| Recently my wife was on a quest to make the perfect pound cake, but before she put butter to flour she did her research. What’s the best butter? Best flour? Eventually she came up with a recipe she felt would prove to be the Queen of all pound cakes. After the recipe came reviews by her test panel, or family members, including myself. Questions were asked, such as, When you first bite into a pound cake, do you want to be aware of vanilla or lemon? It was only then that she would begin to combine ingredients for the final mouth watering product. Very much this same procedure is used when coming up with a new medical device.
Previously we’ve discussed FDA requirements for medical devices as they concern design controls with respect to design and development planning and design input procedures. We’ll now focus on requirements for Design Output, Design Verification, and Design Review Procedures. Design Output and Design Verification Procedures go hand in hand to ensure that design output is properly documented, organized, reviewed, and evaluated in light of design input. What this means is that medical device companies must scrutinize and evaluate what is going into the design process, then make a comparison to what is coming out. The design is ultimately verified when all requirements for the medical device as previously set out have been met. “Design output” is just another name for work product after major phases of the design project are completed, such as when my wife determined which butter would produce the best pound cake. Design output typically takes the form of specifications, notes, calculations, computer programs, mechanical drawings, electrical schematics, printed circuit board (PCB) layouts, bills of materials (BOM), mockups, prototypes, test data, and test reports. These are then utilized by people outside engineering circles to manufacture components and assemble them into a final product. Design Review Procedures ensure that the design output is evaluated by others not directly involved in or responsible for the design work product, much as when family members served as a reviewing committee for my wife’s inquiries into taste preferences in pound cake. Sometimes she’d even ask a friend or neighbor to put their two cents in, and companies, too, will at times go outside and hire consultants to perform this function. By so doing, unbiased opinions are sought out, in the hopes that this fresh set of eyes will be more likely to spot errors, omissions, and misinterpretations that could prove disastrous if put into play. Design reviews are typically conducted after each major phase of a design project is complete. Just as a recipe that looks good on paper may not necessarily taste good, a device design will often seem to work perfectly on paper, then prove otherwise when its manufacture begins or it’s used in the field. Ideally bugs are worked out before the product hits production and, later, the marketplace. Design Validation Procedures make use of prototypes for testing and careful evaluation under simulated or actual use conditions. Does the design safely meet requirements for intended use? Does it conform with industry standards? If not, there’ll be a lot of wasted “dough” going into the trash — pun intended! Next time we’ll explore FDA requirements for Design Transfer and Design Changes. We’ll also talk about procedures for Design History Files. _____________________________________________ |
Posts Tagged ‘forensic engineer’
Medical Device Design Controls – Output, Verification, Review, and Validation
Sunday, September 5th, 2010
Medical Device Design Controls – Planning and Input
Sunday, August 29th, 2010| Have you ever had the divine experience of remodeling a major-use room of your house? Was the general contractor you employed able to understand what you wanted, plan out the work according to your requirements, and finish the job to your satisfaction? Maybe you had the unfortunate experience of hiring one that forgot your requirements, made things up as they went along, and stuck you with a room that looked awful, violated building codes, and didn’t meet your needs.
