Saving money on passive fire protection – designing composite floors in fire: the slab panel method

By Caroli Geldenhuys & *Richard Walls (Pr. Eng.), Stellenbosch University, Dept. of Civil Engingineering, Fire Engineering Research Group.

Passive protection such as intumescent paints, vermiculite boards and spray-on products can be very expensive. Thus, rational structural fire design methods, as presented here, can lead to significant savings. This article presents a brief introduction to a design method, the Slab Panel Method (SPM), which allows engineers to design composite floors for fire.

Believe it or not, when you set fire to a composite steel and concrete floor it just doesn’t want to fall over. It heats up to hundreds of degrees Celsius, beams buckle, floors sag, concrete can crack – but floors don’t collapse because they become giant hanging catenaries. Using results from fullscale
tests this behaviour can now be modelled and designed for, potentially leading to significant savings in the cost of passive fire protection on steelwork – with as much as 40-50% of floor beams not needing protection (see Figure 1). Passive protection such as intumescent paints, vermiculite boards and spray-on products can be very expensive. Thus, rational structural fire design methods, as presented here, can lead to significant savings. This article presents a brief introduction to a design method, the Slab Panel Method (SPM), which allows engineers to design composite floors for fire.

Overview of the Method
The Slab Panel Method is a structural fire design method used for composite steel and concrete floors in severe fires. Certain steelwork can reach above 850°C in the design, but the system still remains structurally sound. The method was developed by Prof Charles Clifton in New Zealand.

See the report R4-131:2006 for complete details regarding calculations. His work was originally based on the results of the famous full-scale fire tests done at Cardington by the BRE (Building Research Establishment), and the tensile membrane work by Prof Colin Bailey. Since then the SPM has been developed based on numerous other research projects as well. Figure 2 shows the eight storey composite steel and lightweight concrete building used at Cardington, where various parts of the building were progressively exposed to severe fires and the overall structural behaviour studied.

The SPM procedure incorporates the reserve strength from a floor system under deformation in a fully developed fire. It is an ultimate limit state design procedure in some ways similar to building design for response to earthquakes, in that certain degrees of structural damage are permitted provided that collapse is prevented, but damage may occur in very severe fires.

How the SPM Works
The SPM design model is based on using yielding-moment action and tensile
membrane enhancement. The procedure is applied to large regions of a floor, known as slab panels, and incorporates the inelastic response of slabs (i.e. floors bend and sag permanently). At ambient temperatures the way loads are transmitted through a composite steel building involves:

The slab -> secondary beams -> primary beams -> columns.

When severe fire conditions occur and the interior secondary beams are unprotected, they lose most of their strength and the load path above cannot be maintained. The beams form plastic hinges and the load-carrying mechanism changes to a two-way spanning system, as illustrated by Figure 3. Here the load carrying path becomes:

The slab panel -> primary supporting beams – > columns.

From this it can be seen that the secondary beams no longer play a major role, and simply form part of the sagging slab panel system. Hence, they do not need to be passively protected. However, it is essential that primary beams are protected as these carry the sagging slab panels.

The SPM theory is based on membrane action which is caused by in-plane forces within the slab. This allows the composite floor slab to bridge over the unprotected beams. This basically means that the rebar in the concrete slab, and the remaining secondary beams’ capacity, allow floors to hang from where support can be found, even when steelwork has failed. Figure 4 shows displacements of the beams that occurred during the fire tests at Cardington. It can be seen that no structural collapse occurred, even though significant deformation has occurred. It is interesting to note that the structure shown in Figure 4 had no passive protection whatsoever, experienced temperatures of over 1000°C, should have failed according to any standard design codes and yet did not collapse.

Under ultimate load conditions at ambient temperature, yield-line behaviour develops first and then tensile membrane enhancement, which occurs as the plastic hinges form. But under severe fire conditions, tensile membrane enhancement occurs first – i.e. the floor capacity increases as it becomes a hanging catenary. In the event of a fully developed fire, the SPM performs as follows:

1. The slab and the unprotected secondary beams may undergo considerable permanent deformation.
2. The primary support beams and columns undergo much less permanent
deformation compared to that within the panel.
3. The load-carrying capacity and the integrity of the floor system are preserved.
4. Both local and global collapse are prevented.
5. The development of the failure patterns in a slab panel is shown in Figure 5. The design equations are based on the final lay-out shown in Behaviour Mode (iv), as also seen in Figure 3.

After a severe fire secondary beams may potentially need to be repaired or replaced. However, very severe fires cause such significant damage, that everything in the building would probably have been destroyed. Recently a structure designed according to the SPM experienced a fire, and the structure survived with almost negligible damage. It is understood that the cost of the damage to the contents far exceeded the cost of the damage to the structure. 

