Application DH 5: Water Separability acc. ASTM and ISO

This test method covers measurement of the ability of petroleum oils or synthetic fluids to separate from water. It is used for specification of new oils and monitoring of in-service oils.

Background Information

The test method is used to find out the ability of an oil to separate from water. The goal is to determine if the oil can fully separate from water.

Although developed specifically for steam-turbine oils having viscosities of 28.8 cSt – 90 cSt (mm²/s) at 40 °C, this test method can be used to test oils of other types having various viscosities and synthetic fluids. It is recommended, however, that the test temperature be raised from 54 °C to 82 °C ±1 °C when testing products more viscous than 90 cSt (mm²/s) at 40 °C.

The outcome of the test shows the ability of an oil to be separated from water. The time needed for that procedure is recorded.

One Device – A Lot of Functionalities – DH 5

Based on its design the DH 5 offers eight positions. This is helpful for a fast sample throughput as different samples can be heated at the same time.
Two extra positions for pre-tempering are available.

Temperature and stirring speed are pre-defined but can also be easily set to different values with the touch screen. An automatic stirring stop after five minutes is implemented in the system. The temperature stability of the bath is ±0.1 °C.

Safety Features

  • Protection cover around the stirrer
  • Over temperature protection
  • Low level protection
  • Safety cut-off, when lifting stirrer


Fig. 1: DH 5

Test Method

A test specimen consisting of a 40 mL sample and a 40 mL quantity of distilled water are stirred for 5 min at 54 °C in a graduated cylinder. The time required for the separation of the emulsion thus formed is recorded either after every 5 min or at the specification time limit. If complete separation or emulsion reduction to 3 mL or less does not occur after standing for 30 min or some other specification time limit (depending on the standard), the volumes of oil (or fluid), water, and emulsion remaining at the time are reported.

Fig. 2: Sample status
(1) after preparation
(2) after stirring
(3) during separation process
(4) at final stage

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