Below are main indicators of dry chemical powder fire extinguishing agent:
1. Water repellency.
Water repellency is an important indicator. The water repellency of ammonium phosphate dry powder fire extinguishing agents,namely ABC dry chemical powder is often prone to problems, and there are many factors. The ammonium phosphate salt is too finely crushed. Although the fire extinguishing efficiency is significantly improved, the water repellency is significantly reduced. As the particle size decreases, the specific surface area increases dramatically, and more silicone oil is needed to meet the surface silicification of ultrafine particles. However, quantitative silicone oil cannot naturally satisfy the surface silicification of ultrafine particles, so the water repellency decreases. In addition, when the particle size is too fine, less than or close to the size of the hydrophobic white carbon black, it will cause ammonium phosphate to adsorb around the hydrophobic white carbon black particles, and will not play a hydrophobic function (4). As a main water repellent function Hydrophobic white carbon black, please pay attention to verify its hydrophobic effect, check its quality, and the amount of addition should be appropriate, the particle size should be fine, otherwise it is difficult to adsorb around the powder; but the particle size should not be too fine, otherwise its hydrophobic performance is not good . Silicone oil should be added in sufficient amount. The amount and dispersion of water and catalyst and the temperature will affect the polymerization and solidification of silicone oil, which in turn will affect water repellency. After adding white carbon black, the wind speed of the dehumidifying port should not be too large, otherwise part of the hydrophobic white carbon black will be lost and the water repellency will be affected. In addition, the powder outlet of the mixing mixer must be sealed to prevent the extinguishing agent from exuding before the siliconization is completed, and finally enter the finished product, which partially affects the water repellency of the finished product.
2 Moisture absorption rate
The moisture absorption rate of ammonium phosphate dry powder fire extinguishing agent is a very important indicator for ABC chemical powder, and moisture absorption is the direct cause of dry powder agglomeration. Excessive moisture absorption rate will cause dry powder to agglomerate during storage and affect its use. The moisture absorption characteristics of ammonium phosphate dry powder fire extinguishing agent are mainly determined by the hygroscopicity of ammonium dihydrogen phosphate. Relevant experiments show that ammonium dihydrogen phosphate can spontaneously decompose into phosphoric acid and ammonia at room temperature: NH4H2PO4-NH3 + H3PO4. Phosphoric acid is a highly hygroscopic compound. Because phosphoric acid covers the surface of ammonium dihydrogen phosphate and continuously absorbs moisture from the atmosphere, resulting in an increase in the absorption rate of ammonium dihydrogen phosphate. Therefore, if phosphoric acid can react with other substances in time, Reducing and removing phosphoric acid will significantly inhibit the absorption rate of ammonium dihydrogen phosphate. For example, calcium phosphate is used to react with phosphoric acid. In addition, the moisture absorption rate of ammonium dihydrogen phosphate is also significantly affected by the size of the particle size and the storage time. The finer the particle size, the longer the storage time and the more phosphoric acid decomposed, the higher the moisture absorption rate. At the same time, the humidity of the external environment has a very obvious effect on the moisture absorption rate of ammonium dihydrogen phosphate. As the humidity increases, the moisture absorption rate increases extremely quickly (5). As can be seen from the above analysis, it should be sought to minimize the exposure of ammonium phosphate dry powder fire extinguishing agents to environments with high relative humidity, especially those with relative humidity above 60%, which is beneficial to reduce the moisture absorption rate of fire extinguishing agents. In addition, a small amount of diammonium phosphate in ammonium dihydrogen phosphate is likely to cause a large hygroscopicity of the fire extinguishing agent because of its high moisture absorption rate. The type, quality, dosage of silicone oil, temperature and fineness of dry powder during polymerization will affect the moisture absorption rate. Some impurities remaining in the mixer, pipelines and other systems, such as sodium bicarbonate, enter the system and come into contact with ammonium dihydrogen phosphate to form a chemical reaction, producing substances with high moisture absorption rate, which affect the product moisture absorption rate.