Software for the SPM
The Heavy Engineering Research Association of New Zealand has developed software to do the numerous calculations required to carry out SPM designs. This can now be purchased from Steel Construction NZ. Alternatively, similar free software that could also be used for this purpose is MACS+ from ArcelorMittal, or TSLAB from the SCI in the UK. Stellenbosch University is currently using the SPM software for research purposes.

Note: before using any of the above software make sure that you read and understand the design theory and methodologies. Rebar and certain detailing requirements are essential for the use of these methods, and the SPM guidelines provide good information regarding this.

The SPM and fire design in South Africa
SANS 10400 – Part T states that rational fire design in South Africa may be used provided that it achieves the same level of safety as implied by the document. These rational designs must be in accordance with BS 7974, which further states that competent persons must demonstrate that due diligence has been applied during the design process and the approving authorities can assess that due diligence has been applied. This basically means that under the auspices of rational design methods such as the SPM could be applied safely and according to SA code requirements (but it is important to discuss this with your local fire chief and fire engineers).

A recent project at Stellenbosch University (Geldenhuys, 2014) sought to calibrate the SPM to suit local South African conditions. It was shown that the SPM can be used as is, with only minor adjustments where New Zealand’s fire loading code is included. For more information on structural fire engineering principles and design you can contact the *corresponding author at Stellenbosch University’s fire engineering research group.

South Africa will soon have additional fire design principles and methods available in the updated SANS 10162-1 structural steel code. The recommendations presented in the Canadian CSA S16 code will be adopted, making fire design available to local engineers in the near future. More details to follow soon…

Entry level into CNC controlled machines It’s not so expensive

Lessons from Spencer’s Voortman visit – Part II

By Spencer Erling, Education Director, SAISC

Voortman recently invited and paid for Spencer’s travel costs to visit their factory in Holland as well as a Dutch fabricator and a German fabricator. This is the second of a series of three articles to share my findings with our members. The SAISC’s grateful thanks go out to the Voortman team and their SA representative First Cut for making this eye opening trip possible. In this article we look at entry level equipment on offer from Voortman. Look out for our next article in Steel Construction No. 3 for 2015 where we will be writing up about the more sophisticated equipment from the Voortman range.

It does sound a bit crazy to say and think that I was going to Holland to find out about the Voortman range of equipment and this would happen in only about one and a half days on site for the whole range. Just how could it be possible?

Even more so when I think back to 1979 when I first went to Germany to purchase Peddinghaus equipment. We planned on a four-day visit to see just their two models of drill line NC machines but this required visits to factories all around the western side of West Germany even venturing into Holland to Ulft and in passing see some of the punching equipment that Peddinghaus was synonymous with in those days.

So how could it be possible to see Voortmans’ vast range of equipment in such a short time? The answer is actually quite simple. Voortman has a strong marketing set-up geared to doing just this. At the heart of the programme is their Experience Centre in which all of their equipment is set up to show and explain their capabilities under one roof. One of the treats for me at their centre is this delightful staircase (see opposite page).

Add to this, they have their own structural steel fabrication shop on site which is a great proving ground for their equipment as well as their production and assembly lines for machines on order. This department is the epitome of European discipline and organisation. Their parts stock control is very sophisticated, computer controlled and items are all automatically withdrawn from their bins and placed into holding bins by order number.

And then finally within an hour and a bit from the centre, there are two very competent fabricators, one sporting a brand new works with an extensive range of Voortman equipment the other having equipment that has been in use for some time now.

What more could one ask for to get to know their range of equipment quickly, efficiently and without fuss? Well done on that score to the Voortman team. It is a few years since I visited the Kaltenbach bi-annual factory based exhibition or the North American Steel Constructtion Conference where many manufacturers show off their equipment, the modern facilities and whole Voortman approach is startlingly refreshing and clearly a winner.

Entry level equipment
Voortman’s approach to software
It is interesting to note that Voortman has developed a software system under the name of VACAM which is used to control the whole range of their machines and handling systems. Apart from the basic common sense that this approach makes, adding new machines or handling equipment to existing facilities becomes, relatively speaking, an easy exercise. Voortman has a team of 15 programmers who are experts at doing just that.

I guess for the small to small-medium fabricator the thought of increasing productivity by purchasing CNC equipment is a daunting concept (especially for those of you who have not done any ‘what if’ assessments of the equipment).

In the article published in Steel Construction No. 6 2014, Chasing profitability for the small to medium steel fabricator, Danny Steyn writes about just how important it is if you want to survive in these tight financial times (and even better – prosper), you must take the plunge and get on the ladder to the future by starting with some CNC equipment. And before going much further let’s throw some numbers at you. Consider the following proposal:

Consider a fabricating company is doing say 100 tons per month for 11 months a year. Sadly, due to competition laws, I really do not know what an hour costs in a workshop these days but I am sure that very few of you get away with less than R450.00 per hour.

