Millwright Quiz of the Month

Since we'll be talking about greasing bearings at cement plants, today's quiz will be about lubrication.  

Did you know that grease is mostly made by thickening an oil with a soap?  Generally, low viscosity base oils are best for low temperature, high speed greas;, and high viscosity oils are best for high temp, low speed grease.  The soap thickener controls water resistance, resistance to wear and tear, and the ability of the grease to stay in place.  The soap content varies from 3 to 50 percent of the grease; it is generally 7 to 18 percent.

Quiz:  can you name 6 different types of grease?  What are the differences between them, in their make or their use?

Feature Industry of the Month

The current feature industry is cement plants.  Cement plants are classified as heavy industrial work, and millwrights do a lot of different tasks at cement plants to keep them up and running.  

Cement is made from limestone and added ingredients.  The mixture is heated until it is a molten lava consistency, which causes it to become cement, rather than just a mixture of powders.  When this lava is cooled, it is reground into a flour-like powder, a few final ingredients are added, and there you have "portland cement", used in the making of concrete.

Because of the corrosive nature of cement powder and many of the raw materials, equipment and machinery at these factories is subject to a lot of wear and tear; even heavy duty components require frequent replacement.  "Routine maintenance" becomes rather a large project in these conditions.  You will find millwrights doing many things during a cement plant shutdown, from greasing bearings to full-scale replacement of entire units, and all things in between.  Some of the things which I personally have performed at cement plants are the inspection and replacement of worn tipping valves and components in the silos and to screw conveyors; changing grease fittings and manifolds; realignment and levelling of walking beams in the cooler unit; installing new plates on these walking beams, (this involves spring bolts); installation of the filters in the "bag house" (ventilation unit); replacement of bearings on fan vanes.  

Here are the web sites of some actual cement companies.  

This page has a nifty flow chart showing the steps in cement making:  http://www.cpca.ca/how.htm/

Blue Circle Cement's site has great diagrams to explain 4 different mehods of cement making:  http://www.cement.bluecircle.co.uk/html/aboutcem_process.html

Castle Cement's page explains the process in detail:  http://www.castlecement.co.uk/makeanim.htm

Answer to the Millwright Quiz:

1.  Simple Soap Greases

Calcium (lime) base--damp conditions, low temps; sodium base--dry conditions because it is water soluble, high temps; aluminum base--water resistant, low temps, good adhesiveness; lithium or barium base soaps--water resistant, high temps.

2.  Mixed Soap Greases

Eg, a commercial mixture of calcium and sodium soaps would combine some of the water resistance of a calcium base with some of the high temperature resistance of a sodium base.

3.  Complex Soap Greases

These are made from special soaps to obtain a type of multi-purpose grease.

4.  Non-Soap Greases

Thickened with things like carbon black, silica gel, or special clays. Used for special conditions of temperature, environment or service life.  

5. Multi-Purpose Greases

Intended as a substitute for several different grades of grease, eliminating the need for you to know exactly which type to choose for each application.

6.  Extreme Pressure (EP) Grease

Additives include molybdenum disulphide, sulphur, phosphorous, or chlorine compounds.  Used for high pressure areas or shock loading.

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