Now imagine what would happen if a medical device company took this haphazard approach to designing new products. Suppose the company’s engineers ignored the input of regulatory, marketing, procurement, quality control, and manufacturing staff? What if they chose not to follow applicable industry standards for performance and safety? And what if they failed to check design calculations or test prototypes for errors before putting the device into production and introducing it to the marketplace? The result is likely to be unfavorable, just like your contractor forgetting that you wanted a black granite countertop, not a beige one. To help eliminate painful and costly scenarios such as these, the FDA requires that medical device manufacturers establish and maintain procedures to control the design of Class II and III devices, and even some Class I. This requirement for a system of design controls is part of the Quality System Regulation (QSR) under Title 21 of the Code of Federal Regulations. In case you’re not too familiar with the Code of Federal Regulations, Title 21 gives the FDA legal authority to regulate food, drugs, and medical devices in the United States. So what falls under the premises of FDA design controls? Well, the FDA requires that a medical device company develop procedures for:
For now, let’s focus on Design and Development Planning and Design Input Procedures. In the Design and Development Planning Procedure companies must carefully plan who will be involved in each phase of product development, as well as how they will interact, all in an effort to ensure that information flows and design requirements are met. The right pool of people would include design engineers, in addition to those employees responsible for making sure that regulations are complied with and those who are charged with securing intellectual property rights to the design. Then there are those who must acquire the physical materials required to manufacture the device and those who will do the actual manufacturing of it. Also, those responsible for quality control, marketing, sales, and product service should be involved. Perhaps others should be involved as well. Mind you, the Design and Development Planning Procedures are not set in stone. They must be regularly reviewed and updated as the project evolves. Now let’s talk about Design Input, which is another term for a design requirement. These inputs can come from inside or outside the company. An example of a requirement coming from within is when Marketing stipulates that the maximum manufacturing cost of the device should not exceed $150 in order to maintain an acceptable margin of profit and be most competitive in the marketplace. A design requirement coming from outside the company would include industry standards that make specific requirements, such as requiring that the device in question be designed to protect its electronics from radio frequency interference. Next time we’ll continue our discussion on medical device design by exploring Design Output, Design Verification, and Design Review Procedures. _____________________________________________ |
FDA Classifications for Medical Devices – Special Controls
Monday, August 23rd, 2010|
For the last couple of weeks we’ve been discussing FDA medical device risk classifications, namely Classes I, II, and III. We also began discussing the FDA system of regulatory controls governing each class, starting with General Controls. This week we’ll examine the more stringent guidelines that come into play within Special Controls. As you would imagine from the name, Special Controls come into play when General Controls aren’t deemed to be sufficient to deal with the situation. Class II and III medical devices, because they pose a higher level of risk to patients than Class I, generally require more FDA supervision than mere General Controls. These devices tend to fall under the auspices of Special Controls. Special Controls include things like special labeling requirements, complying with mandatory performance standards, and perhaps requiring that a manufacturer conduct a Post Market Surveillance (PMS) study. In case you’re wondering, a PMS may be required by the FDA to collect data after a medical device is sold, should there be any unexpected adverse events involving the device. A study of this data would aid in an investigation to determine the number of events, the cause of the events, and how to correct any problems that led to the events. Let’s look at some examples of how Special Controls apply to Class II medical devices. One example would be a cranial molding helmet. These helmets are often used with infants to reshape their skulls into becoming more symmetric. Due to the nature of this device’s application on such a delicate patient, Special Controls include a requirement for special labeling. In this case, the labeling must include warnings to physicians and parents that precautions must be taken during its application to protect patients from possible injury, including eye trauma and impairments of brain growth. Another example would be sutures. Yes, they are considered to be Class II medical devices. In this case, Special Controls require that sutures meet “mandatory performance standards.” What are “mandatory performance standards?” Well, they generally include industry consensus standards for particular medical devices. They are based on industry-wide accepted guidelines to ensure proper product performance. In this example, industry standards for suture material contain specific guidelines as to material composition, diameter size, mechanical strength, and biocompatibility. Adherence to these standards provides the highest assurance that sewn incisions won’t break open when the suture is stressed or the suture material won’t cause some sort of adverse reaction with the patient’s skin. As specific as Special Controls can be, they are sometimes not enough. On these occasions the FDA states, “Class III devices are those for which insufficient information exists to assure safety and effectiveness solely through General or Special Controls.” Under these circumstances more regulatory control may be imposed. This is the case when dealing with medical devices directly responsible for supporting/sustaining human life, such as a cardiac defibrillator. One such FDA control method that goes beyond Special Controls is the requirement to submit a Pre Market Approval application (PMA) to the FDA for approval. This PMA is subject to the most stringent FDA requirements. As a part of the PMA process a company must demonstrate the safety and effectiveness of a new medical device design by producing data and documentation obtained during “adequate and well-controlled” clinical trials. In our series on FDA Classifications for Medical Devices we have merely grazed the surface. Depending on the device in question there may be a myriad of other considerations, so please consult the FDA’s web site for the complete picture: http://www.fda.gov/MedicalDevices/default.htm. _____________________________________________ |
