resulting in dull spindles and inferior surface finish. Consider media for oily liquids and a micron rating suitable for your finishing.
Chemical and Food Processing
And here, it is cleanliness and regulatory compliance first. Seek media that complies with food-contact regulations when necessary, and inquire about extractables and cleaning processes.
Take Into Account Total Cost Beyond Price
A discount part that wears out every week is more expensive than an expensive piece that lasts two months. When you add everything together:
Price of element, and frequency of replacement.
Labor for each change
Time lost during changeouts
Disposal costs for spent elements
Power losses related to pressure drop
A high flow filter that is selected correctly will pay for itself many times over in reduced changeouts.
Think About Maintenance and Ease of Use
It's also good to ask how the elements are changed. Many models are light and can be removed with one hand - that's important when a technician needs to do the replacement dozens of times a year. Consider models with easy-open housings, visible drain and vent ports and gauges that signal when it's time for a change.
If space is limited make sure you have room to pull a long cartridge up and over. People often run out of room on Installation Day.
Common Mistakes to Avoid
Choosing a micron rating that's too fine
Ignoring seal and O-ring compatibility
Sizing for average flow rather than peak flow
Comparing price per element without considering lifespan
Bypassing a pilot test with unique fluid characteristics
Frequently Asked Questions
What's the difference between a high flow filter and a filter?
In high flow filters, bigger cartridges are used, with way more surface area, so you can flow higher volumes in much less room, and with less pressure drop.
How do I know when I need to change the element?
Monitor the differential pressure. When it reaches the manufacturer-specified maximum, or when flow dramatically decreases.
Yes, it is for cleaner water filtration. Can you use a high flow filter in coolant recycling?
Yes. They are commonly used to remove fines and contamination so the coolant can be used longer. Use the media and a micron rating that works with oily fluids.
Should I choose a nominal or absolute rating?
Use absolute if product quality or equipment protection requires virtually all particles to be captured. Use nominal if average collection is acceptable.
Final Thoughts
It's three questions really: What's the fluid?
What needs filtering?
How much flow?
And what's the lifetime cost?
Answer those four questions right, and the options quickly become clear. If in doubt, tell a supplier what your fluid is, what flow rates you need, the temperature and the cleanliness level you are trying to achieve, and ask for a formal proposal.
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