The Promet EExd is the world's first purpose-designed, EExd flameproof-certified, process moisture analyser, and it is needed to ensure that new LNG and other gas sources provide dry gas supplies
Recent hikes in world gas prices have focused the minds of industry and politicians alike on ensuring that consumers and businesses have continuing supplies of natural gas. Increased investment in new undersea pipelines and plans to import gas by tanker as liquid natural gas (LNG) are the main ways in which the UK's gas demands are planned to be met in future. But care has to be taken with these new sources of gas to ensure that they are 'fit for purpose'.

The gas needs to be tested for a variety of potential contaminants, one of the more surprising, perhaps, being water.

If there is too much moisture in the gas, it can cause problems along the pipelines and also during downstream processing.

One of the first stages of gas processing is dehydration as gas from the wellhead is totally saturated with water and liquid hydrocarbons.

This is carried out by a dessicant drying process using liquid glycol injection in contactor towers.

If the gas is not sufficiently 'dry', it can corrode pipelines or risk hydrate formation - the combination of hydrocarbon condensates with water to form, under the high pressures experienced in gas transmission pipelines, solid crystalline hydrates.

These may line the inside wall of the pipes, reducing flow capacity, or even break off into the gas flow risking damage to process valves, filtration and compression stations, potentially blocking the pipeline.

LNG processing requires even less moisture content to be present in the gas.

This is because, at the very low temperatures and high pressures needed, any moisture present has the potential to freeze inside the cryogenic process.

This leads to ice forming which reduces production capacity and can eventually cause blockage.

In this instance, the water vapour content must be maintained at low trace moisture levels of around 0.01 ppmV, which equates to a dew point of around -100C.

So how do you measure such small traces of moisture in such difficult conditions?

Not only are the pressures and temperatures hard to handle, but natural gas is, of course, a highly flammable substance so there mustn't be any possibility of a spark.

This is the problem which Michell Instruments set out to solve with its new Promet EExd analyser.

The Promet EExd is the world's first purpose-designed, EExd flameproof-certified, process moisture analyser.

As specialists in dew point measurement for industrial, process and research applications, Michell Instruments has over 25 years' experience in satisfying the moisture measurement needs of the hydrocarbon and petrochemical industries.

Using all its experience, the company has developed a product which meets all the requirements of clients needing an installed solution in hazardous areas.

Promet EExd features EExd flameproof ATEX and CSA certification, complete zone 1 or 2 installation, and a remote interface option for mounting in a safe area if required.

The process moisture analyser also offers single- and dual-channel moisture control capability, with integrated electronic pressure measurements, within the same single field installed flameproof housing.

The remote interface option provides an advanced graphical display of measurement and status information, data logging and access to program configuration functions for up to 31 analysers.

Each analyser communicates with the remote interface through the Modbus RTU, so transferring all of the functionality of the main unit into the comfort and convenience of an indoor safe environment.

Global access to all functionality is provided through a web browser directing into the embedded website of the remote interface, so facilitating the needs of users with unmanned site and also enabling Michell to provide expert support services without the need for a site engineer visit.

As gas comes from further and further afield, gas producers and transporters can be assured that the Promet EExd will alert them to the first sign of any problems caused by that dangerous substance - water.