ISO 4548-2:1997

Overview

ISO 4548-2:1997 specifies standardized test methods for the element by‑pass valve characteristics of full‑flow lubricating oil filters used on internal combustion engines. It defines how to set up a test rig, prepare the filter (including use of a non‑permeable dummy element or separate housing for spin‑on types), select test liquids, and measure differential pressure, leakage and valve opening/closing behaviour across a range of flow rates. The purpose is to ensure the by‑pass valve maintains oil supply under choke or cold‑start conditions while minimising unfiltered oil flow during normal operation.

Key Topics and Technical Requirements

• Scope: Tests target the element by‑pass valve of full‑flow engine oil filters; complementary parts of ISO 4548 cover other filter characteristics.
• Test liquids & viscosities: Two kinematic viscosities are used to simulate conditions:
  • ~24 mm²/s for typical operating temperature (examples given: ISO VG 100 / SAE 30 at ≈74 °C or ISO VG 150 / SAE 40 at ≈83 °C).
  • ~500 mm²/s for cold conditions (example: ISO VG 460 / SAE 140 at ≈38 °C).
• Test rig components: Sump with temperature control, motor pump, throttle/regulating valves, flow meter, pressure gauges, inlet/outlet pipes with specified tap positions, and sampling/discharge arrangements.
• Filter preparation: Element replaced by a non‑permeable dummy of identical dimensions or valve tested in a separate housing where element removal is impractical.
• Measurements & procedure:
  • Measure differential pressure across the by‑pass valve at at least eight approximately equal flow increments up to 110% of rated flow.
  • Record valve opening and closing pressures (approaching flow points from lower and higher values respectively).
  • Measure leakage at 10% below specified minimum opening pressure and ensure leakage flow has stabilized before sampling.
  • Note any valve noise (oscillation), as it may correlate with wear.
• Accuracy & reporting: Measurement accuracy requirements and reporting formats are defined; differential pressure is expressed in kilopascals (kPa).

Practical Applications and Users

• Who uses it: filter manufacturers, OEM engine designers, independent test laboratories, quality assurance and procurement teams, and regulatory authorities specifying component safety/performance.
• Why it matters: Ensures by‑pass valves provide reliable engine lubrication during cold starts or element blockage while limiting unfiltered oil delivery during normal operation-critical for engine durability and warranty compliance.
• Benefits: Provides repeatable, comparable test results for design validation, supplier acceptance testing, and product specifications.

Related Standards

• ISO 4548 (other parts): Part 1 (differential pressure/flow), Part 3 (high differential/temperature resistance), Parts 4–12 (efficiency, durability, burst, vibration, etc.)
• ISO 1219‑1: Graphic symbols for fluid power
• ISO 11841‑1 / ISO 11841‑2: Filter vocabulary and definitions

Keywords: ISO 4548-2:1997, by‑pass valve characteristics, lubricating oil filter test methods, full‑flow filters, kinematic viscosity, differential pressure, engine oil filter testing.