If you were to save just five hours per ton this works out at a pot of money close to R2.5 million. So in two or three years there is a good chance you will be able to pay off between one and two entry level models. If you do everything manually i.e. sawing, cutting, marking, drilling and the like, saving five hours per ton with a couple of machines is very realistic and probably quite conservative. Just consider how much overheads you can save by your 3D TEKLA package speaking directly to your NC machines.

Can you afford not to be going the route?
Of course the definition of an hour is important here. In my estimating course I teach that the hour that you should be working on is the hours actually recorded to a job, so excluding labourers, grinders, despatch and the like whose costs would be added to the recorded hours. In addition each hour attracts a portion of the company overheads.

If you do not know about these things maybe you should consider doing the SAISC estimating course.

Which machines are available at entry level from Voortman?
You will be pleasantly surprised just what can be found for realistic prices. Somehow everyone automatically seems to start by thinking about a beam drill line. Even before looking at the models available, learn from the experience of those who have already gone the route. On more than one occasion I have been told “had I known what I know now, I would have started with a plate processing machine before a beam drilling machine – of all my NC machines it is the plate processing that works two shifts to keep up with the demand”. Think about it!

Beam drilling
Right at the bottom in its simplest form is the V600. Having only one horizontal drill head it is necessary to turn the beam to enable drilling, slotting and marking to the flanges and the web. To ensure accuracy of holing on each of the three faces, each time the beam is turned by the machine zero is identified for the new face of the steel to be drilled using laser. The drill head moves along the length of the steel.

As with all their drilling equipment, high speed carbide drilling is available (which is dramatically faster than high speed drill bits), as well as the automatic tool changer with five stations (including tapping up to 30mm
diameter, centre point marking and counter sinking) capable of up to 40mm diameter holes.

Next step up is the V613/1000 (the 1000 indicating
nominal maximum width of beam. The actual width maximum is 1050).

Here the big difference when compared with the V600 is that the single drilling head rotates to suit the flanges and the web i.e. two horizontal and one vertical position and the steel passes through the machine compared with the V600 where the machine travels along the length of steel.

In addition to the drilling capabilities mentioned for the V600 it has 2 x 5 station tool changers. Optional extras include layout marking (i.e. where attachments need to be assembled) and numbering marking for part identification, feeder truck or roller feed measuring systems.

We will look at the full beam drilling capability of the V630 machines in the next article.

Beam sawing machines
Unless your business is based on cut-to-size ordering from service centres, one should not think in terms of standalone  drilling machines but rather linking them into a sawing machine station

Thinking along the lines as above, if buying cut-to-size is costing you between 5 and 10% of the basic steel price it does not take rocket science to calculate that to pay off a saw does not need too many tons per month, but do not forget to ask about the cost of replacing the band saw blades which can be quite often for heavily working saws.

The Voortman range of band saws all have the VB description followed by the nominal maximum width capability (VB750, 1050, 1250)

All are mounted on rotating turn tables for any angle of cut, have hydraulic blade tensioners and guides either side of the beam to be cut by width; to keep the cut square and have the options of length stop, roller feed or truck length measuring systems.

One of the items that was a first for me was their “short piece removal” clamping system (useful for short beams or scrap removal). It is also possible to program the machine to return longer length off-cuts back to the stock yard. This works very well for lightly loaded saws as it is quite time consuming.

The great thing is that when you buy from Voortman they will work through your planning requirements and in the case of a saw/ beam drill combo it is possible to have just one operator for the two machines. Layout and movement are designed to minimise handling.

 

New theories related to the structural steel process

By Spencer Erling, Education Director, SAISC

It is just three and a half years since the first article in the series was written, (see Volume 35 No. 2 2011, Some gems from Spencer’s Steel Enlightenment Course for Wits students), a whole bunch of courses later we have enough material for a follow up article. Our grateful thanks goes out to our “innovative but somewhat misguided students” usually in the form of (incorrect) answers to test papers

Background
The courses are usually offered in the last week of the student’s vacation, either at year end or mid-year breaks. You would think that some of the students were working under extreme pressure or round the clock before attending the program (during vacation huh?) but more likely extreme partying because some of them walk in (quite often late) sit down and fall asleep even before they have to listen to one word of my, apparently to them at least, boring subject and delivery.

So it is no surprise that we do get the really garbage answers to straight forward questions from some of our not so good candidates. Of course as the lecturer you begin to question yourself and your (in) ability to get the message across… fortunately with experience you learn who these wonderful answers are coming from and can ignore their poor, sleep driven, performance.

