If you think your gas is dry, you need to read this

As the effects of moisture in natural gas systems are not always immediately evident, some NGV station builders are reluctant to address the importance of installing desiccant dryer systems in CNG fuelling stations. This is despite the fact that there are industry standards and recommended practices for the required dew point of compressed natural gas used for fuelling stations, such as ISO 15403:2000(E).

The most common reason for not installing dryers in NGV stations is the belief that the gas is already dry. However, it should be taken into consideration that although the gas dew point may be as low as -40°C in the pipeline at pipe pressure, the effects of compression will affect the dew point of the gas.

Physical laws dictate that the dew point of a gas increases as its pressure increases. Therefore, although the dew point of the gas in a given pipeline may be very low when it reaches the compressor, it will be significantly higher when the gas leaves the compressor. This is why natural gas desiccant dryers are required in the majority of NGV stations in order to conform to the ISO 15403:2000(E) standard, specifically in areas where lower temperatures are encountered during the colder winter months.