Wednesday, March 31, 2010

Industrial Fan Applications: Pickle Line

The manufacting of sheet steel uses a pickling process after they have rolled the steel. This is a heated high strength hydrocholric acid bath that the sheet steel goes through to remove any slag inclusions on the surface of the steel. If the slag inclusions are not removed, rust can start at that location.

The hydrochloric bath gives off acid fumes, so it must be contained in a sealed environment with a negative pressure to ensure acid fumes do not leak out into the environement. To maintain this negative pressure, an industrial fan is used. This fan sucks air out of the hydrocholric bath hood, and through a scrubber to remove the acid out of the air. Idealy, the scrubber removes all the acid from the airstream so that only clean air goes up the stack. Unfortunately, scrubbers are not perfect and occasionally acid is still entrained in the airstream as it enters the fans.

The acid in the airstream is very corrosive on the fan components. For this reason extra precautions must be taken in the choice of fan materials to protect against corrosion. The main areas of conern are the fan casing, fan impeller, and fan shaft.

To ensure the fan casing withstands corrosion, it can be made out of fiberglass with a c-veil to seal the airstream surface of the fibreglass. However, ,one of the concern about using fibreglass is the strength of the casing. Casing strength is considered for three primary reasons. First, the casing must withstand the static pressure differential between the inside and outside of the fan so as not to deflect excessively. Secondly, the aerodynamic turbulence within the fan casing can cause casing vibrations if the casing does not have sufficient stiffness. Thirdly, in the event of a impeller failure, it is good to have a casing that can contain the pieces of the impeller rather than allowing them to pierce through the casing and damage people and equipment. For these reasons, fibreglass casings should only be considered for lower speed fans.

For higher speed fans, the casing can be contructed out of steel and lined with a corrosive resistant barrier. The best barrier is rubber as it does not get damaged easily and during the application of the rubber, the applicator can do spark tests to ensure that a complete seal is obtained. By using a steel housing with rubber lining, the housing has all the strength of the steel with appropriate stiffeners.

The second fan component requiring special consideration is the impeller. For low speed fan applications, it is possible to use a rubber coated impeller. Note that this is only applicable for very slow fans, since the centrifugal forces generated by higher speed fans along with the aerodaynamic forces in the impeller will cause the rubber to be ripped off the impeller. The best solution for the impeller is to not coat the impeller, but rather use a material which can withstand the corrosion while demonstrating suitable mechanical properties. The two primary materials satisfying these requirements are titanium and Alloy C276. Alloy C276 tends to be lower cost then titanium and has a lower corrosion resistance, but is often sufficiently corrosion resistant as long as it is inspected regulary.

The third fan component is the shaft. By using an overhung arrangement, the only component of the shaft potentially exposed to the airstream is the part between the back of the hub and the casing opening. This can be protected by a shaft sleeve that is welded to the back side of the hub and extends through the back side of the casing.

By making special considerations for the casing, impeller, and shaft, an appropriate fan can be designed for an acidic environment.

Tuesday, March 30, 2010

Industrial Fans: Economic Environment

During the early part of the first decade of the 21st century, the fan industry was in its boom years. The economies of developing world were expanding, which in turn created demand for natural resources to fuel their growing infrastructures along with their domestic consumer industries. Most natural resources require processing before delivering to their final market. This processing often uses industrial fans to contain dust, remove harmful pollutants, and assist in the process of the natural resources. Some of the many applications for industrial fans in the natural resources include copper smelting, dust extraction from copper pulverizing, nickel refining, steel mill blast furnace emissions control.

Another area experiencing a boom in demand for industrial fans was the cement industry. In the process of converting lime(calcium carbonate) to calcium oxide, it must be heated. The kiln ID fan draws superheated gas through the kiln and then through a cyclone separator and/or electro-static precipitator. With the boom in global infrastructure development, cement manufacturers were expanding to meet the demand.

The last two years, we have experienced a cooling off in the world wide economic growth triggered by the sub-prime financial crisis. This has resulting on a sharp drop in infrastructure spending resulting in a drop in demand for natural resources.

Fortunately, the economies of the non-western world, which account for the majority of demand for natural resources, did not experiences as sharp a recession as the western countries. This means that demand for natural resources is already starting to pick up again. This can be seen by the Nickel price:
Nickel reached a peak in 2007, and went to a 5 year low in 2009, but now the prices are on the re-bound. This trend is also occurring in many other natural resource prices.

This means that demand for industrial fans should begin to improve in the next 1 to 2 years. During this time of lower demand, fan manufacturers should make use of this time to optimize the management and methods for engineering and manufacturing fans, along with put effort into establishing their market presence. This will enable them to capitalize on the upcoming boom in the fan industry.

Wednesday, March 24, 2010

Using custom domains with Blogger

I have been using the FTP capabilities of Blogger for a while to maintain a blog on my own domain that was hosted at GoDaddy. However, blogger just announced that they would stop supporting FTP capabilities, thus they would only support blogs that were actually hosted by Blogger (or Google).

