I enjoyed reading your excellent rebuttal. I hope you were reading a y2k compliant book and wake up to find there's still a world where we can discuss the freedom we both care about. Happy new year!
We focus upon the immediate damage that terrorists do -- people killed, families shattered, buildings and airplanes destroyed. While these actions are horrible, the damage we then do to our free society as a result is greater. A terrorist, by harming a few hundred people, can cause a country of millions to willingly allow erosion of its liberties.
The "war on drugs" has had a similar effect upon us. A urine test is now de rigueur for most of corporate America. In the absense of the perceived threat, who would submit to such an invasion of privacy? As with airport security, we cause this injury to our free society willingly, because we, as a society, think that the disease is worse than the cure.
Just because we think that these measures are necessary does not mean that they are benign.
The true cost of terrorism isn't what the terrorist do to you. It is what you willingly do to your own freedoms and liberties as a result of terrorism.
Interesting point. There are some systems that can suffer from water hammer. If I were the guy running the plant, I'd have all the critical pumps and valves under manual operation that night anyhow, and switch them back to auto after I saw that the control system was behaving. For many systems, as a later post points out, it just doesn't matter -- A valve that takes 5 minutes to close just doesn't cause that much of a problem.
I can think of one possible water-hammer problem, though. I programmed the embedded controllers that control the valves of a 96" (diameter) pipeline that carries water from a reservoir to San Jose, CA. To put that in perspective, I believe an old volkswagen could fit inside that pipe. The pipe is very long... it takes hours to drive from one end of it to the other. One of the engineers on that job told me that if one of the downstream valves were shut suddenly (suddenly means about 5 minutes, for valves this big), the immense inertia of the many tons of fast moving water hitting that valve would rip the pipe out of the ground.
Because of that, my embedded controllers contain a program that sequences the valves, shutting down the most up-stream one first, then moving down-stream in sequence.
So, there's one system where water hammer *could* be a problem. But those valves are only shut during an earthquake anyhow, not routinely. (They've only been shut once like that, during the Northridge quake -- I was happy to hear that the pipeline was shut down perfectly).
My job for over 10 years was computerizing fresh and waste-water treatment plants. Based upon my experience, I'm not terribly worried. I am certain there will be problems, but I think they will be little noticed by the public.
A computer-controlled water plant generally has 3 tiers: (1) the master control computer, (2) remote controllers, (3) manual controls. The master control computer communicates with the remote controllers, which do the actual work of monitoring and controlling the plant. The signals from the remote controllers are routed through manual controls (switches) to the various pumps and valves.
The master control computer (could be computers, in the case of a redundant system) is usually some kind of microcomputer. We put a fair number of Gateways, Dells, and other name-brand PC's in plants.
The remote controllers are usually some form of embedded system. The most common remote controllers are purpose-built for the task and are called PLC's (Programmable Logic Controllers).
The manual controls usually (I'll get to the exceptions) exist as regular old mechanical switches in the electrical path between the remote controllers and the pumps and valves. A typical manual control is a switch with three positions: "auto" leaves the remote controller in command, "man" forces the device to be on/open, no matter what the controller says, and "off" forces the device to be off/closed, no matter what the controller says.
Also, the remote control computers are usually programmed to operate independently of the master control station. Whenever the master control station goes down (a fairly routine occurance in most plants), the remote controllers keep the plant running based upon their pre-programmed control algorithms and upon the last instructions ("Keep the tank level between 12 and 15 feet") that they received from the master control station.
Every water plant I computerized in my career had this 3-tier architecture: master, remote, manual-overrides.
Because the remote controllers can carry on for some time (hours, at least), in the absense of the master computer, failure of the master -- say, to reboot it after a Y2K-induced freeze -- is not a big deal. And because of the manual-overrides, the plant can be run manually even if the remote controllers fail or start issuing goofy commands.
The real risk for a computerized plant experiencing y2k problems is not that you won't receive fresh water or have your sewage treated -- it's that the city will be paying large amounts of overtime for the extra staffing it takes to run the plant manually. If a city is dumb enough to not have the staff on call during that critical period, then it IS possible for y2k problems to become visible to the public in some way more dramatic than an increased personnel budget. Also, I worked on a few plants where the engineers were so insanely stupid that they allowed the manual overrides to be built into the remote controllers, not independent of them. I always lobbied hard to have such insanities corrected and was usually successful. Those plants without independent manual overrides are the ones in true danger. But I gotta tell you, the plant designed by such intellectual giants are in serious trouble *without* y2k.
All in all, I'm not worried -- I expect to get water and flush the toilet on the 1st without causing the collapse of civilization.
