Planning out a filtration solution for an application isn't easy. The various factors to consider and calculations to make can be daunting, especially to those approaching filtration for the first time.
A poorly designed filtration process will end up wasting your time, your money, and worst of all—your product yield. Fortunately, we have a lot of experience helping people integrate filtration into their processes and we can help you avoid some of the more common pitfalls.
Here is a list of the most common mistakes and how you can avoid making them when implementing filtration into your process.
1. Not Sizing Filtration Equipment Properly Before Purchasing
Let's start things off with one of the most common (and costly) mistakes we see during the planning stages, purchasing filtration equipment without sizing it to the needs of the application.
The amount of fluid you're processing in a production run is a crucial metric when selecting filtration equipment. That top-of-the line cryo-extractor you have that pushes out 100 gallons a minute won't mean much if your filtration step can only process 5 gallons a minute.
When shopping for filtration equipment, it is essential to factor in your desired flow rate. Otherwise, you could end up with a bottleneck in your process that cripples your production output.
That's exactly what happened to one of our clients in the Brewing industry. He found a used Vapor-Master filter press for a very affordable price and hastily made the purchase. Unfortunately for him, the press was built to accommodate a much smaller batch capacity than he needed.
The result? He ended up having to change out his filters multiple times mid-run. With an appropriately sized filter press, he would be able to run his batches without interruption and would end up with more sellable product at the end of the day.
2. Selecting the Wrong Micron Size for the Filter Elements
Filters are highly customizable and offer a multitude of options to choose from. For example, our String Wound Filters have 10 options for length, 10 options for media, 4 options for core material, 12 options for micron rating, 5 options for diameter and 12 options for end cap configuration–that's 288,000 possible combinations!
Of all these customizations, micron rating is the most difficult to get right. When faced with the vast number of choices it can be tempting to "ballpark" a micron size just to get it over with.
Here's the problem with that: there is no "one size fits all" choice for micron rating, and the micron rating you choose can have drastic effects on your filtration process. If you go too small, you could impede your flow rate. If you go too big, the contaminants you're trying to catch will sail right through your filter.
So how do you pick the right micron size to fit your needs? The answer involves doing some research. First, you need to have an intimate understanding of the condition of your fluid. That means figuring out the size and consistency of the particles you want to remove. This can be done in two ways:
Particle Distribution Analysis
If the size and composition of particles in your fluid remains fairly constant, doing a Particle Distribution Analysis will give you a breakdown of the average particle sizes. This information can then be used to determine the best micron rating to choose for your filter.
If the particle consistency of your fluid varies, your best option is to conduct a Filterability Study. This involves using lab-scale equipment and media to test small samples of your fluid. These tests will determine how quickly your fluid moves through varying filter media and micron sizes as well as the resulting clarity of the filtered liquid.
The results are then dialed into a calculation along with your desired flow rate to determine the size of filter equipment needed, the best filter media and micron rating for your needs.
3. Using Materials that are Not Compatible with the Fluid Being Filtered
You've likely heard the phrase "you have to have chemistry" regarding relationships. Well, the same applies to choosing the right materials for your filter element. If your filter materials are incompatible with your fluid chemistry or temperature, you could be in for a rough ride.
Typically, filter elements are made of three parts: the core, the filter media, and the seals. Let's take a look at what can happen when each of these components becomes compromised by chemical incompatibility.
Incompatible Core Material
For cartridge filters, the filter core plays a vital role in maintaining the structural integrity of the filter. It's literally the backbone of the filter. If the process temperature or chemicals in your fluid jeopardize this structural integrity, the weakened core could buckle under pressure, causing the filter to be crushed. This would then release all the trapped contaminants into the downstream fluid—an undesirable situation to say the least.
Incompatible Media Material
Your filter media is what separates the contaminants from your fluid, so it's best to make sure that it remains strong and intact. When filter material reacts negatively with chemicals or elevated temperatures of the fluid, the pores of the filter media can swell and close off, restricting (or in some cases, completely blocking off) your flow rate. As if that weren't bad enough, if the chemicals in the fluid are particularly aggressive, the filter material could dissolve completely.
The risks are similar when filtering fluids that are chilled to extremely cold temperatures. Plastics can become brittle and lose integrity with extended contact with extremely cold fluids.
Incompatible Sealing Materials
Filters need to form a positive seal when compressed against the sealing surface so that the clean side of the filter is separate from the dirty side. This is achieved through the use of a sealing element such as a gasket or an o-ring.
