Method for detecting oil content in compressed air

1. Weight method

The gravimetric method refers to the method of determining the analytical results of a certain amount of sample

 gas using a constant weight container or medium (filter paper, membrane) device, after evaporation, drying, and 

constant weight. The gravimetric method was an early adopted method for determining oil content in water, and 

there are still many people using the gravimetric method to determine water bodies with high oil content. When using 

the gravimetric method, it is necessary to strictly control the dryness and wetness of the sampling tube, degreased

 cotton quantitative filter paper, and the impact of dust contamination to prevent other oil pollution. During the sampling 

and analysis process, no additional debris is allowed to adhere to the weighed container or medium. The balance weighing

 must be rapid and accurate, as the mechanical and dust impurities in the air during sampling will affect the accuracy of oil 

content. However, the low sensitivity of the gravimetric method determines that it is not suitable for accurately measuring 

the oil content in gases, as the oil content in gases is quite low, and it is clearly not suitable to use the gravimetric method

 for measurement.

2. Infrared spectrophotometry

Compressor oil contains oil substances with obvious absorption peaks in the infrared light region. After a certain volume of 

liquid oxygen is naturally evaporated, the oil remains in the container. Dissolve the oil with tetrachloroethylene and bring to

 volume. Using the Binci LS2600 infrared spectrophotometer (using infrared spectrophotometry) to determine the content 

of oil in liquid oxygen, the accurate measurement of oil content concentration is closer to actual data, and the process operation

 is very simple, accurate, and in line with industry standards.

Method 2: If the compressed gas does not have a liquid oil content, and the gas excluded from it can be added to a customized 

filter cartridge management using special filter paper. After the filter cartridge pipeline, a flow valve is added to record the flow

 rate, and a fixed solvent is used to clean the filter cotton to obtain near real oil content data.

3. UV spectrophotometry

The ultraviolet spectrophotometer (using ultraviolet spectrophotometry), due to its good * * * * degree and high sensitivity, 

can measure trace amounts of oil in compressed gas. If the content is too high, it will exceed the limit detection value. It is

 based on the characteristic absorption of aromatic compounds with conjugated bonds and benzene rings in the ultraviolet 

region contained in the oil. Therefore, this method can be used to determine the concentration of oil in gas samples by measuring 

the concentration of substances with conjugated double bond structures. This method is based on Lambert's law of light absorption.

 Under the condition of pH ≤ 2, the oil substances in the product are extracted by n-hexane using an ultraviolet oil analyzer.

 The extracted liquid is dehydrated by anhydrous sodium sulfate, and then adsorbed by magnesium silicate to remove polar 

substances such as animal and plant oils. The absorbance is measured at a wavelength of 225 nm.

4. Chemical indicator tube method

The main manufacturers of instruments using the principle of chemical indicator tube method are Johnson Controls in the 

United States and Delger in Germany. The oil content indicator of Johnson Controls is equipped with a gas detection agent, 

which reacts with the oil to form a colored layer. Quantitative analysis is conducted based on the depth of the color layer or 

the length of the color changing layer. Delge's oil detection method captures oil mist into the indicator layer of the oil detection

 tube, and under the action of a catalyst, it produces black products with concentrated sulfuric acid in the oil detection tube. The

 color depth is related to the oil content, and the oil content in the air is detected by colorimetry. This method generally only 

determines whether the oil content is greater than a certain value and cannot obtain a specific value. This method is simple to 

sample, but