Nova Analytical Systems: November 2014

Thursday, November 13, 2014

#197 - Borehole and soil gas analysis- Part 2

A while back, we posted some information about analysis of boreholes at decommissioned mine sites. Here is Part 1 of the discussion.

At the time, we mentioned that we have frequently sold the Model 309 Portable O2 / CO2 analyzer for this application. Because some of the samples will be pulled up from deep into the borehole, we can install a heavy duty pump into the instrument. This solution has been great for this application.

One mining company recently contacted us requesting a solution to a problem they were having with water accumulation in their analyzers. In the standard instrument we supply to this company, we incorporate a bowl filter of some kind at the sample inlet to capture any water that may come up with the gas. This approach has usually been adequate for the brief period that they have sampled at each point. However, at some boreholes, water accumulation in the interstices between the back-fill material and the liner has been significant. The analyzer has to pull out a large volume of water from each of the tubes in the bundle before the gas analysis can begin.

To cope with this reality, we proposed a closed catch-pot arrangement that isolates the water while maintaining the extractive suction. In operation, the sample pump pulls on the borehole tube. The entrained water comes up first and simply falls to the bottom of the clear bowl. When the water is evacuated from the tube, the gas sample passes into the detectors for measurement.

This arrangement is nothing new; it’s an old trick that has been around for years. We just haven’t implemented it in such an overt style with a portable analyzer. If you are monitoring soil gas from a tube bundle in a mine tailings borehole, let us know. We can offer a solution.

For information on these and other gas analyzer systems, give Mike or Dave at Nova a call, or send us an e-mail.

1-800-295-3771

sales at nova-gas dot com

websales at nova-gas dot com

http://www.nova-gas.com/

Thursday, November 6, 2014

#196 - Nova Analyzers from the Field – Episode 8

Frequently, we get requests from power plants to offer a solution for hydrogen analysis. We mentioned before in this post and on the website here, that the power industry often uses hydrogen as a coolant for their electric generators. It is quite important in this application to maintain a high-purity of hydrogen. Reduction in purity can reduce cooling effectiveness and possibly allow an explosion potential to develop in the generator.

A common scenario involves older generators that still have the original hydrogen detector. The old H2 detector may be failing and a new instrument using modern technology and components is required.

Old GE Hydrogen panel.

We were sent these pictures from a large power provider in North America. The basic scope of this project was to replace the old OEM hydrogen purity analyzer which was manufactured by GE circa 1950’s. It measured the generator cooling gas, but in recent years, the spare parts and replacement sensors were getting too costly.

From the customer’s inspection of the old equipment, the old electronics consisted of wire wound resistors and transistors which had been obsolete for years. According to them, it was ‘state of the ark’ technology, as opposed to ‘state of the art’. The actual H2 purity measurement apparently used 100 ohm nickel RTD’s (resistance temperature detectors). Gas temperature and dew point of the gas are also usually measured in this application.

The upgrade project required a replacement hydrogen detector. The Nova Model 436 was the instrument of choice for this plant. This was probably because they had excellent success and performance from the portable 380 instrument that is used for the same application.

The generator has a fan on it to circulate the gas. One of the hurdles on this project was to get enough differential across the new analyzer sample cell to avoid having to vent the atmosphere gas out of the generator. They were able to configure the generator gas flow and sample input/output points to produce 0.6 LPM flow out of the generator, through the analyzer, and back into the generator.*

New Nova Hydrogen panel. Model 436N7N4 - The Control Cabinet
is on the left. The Detector Cabinet is on the right.

Recent performance evaluations at the plant indicate that the NOVA appears to have enough flow to measure correctly. The temperatures are measured with Rosemount Smart Temperature Transmitters. Everything seems to working very well now and they are very pleased with the results of their new panel.