Donaldson HNK04/05 Duramax Spin-On Hydraulic Filter Assembly

A RadialSeal medium-pressure spin-on hydraulic filter, 35 and 50 gpm

The Donaldson HNK04/05 Duramax is a spin-on medium-pressure hydraulic filter assembly in two sizes: HNK04 for flows to 35 gpm (133 lpm) and HNK05 for 50 gpm (189 lpm). It uses a RadialSeal design, which makes servicing easier and gives a more reliable seal without torquing to specification, and Synteq synthetic media for high efficiency and dust-holding capacity.

Donaldson lists hydrostatic charge side filtration, pilot circuits, power shift transmissions and kidney loop circuits among the applications. Performance is stated to beta 6(c) = 1000.

This page summarises the manufacturer sheet for quick reference. Compare the figures with your drawing, the existing nameplate and the operating conditions of the installation, and tell us anything that differs so the correct variant can be confirmed in writing before any order is placed.

Technical specifications

Heads and filters

• P568856: Size HNK04; Port SAE-12; Bypass 50 psi
• P568857: Size HNK04; Port SAE-12; Bypass none
• P568858: Size HNK04; Port SAE-16; Bypass 50 psi
• P568860: Size HNK05; Port SAE-20; Bypass 50 psi
• P568861: Size HNK05; Port SAE-20; Bypass none

HNK04 filters (6 and 11 micron) include P569203 to P569206 and P576047; HNK05 filters include P569209 to P569212 in 6 and 11 micron grades and two lengths each.

Selection

Assembly weights run from 1.8 kg for the short HNK04 to 3.6 kg for the long HNK05. Replacement filter lengths are 5.97 and 9.44 inches (HNK04) and 11.63 and 14.24 inches (HNK05). Service indicators include P165194 (electric, 50 psi) and visual pop-up types P575334 (25 psi) and P575335 (50 psi); the head mounting threads are M10 x 1.5.

The page represents the family because the sheet gives one data set for both sizes, including the head, filter and indicator tables. State the size, port, bypass setting and filter micron rating when you request a quote, together with the indicator type, and confirm the fluid compatibility of the media. Donaldson describes improved performance in this series, with higher burst strength, greater fatigue strength and longer filter life than earlier designs. The sheet also lists the applications of case drains, cooling circuits, fluid conditioning systems, fuel transfer, hydrostatic charge pumps, lube oil systems, power transmissions, return lines and side loop systems. Fluid compatibility of the Synteq media (including water glycol and ester fluids) is covered in the Technical Reference Guide, so check it for water glycols and ester fluids.

Choosing between HNK04 and HNK05

Begin with the circuit, not the catalogue. Establish the maximum flow that will pass through the assembly, including flow peaks during cold starts or when actuators retract, and compare it with the flow rating of each size. Then confirm that the maximum system pressure at the installation point stays below the working pressure of the chosen size, remembering that the HNK04 and HNK05 have different pressure ratings. A return line or low-pressure circuit gives more freedom than a charge or pilot circuit closer to the pump.

Next decide on the bypass. A bypass protects the element and the circuit from excessive differential pressure when the element is loaded or the oil is cold, while a no-bypass head ensures that all flow is filtered, which may be preferred ahead of sensitive components. Finally, choose the micron grade according to the cleanliness level the components in the circuit require.

Installation and commissioning practice

Install the head in a position where the element can be removed easily and where spilled oil can be contained. Observe the flow direction marked on the head, use port connections matching the head order code, and support pipework so that the head is not loaded by hose or pipe forces. When fitting a new element, follow the Donaldson instructions for the RadialSeal design rather than applying the torque habits used for older spin-on cartridges.

After installation, fill and bleed the circuit, run the system at low load and check the connections for leakage. If a service indicator is fitted, note its reading when the oil has reached normal operating temperature, since cold oil increases differential pressure and can give a misleading early indication.

Maintenance and fluid cleanliness

Change the element according to the indicator or the maintenance schedule of the machine, whichever comes first, and do not keep running an element that is in bypass. Oil sampling at regular intervals shows whether the selected grade is achieving the required cleanliness. Record each element change so that service intervals can be adjusted based on real operating conditions. When a machine is rebuilt or a pump or other major component is replaced, consider changing the element earlier than usual, because flushing after component work often releases contamination that the element must capture. Keep the head and its surroundings clean during every element change so that dirt does not enter the clean side of the circuit.

GCC operating conditions

Mobile and industrial hydraulics in Oman and the GCC operate in high ambient temperatures and dusty environments. Dust entering through reservoir breathers and cylinder rods increases contamination loading, so element life may be shorter than in cooler, cleaner regions. Keep oil temperature within the rated operating range, clean the area around the head before opening it, and store spare elements in their packaging in a cool, dry place until use.

What to include in your RFQ

Name the head and element part numbers, or state the size, port, bypass setting, micron grade and length required, plus the indicator type and quantity. Mention the hydraulic fluid in use so that media compatibility can be checked.

Documents and quotation

We handle HNK04/05 requests in writing. Check the size, port, bypass setting and media grade in the attached Donaldson HNK04/05 Duramax spin-on hydraulic filter data sheet (Hydraulic Filtration pp. 70-73), then name the quantity. Products of this kind: Filter Housings.