Polymer Filter Elements
Pall Corporation has been providing leading-edge, process-enabling solutions for the plastics industry for more than half a century. Through innovation and experience, we’ve evolved into the largest and most diverse filtration, separation, and purification company in the world. Pall offers a complete line of porous metal filter elements to serve the needs of the polymer processing industry. From intermediates and pre-polymers to final filtration and spin packs, Pall provides the solutions for your specific and exacting filtration needs. Through our polymer element and system design technology combined with our metal fiber and media manufacturing expertise, we deliver a broad array of filter medias and elements for a range of performance points. If your success is measured in microns, let Pall’s polymer filtration technology help you achieve the precision your film, fiber, and resin production requires.
Filters for the manufacture of high performance polymer fibers, films and resins.
Whether you are making ultra-thin films, optical grade resins, or strong fibers, the quality of your polymer has a major impact on end product quality. Implementing the proper filtration system and filters can help you to get the result you want and need. There are a lot of choices when it comes to filters— from media type to element size and design, selecting the right one is essential for getting the outcome you are aiming for. That’s why Pall has invested in providing a wide range of options to fit your specific need and a team of experts that can advise you every step of the way.
Pall uses five advanced types of media to make its family of polymer elements: Dynamesh™ sintered wire mesh, Dynalloy® metal fiber, PMF™ metal fiber, PSS® sintered powder metal, and PMM® composite media. The mechanical properties of each of these media are uniquely engineered for their specific role and for targeting a specific outcome for our customers. Having all of these options ensures that the appropriate media is selected for your process.
Dynamesh filter media is our precision woven wire cloth filter media, specially suited for applications with adverse pressure conditions and low contaminant loading. This media offers good permeability, narrow pore size distribution, and excellent corrosion resistance. Because it uses surface filtration, this is especially good for the capture of hard particulate.
Pall Dynamesh is able to retain its porosity even through an extensive number of compression cycles, therefore offering superior resistance to compression versus the competition. It’s available in a variety of weaves and alloys ranging from 5 to 400 microns and can be manufactured into many element styles, including both candles and discs.
Dynalloy filter media is Pall’s depth-type random metal fiber media. Superior performance starts with the creation of the metal fiber itself—Pall is one of just a few companies globally that has the capabilities to produce the base microscopic filaments. Through our proprietary manufacturing process, metal fibers begin as wire drawn from stainless steel and other metal alloys. The resulting fiber can be as much as 30 times finer than a human hair, allowing for unique and innovative end-products.
The fibers are then sinter-bonded to form a durable, porous structure containing no binders. This media acts as a depth filter and is extremely effective in removing hard and deformable gel-type contaminants. With a porosity of up to 90%, it provides maximum dirt-holding capacity and longer on-stream life than other porous metal media. Dynalloy media is engineered to withstand high differential pressures, high temperatures, and repeated cleanings. It is available in absolute ratings from 1 to 100 microns and comes in 316L stainless steel as well as a variety of high-temperature, corrosionresistant alloys. While Dynalloy media can be customdesigned to your exact specifications, it is also available in two standard formulations.
The X Series is a proven performer with high permeability and dirt-holding capacity, offering consistent and reliable filtration. Our advanced 1000 Series incorporates an “asymmetric” graded pore structure for applications requiring an even greater dirt-holding capacity and extended on-stream life. Dynalloy media can be used in both pleated candles and disc elements.
Like Dynalloy fiber metal media, PMF media also uses the thin metal fibers produced at Pall. However, for PMF media, Pall uses a proprietary method of creating the media, which results in a highly uniform pore structure. The uniformity ensures consistent filtration performance and flow characteristics within each filter.
The medium consists of sintered stainless fibers configured to create a continuous tapered pore structure. The unique structure of PMF medium maximizes dirty holding capacity, resulting in a long service life and is also capable of capturing both hard and soft particulate. Because of its special manufacturing method, PMF media can only be configured into disc elements.
Pall’s H-Series PSS media is constructed of stainless steel powder. The media is manufactured by a proprietary process that produces an open matrix of particles, all sinter-bonded to each other at the contact points. Pall’s unique powder lay-down and sintering techniques are designed to attain and increase void volume and maximum uniformity. Because Pall’s PSS media offers a higher void volume than competing powder metal medias, it increases the dirt-holding capacity and has a slightly reduced pressure drop across the media.
The service life between cleaning cycles is typically two or more times longer, resulting in fewer changeover and cleaning interruptions during polymer processing. PSS media is ideal for polymers that carry a higher ratio of soft versus hard particulate by capturing and shearing gels. This property makes it the most suitable media for use in ultra-thin films or other applications where gel control is essential. Because of the H-Series PSS high strength properties, it can only be formatted in disc form.
Pall’s porous metal membrane (PMM) medium is an extremely robust composite of stainless steel mesh and stainless steel powder. This structure is used as a secondary layer, often coupled with PMF media, in order to provide greater strength, permeability, and gel control. Although this can be combined with other medias, it is most commonly used in disc format filters.
Filter Media Selection
Choosing the right filter media is essential for achieving the polymer characteristics you desire, hitting your quality requirements, reducing down time, and being as cost efficient as possible. With so many options to choose from, let Pall’s team of experts guide you to the filter media that is right for your process.
