Hydraulic Oil Filter Elements – Models 507091 & 502551

Two replacement hydraulic filter elements from the same medium-pressure filter family, designed for return-line and low-pressure inline duties on industrial hydraulic power units, mobile equipment, and compressor lube circuits. Both use glass-fiber composite media qualified to ISO 16889 multi-pass testing, with gradient-density construction for high dirt-holding capacity and stable β-ratio performance. The "-7091" and "-2551" suffixes denote different length / dirt-holding grades within the same housing envelope — confirming the exact dimensional interface (OD, length, thread, or flange pattern) against your existing element is required at time of order.

Key Features

• Glass-fiber composite media, micron grade selectable per circuit position (typical 10–15 µm, β₁₀ ≥ 200; 5 µm available for servo/prop valve protection)

  
  

• Gradient-density structure improves contaminant retention and extends service life

  
  

• Perforated steel center tube, collapse pressure up to 30 bar (return trim) / 42 MPa (pressure trim)

  
  

• NBR end seals standard; FKM available for high-temperature or ester-fluid circuits

  
  

• Rated for continuous operation up to 135 °C in high-temperature return loops

  
  

• Precision filtration: 3–30 µm typical range; special grades on request

  
  

Technical Specifications

Exact OD, length, and mounting interface differ by suffix — confirm against your current element before ordering.

Application Guidance

Both elements serve return-line and low-pressure inline duties on hydraulic power units, screw-compressor lube circuits, injection molding machines, press brakes, and mobile equipment. The glass-fiber media geometry is specifically engineered to maximize dirt-holding capacity in return circuits where flow is continuous but pressure is modest (typically ≤ 6 bar return-line pressure).

Precision selection by circuit position:

• Pressure-line / servo valves: 3–5 µm (protects proportional and servo valves)

  
  

• Return line / general hydraulic: 10–15 µm (filters wear-generated particles)

  
  

• Pre-filtration / coarse return: 20–25 µm

  
  

• Suction line: 80–100 µm (protects pump without excessive suction resistance)

  
  

⚠️ Not all positions need ultra-fine filtration. Installing a 5 µm element in a suction line will increase pump cavitation risk; conversely, a 25 µm element in a servo-valve circuit leaves precision spools under-protected. Match the micron grade to the circuit position.

Fluid Compatibility

• Mineral hydraulic oil (ISO HM, HV)

  
  

• Biodegradable esters (HEES, HETG) — use FKM seals

  
  

• HFC water-glycol — NBR acceptable; FKM recommended

  
  

• Emulsions and phosphate ester — confirm media/seal compatibility before deployment

  
  

• Not for gasoline or strong solvents

  
  

Installation & Service

1. Depressurize the hydraulic circuit to 0 bar; drain or isolate the filter housing.

   
   

2. Open the housing, withdraw the old element by its center tube.

   
   

3. Inspect the housing interior, bypass spring, and seal grooves.

   
   

4. Seat the new element — confirm flow direction (typically outside → inside for return elements).

   
   

5. Renew all O-rings / seals supplied with the element; torque housing bolts evenly.

   
   

6. Bleed air at the housing bleed port; restart and check for leaks at operating pressure.

   
   

7. Replace when the clogging indicator triggers or ΔP reaches the bypass setting (typically 0.5 MPa for low-pressure return, 0.6 MPa for high-pressure line).

   
   

Quality Assurance

• ISO 16889 – Multi-pass filtration performance (β-ratio, dirt capacity, ΔP)

  
  

• ISO 2941 – Collapse/burst resistance

  
  

• ISO 2942 – Manufacturing integrity (bubble-point)

  
  

• ISO 2943 – Media/fluid compatibility

  
  

• ISO 3968 – Flow-fatigue and pressure-drop characterization

  
  

• ISO 3724 – 100,000-cycle flow fatigue test (single-use elements)

  
  

Ordering

Specify 507091 or 502551 together with:

• Required micron rating (5 / 10 / 15 / 20 / 25 µm)

  
  

• Seal material (NBR / FKM)

  
  

• Mounting details (OD, length, thread or flange pattern of your current element)

  
  

Provide your existing element's dimensions or the host machine model and current OEM part number for cross-reference confirmation. Custom dimensions and filtration grades are available on request within the same series.

All values nominal; the precise OD, length, and interface geometry differ between suffixes. Confirm against your current element or housing drawing before installation — verify micron grade matches circuit position to avoid cavitation (too fine on suction) or under-protection (too coarse on servo circuits).