With various heat conduction oils (heat transfer fluids) of different types and specifications on the market, it's a headache for customers to select them for the first time. So, how to select? By type, by initial boiling point, or by distillation range...? Here we provide an optimum method for selection - to select by the thermal stability of the conduction oil.
The thermal stability is the capability of the conduction oil to resist chemical decomposition under high temperature conditions. When the conduction oil runs into the heat transfer system, as the temperature rises, chemical reaction or molecular rearrangement will occur, and the resulting gaseous phase decomposition products, low-boiling residues, high-boiling residues and products fail to evaporate thereof will affect the application performance of the conduction oil. Due to this reason, the State Standard GB23971-2009 Heat Transfer Fluids implemented in China takes thermal stability as one of the key indexes for the Standard, rating the application and safety performance of the conduction oil that differentiates itself from other oils.
The Standard also takes the thermal stability test temperature as the basis for determining the allowed maximum application temperature of the conduction oil, and as the only basis for determining the conduction oil product code (mark). Thermal stability plays a major role in determining the type and class of the conduction oil product. That is to say, with no rating for thermal stability, no determination for allowed maximum application temperature, and thus no basis for marking product type, the oil cannot be called as conduction oil.
Since the State Standard for the conduction oil takes the thermal stability and the allowed maximum application temperature as the basis for marking product class, it has been playing a positive role in regulating the market order, providing key basis for customers to select conduction oils that suit to their application temperatures based on their own process conditions. For years, one of the major reasons behind China's disordered conduction oil market is that the allowed maximum application temperature of most conduction oils is not determined through thermal stability test. Suppliers mark the allowed maximum application temperatures of their products at will and dramatically exaggerated it.China's conduction oil market is full of products marked with maximum application temperatures @320ºC-350ºC. This not only disorders the conduction oil market itself, but also misleads the customers. Once they choose these falsely rated products, serious potential safety hazards will occur. This is also one of the major reasons behind hundreds of conduction oil boiler explosion accidents every year in China.
To effectively implement the GB23971-2009 State Conduction Oil Standard and regulate market order, safeguard production safety, and to promote healthy development of the conduction oil heat transfer technology, China has issued the compulsory Standard. To facilitate the implementation of the Standard, the authoritative testing organization - China Special Equipment Inspection and Research Institute (CSEI) came to be responsible for product type test and thermal stability test.
Mr. Si Rong et al of CBWQA have carried out research on the thermal stability of the major types of conduction oils that are most used in China, and the test data indicates:
- The maximum application temperature of the paraffin base & naphthenic base mineral conduction oil is @300ºC.
- The thermal stability of the mineral conduction oil based on hydrogenated base oil is higher than that of non-hydrogenated, of which the maximum application temperature reaches up to310ºC.
- The allowed maximum application temperature of the aromatic base mineral conduction oil is generally @310ºC, with some up to320ºC.
- The allowed maximum application temperature of the general synthetic conduction oil with Alkyl Benzene as the major composition does not exceed300ºC.
- The allowed maximum application temperature of the DIPHYL DT synthetic conduction oil is @310ºC.
- The allowed maximum application temperature of the synthetic conduction oil with hydrogenated Terphenyl as the major composition can be up to340ºC.
This has provided guidance and reference for customers to select appropriate conduction oils according to their own process and environmental conditions.
According to the results from the thermal stability test of 60 products of 46 suppliers by CSEI from April 2011 through August 2012, only 6 products passed thermal stability test over330ºC. Wherein SCHULTZ S750 - the hydrogenated Terphenyl conduction oil produced by Jiangsu Zhongneng Chemical Co., Ltd., has passed the thermal stability test @340ºCwith deterioration rate @ 5.3% only, the lowest among the products tested. The allowed maximum application temperature of the product is rated @340ºC, and the product is marked as L-QD340 GB23971, a special high thermal stability synthetic conduction oil type, truly high temperature synthetic conduction oil.