The course is an attempt to introduce second year civil engineering students to the whole structural steel process literally from digging iron ore out of the ground to handing over the proverbial front door key. Part of the course is dedicated to field visits to tube makers, fabricators and to erection sites. Some of the questions are aimed at finding out if they have learnt something from these visits in addition to the lectures. All of the questions are straight forward multiple choice or one line answer type. There are no trick questions but we would like to know if the students can think broadly enough to “join some of the dots”

New welding theories
We spend a good two hours covering weld
processes, types (fillet / groove), sizes, positions (flat, vertical up etc), defects and
how to find those defects (NDT) but the
emphasis is on the fact that we use either
flux around or in the rod to create a gas
shield to keep the nasty’s in the air away
from the molten pool (SMAW or FCAW) or
we deliver a gas shield to point of welding
(GMAW).

Upon being asked a question to which we would expect an answer along the lines just described some of the proposed new methods would be (sic)
• The use of Airtight welders (a pity about his need to breath…)
• Use a gun which has the ability to remove the gases from the welding pool (should we try a 45 magnum…???)
• Using a (paint) primer or other protective (paint protective to welding?) coating
• Submerging in water… and along similar lines
• Add water to the weld (to cool off the heat/ melt) (now that should keep the welder guessing just who in the process has gone crazy)

When asked to describe some common weld defects (expecting an answer like cracks, lack of fusion, shape and or size of the weld, distortion) the latest defect is…
• Ingots (yup I guess an ingot could do some real damage to a weld…)

When asked to explain how the welding up of tubes along their length in a tube mill differs from normal (SMAW, GMAW, FCAW, SAW) methods we expect an answer along the lines that induction welding using heat and pressure only and no filler wire is used in tube mills. Tube makers here is new one for you to try (sic)
• The hollow section is fed with carbon from within the tube and melted by heated arc to form the weld

Bolt issues
Yes we all know there a lots and lots of issues around bolts, bolt grades, new bolt specifications and, and, and of course tightening of bolts correctly. The SAISC has for a long time now followed North American methods of tightening HSFG and other preloaded bolts (rather than the torqueing methods adopted by European specifications). Clearly this is an important subject and receives it fair share during the (limited) time available. The turn of the nut method is described carefully and emphasised several times. So sure, one of the questions is to describe the method.

Now pay attention all of you involved in the process of pre-loading bolts. Stop wasting your time and energy you can just (sic)
• Weld the HSFG nuts

Fire protection issues
Why we need to passively fire protect steel and how we do it is the subject of one of the talks. The reason why is ascribed to the fact that at 600°C temperatures steel has lost 70% of it’s yield strength, something that usually leads to collapse. One of my favourite questions is why we passively protect our steel expecting the above explanation as an answer.

Readers in the opinion of one of our budding geniuses we have our theory totally wrong because (sic)

• The greater / higher the temperature degree, the higher the yield strength of steel.

We have been missing out on some readily easy to apply materials for passive fire protection. The latest suggestions are…
• Plastic
• Glass
• Vinyl
• Paper
• Timber
• Using a layer of copper around the structure since copper is a bad conductor of heat

And the winner by far…
• Galvanizing and mixing it with alloy to make it more brittle (shoo! I am clearly confusing them… must remember to try not to confuse them so much in future)

Painting issues
Some time is spent on the fact that steel rusts and that we need to prepare the steel suitably removing rust and other not desirables (i.e. wire brush, shot blast, acid dip etc) to receive paint, the role of prime coats etc.

We have lost out on a very common building material to assist with rust removal
• Concrete encasement

Metallurgists who might read these words of wisdom, did you know that the new role for prime paint is (sic)
• To get to know the quality of the steel

Cladding materials
Naturally any good course on the structural steel process will cover how we enclose our structures (clad) and we cover metal, fibre cement, precast elements, glass and high density polystyrene (LSFB) methods but sadly we have been missing out on two readily available products (with apologies to our recycling industry…)
• Recycled cans
• Motor cars

Steel and concrete interfacing
Finally the course covers the interface between steel structures and concrete foundations and the need to create the ability to adjust the steelwork to suit the (often) incorrect holding down bolts. I emphasise the need for our steel to be adjustable. That is the answer I expect to the question I have occasionally set.

They get full marks for the one word “adjustment”

The following treatise received no marks… but does highlight how easily the students can confuse and mix the different parts of the course (sic)
• Transferring the loads through the base plate into the foundation by a method that wont allow the bolts and the base plate to easily corrode the concrete and create spaces in these connections. Adding a flux between the plate and concrete can do a lot to spread the load uniformly (at a guess he meant grout not flux…)

Disclaimer.
Finally a serious word of warning, do not apply or use any of the above theories or methods without extensive research and testing which I think would be a whole waste of time and effort. If you do, it is at your own risk.

