Gaseous Air Flow and Negative Pressure in Sewer Tunnels Zone 0 Equipment

https://www.ashcroft.com/industrybrochures_pdf/upload/Instrumentation-for-Water-Treatment-Industries.pdf

https://www.wwdmag.com/instrumentation-water-quality-monitoring/2019-top-water-wastewater-projects

Thanks for the information.

The vacuum pressure may be available from the Ashcroft as they have ATEX rate systems but did not specify to zone o, but will inquire.

I believe a company called sensorone can provide, but obviously better to have greater choice.

The more the better.

DMP331 Precision Pressure Transmitter

https://www.sensorsone.com/wp-content/uploads/2013/10/DMP331.pdf

If it's Zone 0 then there is no prospect of humans bring present; if there were then it exposes the risk of being prosecuted under Health & Safety legislation.

So why is <...Air Flow and vacuum pressure...> of interest in this zone?

Yes agreed

A live sewer is always Zone 0 and to access requires special H&S procedures including, force ventilation, full BA sets, correct PPE , training RAMS etc.

The question regarding air flow in a zone 0 remains unanswered. Why is a continuous measurement of air flow needed when there are no humans present?

As there is a requirement to control the H₂S pressure in the sewer as pressures above 0.05 psi are extremely corrosive.

Also if H₂S combines with the effluent the chemical reaction will form sulfuric acid.

Hence the pressure is reduced by extracting the H₂S and treating in an odor control system. to negate the potential corrosive attack on the structures and maintain the H₂S at a pressure where the structures will experience least possible corrosive attack.

Ah. So this isn't about air flow, it's about H₂S flow.

There are a multitude of odour scrubber vendors and an enquiry to these will produce recently adopted standards for these things. Telephone?

It would make more sense to exclude air from the arrangement, thereby pushing the conditions above the upper flammable limit of the substances present. Then there would be no air flow to measure.

Unfortunately the design of gravity sewers cannot be design to run at full bore due to the extremely variable inputs to the system and requirements not to surcharge and overflow.

Although the force main (pumped) systems can be designs to operate at full bore.

Thank you for your contribution to the question always good to explore alternative options.

Thanks for taking the time for such a comprehensive and informative response.

I've been in touch with numerous companies and there are some who have responded they maybe able to assist on the air flow using vane with decoder and others with the sour windmill solution.

As you say it is a big world out there and some good and innovate products continually being developed.

FCI Fluid Components International LLC has been making thermal mass flow instruments since at least the mid 1970s, so they have seen a lot. I’ve used their equipment on various gasses, but not heavy H2S concentrations, light concentrations are common in pulp mills, forest products. Their ST98L in aluminum is rated for Class 1 Div 1 and more, with provisions for corrosion protection, imperative in many chemical process plants. This should be just a walk in the park for them.

Here is a link to a a reliable company that is familiar with all aspects of STP issues,including pressure,gas analysis,etc.

Your problem is not unique and there are plenty of solutions available.

https://krohne.com/en/products/pressure-measurement/pressure-transmitters/

As previously stated,there are many solutions available,so pick the one that best suits your needs.