Advances in lenticular filter module design

Carlson Filtration has enhanced its range of CarLent lenticular modules. Michael Sidebottom discusses the latest developments

Following a previous report about developments in depth filtration techniques,¹ Carlson Filtration has developed a number of enhancements to its range of CarLent lenticular modules. Carlson claims that these improvements have resulted in an even stronger module, capable of resisting higher-pressure differentials and pressure shock.

Traditionally lenticular modules have been produced using the so-called Constant Height Approach. This requires the module to be compressed during manufacture to a predetermined height. Even within the tight tolerances imposed on the assembly of individual leaves within the module, Carlson found that when the assembled module was compressed in this way, it had to impose certain limits on the module's pressure resistance specification.

limited abilities

In order to overcome this, modules can be made using an alternative Constant Pressure Approach. This results in a module with higher pressure differential resistance but with the attendant disadvantage of a variable module height. To some extent, this problem can be overcome by the lenticular housing design, allowing acceptance of modules with different heights. But what if an existing housing has only limited ability to accept such modules? The only answer would be to invest in new equipment.

To overcome these shortcomings, Carlson has combined these two approaches by developing the constant pressure and height approach (CPHA). This approach has been pioneered at Carlson's Technical Development Centre in Barnoldswick using its lenticular module test facilities.

The resulting production method allows modules to be produced using increased pressure during assembly, while maintaining a constant module height. This is achieved by using a variety of inter-leaf spacer ring heights. Modules produced using CPHA can be used in a wider variety of existing housings and be capable of withstanding higher-pressure differentials during use.

attractive alternative

This results in a number of benefits:

• higher flow rates resulting in increased filtration capacity

• higher tolerance to pressure shock and hence more secure filtration

• easier filter assembly because there is no need for a second stage tightening procedure as is required with most currently available lenticular modules

As Andy Sadler, Carlson's technical manager, explained: 'CPHA is an important development because an increasing number of customers can enjoy the benefits of using CarLent modules in their existing housings.

Lenticular filters, figure 1, now present an attractive alternative for traditional filter press users, as they are cleaner to use and require shorter changeover times.'