change-out pressure differential
Pressure across the filter at which it should be replaced.

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Note added at 4 hrs (2016-07-27 10:45:55 GMT)
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Bag Filter Replacement

2.1 Change-out Pressure Differential: The recommended bag filter change-out pressure differential across the bag media is 0.10 MPa (15PSI). Continuing beyond this point will result not only in rapid flow rate reduction and contaminant unloading, but also increase the risk of filter rupture. The maximum differential pressure allowed is 0.23 MPa (35PSI).
http://www.filterek.com/?thread-45-1.html

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5. Filter Change-out
The following operating procedure must be strictly followed for safe operation.
5.1 System Off. Turn off and lock pump, close inlet and outlet valves.
5.2 Pressure Release. To prevent injury, make sure that the nozzle is point at a safe direction. Open vent valve
on Inlet Line slowly to depressurize the housing.
5.3 Open Cover. Must make sure that the interior pressure is zero before opening the cover.
5.4 Take out Used Filter. It is important to dispose used filters according to related environmental regulations.
5.6 Install New Filter. Filter bags must be inserted into the basket. The SOE connector on the cartridge must be
insert properly into cartridge plate.
http://doc.diytrade.com/docdvr/209120/5128070/1201003408.pdf

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Note added at 4 hrs (2016-07-27 10:47:55 GMT)
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Zaleca się wymianę filtrów powietrza w momencie gdy spadek ciśnienia mierzonego na eksploatowanym filtrze dwukrotnie przekroczy wartość spadku ciśnienia deklarowaną dla nowego egzemplarza.
http://www.smay.pl/uploads/tx_smay/product_files/DTR_KAF_01....