Issues regarding the repetition of sampling for ethylene tank cars
Thread Content
For various reasons, our company recently purchased a substandard ethylene tank sample, which was unloaded into a storage tank at the port. The analysis results from both the inspection vessel and the onshore tank were consistent; in terms of purity analysis, the levels of carbon tiers 3 and above were around 40 ml/m3. It is transported to our company using specialized ethylene tank trucks, and samples are taken before unloading for analysis in order to determine the purity of ethylene. The analysis results for C3 compounds and higher are unstable; in most cases, the concentration is above 40 ml/m3. Moreover, when two samples are taken from the same tank truck for analysis, there is a problem of significant differences in the analysis results; similar large differences also exist in the analysis results between different tank trucks that are filled from the same storage tank. In terms of analytical techniques, instrument comparison standards are used for verification, with samples injected by different personnel. The repeatability of the analysis results for the same sample bottle was excellent, and the sampling procedures were carried out in strict accordance with GB/T13289-2014. I think the problem lies in the sampling process; I would be very grateful if experts could offer some advice: handshake.
The analysis results of the port storage tanks, the samples taken by the inspection ship, and the samples from onshore tanks are consistent; this indicates that there are no issues with those samples. If one still disagrees, it may be because the sampling was not representative – there could be problems with uniform mixing, and multiple sampling points are needed. Mixing inside the tank car can result in variations in the quality of the material contained within it. Second, the presence of other components originally stored in the receiving tanks and containers leads to quality variations. To avoid confusion and mutual suspicion due to an inability to identify the cause later on, it is necessary to take more samples for analysis from the ship. Additionally, it is important to ensure that there is no liquid remaining in the tank trucks and receiving tanks. Personal opinions are for reference only