Altanova - Industrial & Commercial

A bit of history…

In the 1888 a French engineer named Maximilian Ringelmann, to optimize the fuel/air ratio for boilers, devised a simple scale (which took his name), allowing for adjustments of the amount of fuel burned to be made, based on the visualization of the smoke leaving the chimney.

This scale is actually a small paperboard, with a central perforation, and around it, five segments printed in increasingly darker gray tint, from full white to full black. Those segments are numbered 1 to 5, 1 being white and 5 black. When looking thru it at the exhaust plume exiting the chimney, one could compare the exhaust flow to any of the 5 colors of the device and equate
the color of the gases to a given one. That allowed the supply of fuel to be adjusted, improving the combustion.

The success of the device was great. When the first practical diesel fueled vehicles appeared around the 1920´s, the Ringelmann scale was quickly pressed into evaluating the operation of the diesel engines as well, despite its obvious shortcomings for such work.

Besides being a subjective measurement (varies from person to person the eyesight and the notion of smoke color), when used in vehicles it is difficult to get a meaningful result of a quick acceleration, making it almost impossible to be repeatable or operator independent.

To avoid the limitations of the Ringelmann Scale, the opacimeter was created.

The opacimeter – what is it?

It is a device to objectively measure the operating status of a diesel engine via its exhaust emissions. Due to its design, there is no risk of subjective evaluations, since the measuring chamber is always the same, and the raw values taken at the Sensor Head are subject to a mathematical treatment prior to being shown as opacity in the display. The opacimeter thus become a reliable
and accurate measuring tool.

how does it work?

The opacimeter measures the smoke from the diesel engine thru the Sensor Head installed at the exhaust tube exit. The signals taken from the smoke passing thru the measuring chamber, are sent to the Monitor, where the mathematical processing takes place, converting the raw numbers in actual opacity values, either in Percentage (%) or k Factor (m^-¹), for presentation at the display or printing. The smoke is generated by accelerating the engine from idle to max RPM, several times, so that smoke values for each can be had.

what types of opacimeter are available?

There are two main types of opacimeters: Full Flow, and Partial Flow, this last one also called a sampling opacimeter, like the Smoke Check 2000.

The partial flow opacimeters take a sample of the exhaust smoke leaving the exhaust tube, and determine the opacity value of it during a quick acceleration of the diesel engine. This type of opacimeter is currently the most common, due to its ease of use and simpler interpretation of the results.

The full flow opacimeters use the full exhaust flow leaving the exhaust tube, in the integral diameter of that tube. The installation in the vehicle is more laborious and readings may be affected by ambient light, wind, etc. Anyway, it is very much used in the USA, being well accepted.

For both options there are yet the portable ones and the movable on wheels. The first ones are easily transported to the work site, thanks to the small dimensions and weight, and in the case of the Smoke Check 2000, with the added benefit of autonomy from external energy sources – it has its own battery. The opacimeters moved on wheels are awkward to take to the work site
(being normally big and heavy), needing vehicles for that, and use external energy supplies from the public grid, since they operate at 110V – 220V or eventually using the test vehicle battery at 12VDC. All that makes this type of opacimeter less appealing, as they are not very practical and more expensive.

Why the engine is accelerated when performing the opacity test?

It is the simplest way to load an engine (make it produce power). Ideally the acceleration should be done in a Dynamometer, where the load can be set to specific levels; however, this is not practicable in day to day situations with the engine installed in the vehicle. The use of a quick acceleration, is the preferred method, as it imposes on the engine the need to overcome its own inertia, as well as the power required to run hydraulic pumps, air compressor, cooling fan, etc.

Why so many accelerations of the engine when testing for smoke?

When performing the opacity test, it is firstly necessary to check the exhaust system for accumulated soot. This is done with several accelerations of the engine, until visually there is no more excess smoke leaving the tube. Only after that, is the sequence established in the regulations (CONAMA Nº 418/2009), run – four accelerations, the first one discarded, and the readings of the remaining three within 0,5 m^-¹. The average thus obtained is the opacity of the engine in test.

What is the use of the opacimeter?

For the fleet owner, it allows the monitoring of the diesel engines, leading to programming maintenances when the deterioration trend is evident. In this way, costs are slashed, as unnecessary interventions are avoided; moreover, tickets are also avoided, because the engines run clean all the time, not emitting excessive smoke.

Another application of opacimeters, is at the gates of a company – it is easy to check for emission status of the vehicles entering and exiting the premises, and only allow entrance for the ones found OK in this regard.

Finally, for the road inspection authorities, the opacimeter is the best way to check the vehicles, with the assurance of testing done with precision and repeatability.

What is the Percentage Scale (%)?

It is a basic scale for measuring the smoke opacity. Originally used in the full flow type opacimeters, presently is also used in the partial flow ones, like the Smoke Check 2000. It is an intuitive scale, as the “0%” (zero) meaning clean air (no opacity), and the “100%” meaning the total darkening, makes easy the understanding by the operator. Also it is a scale where the maximum of 100% opacity can be reached – this value is not defined in the Factor k scale.

What is the Factor k (m^-¹) Scale?

It is another way to measure the opacity, employing smoke density in a fixed length (called effective optical length of the measuring chamber). That is why it is shown as 1/m or technically, m^-¹. This is achieved via a mathematical treatment of the opacity, and its main advantage is that it is immune to the diameter of the exhaust tube, as the measurement is taken inside
the chamber of the Sensor Head. As it has been found that the smoke density is primarily dependent on the particulates in the smoke, the k measurements are very stable and reliable. The k Factor is the scale adopted in Brazil by the main agency dealing with the matter (CONAMA).

Does the opacimeter check the exhaust gases composition?

No. The opacimeter measures a physical characteristic of the exhaust gas – namely the opacity. The composition of the exhaust gases, where they are differentiated in CO (Carbon Monoxide), CO₂ (Carbon Dioxide), O₂(Oxygen), HC (Unburned Hydrocarbon) and eventually NO_x (Nitrous Oxides), is only verified in gas analyzers. These are chemical micro-laboratories for gas analysis, and for diesel engines there is also need of previous filtering of the exhaust gases, otherwise the gas analyzers will
quickly clog with particulates.

Why the Smoke Limits are always decreasing in new vehicles?

This is a consequence of the continuous development of the technology of diesel engines. This development is driving down the levels of smoke emitted by the engines, with cleaner combustion and less fuel consumption as side benefits. That is clearly shown in that a few years ago a value of 70% opacity as accepted normally. Today, with electronic diesel injection, turbocharging, and other enhancements, an opacity around 5%-10% is normal.

CONTACT

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altanova@altanova.com.br
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Zip code 13500-575
Rio Claro, São Paulo State, Brazil

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