Diesel - ASTM D445

The PSL Rheotek RUV-2 determins the kinematic viscosity of diesels, distillate fuels, gas oils and bio-diesel fuels using glass capillary viscometers in full compliance with ASTM D445, IP71 Part 1, ISO 3104. Typically, specifications such as ISO 8217 Marine Fuel Standard, require measurements to be made at 40 deg. C. The RUV-2 also has the capability to measure at other temperatures e.g. 20 deg. C, 100 deg. F or 104 deg. F.

The RUV-2 accommodates suspended-Level type Ubbelohe viscometers as specified in ASTM D446, ISO 3105. These are the most precise viscometers for determining diesels and are not sample volume dependent. Furthermore, the calibration constant is valid for all temperatures of use. The RUV-2 fully complies with standard methods of test - following the procedure for transparent liquids.

In particular, the RUV-2 mimics the standard test methods as follows:

- glass viscometers are calibrated to ISO 17025 - providing uncertainties as well as independent traceability to national standards

- the viscometer bath set-point is controlled to an accuracy of +/- 0.02 deg. C (or indeed much tighter). The set-point temperature, accuracy and uniformity of the bath can be verified with an external reference thermometer (the PSL Rheotek F100 with calibrated PT100 probes is recommended)

- flow times are measured in milli-seconds, by accommodating the glass viscometers into an external measuring head holder. The detection system is built into the measuring head holder (not the glass tube). A precise nIR emitter and detector are used to capture the meniscus. - and flow times can be independently verified

- two successive flow times are measured in the same timing bulb, without emptying or re-charging the viscometer - in accordance with the determinability requirement (determinability is the % difference between two measured flow times) is calculated and verified against the method requirements.

- glass viscometers as well as all wetted parts of the viscometer system are cleaned in-situ with a first solvent miscible with the sample, followed by a drying solvent.

The following results are reported:

- flow times measured (s)

- determinability % achieved

- whether the required determinability has been obtained (for gas oils at 40 deg. C, the requirement is the average determined value +1 multiplied by 0.0013. For biodiesel fuels the requirement is 0.0037 x the average determined value (0.37%).

- the kinetic energy correction (this is automatically applied for shorter flow times). The method requirement is that the KE correction shall not exceed 3% of the measured viscosity.

- the kinematic viscosity result in mm²/s, cSt

- minimum, average and maximum temperature recorded during the flow times