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The numbers 3 and 4 above represent the design revision of the media, with 4 being the current design. These elements are equivalent in form, fit, and function.

BN vs BH (low collapse vs high collapse)

BN refers to a low collapse element, which has a maximum collapse rating of 290 psid. This element is used in filters that include bypass protection. BH refers to a high collapse element, which has a maximum collapse rating of 3000 psid. This element is used in filters that do not include bypass protection, thus the need for a higher rated element to withstand adverse conditions.

Absolute vs Nominal

These terms refer to the efficiency of the element. Absolute is a high efficiency element that utilizes depth filtration (multi-layers). Nominal is a standard efficiency element that utilizes surface filtration (single layer, i.e. wire mesh or paper). ISO 16889: 1999 defines a depth filtration high efficiency (absolute) element as having a beta ratio of ßx>= 75, as determined by a multi-pass test. No industry standard exists for determining the efficiency of a surface filtration standard (nominal) element, therefore it does not have a beta rating.

You have so many different element media options (ECO/N, MM, AM, W/HC, etc)? Please explain the differences and advantages of each?

ECO/N refers to our Ecomicron element. It is an all plastic construction, designed to be Incinerable and to allow for lower shipping costs. MM refers to our Mobilemicron element, designed specifically for the mobile market. Its lightweight construction also has the added advantage of a low clean element ?P per flowrate for cold start conditions. A higher dirt holding capacity allows for fewer element change-outs, saving both time and money. W/HC and P/HC refer to wire mesh and paper media, respectively. These are both surface filtration elements (nominal), refer to #3 above. AM refers to our Aquamicron (water removal) element. This element is designed to remove free water from oil. Water retention capacities are provided in the Aquamicron sales brochure.

Is my element cleanable?

BN, BH, MM, ECO/N, AM, and P/HC are not cleanable. W/HC (wire mesh) and V (metal fiber) are the only cleanable elements.

How do you clean, cleanable elements? How many times can you clean them?

​The W/HC and the V elements can be cleaned up to a maximum of 5 times. HYDAC provides a procedure for cleaning these elements in the DF Series filter maintenance instructions, located on our website at: ​Catalogs (select Filters from the list, or search the Service and Parts at the search bar up top, then select the DF link and refer to Page 3).

Do your elements have a shelf life?

HYDAC recommends that elements be stored in a controlled environment (temperature, humidity, dust, dirt) for a maximum of 2 years.

Is the bypass field adjustable or replaceable? What is required to change the by-pass?

With few exceptions, the bypass is neither field adjustable or replaceable by itself. For low pressure (return) filters, the bypass is located in the element. In this case it is only necessary to change the element and the indicator (the indicator should be selected to trip at 1 bar or 14 psid below the bypass cracking pressure). For high pressure filters, the bypass is located in the filter head. Therefore it will be necessary to change-out the head as well as the indicator. In both instances, we would recommend that the filter nameplate be changed to reflect the filter modifications and that the seals be replaced at time of change-out. Note, low pressure (return) filters will have an ‘R’, ‘RK’, or ‘RN’ in the replacement element model code and pressure filters will have a ‘D’ or ‘DN’ in the replacement element model code.

Do you have an interchange list for elements?

Yes we do. These are listed on our website:

Can you provide interchanges for clogging indicators?

​No, we do not interchange competitor indicators.

What flowrate can my filter handle?

The filter housing determines the maximum allowable flowrate for a filter. HYDAC defines these values in our housing pressure loss curves, located on the last page of every filter tech data sheet (also referred to as the sales brochure). Flowrate should never be used as the sole deciding factor in filter selection. The clean element pressure drop should be calculated for both the operating temperature and for cold start conditions. These pressure drop calculations determine filter selection. Refer to # 12 below for additional details.

How do I size a filter?

