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the feature industry this month is....
Petro-Chemical Refineries
Last month, we spoke about millwright work at sugar refineries. The word "refinery" brought to mind one more common job site for construction millwrights: those of oil companies.
A technology which is used a lot, both by the various industries which need millwrights, and by millwrights themselves in the performance of their jobs, is that of pneumatics. Simply, this is the use of compressed air to do work. It all works because of Boyle's Law, which shows that the volume of a gas is inversely proportional to the pressure upon it: ie, gas compresses when more pressure is applied to it. This is expressed as P1.V1=P2.V2, or the initial pressure times volume equals the resultant pressure times volume. To be entirely accurate, this is usually combined with Charles' Law, which states that the volume of a gas is proportional to its temperature. In other words, gas expands when heated. Charles' formula can be stated as V1.T2=V2.T1, giving us the Combined Gas Law as P1.V1.T2=P2.V2.T1. (Note: in calculations, temperatures used are in absolute degrees.)
What this all really means is that we can make gases do work for us. In a simple pneumatic system, we compress air to give us potential energy, and we use this energy when we release it at a piston or pneumatic motor. In the case of a piston, we can create much more force than we started with when we apply the fluid energy of compressed air to a mechanical actuator of greater surface area. That is to say, if the system is pressurized to so many pounds per square inch (psi), then by putting a larger piston at the actuator end than at the input end (more square inches) you will get more force (pounds). To put that in a formula, Force(in pounds) = Pressure (in psi) x Area(in square inches).
Quiz Question:
Here is a diagram of a pneumatic system. The surface area at "A" is 10 square inches, and the area at "B" is 15 square inches. If you apply a force of 50 pounds initially at "A", what force will you end up with at "B"?
Here's a bonus question: Let's say the volume of the inner space between "A" and "B" is 25 cubic inches. If you increase the temperature of that space from 60 degrees F to 90 degrees F, how does that affect the resultant force, if at all?
Oil and related products from refineries are used in a wide range of places and purposes. It's a finite source of energy and raw material, created ages ago by the death of prehistoric creatures. Under eons of pressure, the bodies of dinosaurs (and less impressive beasts) become what we drill for in oil areas.
It is usually drilled out of pockets in the bedrocks and pumped to the surface, where the refining process occurs. Sometimes there isn't even much of a process required, as in the case of natural gas, which is found at the top of an oil pocket. Basically, the stuff is separated into various "light" and "heavy" products by taking advantage of their different boiling points, all the way from asphalt tar to propane.
Here are a few links to sites related to chemical refineries:
You might not even believe how many things come from petro-chemical refining. Here's a page that lists an amazingly long list of everyday products derived from petroleum: http://www.petroleum.co.uk/is23.htm
This site gives a history of petroleum, touches on the different levels of product refined, and gives a diagram of the refining process: http://www.petrox.cl/english/petrol.htm
This is the Canadian government page of international trade report for this industry, with statistics on production, links to companies, and more: http://strategis.ic.gc.ca/SSG/gi36111e.html
The Institute of Petroleum site has a listing of links to companies, news, and courses: http://ibp.powerweb.co.uk/dbtw-wpd/textbases/addresses.htm
The Canadian Association of Petroleum Producers has a page on their site called "Our Industry", which discusses different projects underway (eg Hibernia, Terra Nova offshore drilling), pipeline systems, and refineries. http://www.capp.ca/
When you apply the 50 lb force to "A", you can calculate the pressure created on the inside of "A" by the formula: P=F/A. This gives you 50/10 or 5 psi. With 5 psi is acting on "B", you convert the formula to F=P x A to calculate the resultant force. In this case, 5 x 15 = 75, so you have a resultant force of 75lbs at "B".
For the bonus question, you must first convert the temperature in Fahrenheit into absolute temperatures. Absolute zero is defined as -273 degrees C or -460 degrees F. Once you've done that, given that you have 5 psi pressure in the space between A and B, you can use the gas law P1.V1.T2=P2.V2.T1. This gives you
5 x 25 x (90+460) = P2 x 25 x (60+460). Thus P2 = 5.29 psi. If you then use this pressure in the previous formula, F=P x A, you will then find a resultant force of 79.4 lbs at B instead of 75.
Hopefully these simple excercises give you a taste of what can be accomplished with pneumatic systems.
See you on the next monthly update of the Construction Millwright Feature Page!
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