At Pall, we design and manufacture metal filter elements for polymer and pre-polymer processing in a variety of styles that include candle, disc, and pack disc. Manufactured from stainless steel and a variety of hightemperature, corrosion resistant alloys, our elements are built to withstand numerous cleaning cycles.
- Nitronic® 60, an anti-galling and wear- resistant stainless steel, offers extended thread service life
- Outer guard (option) protects the media from inadvertent damage during handling
- Pleating maximizes the lter area, resulting in extendedon-stream life and reduced operating costs
- Internal volume reducer and streamlining cone (optional) enhances ow and eliminates low ow areas
- Dynalloy sintered metal ber lter media, supported by wire cloth, offers unparalleled ltration performance and endurance to cleaning
- All stainless-steel welded support core for uncompromising performance in adverse pressure conditions up to 175 bar (2540 psid)
- Internal hex design (optional) facilitates element removal/ installation and eliminates external wrenching ats and low ow areas at the mounting plate interface
Pall’s candle filters are rugged, with all welded construction and are designed to withstand the rigors of polymer processing. They are highly effective in removing hard and gel-type contaminants in high-pressure, highviscosity polymers. Using our Dynalloy or Dynamesh media, they are engineered to withstand repeated cleaning cycles for long service life.
Through years of experience and customer feedback, we have optimized the candle filter to perform under the most intense quality requirements. Every subtle feature of Pall’s candles has a purpose and an impact on performance.
Durability—cleanable and reusable for rigorous polymer service.
Adapter—made from Nitronic1 60 material. Nitronic 60 material is the best anti-galling and wear-resistant stainless steel available. Nitronic 60 material has outperformed 304 stainless steel in corrosion resistance and is superior to 316/316L stainless steel in pitting resistance. The result is extended thread service life. Conventional candles typically use 304 stainless steel or equivalent material for their adapters.
Internal hex design—facilitates element installation/ removal and eliminates external wrenching flats and low flow areas at the mounting plate interface.
Outer Guard—designed to protect the media during handling, operation, and cleaning.
Pleat technology—pleating maximizes the filter area resulting in an extended on-stream life and reduced operating costs.
- All metallic 316L fibers with other alloys also available. • 100% fiber media manufactured by Pall..
- 100% integrity tested in final configurations.
- Standard and custom designs are available.
Pall offers candles with both traditional fan pleating as well as a patented laid-over-pleat design. Both our fan-pleat and Ultipleat® laid-over-pleat candles are constructed with a strong support mesh to help pleats resist bending and pinching, and maintain spacing. Because of the unique lay-over-pleat in our Ultipleat style candles, they pack a higher surface area than traditional fan pleats making them desirable for those processes where changeovers occur frequently and are especially costly or time consuming. Discover our Ultipleat Plus fiber metal filters, which are ideal for pre-polymer and polymer melt applications.
Traditional fan pleat geometry
Ultipleat geometry - adds up to 50% more filtration area
Pall’s disc filters are ideally suited for fine filtration of high-viscosity polymers and are highly efficient at removing hard and gel-type contaminants. Pall provides many options when it comes to metal disc filters: depending on your individual process conditions, quality requirements, and media selection, a standard or custom design may be right for you. Standard outer diameters are 7 inches and 12 inches but other diameters may be available as well.
Each disc is constructed of a support layer, a hub, a filter media, and a spacer. Depending on the media selected, there may be as many as five layers while there can be as few as two.
Typical disc construction
There are two options for the support layer: mesh and slotted support. The mesh support is an economic choice for applications using Dynalloy or Dynamesh media. Although it creates a slightly higher pressure drop, it is generally acceptable for standard applications. The second option is to us Pall’s patented slotted drainage support. This rigid support adds strength and durability to the disc filter while easing its cleanability. It also enhances polymer flow while minimizing the residence time of the polymer within the filter assembly. By reducing the polymer residence time, users can significantly reduce the creation of gels and degraded polymer at high temperature, greatly improving the appearance and performance of thin film products.
Depending on the type of support layer required, the micron rating needed, and the level of sealing necessary, Pall has a center hub type that’s right for your application. Hard, semi-hard, and soft hubs are all common for polymer filter discs.
Hard Hub for maximum sealing
Soft hub for most economical solution (not recommended for micron ratings under 10 um)
The space between discs in a stack is an important parameter because maintaining the correct spacing helps to ensure that the polymer flux rate at the edge of the disc is the same as the flux at the center of a disc, therefore reducing residence time distribution. Intersegment spacers maintain that spacing and can play a role in minimizing the impact of unbalanced forces that can be generated during process upsets or improper filter startup or shutdown.
- Precision machined hard hub design (option) utilizes stainless steel o-rings or gaskets for a reliable, metal-to-metal seal
- Standard outer diameters (nom.): 178mm (7 inches), 305mm (12 inches), 337mm (13.25 inches)
- Available with Dynalloy sintered metal ber media for superior ltration down to 1 micron
- Spoke spacers maintain spacing between adjacent discs to ensure unrestricted flow
- Available in pressure ratings up to 210 bar (3045 psid)