What to look for when choosing a portable dew-point tester for natural gas

A portable dew-point tester is a tool for engineers working in the field and will be used in addition to an online hydrocarbon and water dew-point analyzer to confirm natural gas quality. Online analyzers provide continuous online measurements for hydrocarbon dew point (HCDP) in natural gas. Many of these online analyzers – including the Michell Instruments’ Condumax II Hydrocarbon Dew-Point Analyzer – will also provide water dew-point analysis at the same time. In contrast, portable dew-point testers provide fast and simple tests for HCDP and water dew point at different sample points in the system.

If you want to understand more about how hydrocarbon dew point is calculated in a gas mixture, read our previous post ‘What is hydrocarbon dew point?’

Why is it important to measure hydrocarbon and water dew point?

Hydrocarbon and water dew point are both critical parameters of quality for natural gas. All transmission quality natural gas must meet international gas quality specifications governing transmission, storage, distribution, and utilization, such as CEN – EN16726, by making measurements in conformity with ISO6327 or ASTM D1142.

While online hydrocarbon and water dew point analyzers are installed at critical points in each site – such as the point of custody transfer in natural gas pipelines – portable instruments are important for engineers to test the natural quality at different sample points in the whole process. This enables them to pinpoint leaks or processing deficiencies and determine any quality issues in specific locations. Often portable dew-point testers are used to verify the measurements of the online analyzers as part of a routine maintenance program.

How to choose a portable hydrocarbon dew-point tester

There are several models of portable dew-point testers and transportable hydrocarbon dew-point analyzers on the market. These questions will help you compare the features and benefits of the models on the market:

• Does it have global hazardous area certification? Being able to use the dew point tester to measure hydrocarbon dew point directly in the hazardous area without a need for a hot works permit means measurements can be made quickly and easily. Support staff can respond quickly with spot-check measurements to determine the cause of process upsets, for example.
• Is it lightweight and portable? It goes without saying that a portable instrument needs to be easily carried and have a long battery life so that it can perform reliably in the field as well as being easily transported.
• Are the measurements reliable? All manual visual portable dew point testers use the chilled mirror technique to measure hydrocarbon dew point. Although this is the most reliable method to determine the dew point as it relies on direct observation of the actual formation of condensate on a chilled mirror surface, there are variations in how this technique is applied. When choosing an instrument, the ability to provide accurate and objective data for each measurement point is also important and not all models provide this.
• Does it conform to the international gas quality specifications? As mentioned above, natural gas must conform to international standards such as CEN16726 or EASEE-gas CBP-2005-001-02. Any portable dew-point tester must have a suitable accuracy to satisfy these.

PST recommends

The Michell CDP301 Condumax Dew Point Tester – launched in 2020 – is the only portable manual dew-point tester currently on the market to meet all the criteria listed above.



It has full hazardous area certification from ATEX, IECEx and cQPSus and can be used in Zone 1 or 2 and Class I, Division 1 hazardous areas. As well as providing fundamental measurements of both water and hydrocarbon dew point using the latest developments in the chilled mirror technology, it also allows for completely objective records of measurements.

A full colour HD video camera displays the mirror surface so that the formation of condensate can be easily seen and recorded for later review. See the instrument in action here. It is sensitive enough to measure hydrocarbon condensate to 5mg/Nm³.

At less than 9kg, it is easily portable and is capable of operating without mains power for up to 8 hours. The CDP301 is supplied with both a rucksack and a wheeled hardcase and a full range of options are available to ensure the instrument can be easily transported and set up at site, ready to use in minutes.

Get expert advice for your application

Contact us to find out more about the CDP301 and how it can help in your natural gas quality application.