FDA Classifications for Medical Devices – General Controls
Sunday, August 15th, 2010|
When I was a kid in Chicago back in the 1960s there was a show on television called Bozo’s Circus. Lucky kids were picked from the audience to play a bucket game. There were six buckets in a row, as I remember, each about a foot from the last. The kids had to stand in front of the first bucket to play. By the time the kids got to throw their ball into Bucket No. 6 there was probably ten feet for the ball to travel. So what would happen if the ball didn’t sink into the desired bucket, which would happen more often than not it seemed? Then Ringmaster Ned would direct Cookie the Clown to chase down the rogue balls. So what does this have to do with the FDA and medical devices? Well, in the loosest of terms you may think of the FDA’s classification system as Buckets 1 through 6 and Ringmaster Ned as the regulatory agent of the game. Okay, I’m really stretching on this analogy, but I did want to introduce some levity into the discussion! Last week we discussed the fact that the FDA classifies medical devices into three main categories, Classes I, II and III, Class I devices posing the least risk to patients, Class III the most. Now we’ll see how the FDA regulatory control system functions to oversee the medical devices within each classification. To begin with, you should be aware that regulatory controls are themselves divided into General and Special Control categories. In this article we’ll focus on General Controls. General Controls can apply to medical devices within all three FDA risk classifications. They include requirements for: – Registering of medical device manufacturers, distributors, repackagers, and relabelers with the FDA. This registration basically lets the FDA know they exist as an entity, and it gives the Agency information about who to contact should the need arise. – Listing medical devices with the FDA so the Agency can keep track of what kind of devices are being marketed in the United States. – Manufacturing devices in accordance with FDA Good Manufacturing Practices (GMP). GMP regulations require a quality approach to manufacturing, an approach which is designed to minimize or eliminate instances of contamination, defect, and error which could contribute to harm or kill a patient. GMP regulations address issues like sanitation, quality control, complaint handling, and record keeping. Effective complaint handling and record keeping systems are key in identifying and resolving issues that may pose increased risk to patients. – Labeling devices. The FDA requires that medical device labeling provide explicit directions for use. The labels must also contain appropriate warnings as needed to ensure the safe and effective use of the device. – Submitting a Premarket Notification to the FDA for approval before marketing a device, also referred to as a 510(k) within the industry. This name comes from the section of the federal regulation that deals with it, that is to say, companies must submit 510(k) documents to the FDA to demonstrate that the device they wish to market is comparably safe and effective as other equivalent devices already on the market. A 510(k) can only be submitted if Premarket Approval (PMA) for the device is not required. We’ll talk more about this in a future article on Special Controls. Now, because they pose such a low level of risk, many Class I medical devices are exempt from the requirement for 510(k) submissions altogether, and they may even be exempt from compliance with GMP regulations. In a nutshell, General Controls help the FDA keep track of what products are being sold by whom, and how effective and safe those products are. It also provides guidelines to medical device companies to help ensure their introduction of safe and effective products to the public. So what happens when a device falls outside of the parameters of the General Controls watch? That’s when more stringent guidelines come into play, for it has now entered the realm of Special Controls. _____________________________________________ |
FDA Classifications for Medical Devices
Sunday, August 8th, 2010|
Hardly a week goes by that the FDA, that is the Food and Drug Administration, is not in the news. From the recall of drugs found to be harmful after the fact, to investigations of medical device suppliers and inspections of salmonella contamination at meat processing plants, the FDA is responsible for overseeing and regulating a wide range of products and processes. It’s stated purpose being: The FDA is responsible for protecting the public health by assuring the safety, efficacy, and security of human and veterinary drugs, biological products, medical devices, our nation’s food supply, cosmetics, and products that emit radiation. http://www.fda.gov/AboutFDA/WhatWeDo/default.htm From its humble beginnings at the beginning of the last century as the Pure Food and Drug Act, it has grown to regulate more than $1 trillion worth of consumer goods, about 25% of that said to be attributable to consumer goods expenditures in the United States. In 1976, the FDA began classifying medical devices, using a three-tiered system to distinguish them according to level of risk to patients. Class I devices present the lowest level of risk and requires the least regulatory control, while Classes II and III represent higher levels of risk. Just to give you some perspective, Class I medical devices include things like tongue depressors, bedpans, arm slings, and hand-held surgical instruments. In the Class II category are things like surgical drapes, blood pressure cuffs, catheters, wheelchairs, heating pads, and x-ray film processing machines. And I’m sure you’ve guessed by now that Class III devices are for the heavy-hitters, including things like defibrillators, heart valves, and implanted cerebral stimulators. So why does the FDA classify medical devices? Practicality is one key reason. It would be highly impractical, if not downright impossible, for the FDA to subject manufacturers of low risk Class I devices, like tongue depressors, to the same scrutiny as manufacturers of Class III devices, such as heart valves, etc. Along with miles of red tape would come a huge financial burden that would effectively raise the price of your common tongue depressor through the roof and, undoubtedly, force the manufacturer out of business. Hand in hand with medical device classifications are regulatory controls imposed by the FDA. We’ll see how they fit into the picture next time. _____________________________________________ |
Where Are The Best Engineers?
