Ralston Instruments Gas Sampling Pump for Low Pressure Applications

The composition of natural gas changes over time due to changes in the natural gas reservoir, because of this there is a need to sample the gas to determine its composition.  Sampling of natural gas to determine the composition is important for custody transfer and fiscal metering so that both buyers and sellers are confident of a fair transaction.  Contracts are typically concerned with the BTU or energy content of the gas and the hydrocarbon dew point of the gas.  There are many robust automatic gas sampling systems such as on-line GCs (Gas Chromatographs) in the field that can perform on-line sampling.  These are systems that are expensive, require frequent maintenance and are usually only justified when large volumes of gas are being moved.

But what about low pressure, low producing wells or pipelines?  The companies involved typically cannot justify on-line GCs or other automatic sampling systems.  In these cases spot sampling is recommended.  This means collecting a representative sample at a specific moment in time that can be taken to a laboratory for analysis.  Much of the natural gas produced today has contamination and heavy hydrocarbons – otherwise known as “wet” gas.  If these liquids condense when a sample is taken – known as reading the hydrocarbon dew point – then the sample can be no longer considered representative.  Thus it is important to preserve the liquids in the same form that they appear in the gas.  The Ralston SPOV gas Sampling Pump helps make this process easier by taking a gas sample from a low pressure or low flow pipeline or well and putting it into a sample cylinder with out changing the gas composition by staying under the hydrocarbon dew point (HCDP).

The SPOV Gas Sampling Pump is constructed in accordance with API 14.1 and CPA 2166 standards on natural gas sampling.  Materials of construction are hard anodized aluminum, stainless steel and has Viton seals and is lubricated with hydrocarbon-free lubricant.  All of these things help to prevent contamination of the sample as well as resisting H2S, mercury and other active compounds found in natural gas.  The Ralston SPOV Gas Sampling Pump is an excellent new tool to perform effective sampling that provides good representative gas composition data in cases where on-line GCs are not justified.