How to Pick the Proper Filtration Equipment
Filtration is the process of removing any undesirable matter (solids or otherwise) from a process stream such as liquid or air. The incoming stream prior to filtration is called the effluent while the outbound stream after filtration is referred to as the filtrate.
In any fluid-handling operation, filtration helps to maintain peak productivity by improving the performance quality through the removal of any undesirable contaminant. There are numerous filtration applications in markets such as chemical, food and beverage, paints and coatings, pulp and paper, power generation, and other industrial processes which require specific and properly-selected filter equipment. Selecting the right equipment is a crucial component to optimizing your operations. To determine the proper filtration equipment requirements, one must understand a host of process conditions and variables that may influence selection decisions.
There are two golden rules to consider when selecting filtration equipment. The first is that the nature of the contaminant will always dictate how exactly it will be removed. Impurities being removed react differently to various filter media. Optimal removal will be dependent primarily on particle size and shape, if the particle is a solid or deformable, how the particle behaves in fluid, and is it inert or “alive”? Fully understanding what the contaminant is all about will help assure the correct filter type and filter micron size are selected.
The second golden rule is that the process conditions and process variables will dictate the material selection of the equipment. Among the various process conditions and variables, here are the key factors to consider for proper filter selection.
- The viscosity of a fluid
Viscosity is the measure of how resistant the material is to flow. This can depend on how thick and sticky the material is. Filtering viscous fluids down to lower micron sizes will typically require larger filters and also a properly selected pump as these viscous fluids are more resistant to flow.
- Flow rate
The amount of material pushed through a filter in a given time determines how large the filter and filter housing need to be. With higher flow rates, one must make sure to have enough filtration area in order for the filter to perform properly and be optimally efficient.
- The temperature at the point of filtration.
The filter material must be durable enough to withstand the actual process temperature of the application.
- Chemical compatibility issues
Chemicals that do not change their physical properties and remain chemically stable while interacting are considered compatible. The given fluid’s chemical make-up and how it might react with the filter media, filter housing material, and seal material must be considered to avoid any deterioration due to chemical incompatibility.
- The Inlet pressure of the pump
Inlet pressure affects the filter performance the same as the flow rate. Most industrial filters are rated up to a forward pressure of 150 PSI; while hydraulic filters can be routinely rated to 500 PSI and greater. However, every filter media has a maximum differential pressure it can handle prior to change-out and to prevent inefficiencies. The difference between the inlet pressure from the pump and the outlet pressure drop after the fluid goes through the filter is the differential pressure. Every type of filter media will have a maximum recommended differential pressure rating which determines the point when that filter needs to be changed.
- The desired capture efficiency.
The size of materials allowed to pass through the filter is determined by the micron size. Typically, a filter is either manufactured with a nominal or absolute micron rating; which denotes the smallest size particulate that the given filter will remove. Again, the size of the contaminant will typically determine the desired “capture point” and then % removal requirements will determine just how clean one’s system needs to be. In all cases, the lower the micron size, the smaller the particle size captured.
- Initial clean differential pressure desired.
As stated above, the differential pressure is a measurement of the difference between the downstream and upstream pressure readings. Ideally, and for the longest filter service life, a filter system should be sized for the lowest allowable clean differential pressure drop when a new filter is installed. In the majority of process applications, a clean differential pressure drop of no greater than 5 PSID is a typical target point.
- Where in the process line is the filter going to be installed?
The system setup, piping, and types of connections need to be considered as the size and dimension of the filter housing and its orientation need to be considered.
- Batch vs Continuous
In general, there are two main types of filter processes; a batch process and a continuous process. A batch process is a shorter, more definitive-run filtration process usually seen in applications such as paints, coatings, inks, and chemicals. Typically, bag type filters are used for these materials, where they are changed every batch and are typically less costly than filter cartridge elements that are designed for longer runs but more expensive.
A continuous process is a longer (continuous), more constant process/operation typically greater than 24 hours and sometimes even weeks, months, years, etc. Continuous process applications include boiler room water, some RO/DI water systems, hydraulic-driven oil applications, plant air systems, etc. Cartridges are the predominant choice for continuous filter systems as they offer superior cleanliness, longer life, and much wider media and micron choices.
Determining and verifying all this information can be time-consuming. Anderson Process’s in-house filtration equipment experts know filtration technology inside and out. Our team will take the time to learn about the unique challenges of your operation; all while assisting and guiding you to properly navigate the selection and specification process. Coupled with our comprehensive line of filtration products, our joint analysis will allow us to determine the optimal filter specifications to integrate into your process to enhance efficiency, output, and profits.