ProMinent DULCOMETER PH-501 Assembly And Operating Instructions Manual page 849

Servicing frequency of filter elements is not time predictable. A differential pressure indicator, with a continuous
gauge reading, should be installed across the inlet filter. It will tell how much of the service life of the filter
element has been used. It will also eliminate both premature filter servicing and premature blower failure due to a
plugged filter when the filter pressure drop is used to establish maintenance points. In all cases refer to the filter
manufacturer's service instructions. Due to the many types of filters, it is not practical to give specific instructions
covering all models.
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