Filtration

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For information on the type of filter used by each filtration method, click on the links in this column next to each method.

What types of filtration media are used in automatic vacuum filtration?

The filtration medium (septum) used in automatic vacuum filtration, depending on the application, can be

disposable media
permanent belt
wedge-wire drums
micro-screen drums
micro-screen discs

What types of media are used in automatic pressure filtration?

The media used are

flat bed filter
pre-coated tubes
automatic back-washing tube filter
automatic back-washing strainer

What types of media are used in manual pressure filtration?

The types of media for this system are

disposable cartridges
disposable bags
basket strainers

Filtration is the most widely used method of clarifying metal removal fluid and offers the best results. Dirty MRF is passed through a filter that traps and removes contaminants.

What are the different methods of fluid filtration?

There are three main methods of filtration:

automatic vacuum filtration

automatic pressure filtration

manual pressure filtration

New filtration equipment should be tested and the clarity of the metal removal fluid should be recorded, either as parts per million (centrifuge test) or mg/mL (gravimetric test). The recorded clarity can then be used as a benchmark against which the effectiveness of plant equipment can be measured. This clarity benchmark will be valuable should problems arise with part quality; it will allow you to tell whether the filter operation is performing correctly.

What is automatic vacuum filtration?

This is one of the most common types of filtration. A vacuum is created on one side of a septum (filtration medium), usually by means of pump suction. As the dirty MRF is drawn through the septum, the contaminant is trapped and forms a filter cake. The actual fine filtration is obtained by drawing the MRF through the filter cake. As the filter cake increases, the vacuum required to draw the MRF through rises, and the pump output decreases. At a pre-selected point, usually 10" Hg. (approximately 5 psi), an index cycle is initiated to purge the accumulated contaminant.

The advantages of the system are that (1) only one set of pumps is required, and (2) Since the pumps are located on the clean side of the filtration medium, they pump clean MRF and will not be subjected to wear caused by chips and contaminants.

The disadvantages are that (1) the system is limited to approximately 10" hg.vacuum differential, so it will index more frequently than a pressure filter, and (2) some chip migration can occur when the filter indexes.

What is automatic pressure filtration?

Filters collect contaminant on a septum as the MRF is pumped through the septum under pressure. The filter medium traps contaminant and a filter cake forms. The actual fine filtration is obtained by pumping the MRF through the filter cake. As the filter cake increases, the pressure required to pump the MRF through increases, while the pump output decreases. At a pre-selected pressure, an index cycle is started that purges the accumulated filter cake and exposes a clean septum..

What is manual pressure filtration?

In this system, contaminant is collected on the septum as the MRF is pumped through. The system has no means of expelling the contaminant, so the septum element must be cleaned or replaced. These units are mounted in pairs so flow can be diverted to one while the other is being serviced.