Slashdot Mirror
I enjoyed reading your excellent rebuttal. I hope you were reading a y2k compliant book and wake up to find there's still a world where we can discuss the freedom we both care about. Happy new year!
Yes, I do mean this.
We focus upon the immediate damage that terrorists do -- people killed, families shattered, buildings and airplanes destroyed. While these actions are horrible, the damage we then do to our free society as a result is greater. A terrorist, by harming a few hundred people, can cause a country of millions to willingly allow erosion of its liberties.
The "war on drugs" has had a similar effect upon us. A urine test is now de rigueur for most of corporate America. In the absense of the perceived threat, who would submit to such an invasion of privacy? As with airport security, we cause this injury to our free society willingly, because we, as a society, think that the disease is worse than the cure.
Just because we think that these measures are necessary does not mean that they are benign.
The true cost of terrorism isn't what the terrorist do to you. It is what you willingly do to your own freedoms and liberties as a result of terrorism.
Interesting point. There are some systems that can suffer from water hammer. If I were the guy running the plant, I'd have all the critical pumps and valves under manual operation that night anyhow, and switch them back to auto after I saw that the control system was behaving. For many systems, as a later post points out, it just doesn't matter -- A valve that takes 5 minutes to close just doesn't cause that much of a problem.
I can think of one possible water-hammer problem, though. I programmed the embedded controllers that control the valves of a 96" (diameter) pipeline that carries water from a reservoir to San Jose, CA. To put that in perspective, I believe an old volkswagen could fit inside that pipe. The pipe is very long... it takes hours to drive from one end of it to the other. One of the engineers on that job told me that if one of the downstream valves were shut suddenly (suddenly means about 5 minutes, for valves this big), the immense inertia of the many tons of fast moving water hitting that valve would rip the pipe out of the ground.
Because of that, my embedded controllers contain a program that sequences the valves, shutting down the most up-stream one first, then moving down-stream in sequence.
So, there's one system where water hammer *could* be a problem. But those valves are only shut during an earthquake anyhow, not routinely. (They've only been shut once like that, during the Northridge quake -- I was happy to hear that the pipeline was shut down perfectly).
Wayne Conrad
My job for over 10 years was computerizing fresh and waste-water treatment plants. Based upon my experience, I'm not terribly worried. I am certain there will be problems, but I think they will be little noticed by the public.
A computer-controlled water plant generally has 3 tiers: (1) the master control computer, (2) remote controllers, (3) manual controls. The master control computer communicates with the remote controllers, which do the actual work of monitoring and controlling the plant. The signals from the remote controllers are routed through manual controls (switches) to the various pumps and valves.
The master control computer (could be computers, in the case of a redundant system) is usually some kind of microcomputer. We put a fair number of Gateways, Dells, and other name-brand PC's in plants.
The remote controllers are usually some form of embedded system. The most common remote controllers are purpose-built for the task and are called PLC's (Programmable Logic Controllers).
The manual controls usually (I'll get to the exceptions) exist as regular old mechanical switches in the electrical path between the remote controllers and the pumps and valves. A typical manual control is a switch with three positions: "auto" leaves the remote controller in command, "man" forces the device to be on/open, no matter what the controller says, and "off" forces the device to be off/closed, no matter what the controller says.
Also, the remote control computers are usually programmed to operate independently of the master control station. Whenever the master control station goes down (a fairly routine occurance in most plants), the remote controllers keep the plant running based upon their pre-programmed control algorithms and upon the last instructions ("Keep the tank level between 12 and 15 feet") that they received from the master control station.
Every water plant I computerized in my career had this 3-tier architecture: master, remote, manual-overrides.
Because the remote controllers can carry on for some time (hours, at least), in the absense of the master computer, failure of the master -- say, to reboot it after a Y2K-induced freeze -- is not a big deal. And because of the manual-overrides, the plant can be run manually even if the remote controllers fail or start issuing goofy commands.
The real risk for a computerized plant experiencing y2k problems is not that you won't receive fresh water or have your sewage treated -- it's that the city will be paying large amounts of overtime for the extra staffing it takes to run the plant manually. If a city is dumb enough to not have the staff on call during that critical period, then it IS possible for y2k problems to become visible to the public in some way more dramatic than an increased personnel budget. Also, I worked on a few plants where the engineers were so insanely stupid that they allowed the manual overrides to be built into the remote controllers, not independent of them. I always lobbied hard to have such insanities corrected and was usually successful. Those plants without independent manual overrides are the ones in true danger. But I gotta tell you, the plant designed by such intellectual giants are in serious trouble *without* y2k.
All in all, I'm not worried -- I expect to get water and flush the toilet on the 1st without causing the collapse of civilization.
Wayne Conrad