Sunday, August 1st, 2010|
Smart people say smart things, right? Consider the following quote by Duke University adjunct professor Vivek Wadhwa, who testified before a House Committee: “If a certain type of engineering job can be done more cost effectively in India or China, why should we invest in graduating more of those types of engineers?” Professor Wadhwa is said to have spoken before the House as a means of response to many engineering students’ fears of not finding a job upon graduation due to outsourcing, according to a somewhat dated, yet still applicable, article by Ed Burnette at zdnet.com. ( http://www.zdnet.com/blog/burnette/us-vs-china-vs-india-in-engineering/125 ) As to the quality of engineers graduating from China and India, Professor Wadhwa states, “…the vast majority of Indian and Chinese graduates are not close to the standards of US graduates.” And this sentiment is apparently shared by the Federation of Indian Chambers of Commerce and Industry and the World Bank, who claim that 64 percent of Indian employers surveyed are: “’somewhat,’ ‘not very,’, or ‘not at all’ satisfied with the quality of engineering graduates’ skills…”, this according to taatparya’s blog at vidyaweb.com. ( http://vidyaweb.com/?q=node/17 ) Despite the poor review, one Indian writer, Swati, in saching.com poses this observation, “Then why are Indian software engineers in demand all over the world,” and continues to explain why: Because “Indians are very hard working and they go through competition in every stage of life. If you live in a Western country, you will never be able to co-relate what hard work means in Indian culture. India has 1.1 billion people and a large middle class, therefore competition and hard work starts right from the early school level itself. There is no concrete social programs and people know that they have no choice except to work hard, additionally there are social pressures to excel in life.” Values, apparently, that Americans appear to lack. ( http://www.saching.com/Article/Quality-of-Engineering-in-India—Software-Engineer-vs–Professor/376 ) Let’s return to our home shores for a moment. No doubt you have read an article or two concerning the recently publicized outcome of this year’s round of state academic testing on our American children. As in years past, they have not fared well. In my hometown, which is said to be representative of the norm, only 46% of 3rd graders can read. The results for math and science testing are, expectedly, even worse. So who or what is to blame for this poor showing? We know who the usual finger pointing is directed at. And how is the problem to be solved? Most of us are familiar with the proposed solutions as well. If you take the time to read the cited articles in their entirety, a picture emerges. It’s a picture showing diverse people airing similar complaints. Times are changing, of that we can all be certain. We’ll take a closer look at some of the world’s engineering challenges in the weeks to follow. _____________________________________________ |
Coal Fired Boiler Explosions
Sunday, July 25th, 2010|
Try this for a tongue-twister: Coal fired electric utility power plant boiler… If you’ve been reading along with us for the last couple of weeks, you now have a pretty good idea of what these are and what they do. These boilers are contained within furnaces in coal fired power plants. The furnace’s job is to combine coal and air to create a combustion process. It is like a big, insulated enclosure that keeps the heat energy from the combustion process from escaping before it can be absorbed by the water and steam in the boiler tubes. The heat energy is then funneled to the steam turbine to spin an electrical generator, creating the energy which will eventually find its way into our homes and businesses. During the operation of the boiler, coal and air must be introduced into the furnace at carefully measured rates to maintain a proper fuel-to-air ratio which will enable the release of heat energy from the coal at a safe, controlled rate. Fuel-air ratio is the amount of coal entering the furnace divided by the amount of air entering the furnace. If this ratio isn’t precisely maintained, conditions may be right for an explosion to occur. Specifically, the ratio has to fall within an “explosive range.” Once within this range, all that is needed is an ignition source, such as hot ash, or even mere static electricity, and the result may be a furnace explosion. There are certain times at which furnace explosions are more likely to occur than others, such as when the boiler is being started, operated at less than full capacity, or shut down. When a furnace explodes, a pressure wave moves out from the center of the blast. This pressure wave will bear up against the sides of the furnace with great force, and if the pressure is high enough the sides of the furnace, which are made of heavy steel components, will actually bend and split open. Boiler tubes may even rupture, releasing high pressure steam and water into the power plant and furnace. At the very least, the boiler will be down for expensive repairs and no electricity can be produced by its turbine generator. This down time can last for many months and results in lost revenue to the energy producer. Aside from an explosive fuel-to-air ratio, there are other potential causes of furnace explosions. For example, poor coal quality can lead to incomplete combustion, or the flame going out completely, encouraging