Frequently Asked Questions – Process Filtration

Written by Donaldson

Q. How Often Should I Replace My Housing Gasket (O-Ring/Sealing Ring)?
A. Housing Gaskets should be replaced each time the element is replaced. Filter housing gaskets protect against leaks and may wear or experience deformation over time or when the housing is opened for element replacement. Installing a new gasket at each element replacement interval ensures that your filter housing is operating under optimal conditions.

Q. Do I Need to Buy an Element Gasket with My Element?
A. Donaldson filter elements include standard o-ring(s). The photo below shows the (blue) element gaskets installed on the element.

Q. What Gasket Material Type Should I Use?
A. Donaldson offers several gasket materials for our element and housing gaskets. Your gasket selection will vary depending on the application, temperature or chemical compatibility.

Q. How Often Should I Change My Element?
A. Our element replacement recommendation depends on the type of element.

Industrial Elements
For coalescing/particulate filter replacement, Donaldson guarantees performance and element integrity for 1 year. Thus, element replacement should occur annually or sooner if indicated by high-pressure drop. The life of activated carbon elements depends on the challenge contaminant. The filtration mechanism used in activated carbon is adsorption; once the active sites are occupied, additional hydrocarbons have no place to settle and will continue downstream. There is no differential pressure change on an activated carbon element. Thus, we recommend changing activated carbon elements every 6 months. Since most lines have particulate, coalescing, and activated carbon filters, Donaldson recommends changing all industrial elements every 6 months.

Process Elements
In general, process elements are not changed based on loading. By design, the bulk of particulate contaminant has been handled upstream with our industrial elements. We judge element life in terms of cleaning/sterilization cycles. Most of our depth and membrane elements can withstand more than 100 sterilization cycles. The stainless steel P-GS and P-GSL N elements can handle multiple back-flush or ultrasonic cleanings – as many as 6 ultrasonic cleanings before integrity degradation. Donaldson recommends that users change their process elements at the values mentioned above or that the elements are integrity tested to determine if they are in good working condition.

Q. What Is the Best Way to Sterilize My Elements?
A. We sterilize elements differently depending on the conditions, application, and type of element.

Q. When Do You Need to Use a Sterile Product Versus a Sanitary Product?
A. Sterile and Sanitary are often confused. In general, sterile is a condition and sanitary is a characteristic.
Sterile means free from live bacteria, germs or other microorganisms. Sterile filters inhibit these microorganisms from passing downstream. A sterile filter will remove contaminants to a log reduction of 7. Thus, if we have 30 million particles upstream of the filter, a sterile filter may allow up to 3 particles to pass downstream. For example, Donaldson’s P-SRF sterile air filter is used to produce air that is free of bacteria.

Sanitary means free from disease or infection causing agents. In general, sanitary is a high standard of cleanliness. Our PG-EG, PF-EG and PG-IL sanitary filter housings are designed using stainless steel and tri-clamp connections so that they are kept in a state of cleanliness, allowing them to be free of the filth or pathogens that can endanger our health. In general, sanitary filter housings are made using 316 stainless steel and tri-clamp connections.

Q. What Is the Difference Between a Depth and Membrane Element?
A. “Depth” and “Membrane” are terms that refer to the nature of the media itself.

Depth media are typically made up of many layers of fibers. Usually, the fibers are coated with a binder material that holds the individual strands in place. While the passages through a depth media vary in size, the binder limits the openings to some maximum size. One of the biggest advantages of a depth element is that it provides a higher particle loading capacity than does a membrane element.
Membrane media are processed so that uniformly-sized holes are created through the membrane material. The uniformed media allows the capture of particles based on a specific size. In other words, any particle larger than the pore size of the media will get captured. Some particles will penetrate deeper into the membrane, but most are captured at the surface.

Q. What Is the Difference Between a Nominal and Absolute Rated Element?
A. Nominal and absolute can have different meanings depending on whom you are talking to.

Nominal: Donaldson defines nominal as an efficiency less than 99.98% at a given particle size.
Absolute: Some manufacturers state that an absolute rating means that 100% retention of particles at a given size. However, such data assumes ideal laboratory conditions, uniform particle size, constant flow rate, and constant particle challenge. In practice, 100% particle retention is difficult to achieve. Donaldson defines absolute as an efficiency equal or greater than 99.98% at a given particle size.

Q. Where Does Donaldson Product Ship from – What Is the FOB?
A. Donaldson’s Compressed Air & Process product ships out of our distribution center in Greeneville, TN.

Q. What Can I Use to Conduct Integrity Tests on Membrane & Depth Elements?
A. Depth and membrane elements are tested in two different ways:

Depth: Depth elements are tested by conducting a DOP (Di-Octyl Phthalate) Test. During this test, the filter is challenged with aerosols that are between 0.2 and 0.3 µ (the most penetrating particle size). The filter passes or fails the test based on the amount of aerosol contaminants that penetrated the filter. Donaldson sells a DOP test device called the “Donaldson Filter Test Center.”

Membrane: There are a number of integrity test methods used on membrane elements: Bubble Point, Forward Flow, Water Intrusion, and Pressure Hold Test. The type of test used is based on the data desired as well as the type of element (e.g. hydrophilic or hydrophobic) being tested. Donaldson offers a flexible test device called the Membra-Check that can conduct the integrity tests listed.

Q. Is the UFM-D Series Condensate Drain a Direct Replacement for the Phased out UFM-T Series?
A. Not entirely. While the connection ports match up size for size, the older UFM-T drain was considered omni-voltage. That is, it would accept AC voltage from 90V to 240V, or 12V-30V DC without needing adapters or transformers of any kind. The new UFM-D drain is a single voltage: 115V AC standard in the US. For 230V AC or 24V DC, we can make available a drain with BSP connections.

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