Varnish Potential Analysis

What the Test Does

ASTM D7843 works by filtering a small amount of your turbine oil through a special membrane. Any degradation by‑products collect on the patch, and the colour of the patch is measured to produce a ΔE varnish potential score.

Low score = oil is in good condition

Higher score = varnish is forming and action may be needed

The method is simple, reliable and widely used across the power generation and industrial sectors. We simply require 100ml of fluid from the turbine or asset for analysis.

Why Varnish Matters

Varnish is one of the most common causes of turbine reliability problems. It can lead to:

Sticking or slow‑responding control valves

Bearing temperature spikes

Filter blockages

Reduced efficiency and increased energy use

Unplanned downtime and costly repairs

Regular D7843 testing gives you the visibility to prevent these issues before they start. Turbine manufacturers even recommend monthly testing for critical systems.

What You Get from FA‑ST

FA‑ST offers ASTM D7843 testing as part of a complete oil‑health and filtration service. You receive:

A clear varnish potential score

An image of your membrane patch

Expert interpretation in plain language

Recommendations on whether action is needed

Support with varnish removal using FA‑ST filtration rigs

Our filtration rigs are specifically designed to remove varnish‑forming contaminants, helping bring values back under control and extending the life of your turbine oil.

Benefits for Your Operation

Early warning of oil degradation

Reduced risk of varnish‑related failures

Longer oil life and lower operating costs

Improved reliability of turbines and hydraulic systems

Confidence that your oil is performing as it should

Ideal for

Power generation turbines

Industrial turbines

Hydraulic systems using non‑detergent oils

Any operation where reliability and uptime matter

Not suitable for

Turbine oils that contain dyes or leak detection fluid

Turn Around time for results 6-8 working days