ASTM D5949 Test Method for Pour Point of Petroleum Products (Automatic Pressure Pulsing Method)
6. Apparatus
6.1 Automatic Apparatus - The automatic pour point apparatus described in this test method consists of a microprocessor controlled test chamber that is capable of heating and cooling the test specimen, providing a controlled pulse of compressed gas onto the specimen surface, optically detecting the specimen surface movement, and recording the temperature of the specimen as described in detail in Annex A1. It is specifically designed to detect the lowest temperature at which movement of the surface of the specimen is observed upon application of the pulse.
6.2 The apparatus shall be equipped with a specimen cup, an array of optical detectors, light source, pressure pulsing unit, digital display, Peltier device, and a specimen temperature measuring device.
6.3 The pressure pulsing unit consists of a stainless steel tubing, 250 mm +/- 2 mm long and 1.1 mm +/- 0.1 mm inside diameter. This tubing is connected to a constant pressure source at one end, which serves as an inlet. The other end of the tubing, which serves as the outlet, is bent and positioned such that it is pointing to the center of the specimen at an acute angle. The distance between the outlet and the center of the specimen is 8 mm +/- 2 mm.
6.4 The Peltier device shall be capable of heating or cooling the test specimen at a rate of 1.5 °C/min +/- 0.1 °C/min.
6.5 The temperature measuring device in the specimen cup shall be capable of measuring the temperature of the test specimen from -80 °C to +70 °C at a resolution of 0.1 °C.
6.6 The apparatus, if required, shall be equipped with fittings to permit the circulation of water or other liquid cooling media to remove heat generated by the Peltier device and other electronic components of the apparatus. Newer models have internal sources of liquid cooling media and do not require such fittings.
6.7 The apparatus shall be equipped with fittings to permit the delivery of nitrogen gas to the pressure pulsing unit. Newer models have internal sources of compressed gas and do not require such fittings.
6.8 Ultrasonic Bath, Unheated - (optional) - with an operating frequency between 25 kHz to 60 kHz and a typical power output of ≤100 W, of suitable dimensions to hold container(s) placed inside of bath, for use in effectively dissipating and removing air or gas bubbles that can be entrained in viscous sample types prior to analysis. It is permissible to use ultrasonic baths with operating frequencies and power outputs outside this range, however it is the responsibility of the laboratory to conduct a data comparison study to confirm that results determined with and without the use of such ultrasonic baths does not materially impact results.
7. Reagents and Materials
7.1 Coolant - Tap water or other liquid heat exchange medium sufficient to remove heat generated by the Peltier device and other electronic components from the apparatus. To achieve specimen cooling to -60 °C, supply circulation of liquid cooling medium at +25 °C or lower, if required, to the apparatus. Obtain cooling performance data from the apparatus manufacturer if lower specimen temperatures are desired or if the tap water temperature is higher than 25 °C.
7.2 Dry Nitrogen Gas - Nitrogen gas with a dew point below the lowest temperature attained by the specimen (Warning - Compressed gas.)(Warning - Inert gas can be an asphyxiant when inhaled.) Newer models have internal sources of compressed gas and do not require external dry nitrogen gas.
7.3 Precision Volume-Dispensing Device, capable of dispensing 0.150 mL +/- 0.005 mL of sample.
7.4 Cotton Swab, plastic shaft cotton swabs to clean the sample cup.
