---
title: "ASTM D4305"
url: "https://mat-cs.com/astm-d4305/"
description: "This test method covers the determination of low temperature flow behavior, through a screen-type test filter, of aviation turbine fuels, which can contain separated solids as wax."
---

ASTM Standard Withdrawn 2010

# ASTM D4305

Standard Test Method for Filter Flow of Aviation Fuels at Low Temperatures

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## Significance and Use

The lowest [tem](https://covalent.com/techniques/electron-microscopy/transmission-electron-microscopy-tem/)perature at which aviation fuels remain free of solid hydrocarbon crystals, which may restrict the flow of fuel through filters in an aircraft fuel system, is a key safety parameter in the specification and use of fuels. In Test Method D 2386, the freezing point is defined as the temperature at which all crystals disappear following a cooling and warming cycle. In this test method, a cooling and warming cycle is also employed; however, the test result is defined as the flow point, which is the temperature of the specimen at which a test filter becomes unblocked on warming.

## Scope

1.1 This test method covers the determination of low temperature flow behavior, through a screen-type test filter, of aviation turbine fuels, which can contain separated solids as wax.

1.2 Procedure A employs a 26-μm test filter and is the recommended procedure. Some existing instruments are fitted with a 42-μm filter, and Procedure B is retained to enable their continued use.

1.3 The use of Procedure A (26-μm test filter) with fuels that have a viscosity of greater than 5.0 mm2/s (cSt) at -20°C, as determined by Test Method D 445, can affect the precision and the simulated freezing point obtained on such fuels and can give a higher (warmer) result than the conventional freezing point obtained by Test Method D 2386.

Note 1—The principle of this test method relies on flow through a fine-mesh test filter, and, hence, the result can be affected by the viscosity of the sample. When using Procedure A, a no-flow condition is reached when crystals block the test filter or the viscosity exceeds about 14 mm2/s (cSt); sample with a viscosity of greater than 5 mm2/s (cSt) at -20°C may exceed the 14-mm2/s (cSt) threshold at a temperature before crystals are formed. If viscosity affects the result before crystals are formed, then the reported value of the no-flow temperature of the sample will always be warmer than the actual freezing point, and therefore fail-safe and an indicator of possible flow anomalies at low temperature.