Hempel supplies 170 000 litres paint FOR e4 sundsvall bridge

Work commenced in spring 2011 on the Stockvik-Skönsberg stretch of the E4 European Route project in Sweden that includes the construction of 33 different bridges. A specific Hempel sales and R+D team in Germany and Sweden came together under German leadership to design and implement the supply of 170 000 litres of coating materials for the new Sundsvall Bridge, the 2 109 metre flyover spanning the Sundsvall Fjörd at a height of 33 metres due to open to traffic in autumn 2015.

Finally a high-solid PUR-Topcoat of HEMPATHANE 55610 tinted to RAL 7037 dust grey. This system is NORSOK M-501 certified and provides fast-curing, highperformance, permanent protection for harsh weather-exposed steel. In accordance with Norsok standards Hempel has a proven track record for protecting offshore wind turbines and oil and gas platforms erected in similarly aggressive environments all over the world, as well as an important differentiating factor, in that The prevailing environment in Sundsvall is DIN EN ISO 12944 classed as C5M-high marine atmosphere with wet, saline sea air, severe weather variability and sub-zero temperatures in winter. The Swedish authorities awarded the order to the joint venture “Sundsvallbroen PBM” (PBM = Arge partner: E. Pihl & Son, Max Bögl, Josef Möbius AG). For Max Bögl GmbH & Co. KG, Germany’s largest private steel construction firm, this represents the company’s biggest bridge construction project to date. Amongst other references for the project is Strelasund Bridge, Stralsund, which is also in the Baltic Sea and painted with Hempel.

For exposed bridge structures, the system being used is a shop-applied 3-coat system based on a zinc-rich primer of HEMPADUR PRO ZINC 1738G, followed by a two-component mineral iron oxide coat of HEMPADUR MASTIC 4588F, and the Hempel system calls for just one intermediate coat and therefore represents faster turnover in the production shop.

For inside, unexposed bridge parts, a single layer of HEMPEL’S 457DE two-component, polyurethane coating with zinc phosphate is used. A second NORSOK certified system, comprising an aluminium pigmented primer and intermediate coat of
HEMPADUR MASTIC 4588W, covered by a topcoat of RAL 7037 tinted HEMPATHANE 55610, is being supplied on site in Poland and Sweden for pre-assembly and assembly parts and repairs. This two-component, polyurethane topcoat provides good gloss and colour retention to ensure that the bridge continues to display the full merits of this feat of international engineering for many years to come.

Chasing profitability – for the Small to Medium Steel Fabricator

Story and Photos by Danny Steyn, BSC Mech Eng

About Danny Steyn

Danny Steyn is a mechanical engineering graduate from the University of Natal (Durban, South Africa) now living in the USA. Through Ocean Machinery, he and his partner Hunter Fry, have completely re-written the way that small to medium fabricators process steel.

Danny has had the privilege of visiting more than 6 000 steel fabricators around the world and with over 900 Ocean CNC machines installed worldwide, he has a rare insight into the way fabricators around the world are addressing the ever increasing issue of labor productivity.

Background
It was late 2001. The boom was over. NASDAQ and the tech sector had imploded and come crashing down just a few months earlier. The US economy was in a state of turmoil and uncertainty and fear was written on everyone’s faces.

Yet there we were, a very small and relatively unknown machinery company, selling CNC automation into small mom-and-pop steel fabricating shops across the USA at a rate completely unheard of before.

How was it possible that in the midst of this drastic downturn in the economy, that we were selling more machines than in any time in our history?

At the time we were just as surprised by our success as anyone else, but with hindsight and analysis, it became clear to us that there was a strong macro trend emerging in the fabricating arena, and it was now for the first time happening at the level of the small to medium fabricator.

Let’s face it, there’s no way to sugar coat this; life as a small to medium steel fabricator has always been a pretty tough way to make a living. Just getting  started was hard enough. You needed a bottomless pit of money, expensive machinery, a good location, patient vendors, great cash flow, steady paying customers and an expensive skilled, energetic and well-disciplined workforce. No one said it was going to be easy.

And for the most part small steel fabricating shops are either swamped with work or don’t have enough work, and their owners are always too busy with the day to day pressures of satisfying customers, chasing up orders, dealing with uncooperative vendors and employees and the never-ending administration of running a business that they have built painstakingly from scratch. They seldom have the time to give much thought to how they can be making incremental productivity improvements in their operations. For the most part they just keep on doing what they have always done, and for most fabricators, productivity is an often-misunderstood term.

But unless the fabricator gets out from under this cycle, and seriously starts looking at productivity, there will be a lot of hard work, sweat and grind, and very little profit at the end of the day.

