ASTM D7843-25e1 PDF

Full title and description

Standard Test Method for Measurement of Lubricant Generated Insoluble Color Bodies in In-Service Turbine Oils using Membrane Patch Colorimetry — a laboratory procedure that extracts insoluble contaminants from in-service turbine oil onto a membrane patch and quantifies the patch color by spectrophotometer reporting a ΔE value on the CIELAB scale.

Abstract

This test method describes the membrane patch extraction of insoluble, lubricant-generated color bodies (varnish/insolubles) from turbine oil samples and their objective color measurement by spectrophotometric analysis. Results are reported as a ΔE (CIELAB) value used for condition monitoring and trending of lubricant health. The method is not suitable for oils containing dyes.

General information

• Status: Active.
• Publication date: February 1, 2025 (D7843-25e1); includes an administrative update/amendment recorded April 9, 2025.
• Publisher: ASTM International.
• ICS / categories: 75.100 — Lubricants, industrial oils and related products.
• Edition / version: D7843-25e1 (2025, edition/e1).
• Number of pages: 6 pages.

Scope

This test method extracts insoluble contaminants from a sample of in-service turbine oil onto a membrane patch and measures the color of that membrane patch with a spectrophotometer; results are reported as a ΔE value on the CIELAB scale. The method excludes turbine oils intentionally formulated with dyes and is intended for use as a condition-monitoring/trending tool within a broader lubricating-oil analysis program.

Key topics and requirements

• Membrane patch extraction procedure for isolating insoluble color bodies from oil samples.
• Spectrophotometric measurement of membrane patch color and reporting of ΔE (CIELAB) values.
• Limits on applicability — not appropriate for dyed turbine oils and intended for in-service oil condition monitoring.
• Specification of instrumentation, calibration, and data-reporting conventions to ensure repeatability and comparability.
• Guidance for using results as a trending tool and for integration with broader lubricant-condition practices.

Typical use and users

Used by oil analysis laboratories, power-plant maintenance and reliability engineers, asset owners/operators, OEM lubrication specialists, and condition-monitoring service providers to detect formation of insoluble varnish/contaminants and to trend lubricant health as part of preventive maintenance programs.

Related standards

This method is developed under ASTM Committee D02 and is referenced by or linked with other lubricant and oil analysis standards and practices (examples include Practice D4378 and test/practice references such as D6224, D6439, D7155, D7918, D8323, and D8506). D7843-25e1 revises/supersedes the earlier D7843-25 designation.

Keywords

membrane patch colorimetry; turbine oil; varnish; insoluble color bodies; ΔE; CIELAB; oil condition monitoring; lubricant analysis.

FAQ

Q: What is this standard?

A: ASTM D7843-25e1 is a test method that describes extracting insoluble, lubricant-generated color bodies from in-service turbine oils onto a membrane patch and quantifying patch color with spectrophotometry (ΔE, CIELAB).

Q: What does it cover?

A: The procedure for patch extraction, spectrophotometric measurement, reporting conventions (ΔE on CIELAB), applicability limits (not for dyed oils), and how to interpret results for trending within a lubricant condition-monitoring program.

Q: Who typically uses it?

A: Oil analysis laboratories, condition-monitoring and reliability engineers at power plants and industrial facilities, OEM lubricant specialists, and third-party oil-analysis service providers.

Q: Is it current or superseded?

A: It is current and published as D7843-25e1 (2025). The e1 edition (2025) replaces the earlier D7843-25 text and includes subsequent administrative updates recorded in April 2025.

Q: Is it part of a series?

A: It is part of ASTM Committee D02’s suite of lubricant and oil-analysis methods and is commonly used alongside related ASTM D-series practices and test methods (for example, Practice D4378 and other referenced D standards).

Q: What are the key keywords?

A: Membrane patch colorimetry, turbine oil, varnish, insoluble deposits, ΔE, CIELAB, oil condition monitoring.