Does hydrogen dissolve in lubricating oil?
Thread Content
In our company’s hydrogenation unit, the viscosity of the lubricating oil for the new hydrogen compressor has decreased from 150# to 78; its flash point has also dropped, and there are signs of water contamination. Is it caused by hydrogen dissolving in the lubricating oil?
Hydrogen is slightly soluble in lubricating oil, but as the viscosity of compressor lubricating oil decreases, its flash point also drops; the presence of water should not be attributed to hydrogen dissolution, or rather it is not the main factor. I’m not aware of the specific details regarding your new hydrogen generator; it would be more logical to assume that light hydrocarbons and water present in the hydrogen end up in the lubricating oil. It is recommended to investigate the cause from this perspective.
Under certain pressures, hydrogen gas dissolves slightly in conventional hydrocarbon-based lubricants, which reduces the viscosity of the compressor lubricant as well as its flash point, and consequently diminishes the lubricating properties of the oil. In such cases, it is preferable to use fully synthetic hydrocarbon-oxygen-based lubricants. Compressor oils can be used for compressing the following gases: liquefied petroleum gases, such as propane and butane； Liquefied natural gases, such as methane and ethane; hydrocarbon petroleum gases, such as ethylene, propylene, and butylene ； Industrial gases, such as ammonia, vinyl chloride, and butadiene. Last edited by xlxderun on 2009-2-18 16:08.]
Since the purity of the new hydrogen is around 90% and it contains some hydrocarbons, it can easily dilute the lubricating oil and reduce its viscosity, leading to warnings related to bearing temperature or damage. It is recommended to check whether there are any issues with the nitrogen seal or the intermediate isolation gas.
The solubility of hydrogen in toluene, n-heptane, and petroleum fractions increases with rising temperature and pressure, as well as with increasing boiling point of the fractions; however, its solubility in residue at atmospheric pressure is lower than that in wax oil and diesel.
Hydrogen is slightly soluble in lubricating oil, but this does not lead to significant dilution. Does the presence of water mean that the hydrogen is not dry enough? A mild degree of dilution is acceptable, but if it is severe, other factors should be considered, such as whether the gas is pure and whether it contains hydrocarbons.