In industries requiring high cleanliness and precision filtration, such as pharmaceuticals, food, chemicals, and bioengineering, the Plate and Frame Filter (also known as a Sheet Filter) is an indispensable, mature, efficient, and reliable piece of equipment. It serves as a preferred solution for liquid clarification, sterilization, and impurity removal, thanks to its unique design, excellent performance, and operational flexibility. In this post, Yuwei Filtration will discuss the role of plate and frame filter in precision filtration.

Core Components of a Plate and Frame Filter

A typical plate and frame filter system consists of the following main parts, where the precision of its design is fundamental to ensuring filtration efficiency:

1. Stainless Steel Frame: This is the main structure of the equipment, typically made of 304 or 316L stainless steel, ensuring excellent corrosion resistance, hygiene, and structural strength to withstand operating pressure.
2. Filter Unit: This is the core working area, composed of multiple alternately arranged “Plates” and “Frames”.

• Filter Plates: Their surfaces feature complex channels that provide a path for the filtrate (filtered liquid). They support the filter medium and guide the filtrate toward the outlet.
• Filter Frames: Located between two filter plates, they form a chamber to hold the liquid to be filtered and also provide space for the filter cake (trapped solids) to accumulate.
• Filter Sheets/Pads: As the key filter medium, these specially made sheets are sandwiched between the plates and frames. They come in various pore sizes and grades to achieve different filtration levels, from coarse to fine sterilization.

1. Compression Mechanism: Usually a hydraulic or manual screw mechanism used to press all plates and frames together into a tight, sealed unit before filtration, preventing leakages.
2. Piping and Valve System: Includes inlets, outlets, vent valves, pressure gauges, etc., for controlling fluid flow, venting air, and monitoring pressure.

Working Principle and Process

The plate and frame filtration process is essentially a combination of “sieving” and “adsorption”:

1. Preparation & Assembly: Select the appropriate type and grade of filter sheet. Place it between the plates and frames, then lock the entire system using the compression mechanism.
2. Pre-wetting & Deaeration: Pump a small amount of clean liquid (e.g., water or solvent) to wet the sheets and fill the chambers, expelling air to prevent issues.
3. Filtration: The liquid to be filtered is pumped into the frames. Under pressure, the liquid passes through the filter sheets. Particles, impurities, and even microorganisms are trapped on the surface or within the depth of the sheets, while the clarified filtrate gathers in the plate channels and exits via the outlet.
4. Cake Formation & Cycle End: As filtration proceeds, trapped solids gradually form a “filter cake” in the frames. When the cake reaches a certain thickness, resistance increases, and the inlet pressure rises to a set value, indicating the end of the filtration cycle.
5. Disassembly & Cleaning: Release the compression mechanism, remove the spent sheets full of solids, thoroughly clean and sterilize the equipment, replace with new filter sheets, and prepare for the next cycle.

Primary Uses and Application Fields

The uses of the plate and frame filter are extensive, particularly suitable for:

• Pharmaceutical Industry: Sterilizing and clarifying injections, eye drops, biologicals; separating crystalline slurries of active pharmaceutical ingredients (APIs).
• Food & Beverage Industry: Clarifying beer, wine, juice, and potable water by removing yeast, colloids, and other suspended matter.
• Chemical Industry: Purifying various chemical reagents, recovering catalysts, clarifying paints and coatings.
• Electronics Industry: Final filtration of high-purity chemicals.

Advantages and Features

1. High Precision & Clarity: Specialized filter sheets can provide absolute precision filtration, ensuring sterility and high clarity of the filtrate.
2. High Dirt Holding Capacity: The frames provide ample space for cake buildup, making it especially suitable for liquids with higher solid content.
3. Operational Flexibility: By changing the filter sheet type, the same equipment can easily handle filtration tasks of different precision levels and flow rates.
4. Non-Contaminating: All wetted parts are made of stainless steel and specialized filter sheets, preventing secondary contamination and complying with strict standards like GMP and FDA.
5. Cost-Effectiveness: Compared to some single-use membrane systems, plate and frame filters (especially with regenerable sheets) can offer lower long-term operating costs for specific applications.

The stainless steel Plate and Frame Filter, particularly the systems built around it, is a mature and high-performance equipment for precision filtration. Its robust construction, flexible design, and the efficient separation achieved through the plate and frame filtration principle make it a critical link in ensuring product quality across numerous industries. Whether used for final liquid sterilization or large-scale clarification as a pre-treatment, it continues to demonstrate its irreplaceable value through reliability and economy.