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FAQs on Filters & Filter Bags

Q) Can I gravity feed through Scintex filter bags? 

A) It is recommended that you use a filter housing to house and support the filter bag then move fluid
through the filter bags under pressure with a pump. This will provide the highest efficiency and best
filtration. If you are on a budget you can gravity feed through the filter bags, however, go with the largest
size bag the 02 - 7" x 32". This will allow you to put a higher head pressure on the bag and move fluid
through faster. The finer the micron rating the slower the fluid will flow through the bags.

Q) Can I wash the filter bags out?
A) The bags are disposable and once used and full of filtration particulate should be discarded. If you do
choose to wash the filter socks the micron rating will no longer be valid. If you insist on washing out filter
bags you will be better to purchase the Nylon Mesh filter bags as they are more durable to this activity.

Q) Nominal vs Absolute Filter Bags
A) Scintex supplies nominal rated filter bags at 90% or above based on normal operating conditions and
pressures. A filter bag exchange should be performed with 1psi of pressure drop across the bag to
maintain the nominal rating. On request we can supply absolute rated filter bags but they will be far more
expensive and quoted on demand.

Nominal = the SMALLEST size particle that may get trapped.
The nominal rating refers to a filters capability of cutting off a nominated minimum percentage by weight
of solid particles of a specific contaminant (usually based on glass beads) greater than a stated micron 2 OF 2 size.

For example, a Scintex 25 Micron filter bag, nominal rated, will retain 10% or greater of particles below
25 Microns in size, by weight. All conditions such as flow rates, pressures, temperatures, fluid types etc
will impact on these figures.

Absolute = the LARGEST particle size that can get through the openings in the filter element.
The absolute rating, of cut-off point, of a filter refers to the diameter of the largest spherical glass particle,
normally expressed in microns that will pass through the filter bag under laboratory conditions. It
represents the pore opening size of the filter medium. Filter bags with an exact and consistent pore size
will have the best chance of having an exact absolute micron rating

Q) At what pressure differential should I change the filter bags?

A) As a rule of thumb you should change the filter bags when there is a pressure differential across the filter bag of 8-15 PSI. If the pressure change from bag inlet to outlet increases quickly this is also a sign the bag has been used up and should be changed. Some trial and error can be used for your application and these figures are only a guide.

Q) What is the maximum operating pressure of the filter housing and bags?

A) Scintex recommends 100 PSI as the maximum operating pressure.

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