Standards Development

Scope

This standard specifies a method for the laboratory determination, using a weighing digital liquid density meter (WDDM), of the density of crude petroleum, liquid petroleum products, and mixtures of petroleum and non-petroleum products normally handled as liquids and having a Reid vapour pressure (RVP) of 100 kPa or less. This standard is suitable for determining the density of liquids with sufficient fluidity at the test temperature and pressure.

Purpose

Density is a very important measuring parameter of oil for quality evaluation and quantity calculation.

The purpose of giving this proposal is offering an efficient, accurate and automatic method of using weighing digital density meter(WDDM) to determine density of liquid petroleum and petroleum products.

The WDDM method in this proposal is based on Archimedes' principle. A float connected to the force sensor through the pendant cord is lowered in the sample and statically immersed. The force sensor measures the tension given through the pendant cord and converts the tension into an electrical signal. The data display unit processes the electrical signal and displays its corresponding density value.

The main apparatus(WDDM) used in this proposal is capable of determining density with a resolution of 0.05kg/m3 at least, to an accuracy of ±0.2kg/m3 or better. This new method gives the precision of test results as follows:

Table 1 ¬— Repeatability

- see attached Compared with the known density determination methods (ISO 3675:1998, ISO 3838:2004,ISO 12185: 1996), the WDDM method has the following advantages:

1) Compared with ISO 3675:1998, although based on the same measuring principle, the WDDM method is more accurate and auto-implemented;

2) Compared with ISO 3838:2004, the WDDM method is more easily to operate for liquid products;

3) For ISO 12185:1996, the test sample(less than 1ml) in the u-tube may be not representative, while the sample need of WDDM method is about 300ml, which addresses the problem of sample representativeness.

This proposal has been verified by the market.

This proposal is already established National standard(NB/SH/T 0874:2014) of China, which is popular with many users (such as oil companies and research institute ) for its convenience and accuracy.

Overall, the proposal of WDDM method is worth of an International Standard, which add a method to the density determination pool and offer a choice for the testers.