If the filter doesn't seal properly, the unfiltered fluid will mix with the clean fluid causing all kinds of problems downstream. This scenario is known as "bypass" because the dirty fluid is bypassing the filter media—like hopping the turnstile on the subway.
Incompatible fluids can erode or even completely dissolve these seals, literally opening the flood gates for your unfiltered fluid.
Using a Chemical Compatibility Chart
As illustrated above, a lot can go wrong when your filter materials aren't the right match for your fluid. Thankfully, the solution is simple: use a chemical compatibility chart! These charts provide tabular data that will help you find the perfect match for your fluid.
4. Getting the Wrong Type of Pump
Your fluid needs a driving force to move it through your filtration system. The most common and effective way to do this is by using a pump. Not all pumps are created equal, however, and the type of pump you use can have drastic effects on your filtration process.
Double diaphragm pumps are a popular and powerful way to move liquid through a system. Using this type of pump for filtration, however, offers less than desirable results.
Filters prefer a constant flow versus the surged flow generated by double diaphragm pumps. When the flow rate rapidly changes, particles that would normally be trapped by the filter media can be pushed through to the clean side. The repercussions of this can be particularly dire if the filter is being used to protect expensive downstream equipment.
The solution is to use a pump that generates a constant flow of fluid. Centrifugal pumps and gear pumps are great alternatives to diaphragm pumps and should always be considered when planning out your equipment setup.
Here are some things to consider when choosing a pump:
- Viscosity of your fluid
- Batch size of your production runs
- How far the fluid is being driven
- Any components in your process stream that will offer resistance to flow.
5. Mixing Up the Inlet and Outlet of the Filter Housing
So far, we've focused on mistakes made during the equipment selection phase. Now we'll take a look at mistakes made during the installation and operation phases.
One of the most common installation mistakes we've seen is when someone swaps the filter housing inlet and outlet when piping it into their process. While it may seem harmless, reversing the piping of your filter housings can cause serious issues.
We've talked about the dangers of backflow in a previous article and how it can damage your filters. Unless specifically designed for backflushing, filters can only handle flow in a single direction. With the exception of filter bags, this direction is almost always from the outside in. Reversing this direction will impede the flow rate and has the potential to damage or destroy the filter.
Luckily, most filter housings will label or mark the inlet and outlet pipes with the proper flow direction. The filter equipment manual will also feature this and other important information—a topic we will dive deeper into in the next section.
6. Neglecting to Read the Filtration Equipment Manual
According to the U.S. Bureau of Labor Statistics, contact with objects and equipment was the fourth leading cause of workplace related fatalities in 2019. With that in mind, it's safe to say that ensuring your equipment is installed and run properly should be a top priority. Even so, there are still those who look at manuals as more of a "guide" than a strict set of rules.
The problem? This isn't some bookcase you bought from IKEA. The instructions aren't just a suggestion and ignoring them can have devastating repercussions. By disregarding your equipment manuals and SOPs, you not only risk damaging your equipment—you risk the health and safety of whoever is operating that equipment.
For example, every filter housing has a maximum pressure rating at a given temperature. This information will always be included in your equipment manual and will often be printed somewhere on the equipment as well. Operating outside these limits can irreparably damage your equipment and in some cases, lead to serious or fatal injuries.
Whenever buying used equipment, first ensure the equipment still has its original installation and operation manual.
Grim as that may seem, the solution is as simple as reading the manual! Most manuals do a good job of calling out safety information in such a way that is immediately recognizable.
7. Forgetting to Vent the Air from the Filter Housings at Startup
Let's end on a mistake with less gloomy consequences. When starting up your filtration equipment for a run, it is important to vent the air from the filter housings as they get filled with liquid—a step that is often skipped by first-time users.
Why is this an issue? The air trapped in the housing forms a bubble that keeps the liquid from filling the housing completely. This prevents the liquid from occupying the full surface area of the filter inside, stunting the overall flow rate.
To account for this issue, most housings have either a vent port or a built-in vent valve that allows air to escape the housing as it fills up with liquid. Once the air is completely vented from the housing, the vent valve can be closed, and the filtration process can continue at optimal efficiency.
As you can see, there are many ways to miss the mark when it comes to implementing filtration into a process. Hopefully, you'll walk away from this article with a better understanding of why these issues are important and how you can avoid them.
The bottom line is this: when the obstacles in your path become overwhelming, don't let the pressure lead you into making hasty decisions out of desperation. Instead, reach out to someone who has walked the road before. We've done this many times and we can help you keep your business on track.