ASTM D1881-17 Standard Test Method for Foaming Tendency of Engine Coolants in Glassware

The standard “ASTM D1881-17 Standard test method for foaming tendency of engine coolants in glassware” developed by the American Society for Testing and Materials (ASTM) describes a simple glassware test method for evaluating the foaming tendency of engine coolants under laboratory controlled aeration and temperature conditions.

For the purposes of this standard,

• Breakthrough time refers to the time required for the foam to collapse (after the air supply is shut off) until an eye first appears on the surface of the test solution.
• The eye refers to the appearance of a foam-free area on the surface of the test coolant surrounded by a ring of foam adhering to the cylinder walls.

The testing method consists of the following steps:

• The coolant and ASTM Type II water solution are held at a constant temperature of 88 degrees plus/minus 2 degrees by means of a suitable temperature bath while blowing air at a constant rate for 5 minutes.
• The volume of the foam and the time it takes for this foam to break are measured.

The test method generally separates coolants with excessive foaming tendency from those that are suitable for further evaluation to determine their performance in actual service. In service, the foaming tendency of a coolant solution may increase due to service aging or contamination. A properly operating pressure cap will tend to suppress foaming in coolant solutions.

The equipment used in these tests includes:

• Vessel: A 45 mL graduated vessel made of heat-resistant glass, with a diameter of 50 to 380 mm and a length of 500 mm.
• Temperature bath: A heat-resistant glass container large enough to permit immersion of the graduated beaker up to at least the 350 mL graduation mark. A 4000 mL beaker is sufficient.
• Heat source: Any heating system that can maintain a uniform bath temperature of 61 degrees. A 750-watt electric hot plate is sufficient.
• Aerator tube: Spherical gas diffuser stone, 25,4 mm in diameter, made of fused crystalline alumina grain, which, when tested in accordance with the method given in the annex to the standard, meets the following requirements: Maximum pore diameter not greater than 80 µm, permeability 2,45 to 3000mL air/minute at 6400 kPa pressure.
• Temperature measuring device (environmental thermometer or thermocouple): An ASTM partial immersion temperature measuring device with a range of -20 to plus 150 degrees and that complies with the thermocouple requirements outlined in ASTM E230/E230M-11.
• Air supply: A clean, dry source that is free of grease and other contaminants and capable of maintaining the prescribed flow rate through the diffuser stone.
• Timer: A stopwatch or suitable timing device accurate to 60,2 seconds.
• Vent: A three-way valve placed in the metered air supply line just before the vent pipe.
• Typical mounting setup: A typical apparatus using a hot plate heat source is shown in the figure in the standard.

Materials and reagents used in these tests include:

• Purity of water: Unless otherwise stated, the term water means reagent water as defined in the standard “ASTM D1193-06 Standard specification for reagent water”.
• Acetone for washing and drying test equipment: Acetone is highly flammable.
• Test coolant conforming to “ASTM D3585-08 Standard specification for ASTM reference fluid for coolant testing”: Unless otherwise stated, references to the reference test coolant mean coolant that does not contain antifoaming agent as defined in ASTM D3585-08.
• Cleaning bath: Refers to the acid or base cleaning solution used to clean glassware between tests. The selection of cleaning baths depends on individual needs. For example, Nochromix and alcoholic sodium (potassium) hydroxide are common acid and base cleaning baths, respectively. Cleaning baths are strong oxidants and strong acids and bases.

According to this standard, the test conditions are as follows:

• Test temperature: The temperature bath should be kept at a constant volume (350 to 375 mL mark on the graduated cylinder) throughout the test. The test solution should be maintained at 88 degrees plus/minus 2 degrees throughout. This temperature is suitable for both high-boiling and low-boiling refrigerants.
• Ventilation rate: The ventilation rate should be 1000 plus/minus 25 mL/min.
• Number of tests: The reference coolant should be tested to determine if the glassware and test equipment are contaminated with residual defoamer. If the reference coolant produces a foam volume greater than 250 mL and a break time greater than 8 seconds, the reference coolant is drained from the glassware, rinsed with Type II water, and used in the preparation of the test coolant.

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