unburned coal particles to settle and accumulate in the furnace. The accumulation of coal can grow to the point where it forms an explosive mixture when combined with the right amount of air. So how can boiler explosions be prevented? The National Fire Protection Association (NFPA) looked into the problem and developed an industry standard. This standard is known as NFPA 85, Boiler and Combustion Systems Hazards Code. Its purpose is to contribute to operating safety and prevent uncontrolled fires, explosions, and implosions of coal fired boilers. NFPA 85 lays out guidelines to follow when designing, building, and operating boiler fuel handling systems, air handling systems, and combustion control systems. Following its guidelines will certainly significantly decrease the probability of explosions occurring. Another means of explosion prevention includes implementing a boiler operator training program. These enable attendees to better understand operating procedures and equip them with the knowledge to safely control the combustion process, particularly when a furnace explosion is most likely to occur. This training can be done with a combination of classroom instruction along with time on a simulator and may be followed up with hands-on training in the plant itself. Lastly, boiler explosions can be prevented by implementing an effective inspection and maintenance program to locate and repair or replace boiler components, averting the possibility of a potential disaster occurring. Things such as check lists can be used to ensure that nothing is missed. This is a strategy that all pilots must use before starting their planes, and it is now being used in hospitals as well to cut back on the rate of patient infection due to carelessness on the part of hospital staff. Hey, we’re all human, and humans are not perfect. But remember that an ounce of prevention is truly worth a pound of cure, and then some. A properly placed check on the list could mean lives will be saved. _____________________________________________
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Coal Power Plants, Far From Perfect
Sunday, July 18th, 2010|
Did you know that even a perpetual motion machine will eventually come to a stop due to uncontrollable factors? Well, uncontrollable factors are at play in power plants, too. If you recall from our last article, heat rate is industry jargon for gauging how efficiently a coal-fired power plant is operating. We learned that heat rate can be affected by things like missing thermal insulation on pipes and equipment. Missing insulation is, of course, a thing that is under human control and easily corrected, but there are some things that affect heat rate that we just can’t do anything about. They’re called, appropriately enough, uncontrollable factors. Uncontrollable factors exist because anything devised and made by fallible humans who are beholden to the myriad laws of the universe cannot be 100 percent efficient. At their best utility coal fired power plants have an overall efficiency of between 30 and 40 percent. That means 60 to 70 percent of the energy available in the coal gets lost in the process of generating electricity. A terrible waste, right? And yet there’s nothing we can do to trim these losses until improvements in the present level of technology take place. Just as our ability to track microbes is dictated by the strength and accuracy of our magnifying equipment, so are we hampered by the tools we have at our disposal to deal with inefficiencies such as energy losses. So where does this energy get lost due to uncontrollable factors? The first and probably most obvious place to look is the smoke stack. Energy is also lost in three other ways: friction between equipment parts, auxiliary power consumption, and in a piece of equipment known as a condenser. Let’s look at each. In the most basic of terms, when coal is introduced into a power plant boiler it is combined with air and burned. This burning process releases heat energy, but it also forms gases that contain nitrogen and compounds like carbon monoxide and carbon dioxide. There’s also some water vapor formed by moisture in the coal and air. These gases and vapor absorb some of the heat energy released. To keep the combustion process going the gases and vapor must be removed from the boiler by powerful fans and sent up the smoke stack. Now, boilers are designed to absorb much of the heat energy from the gases and vapor that make their way to the stack, but they cannot possibly absorb it all. The result is that a significant amount of heat escapes up the smoke stack into the atmosphere along with the gases. Friction between parts is present everywhere in a power plant. It exists in the bearings on the shafts of motors, pumps, and steam turbines, slowing them down and hindering their operating capacity. Friction also exists where moving water and steam are present, impeding their ability to flow through piping systems. There is even friction working against the steam as it flows through parts in the turbine. Extra energy has to be expended to overcome this friction. This is energy that could be used to generate electricity. Now at some point in your life you’ve probably heard it said, “You need money to make money,” and this is very true. It takes a certain investment of resources to produce a profit-making enterprise. This investment principle holds true for the making of electricity, too. The bottom line is you need electricity to