TECHNICAL REFERENCE
Filter media, amount of contamination, the flow rate, and fluid viscosity are all factors in the importance of sizing the filter for the system requirements. Filters that are too small won’t be able to handle the system flow rate and will create excessive pressure drop from the start. The results could be filter operation in the bypass mode, filter failure, component malfunction, or catastrophic system failures. Filters that are too large for the system can be too costly. Oversized filters require more system oil and higher cost replacement filters. Optimal sizing is best.
3. Flow Higher flows create higher pressure drop. WitH fast moving fluid, there will be more friction causing higher pressure drop across the media. 4. Fluid Viscosity Measured in centistokes (cSt) or Saybolt Seconds Universal (SSU or SUS), fluid viscosity is the resistance of a fluid to flow. As fluid viscosity increases, the cSt rating increases. Higher fluid viscosities also mean higher pressure drop because the thicker oil has a tougher time passing through the layer of media fibers. Cold start fluid is a good example of highly viscous fluid. See chart below.
Viscosity/Temperature Chart A.S.T.M. Standard Viscosity-Temperature Chart for Liquid Petroleum Products (D 341-43) Saybolt Universal Viscosity
SAE 20 SAE 140 GEAR OIL
SAE 30
SAE 40
SAE 50
TYPE A
10W-30
AUTOMATIC TRANSMISSION FLUID
SAE 10
MIL-H-5606
KEROSENE
DIESEL FUEL
JP4 AVERAGE
Hydraulic Filters & Accessories • 25
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