Nova Analytical Systems: Nova field pics

Showing posts with label Nova field pics. Show all posts

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.

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/

* Nova analyzers usually operate best with a flow of 1 LPM. However, in this case, the flow of 0.6 LPM will be sufficient as long as they calibrate at that flow rate.

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Wednesday, September 17, 2014

#190 - Nova Analyzers from the Field – Episode 7

This portable CO2 analyzer is about 10yrs old and is the property of a large North American railway company. We have periodically sold these instruments for use in locomotive repair.

Many locomotives have large diesel fuel tanks that occasionally require welding. However, even with all of the fuel drained out, there is still a significant risk of the residual fumes exploding in the presence of oxygen and a spark. Welding repairs on the tank provide a dangerous source of ignition.

A good way to eliminate this risk is to purge the tank with carbon dioxide (CO2). If the tank is rich in CO2, the tank atmosphere will not support combustion. To ensure that the CO2 purge atmosphere is maintained, a portable analyzer can be used.

The measurement range on these analyzers is 0-100% CO2 in air using an infra-red detector. This model is available with a LOW CO2 alarm and audible beeper. The set point is adjustable. On the unit shown above, the alarm is set at 60%. That means that the alarm will sound when the tank atmosphere drops below 60% CO2.

The unit shown above was not functioning probably due to a worn pump. After the pump was replaced and the detector re-calibrated, the unit was returned to the railway for active duty again.

This instrument is still readily available from Nova. Give us a call if you need to monitor a CO2 atmosphere.

Here are a couple of other train-related posts in the Nova blog.

http://nova-gas.blogspot.ca/2013/05/120-rapid-train-loading-systems-by.html

http://nova-gas.blogspot.ca/2013/06/126-takraf-train-post-was-big-hit.html

Notes:

Locomotive pic

Thursday, January 23, 2014

#168 - Nova Analyzers from the Field – Episode 4

We received this beauty into our service department recently. This is a continuous H2 / CO2 analyzer that has been connected to a heat treat furnace for about 14yrs now.

As can be seen, the unit is covered inside and out with black grime. The tubing has turned yellowish-brown. The jet black bowl filters at the bottom of the picture were actually transparent when they were new. It is a small miracle that the detectors were able to function for so many years in such harsh conditions.

Some of the black grime may be soot resulting from combustion of fuel in a low O2 environment. Some furnaces are operated this way intentionally to produce a certain atmosphere around the metal products that are being heat treated. However, most of the surfaces on / in this analyzer are also quite tacky / sticky.

Some types of metal heat treating, such as sintering, employ waxes and binders as part of the manufacturing process that later burn off in the heat treat furnace. These oil vapor products can later condense onto cooler surfaces and gradually accumulate there. That may be what is coating the various surfaces of this analyzer. This coating is probably also present on the optical surfaces in the detector assembly.

Infra-red detectors need to ‘see’ through a set of glass barriers and then through a volume of the sample gas. Some vapors deposit a colored film which will eventually become opaque like the black bowl filters mentioned above. If the detector can’t see through its window, it cannot make measurements.

Even non-optical detectors are sensitive to oil vapor contamination. We see this issue in the power industry on large generators. Electric generators are sealed with oil which can be vaporized over time and be pulled into a hydrogen purity analyzer. Oil-contaminated hydrogen detectors will not function properly. So we always provide an oil vapor filter assembly with the generator atmosphere analyzers. Maybe that would have been a good investment on this analyzer from the field.

I notice that this particular analyzer has a water-cooled condenser mounted on the left side of the cabinet (not visible in this picture). The purpose of this component is to help remove water from the sample gas. The condenser is basically a tube within a tube. Cold water is filtered and flowed into one end of the outer tube, and out at the other end.

The cold water surrounds the inner tube and keeps it cool. On the inside of the inner tube, the cool tubing wall causes moisture in the sample gas to condense out. The condensed water runs down and is collected and drained in the condensate traps which mount on the bottom of the analyzer. The dried sample gas continues on into the analyzer. Of course, this whole concept only works if there is a continuous supply of cold water. In some regions, this cannot be guaranteed.

Another quirk of this analyzer is the fact that there is only a display for the H2 reading even though there is also a CO2 detector. In this application, the H2 reading was critical, but the CO2 reading was not. However, the presence of CO2 will interfere with accurate an accurate H2 reading. So we measure the CO2 and actively compensate the H2 reading. This keeps the H2 reading accurate even if the CO2 levels vary continuously.

It is hard to say what the future of this particular analyzer will be. I assumed that it was un-repairable. However, the owner wanted to try replacing the tubing and some of the other internal components. They probably also had to clean the optical surfaces in the detector as much as possible. How much longer the analyzer will stay functional, is anyone’s guess. But we are pleased to see that a Nova instrument has remained operational in adverse conditions for this long.

A new version of this equipment is still readily available. Check here in the heat treat section of our website.

Episode 1 - old portable flue gas with dual CO channel
Episode 2 - portable ppm H2 analyzer for university metallurgical lab
Episode 3 - ex-proof H2 analyzer in South Africa

If a system like this is of interest to you, contact Nova for details.