make electricity. Specifically, you have to use significant amounts of electricity to power machinery that is essential to move coal, air, combustion gases, and water through the process of making electricity in the power plant. This is called auxiliary power. It’s the electricity siphoned off by the various pieces of equipment in a power plant in its quest to generate electrical energy to be sold to customers. Another major factor at play in uncontrollable energy losses is in a piece of equipment integral to the very function of power plants: the condenser. It comes into play when water is boiled to make steam which then travels through the turbine, spinning its electrical generator and creating electric power. Unfortunately even the most efficient of steam turbines cannot use 100% of the heat energy coming at it from the steam. You see, after steam leaves the turbine, it’s turned back into water by a condenser so it can be sent back to the boiler to be turned into steam again. One of the reasons that this is done is so that the boiler does not have to be continuously filled with fresh, purified water. Water purification is necessary to keep minerals, seaweed, fish scales, and other nasty things from clogging up and damaging the boiler and steam turbine, and purified water is not as readily available as, say, lake water. The condenser acts as a heat exchanger that is hooked up to the steam turbine exhaust. It has tubes inside of it in which cold water flows, water which is drawn in from a nearby body of water, most often a river or lake. As steam blows across the outside of the cold water tubes in the condenser, it gives up its remaining heat energy and condenses into water again, then it is returned to the boiler to repeat its journey. The river water within the tubes of the condenser flows back into the river, carrying with it the heat energy removed from the steam. That wraps up our discussion about coal power plant efficiency. Next time we’ll discuss a new topic: coal fired power plant furnace explosions. _____________________________________________ |
Coal Power Plant Efficiency
Sunday, July 11th, 2010|
Is there any price a man dying of thirst in the desert would not pay for a tall glass of cold water? What is the point at which Americans will decide they can do without heat, refrigerators, electric lights? My neighbor refuses to run the air conditioner, even when it’s 90 degrees and 90 percent humidity. They have obviously made the choice to sweat and be uncomfortable in their homes rather than pay high utility bills. Most of us are concerned with the environment, but when times are hard like they are now many of us become more concerned with our pocketbooks. Just as we need to make our financial ends meet, so do energy suppliers. Without a certain level of profit, their service to us will decline, and regular, dependable delivery of their precious commodities to us will suffer. If they were to go out of business, what then? Reading by candlelight may be romantic for a night or two, but nights on end? Let’s consider the energy provided by coal-fired power plants, for example. They’re in the electric utility business, and they provide us with the lion’s share of our energy. To keep a handle on operating costs, power plant engineers monitor how many British Thermal Units (BTUs) of heat energy are going into the power generation process versus how many kilowatt-hours of electricity are coming out. What’s a BTU and what does it matter to us? Well, it’s the amount of heat energy your kitchen stove uses to raise the temperature of one pint of water by one degree Fahrenheit. As for a kilowatt-hour, that’s a thousand watts of power produced over the space of an hour– enough to light ten 100 watt light bulbs. Now that we’ve explained the key term, we can explore the notion of heat rate, terminology very important to efficient power plant operation. Heat rate is simply the ratio of BTUs to kilowatt-hours. So what’s the importance of monitoring heat rate? For one thing, in order to get the most bang for your buck you want to keep the heat rate as low as possible. When the heat rate is high, you’re burning more coal than you have to because you’re wasting heat energy. This results in higher electricity costs to the consumer. This is exactly the situation at play when low sulfur coals are used as compared to the better burning coals of yester-year. So where does the wasted heat energy go if it isn’t being converted into electrical energy? For one thing, it can be lost through steam and water leaks in the power plant piping system. There are other losses too. Another way to lose heat energy is when thermal insulation is missing from pipes, causing heat to escape into the atmosphere. The opposite side of inefficiency is presented by the problem of too much heat energy building up, unable to be transferred to the steam. This is the result if ash is allowed to accumulate inside the boiler, acting as a thermal insulator. The heat has nowhere to go except up the smoke stack and into the atmosphere. Needless to say it’s important to keep heat rate as low as possible by keeping power plant equipment insulated and in good repair. But there are some things that affect heat rate that we just can’t do anything about, they’re known as “uncontrollable factors,” and we’ll learn about them next week. _____________________________________________
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Low Sulfur Coal – What Does It Cost?
