SOCLEMA > Applications > Petrochemicals / Refining

Liquid hydrocarbons, solutions adapted for SOCLEMA sampling

Hydrocarbons are organic compounds composed exclusively of carbon (C) and hydrogen (H) atoms. They are all different because of their origin and chemical composition.

They are of great commercial importance as they are used as fuels, fuels, lubricating oils and petrochemical synthesis feedstocks. It is therefore important to analyse them.
Sampling is necessary to determine their physical and chemical properties, such as water and sediment content, viscosity, density, or vapour pressure. A distinction must be made between manual and automatic sampling.

Manual sampling of liquid hydrocarbons

Manual sampling is used when the mass to be sampled is homogeneous. The ISO 3170: 2004 and ASTM standards D4057 provide guidelines for the manual sampling of liquid and semi-liquid petroleum products, crude oil, intermediate products, and water or heavy components associated with petroleum products.

These texts standardize the conditions for taking samples of liquid or semi-liquid hydrocarbons from tanks, drums or pipelines by manual means. The standards specify procedures to reduce or eliminate the loss of light fractions that may occur during sample handling. These operating procedures are intended toobtain samples to determine the quality of the hydrocarbonsthe water content and the presence of other impurities that are not normally part of the transferred liquid.

The standards provide a guide to the equipment to be used, the preparation of the container and manual sampling procedures to ensure the safety of the personnel involved. He there are many possible types of samplers with bottles, cylinders, containers that can be made of glass, plastic or metal.

Preferably, equipment should be selected that does not require the sample to be transferred from the initial container to an intermediate container. The equipment used must be designed and manufactured to ensure that it meets its function. It must be strong enough and perfectly hermetic to preserve the initial characteristics of the sample. The construction materials must be compatible with the sampled product and there must be no interaction between the two, otherwise the integrity of the sample could be affected.

Automatic sampling of liquid hydrocarbons

Manual sampling is appropriate when the liquids to be sampled are homogeneous, and their composition and quality do not vary significantly over time. When this is not the case, automatic sampling is the recommended procedure Continuous or repeated collection of small samples ensures that all changes are reflected in the collected sample. The ISO 3171 standards: 1999 and ASTM D4177 provide guidelines for the automatic sampling of liquid petroleum products.

It is essential that the samples be representative because they allow the determination of the physico-chemical properties that are used to establish volumes and prices in accordance with commercial and regulatory specifications. To ensure that the sample is as representative as possible, it is essential to ensure that recommendations related to the homogeneity of the sample at the sampling point and to the sampling frequency are respected. Non-homogeneous hydrocarbons must be mixed at the sampling point; the volume must be consistent and sampled from the stream in such a way that it is representative of the total volume. The sample must be stored in the collector without being altered. The samples must be mixed to ensure that the final sample provided to the analyzer is representative.

Automatic sampling systems consist of a system for conditioning the flow upstream of the sampling point, a system for physically taking the sample, a system for measuring the flow rate, a system for controlling the volume taken and a tank for collecting and storing the samples. Depending on the application, it may be necessary to isolate some components or the entire system. The sampling system can be installed on the main line or on a fast loop. These two facilities provide a representative sample.