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 of ~ 30- 60 gallons per square foot per hour.

After precoating, the 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 the 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 their ease of operation and cleaning. There are also more variations of horizontal pressure filters due to their 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 possible filtration area. With vertical pressure filters, it is possible to have multiple vessels in one system, whereas 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.

Stop damaging your pressure 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 leaking?

If a replacement gasket is cut with straight ends, it may not create a perfect seal. Cut another gasket with angled ends and install.

 

Pressure Leaf Filter Wear Parts