This column is moderated byĀ BĆ©la LiptĆ”k, automation and safety consultant and editor of the Instrument and Automation Engineers' Handbook (IAEH). If you have an automation-related question for this column, write toĀ [email protected].Ā
We've experienced unreliable readings ofĀ rod positions, and when alarm conditionsĀ caused the machine to stop, no wear beenĀ found on the rider ring. This has occurredĀ many times. Please suggest what could beĀ causing the false readings.
Bhartendu Nayak
[email protected]
A: You mentioned rod drop sensor and XY. ForĀ clear understanding, please send me the P&IDĀ or general arrangement, so I can understandĀ exact positions.
Further, when you checked linearity and factorĀ using a wobulator, did you also use targetĀ material that was the same as that of the shaft?Ā A wobulator has typical target material whichĀ must be replaced by materials that are similar toĀ that of the shaft.
Also, did you check the 3500 rack configurationĀ software to ensure the probe factor is theĀ same as you calculated via the wobulator?
Debasis Guha
[email protected]
[The specialized nature of proximity probe measurementsĀ requires a specialized calibration instrument,Ā capable of introducing fixed gap (i.e.,Ā position), changing gap (i.e., vibration), and rotativeĀ speed signals into the transducer for verificationĀ and testing purposes. One example is the BentlyĀ Nevada TK-3, where a fixed gap is provided byĀ clamping the probe into a stationery position, whileĀ a movable target on a spindle micrometer is adjusted.Ā Simulated vibration is provided by clampingĀ the probe into a movable swing arm, observingĀ a precision-machined wobble plate that rotates,Ā and introducing a known amount of changing gapĀ with each rotation. Finally, shaft rotative speed isĀ simulated by observing a notch on the side of theĀ rotating wobble plate.
TK-3 wobulator provides all of these functionsĀ in a portable kit that allows users to test andĀ verify the entire measurement path, from the tipĀ of the probe all the way through to the monitorāsĀ Ā visual indicators, relay contacts, and digital/analogĀ interfaces.āEd.]
Q: In your column, "Is global warming likeĀ level control?" you explained that globalĀ temperature will continue to rise even after weĀ cut back on our carbon emission. You comparedĀ this process to that of a tank of water,Ā in which the level will contonue to rise evenĀ if we start filling it slower. That logic makesĀ good sense, but you did not give numbers onĀ when will our "tank" (the carbon concentrationĀ in the atmosphere) will get to the level setĀ as a limit by the Paris Agreementāhow muchĀ time do we have to make this "control loop"Ā function?
Z. Friedmann
[email protected]
A: Excellent question. To answer it, I prepared Figure 1, in which the values of the four key variables of this process are shown over about a century. I simplified the plot by substituting straight lines for the nonlinear curves and distinguished them by color. Green is the weight in gigatons of the accumulated carbon in the atmosphere (GTC), brown is the CO2 concentration in the air in parts per million (CO2 ppm), blue is the weight in gigatons of the yearly emitted carbon(DTyC), and red is the total rise of global temperature in °C. At the top, I've shown the temperature rise limit set by the Paris Agreement (1.5 °C).
Figure 1: Global CO2 emissions (blue line) are currently accelerating, which if continued, will cause global warming to reach the Paris Agreement limit of 1.5 °C as early as 2040.
The CO2Ā concentration, the temperature rise, the carbon content of the atmosphere and the yearly emission are all rising andĀ it is expected that the Paris-Katowice limit will be exceeded sooner than 2040. (āT(°C) = Temperature rise[1], GTyC =Ā Giga-Ton perĀ year ofĀ Carbon emission, GTC = Giga-Ton of Carbon in the atmosphere, CO2Ā ppm = carbon dioxide concentration in the atmosphere).
[1] The value of the temperature rise depends on how the reference line is selected? If we consider the reference to be the averageĀ Ā temperature between 1880 and 1889, in that case (according to the NASA report, published in the New York Times on 2019 February 7, the rise in global temperature (āT) in 2016 reached 1.2 °C and in 2018 it was around 1.1°C.
As you can see in the figure, the planet is warming very slowly (1 °C to 2 °C per century). This might be suprising with such a great heat input from the sun, which equals the heat content of four Hiroshima bombs per second. The reason is the trumendous cooling capacity of the oceans and ice caps at the poles. As to the amount of ice, Antarctica alone is larger than the U.S. and is covered by a 7,000-foot-thick mountain of ice, which is the height of six Empire State buildings. Imagine what happens to the ocean levels when all that ice has melted.
Now, when process control engineers look at this process and are told to return it to preindustrial conditions, they would configure a control loop to do it. The setpoint of the loop is a 0.0 °C temperature rise (which corresponds to a CO2 concentration of 300 ppm), and the manipulated variable is the CO2 emission rate (flow into the atmosphere) because that flow causes the heating. So, we have a temperature control loop that's throttling (reducing) the emission flow. This flow today is 10 GTyC per yearāin other words, about 1.5 tons of carbon (about 5Ā tons of CO2 per year) is sent into the atmosphere per person on our planet. But we have two problems that need to be answered before this loop will function:
- What do we manipulate to lower the flow of emission?
- How do we remove the excess CO2 (880 - 580 = 300 GTC) that's alseady accumulated during the past century?
Answering these questions is not easy. I'm in the process of writing a book on this very subject, which will be published later this year by ISA.
In answering the first question, we see on the figure that if our emission rate rises at about the same rate as it does today, we'll reach and exceed the limit set by the Paris Agreement by 2050-60. Naturally, if the rate rises, we'll reach the Paris limit sooner. As of today, that is the case, as global emission increased by 3.4% last year compared to 2017. If that continues, the Paris limit will be reached by around 2040 (with the consequence we all know).
So, how do we go about throttling the yearly emission? The answer is obvious: by making it profitable to do. And how do we make it profitable? By taxing the use of fossil energy and investing the collected tax into subsidizing the development of green energy use.
Solving the other problem (removing the accumulated 300 GTC of carbon from the air) is more difficult and it will take many pages in my forthcoming book to cover it. Here, I will just say that we have two options: Option A is to do nothing, which will result in continued rising of the global temperature and will bring the known consequences, or Option B, which is to develop new technologies. Some of my ideas have already published in Control in connection with the reversible fuel cell (RFC), which you can also learn about by listening to: http://techchannel.att.com/play-video.cfm/2011/8/25/Science-&-Technology-Author-Series-Bela-G-Liptak:-Post-Oil-Energy-Technology.
BƩla LiptƔk
[email protected]

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