And to complicate matters, in countries where fabricators have always had access to an abundant supply of relatively cheap labor, and an ON-OFF approach to labor, they have been able to crew up when we are swamped with work, and trim down when they are short of work.

This ON-OFF approach to labor has had long-term negative effects on our understanding of how to make productivity improvements. In other countries where employees are typically very difficult to terminate, owners take a long hard look at all possible options prior to hiring a new employee who might end up being employed for the next 20 years! Two of the most commonly considered tactics are outsourcing (contracting) the work, or investing in machinery to do the work, as the machine can be paid off in a few years and it will continue to work for free for many more years, while the new employee will require a salary for as long as they are at the company.

Becoming a low cost producer

When commodity mineral prices are going through the roof, no-one cares about productivity. Mines need the steel now and are prepared to pay. But no commodity prices remain elevated indefinitely. They always come back down, and that’s when you know you can’t continue doing it the same old way.

Becoming a low cost producer has to be the single most important goal of any fabricator. And improving productivity is the only way that this goal is achieved – steadily, incrementally, and methodically. One-step at-a-time.

So how do you start going about this process of becoming a low cost producer?

By and large, the costs for all fabricators with respect to their steel costs, wages, overheads, consumables etc, are all very similar. And most have very little ability to control these costs. The only real variable in the mix is how many man/hours he has in each ton of fabricated steel. By extracting man/hours per ton, the fabricator is able to dramatically lower costs, improve the bottom line, and be more competitive in the bidding market.

One of the first areas that should be addressed is any tedious repetitive manual operation that can easily and economically be extracted from the fabricating process. Throwing labor at a problem often appears on the surface to be the quick and easy solution, but experience dictates that this is often the most expensive approach in the long term.

With the ongoing improvements in steel fabricating machinery, many activities that have traditionally been done manually can now be done with some form of automation, and the cost of automating the plant has dropped to very affordable levels. And nowhere is this more apparent than in the approach to beam fabrication.

In the past, the small to medium fabricator had two options; either manually lay out and mag-drill the holes, or he could invest a tremendous amount of capital in a conventional beam drill line. For the average fabricator this was always out of his reach, but nowadays there are several options designed to increase the productivity of the hole drilling process.

But if you just focus on the cost of layout alone, the most expensive person on the shop floor, your layout man (also known as the marker in SA terminology), has to repetitively layout a variety of parts including, beams, base plates, angles, channels etc., and yet, the actual process of laying out adds ZERO value to the steel. It is only the subsequent processes of drilling / punching / welding etc., that actually transform the profile and add value. So here we are with this conundrum – our most expensive man adds no value.

So from purely a cost perspective, layout has to be the area we focus on first. So how do we remove the layout activity from the process of fabricating steel?

Extracting man hours per ton

Today there are fortunately many affordable solutions on the market and all of them embrace some form of automation, essentially CNC fabrication. In the realm of beam fabrication, the proven solution for the small to medium fabricator doing less than 400 tons per month, is the single- spindle beam line like the Ocean Avenger. With more than 600 of these machines installed in 60 countries worldwide, it is this machine that has literally transformed fabrication for steel fabricators that would never otherwise be able to afford larger and more expensive multispindle beam lines.

And the flexibility of the single spindle drill to process the entire spectrum of
profiles including angles, base plates, channels, stair stringers etc. has made it very attractive to even the smallest of fabricators who do miscellaneous metals and just a hint of structural steel. Moreover, the ability to tackle the heaviest jumbo columns, as well as large tonnage projects, has allowed the steel fabricator to cast the net to a far wider range of jobs than he had traditionally gone after, and because of this we have seen many small fabricators with exceptional tonnage and revenue figures for relatively small shops.

Furthermore, with the advent of the 3-D detailing software that has become so
prevalent and more affordable, the ability to import data from the detail drawings, directly to the CNC machine, essentially eliminating the unnecessary costly and potentially inaccurate step of laying out the steel, has made additional improvements in productivity, speed and accuracy.

Workflow and material handling are also two of the most overlooked areas in small fabricating shops. Steel is heavy and it takes expensive labor to move it. Those fabricators who have taken the initiative and studied the material handling aspect of the structural steel business, using standard time and motion studies, are horrified to find out that as much as 50% of their labor costs go into moving the steel out of raw material storage, through the various processes on the shop floor, and finally to finished goods.

Obviously any process that reduces material handling goes a long way to improve profitability. Good overhead cranes, conveyors, beam flippers and other simple-tointroduce systems will greatly reduce the double and triple handling that robs companies of their profits.

The future
Going back to our first ventures into CNC automation back in 2001, our original feelings were that we would expect that around 10% of the small to medium fabricators would adopt some form of CNC fabrication. Today the picture is significantly clearer. Except for the smallest of shops, 100% of ALL small to medium fabricators will HAVE to make the transition to CNC fabrication, in order to remain in business. They have NO option. It’s no different to the way we had to embrace the fax, cell phone, internet and email, despite how much we might have resisted at the beginning.