As stated in # 11 above, the clean element pressure drop is used to determine filter selection. This pressure drop is derived from a calculation, which takes into account the pressure drop due to the empty housing and the pressure drop due to the element. These are combined to determine the total filter clean element pressure drop. This calculation should be done for both the operating temperature and for cold start conditions. Instructions on how to calculate this pressure drop are located on the last page of every filter tech data sheet (also referred to as the sales brochure). As a minimum, you will need to know the maximum operating pressure, the flowrate, the oil viscosity (SUS), and the desired micron rating (or desired cleanliness class or critical component in the system).

What micron rating do you recommend for my filter?

If the desired micron rating is not known, then it can be determined by either the desired cleanliness class or by the most critical component in the system. With this information, you can cross over to a micron rating using a HYDAC-provided chart. This chart can be found in the Hydraulic & Lube Oil Filters catalog, entitled ”Finding the cleanliness level required by a system”, our catalog is located here at: Catalogs.

Where can I find maintenance instructions for my filter?

Maintenance instructions are located on our website: Catalogs (select Filters from the list, or search the Service and Parts link from the search bar above.

What fluids are compatible with your filters?

​With proper o-ring seal selection, our filters are compatible with hydrocarbon-based fluids; including petroleum oils, synthetic oils, water-glycols, oil/water emulsions, and high water-based oils.

What option(s) are required for phosphate ester?

​HYDAC recommends EPDM (EPR code in HYDAC catalog) seals and the appropriate SO modification as referenced in the ”Supplementary Details” section of the Model Code breakdown for each filter. Refer to the second page of the filter tech data sheet (also referred to as the sales brochure)

What option(s) are required for water-glycol?

As a general rule of thumb, HYDAC recommends FPM Fluoroelastomer (V code in HYDAC catalog) for water-glycols. However it is recommended that this requirement be verified with the water-glycol manufacturer. Paper (cellulose) media should never be used with water-glycol. In addition, differential indicators should include the ‘W’ model code option.

What is the difference between a static clogging indicator and a differential clogging indicator?

A static clogging indicator is used in return line applications, where the filter outlet is open to atmosphere. Therefore, static indicators reference atmospheric pressure. Differential indicators are used in all inline applications.

Why do you not offer Aquamicron water removal media with all of your filters? Does the Aquamicron remove free and dissolved water?

​Aquamicron media is designed for the removal of free water only. It does not remove dissolved water. The Aquamicron media captures water via a chemical reaction. The free (undissolved) water in oil reacts with the Aquamicron media to form a gel that is trapped within the element. Higher flowrates would not allow enough time for this chemical reaction to take place. Therefore the Aquamicron media is not available for high flow conditions.

What is the recommended clean element pressure drop for: mobile, industrial, lube application?

As a general rule of thumb, HYDAC recommends that the clean element pressure drop be no more than: 10-15% (at average flowrate) of the clogging indicator trip setting for lubrication systems, 20-25% for industrial applications, and 20-30% for mobile applications. Be sure to also check the pressure drop at cold start temperatures and maximum flowrates. If at these conditions the pressure drop is greater than 50%, then the next larger size should be selected. Note, make sure that the filter port size is large enough to handle the desired flowrate.

Where can I find the Filter-IT filter sizing program?

​Filter-IT can be downloaded from our German website:

Do you sell seals separately?

No we do not. We sell seals together in a seal kit. Part numbers for seals kits can be found in the filter maintenance instructions, which are located on our website: Catalogs (select the catalog in the list below or search Service and Parts with the search bar at the top).

Can I buy direct from HYDAC?

HYDAC works through a network of distributors. This list of distributors can be found on our website: Distributor

Out of stock situation guidelines:

– FPM seals (V code in HYDAC catalog) can be used in place of our standard nitrile seals (NBR code in HYDAC catalog).
– BH can be used in place of BN but not the other way around.
– ECO/N and BN4HC elements can be interchanged as long as the customer is made aware that switching to BN4HC means metal components.