By Spencer Erling,
Education Director, SAISC
I have just finished my 10th enlightenment course at Wits University which started in 2002. I have done nine at UKZN and a few at other universities over the last couple of years.
Generally the course is a DP plus test course (Due performance, i.e. attend all the lectures, welding experience, factory and site visits and achieve 50% in a test).
The objective of the course is to explain and expose second year civil engineering students to the structural steel process from digging iron ore out at the mine, steel making, explain design, detailing, the fabrication process, welding including an opportunity to do a bit of SMAW (Stick welding), bolts, transport, erection, corrosion protection, fire protection, what we clad buildings with, how we connect the steel to concrete foundations etc. etc.
Over the years I have developed a stock of questions that I mix and match each year to produce a new exam.
The answers are generally well done, on average I get about an 80% pass rate and on a few rare occasions (I just could not get that class at the unnamed university to co-operate and pay attention) it drops as low as a 55% pass.
But I do get some gems of answers to my questions. I would love to share some of these with you.
Maybe they will open up some new theories for us…
Question: What is the minimum nominal yield strength in MPa of a steel bolt made from grade 8.8 material?
Expected answer:
First 8*100 gives ultimate tensile = 800 Mpa. Multiply that by the second .8 = 640 Mpa the yield strength.
Some of the gems:
• They write out 8*100 *.8 = (some amazing answers) about 450 Mpa but it could be anything from 430 Mpa to 470 to 730 to 870 to 4000 Mpa (they do not bring calculators to the exam and boy does it show. Clearly mental arithmetic is not their strong points).
• 800 kips (Kilo pounds per square inch) in MPa?
The best of the gems:
80% of 800 Mpa “I have forgotten how to do maths” (this from a second year civil engineering student with, I would guess, not too bright a future?)
Question: Give the three main steps in the turn of the nut method of tightening friction grip bolts.
Expected answer:
Snug tighten the bolt group, make two marks opposite each other on the bolt and the nut, do an extra part turn (depending on the grip length of the bolt).
Some of the gems:
• Only a one part answer in this case: Weld the bolts.
• Tighten by turning to 0.2mm. Hem… must own some special equipment?
• Hammer the bolt into 15° position. If it does not snap it is strong (I guess he was confused by the test for shear stud welds).
The best of the gems:
Rotate the nut anticlockwise, rotate the nut clockwise. (Clearly a politician with job creation in mind, definitely designed to keep workers busy for a long, long time).
Question: Name the two basic methods of protecting the weld pool from the atmosphere.
Expected answer:
Use of flux covered or cored welding rods to create a chemical reaction at the weld pool, creating a gas shield to keep undesirables (hydrogen etc.) from contact with the weld pool. Deliver a gas shield to the weld pool through the welding equipment to keep undesirables away (Mig/Mag process).
Some of the gems:
• Cover the welding rod in thin plastic. (I guess he got confused about how to keep low hydrogen rods dry
– keep them in the hermetically sealed bags they are delivered in).
• “Oil it”
• Plastic and glass (these answers from the same expert).
The best of the gems:
Dip the weld pool into paint.
Now after marking all these papers it is clear to me that many of the students mechanically answer questions without thinking about earlier questions. Look at this pair of questions and answers. I like to ask about the melting point of iron, or the temperature in furnaces. It is usually near to the start of the paper as steel making is early on in the process.
Question: What is the melting point of iron?
Expected answer:
1530°C up to 1600°C. (Generally this question is answered well but occasionally I get a few random answers e.g. 600°C and very occasionally 8000°C. Wow, that steel mill must really be a hot place to work in!)
2 or 3 pages later I pop the question: What is the critical temperature in the case of a fire for a steel structure and why?
Expected answer:
600°C. That is the temperature at which steel has lost 70% of its yield strength.
One of the gems:
Remember the answer to the earlier question – 600°C because that is the temperature steel melts (that steel mill must be the cheapest producer in the world. Boy, they were clever to get the melting point of steel down to 600°C!)
Question: Name three types of material used to ‘passive’ fire protect steelwork.
Expected answer:
Sprayed or plastered vermiculite cementitious covering, fire proof boards, intumescent paint, cover in concrete or bricks.
Some of the gems:
• Use glass to fire protect
• Use plastic
• Waterproofing
• Box out in wood (?)
• Spray cans (sic). (I suppose if we can build up a thick enough layer of aerosol cans to the steel and find a way from preventing them from exploding we may just be on to something).
The best of the gems:
Add water to the steel when we make it. (Ouch!)
Question: Name two common methods of removing rust from steel before painting.
Expected answers:
Hand or mechanical wire brush, sand or shot blast, acid dip.
Some of the gems:
• Rinse in the zinc bath (what happens next?)
• Add acid to the steel. (I don’t suppose this is worse than adding water.)
Question: What is the purpose of a prime coat of paint on steel?
Expected answer:
Protect the prepared surface until the full specification is applied, act as a bond between later coats.
A new theory expert answer – Make the steel stronger
Question: What are the main constituents in pricing of steel (or for that matter any material)?
Expected answer:
Material costs, labour costs and equipment costs.
The gem:
The price of oil…
Question: Name three common welding processes.
Expected answer:
SMAW (stick), GMAW (Mig/Mag), FCAW (flux cored), SAW (submerged arc)
The gem:
Hot welding rods.
A few final gems:
• I carefully explain steel making as a two-stage exercise i.e. make pure iron (they enjoy the old name ‘pig iron’). I sometimes ask them about this. The gem theory… ”remove the steel from the iron”.
• For some reason, not in answer to a question, the student was describing scarfing of welds in tube making: Smooth the welds with water. (A new method if we can get it right!)
• Concrete is heavier than steel…
• Steel can burn unlike concrete…
If you truly believe some of these new theories are worth pursuing contact the writer. I have kept the names of the geniuses involved. This is just in case you would like to employ them to conduct the studies or maybe even more importantly to ensure they do not get too close to your works.