It is absolutely crystal clear. It is no longer possible to throw labor at this work, and expect to see any profits left at the end of the day. Making an investment in your company, its employees and its future will reward you handsomely. And as we all know, the sooner you do it, the sooner you perfect its use and the sooner you start getting the gains.

They say it’s “the early bird that catches the worm” and this holds true in embracing change. Putting off the inevitable is delusional, and moreover it’s robbing you of precious time to become competitive and highly profitable.

We wish you an enlightening journey on this quest to become more efficient and profitable. Don’t hesitate to contact me if you want to learn more about how we have changes the lives of hundreds of fabricators around the world.

 

SA Fabricators – are we no longer productive& competitive?

Lessons from Spencer’s Voortman visit – Part 1

By Spencer Erling, Education Director, SAISC

At the SAISC board and council meetings a subject that is often raised is “are South African fabricators still world-class technically and at the same time cost effective (through productivity)?”

The answer to the former is a most definite yes, if not better than world-class because of an over emphasis on quality, cleaning and polishing. This will be explained in more detail below.

The answer to the latter is – I am not sure. On the one hand we are still exporting well over 100 000 tons per year. On the other hand we are still losing business to Asian and European companies. But based on what I saw in Europe there is every chance we will not be cost effective for very long, despite the short windows of breathing space that the weakening rand does present to us. (Our exports should not be sold based on a weakening rand, we must have much more to offer than that!) Once again we will discuss this in more detail below.

What makes European companies more productive than SA companies?
It is common knowledge that there are certain issues that increase the cost of doing business in South Africa. Examples include:

1. Security of our facilities
a. We each have a mini Fort Knox (the USA facility that houses the countries gold stocks) where high electric fences or walls, electronic gates and security guards are all the order of the day.
b. The famous expression “there are no free lunches” applies. Someone has to pay for all these items that you do not see in Europe, nor for that matter in the USA.

2. BBEEE
a. There is no doubt that this is another cost that our competitors do not have. This cost varies dramatically from fabricator to fabricator. Please don’t get me wrong, we do need to empower the previously disadvantaged.
b. Somehow we seem to have lost sight of that one critical item that should be the cornerstone of genuine empowerment – that is education and training, more education and more training.

3. Job creation
a. In SA one of our biggest issues, which clearly is fuelling crime, is the lack of employment opportunities. We should not be thinking of paying off workers but should rather be making every effort to up-skill our existing staff.
b. During the recent recession in Germany, unlike in SA where as soon as there is a downturn we stop training completely (to save money?), the German government actually paid companies to retrain and up-skill workers who otherwise would have been discharged and been on the dole (at a cost to Government anyway). There has to be a lesson for us in that policy.
c. Perhaps the most significant observable difference between a SA workshop and the European shops I visited is how few workers are to be seen and of course this translates into (low) man hours per ton.
d. Nevertheless, despite the relatively low pay our semiskilled workers earn, because we have so many of them in our workshops, our rate per ton for labour ends up being relatively high.

4. Overkill when it comes to quality and safety (sorry about the bad pun)
a. Companies in the construction world all report to us that the over emphasis on safety is not having the desired effect. The accident rate is not improving substantially but the productivity has dropped (by as much as 30% reports one company member).
b. There are serious double standards being applied on major contracts. Steelwork being imported from other countries has not been ‘spit and polished’ anywhere near to the same standard that is being demanded of SA fabricators. Inspectors have not been adequately trained in what is ‘fit for purpose’. Can you imagine what motivates an inspector to use a torch and dentists mirror to look for spatter and sharp edges in an otherwise not visible part of a product that is not going to get painted?
This is just one example.

5. Labour legislation and the power of the unions
a. No one in our industry needs to be reminded of these issues. The July 2014 Numsa and other unions led strike in the industry, the platinum strike, truck drivers and, and, and… have had a serious impact on the ability of our fabricator members to survive. Money that was being set aside to be spent on productivity improvements has been used up just to stay alive.

6. Planning, layout and cleanliness
a. It just jumps out at you how clean with concreted floors and yellow walking lines and generally organised their shops are. Compare that with our typical steel stacked anywhere disorganised SA shop.

So what can we learn from our European colleagues?
Accepting that the items mentioned above represent part of an overhead cost structure that is beyond our control, we never the less have to get cleverer and more productive.

Apart from the few workers on shop floors, the next most noticeable difference between the SA workshop and their European colleagues is the emphasis on reducing handling activities. This leads directly to the smaller workforce. No longer is the emphasis just on numerically controlled equipment with faster drilling speed, movement speed within the machine but perhaps even more attention is now being paid on eliminating handling involving human hands.

