Featured Blog Post
- Six Tips for Properly Breaking In Your New Belt Press Filter Belt
- Three Ways to Optimize Pulse-Jet Baghouse Performance
- Selecting the Proper Filter Cloth
- Four Things to Consider When Purchasing Filtration Equipment for Liquid Solid Separation
- Stop Leaks to Recover Operating Costs on Dust Collectors
Pressure Leaf Filter Basics
What is a Pressure Leaf Filter?
Pressure leaf filters are liquid filtration systems consisting of 10 to 60 leafs that are stacked inside a vertical or horizontal vessel. The leafs are drainage systems that support a wire or textile cloth cover. Since the filtration process is contained within a pressure resistant vessel, it can be an ideal solution for hazardous processes.
How do Pressure Leaf Filters Operate?
A filter cycle begins with the vessel sealing in the shaft and its filter leafs. Then, precoat is introduced. A precoat tank containing filtrate and filter aid (diatomaceous earth, perlite, etc.) is agitated for around 10 minutes. Then, the mix fills the vessel, vents all the air, and pressurizes. The precoat runs for 15 minutes at a fluid rate around 30- 60 gallons per square foot per hour.
After precoat, slurry is forced through the vessel under pressure. Solid particles are trapped in the precoat, or filter media while clarified liquid passes through and into a filter leaf. The liquids pass from leaf to the shaft’s interior, then out of the filter into a holding tank.
Between batches, liquid cake or sludge is drained from a valve. Dry cakes require a much larger opening, sometimes the entire vessel slides back for access to the leafs for discharge and cleaning.
What are the two types of Pressure Leaf Filters?
There are two types of leaf filter vessel configurations: horizontal and vertical pressure filters. Horizontal pressure filters are the most commonly operated due to the ease of operation and cleaning. There are also more variations of horizontal pressure filters due to the operation and installation methods. Vertical pressure filters are often used for small-flow, granular media filtration. Horizontal vessels are typical for larger flows because the horizontal layout increases the filtration area possible. With vertical pressure filters, it is possible to have multiple vessels in one system, where as with horizontal pressure filters, it is possible to have different cells in the same vessel.
Troubleshooting Pressure Leaf Filters
Torn or bent filter leafs can be the result of excessive body feed or running the filter too long between cleaning cycles. NFM can repair damaged leafs. We salvage good components and repair or replace only what is damaged. Typically a rebuilt leaf is around half the cost of new. We can repair or replace any OEM’s filter leafs.
Stop damaging your leafs by following these steps:
- Keep differential pressure at 25 to 30 PSI between cleaning cycles. Do not depend on a set time cycle.
- Cut back on the body feed.
- Only precoat the frames until the filter aid is ¼” thick.
- Check to see if your filter media has blinded.
New door gasket is leaking. If a replacement gasket was cut with straight ends, it may not create a perfect seal. Cut another with angled ends and install.
Pressure Leaf Filter Wear Parts
NFM Repairs and Recovers Leafs From Every OEM
Do you have damaged pressure leafs? We can repair and replace all or part of the leaf. Contact NFM, and we’ll set up a free repair order for one of your leafs. You will only pay for freight. We do this to demonstrate our craftsmanship and to provide a quote for repaired leafs as well as new replacements.
Want to save labor and shop space? Send us your leafs for bag recovery.
Still not sure how to fix your filter? We make house calls! Contact NFM today!
Contact A Technical Expert
Call us today to learn how our expertise can provide you with the filtration solution you’ve been looking for. We’ll build a relationship with you that will last well beyond the sale, providing you with unparalleled customer service and technical filtration expertise.