Sunday, July 4th, 2010|
Are you familiar with the adage, “Things are not always as they seem”? It’s probably come into play in your life at one time or another, like when you opted to buy the cheapest model of something, only to find out that its life span was two weeks before falling apart. Not such a bargain after all. Well, it’s kind of that way with low sulfur coal and its application in electric power production. All coals contain some sulfur, their content ranging from trace amounts to as high as 8%. This sulfur ends up as a byproduct of the combustion process, meaning it is released into the atmosphere when coal is burned. There it combines with moisture in the air to form sulfuric acid. If you will remember from last week’s blog, this is the stuff that forms acid rain, able to dissolve marble statues, corrode metal, and disrupt eco systems. In the process of generating electricity for homes and businesses, many utility power plants of the past burned coal with high sulfur content. This was the case through the middle of the 20th Century. This coal was brought into power plants by trains and river barges from nearby coal mines. In some cases power plants were actually built next to the mines, thereby eliminating shipping cost. It was effective and cheap. Then, in 1963, the Clean Air Act was signed into law, its purpose to improve, strengthen, and accelerate programs for the prevention of air pollution. By 1970 the Act had empowered the federal government to set and enforce national air quality standards for sources of air pollution, like coal burning power plants. Under the Clean Air Act, government was able to mandate to utilities that they reduce sulfur emissions or face court injunctions to shut them down. Caught between a rock and a hard place, utilities learned to comply, switching over to lower sulfur coals. But the story doesn’t end here. That lower sulfur created a whole host of new problems, for the power plant and their consumers. To begin with, low sulfur coals are scarce in areas of the country where electricity is needed most, like the densely populated eastern half of the country. It has to come from mines in the western states like Wyoming, and for a power plant located in Chicago, for example, this can get costly. A lot more costly than simply getting the coal, high sulfur content coal, that is, from nearby mines in southern Illinois. The result is higher transportation costs, and this cost is passed on to consumers. Another problem with low sulfur coals is that they tend to release less heat energy than higher sulfur coals when they are burned. That means that you have to burn more of it to generate the same amount of power. As a result, utilities ended up having to buy more coal, another cost that was passed on to the consumer. Yet another issue with the switch from high sulfur to low sulfur coals involved the reconfiguration of power plants that was made necessary. You see, when power plant boilers are designed, they have a particular type of coal in mind, and that originally was high sulfur coal. In addition, many power plants have been required to install equipment to scrub sulfur from the gases produced when the coal is burned. This scrubbing equipment is expensive to purchase, install, and operate. Pollution control equipment like this consumes power, but it does not facilitate the process of generating electricity. In addition to these costs, the switch to low sulfur coal causes many other problems that can raise the cost of operations and make the power plant less reliable. For example, some low sulfur coals have properties that tend to make ash stick to the surfaces inside of boilers, often leading to boilers overheating and springing leaks. If these leaks are bad enough, the boiler has to be shut down for cleaning and repair, and when this happens the electrical generating unit has to be taken off the utility grid. The net result is less power being available to meet consumer demand. We can thank the Clean Air Act for effectively reducing the amount of airborne pollutants, but we must acknowledge the cost to do so. Electric utilities are for-profit corporations, not charities, and someone has to pay for the increased coal consumption, higher transportation costs, equipment additions, and operating problems that are a result of the usage of low sulfur coal. That someone is the consumer. _____________________________________________
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