Fortunately, they have a feature that still enables my blog to be posted at my domain name. Under the publishing part of settings, I am able to specify a unique domain name. In my case I use blog.johnhufnagel.com. The blog.hufnagel.com is set up as a sub-domain of hufnagel.com. I am then able to set up a sub-domain at my domain registrar (which happens to be GoDaddy). Sample instructions for this can be found at How Do I create a cname record for my custom domain

After the subdomain is set-up, it will automatically point to ghs.google.com which is the location where the subdomain for the blog is hosted.

Thus, the blog is hosted by Google, I get to use my own domain.

Google also provides the options of buying a domain name directly through Google. This is a more straight forward approach if you only want to do blogging on your website. Since there are a lot of other features I wanted on my website, I preferred to have my domain name registered with a conventional hosting company.

Tuesday, March 23, 2010

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Sunday, March 7, 2010

Ethics and Lying

I was just reading an article about Consequentialism. One of the first examples of ethical issues is a discussion about lying. I find it interesting that the authors of the article would choose to discuss lying rather than cheating or killing (ie: in the case of warfare for a justified cause), adultery, or abortion. All these other topics have significant ethical contriversies associated with them.

Over the past year I have been reading a lot of authors on ethical theories (you may notice by looking at some of my previous blogs). A lot of ethical theorist discuss lying. I guess lying is a good litmus test for an ethical theory because it challenges the major theories of Utilitarianism (judging the rightness or wrongness of an action based on the amount of utility-or benefit that action causes to the world) and rules based ethics (Deonteology: judging the morality of an action based on the action's adherence to a rule or set of rules)


A classical challenge for the ethics of lying is as follows. During the second world war, Germany was invading Holland. As the Germans soldiers would go from house to house, they would seek out any Jews and kill them. Some dutch people wanted to protect the Jews. Even if they were not Jews themselves, they did not believe it was right to allow the Jews to be killed. These people would hide Jews in their houses. When the German soldiers would come knocking on their front doors asking if there were any Jews in the house, they would lie to them and tell them there are none in the house.

Was it right or wrong for the dutch homeowner to lie about the presence of Jews in their house? Would it have been better for the dutch person to not harbour Jews in their house so they would not be forced to deal with the ethical dilemma of lying? There are certain things we do because of our basic ethical standards (ie: we do not run over elderly people as they cross the road). But there are other things we do that go beyond the basic ethical rules. Some of us go to Haiti to help with disaster relief. Other people help out at the food bank, or spend a bit of extra time with their children in a loving way. These are things that we do above and beyond our basic ethical standards - we would not be considered wrong by society if we did not do them, but because we care (are driven by an internal motivation), we do these things.

The people that harboured Jews in Holland did so because they cared - there was no law saying they had to, not even a socially established norm saying they had to. However, to complete this act of caring, they have to go against a socially accepted ethical standard.

Utilitarians would say that the final result of saving the life of the Jew justified the act of lying.

A deonteologist has a bit more complicated answer. The simple answer is that ethics is based on rules. One of those rules is "do not lie". This would be consistent with Kant's categorical imperative: "Act only according to that maxim whereby you can at the same time will that it should become a universal law." If you just look at issue about lying, then of course you would want it a universal law that people do not lie - otherwise it would be no use having a conversation with someone because you never know when they are telling the truth.

However, if you were to look at a larger maximum of "when faced with a choice between telling the truth and causing a person to die, or lying and saving their life, choose lying", then you could say a larger universal maximum still applies.

However, there is a more complicated answer. The deonteologist also say that there is a ranking system amongst rules. They would probably argue that saying something that would cause someone to die (if the dutch person told the soldier the truth, then the soldier would kill the Jew), is a worse act then lying. Therefore, it is better to do the least harmful act. Now comes the next big questions: how does the ranking system work?

The ranking system would likely go something like this: most important is to protect innocent human life, the next order of importance is upholding rules such as truthfulness etc.

So, you have just observed how lying in a certain context can be justified by the principal ethical theories.

It makes me feel uneasy justifying something I feel is wrong. I grow up learning that lying is wrong. We are trained from an early age to instinctively see it as wrong. Now we look at a situation where it seems that it is the right thing to do. In this type of situation, I would probably act to preseve life, but I wouldn't "feel" right about it. I guess it is not always that easy to do the "right" thing - the idealized perfectly right thing, in an un-ideal, imperfect world.

Wednesday, March 3, 2010

Creating Section Views of Fan Impellers using Solidworks

The parametric capabilities of Solidworks creates many capabilities to re-use parts and assemblies by just changing some dimensions in the parts or assembly sketches. One of the things that is tricky though it to create section views will properly section a scaled drawing.

When creating a section view, the user is asked to draw a line for the section. If the part or assembly is scaled larger then the original line, then the section view is not cutting through the entire section. This can cause errors in the section view meaning that the whole section view has to be re-created.

To ensure that the line defining the section view scales correctly with scaling changes of the part, the section view line has to have relationships with the geometry of the part or assembly. For fan impeller drawings, the best way I found to do this was to snap onto the quadrants of the outside diameter of the impeller when making the line.


Thus the line is defined as going from the top quadrant down to the bottom quadrant. As the impeller is scaled, the line defining the section view is scaled and the section view is maintained.