So we find machines with mechanical feed tables and discharge tables handling the steel component to the next step in the process, which could be a choice of, for example, after hole drilling the steel may need to go to notching (coping) and or marking to show where attachments will be assembled.

This would be achieved by a left or right movement once the component is out of the machine.

Another example would be after the sawing process. There is a choice of returning the off-cut (if long enough) back to the stockyard and if short enough directly to the open fronted scrap bin which is strategically placed close to the discharge end of the saw. But no this does not involve a crane action, a hand driven fork lift with a magnet picks up (as in our case) three pieces of off-cut and deposits this in the bin.

So what I hear you say, what makes this mind bogglingly amazing is that there will be only one operator for two or three machine stations. Some strategically placed closed circuit video cameras with a display at each of the machines enables the operator to know when one of the machines need human intervention. And with all that going on he still has time to blow off the milled shavings from the saw with a compressed air gun before the steel moves to the next station.

In SA we have at least one operator for each machine and he may well have at least one assistant – none of whom would bother to remove the swarf.

Other ways to reduce handling time and associated delays
Apart from the mechanical handling systems programmed by 15 programmers to suit the equipment and possible routes to and from them there are lots of other tricks I learnt:

1. For years now I have been beating the drum for more jib cranes strategically mounted on columns to eliminate crane bottlenecks. So this for example could be at a drilling machine where the jib crane would take items off a bundle to load onto the machine.

The Dutch have taken this one giant step further. A fixed jib (really a cantilevered crawl beam) is mounted on a special crane beam as well as the main crane beam both of which are designed to carry the horizontal thrusts of the cantilevered system. Apart from the way it is mounted, the crane operates just like any electric overhead travelling crane (EOT) (see photo on page 28).

2. It is quite common for fabricators to blast the steel before doing anything else to it. In the SA environment a bundle of angles (say 100 x 100 x 10L) would be split open and the angles passed through the shot blast machines in batches to suit the width of the machine. After blasting the angles would be stacked neatly in a similar bundle and transferred by crane to the next step where the bundle would then be opened up one at a time again.

Not so at Voortman where they come out of the shot blasting machine in batch widths; packed onto dunnage (same width); then transferred by side loader to the next station and stacked one layer on top of the next ready for immediate use one at a time (for in this instance the punch machine). This looked to me to be an amazing saving of time unbundling and rebundling (below right). And no chain saw damage is a bonus.

3. Some years ago we were lucky enough to visit UK shops including Severfield Rowen’s Dalton works where the steelwork was trundled through the works on mechanical trolleys and the artisans moved with the trolleys doing their work. The main trick for the success of their operation was sorting the steel items with their drawing in advance of the artisans doing their work. Their Mig Mag welding machines had support arms with very long hoses to reach the middle of the trolleys.

The Voortman take on this was the same emphasis on sorting the steel for the artisan. The steel was moved to a station (one of 64) each with its own welding machine (photo 1) (Mig Mag with short hoses – no stick welders to be seen). The assembly, checking, welding and fettling was all done at this station. The only movement was then to despatch, where trailers were waiting to be loaded. Mig wire was from the Jumbo rolls we first saw in the UK (photo 2). Welding fume extraction is now obligatory.

4. Great attention to welding details are given even as far as different size welds for the web and flanges of this beam. In the SA situation we probably don’t even call up the weld sizes on our drawings let alone differentiating between web and flange sizes (photo 3).

5. Magnet and suction lifting devices are extensively used
(photos 4 – 6).

This article has concentrated on minimising handling. Watch out for the other articles which will cover the Voortman range of machines.

Lessons from spencer’s voortman visit – part iii numerically controlled machines – the more sophisticated range

By Spencer Erling, Education Director, SAISC

In this article we look at the sophisticated equipment on offer from Voortman. Hopefully you have seen the previous article in Steel Construction Vol. 39 No. 2 2015 where we wrote about the entry level range of equipment from Voortman. If you issed it you can find a copy on www.saisc.co.za. If you are interested only in the really sophisticated new developments, you may want to jump to the section headed:

The exciting new stuff.

In the previous article we did some numbers as to potential savings by going he NC route. Calculating potential savings and payback period would be along the same lines but taking the bigger annual production into account.

Beam drilling and sawing
The V630 machines come in two models based on maximum width (1000 and 1250). Each axis has its own drill and automatic tool changer (five options per axis i.e. one for each of the flanges and one for the web). As with all their drills, it has a 40mm maximum hole capacity, high speed carbide drilling, centre point marking, tapping and countersinking ability. Optional extras include layout marking; numbering; feeder truck or roller feed measuring systems, and of course are at least two to three times as fast as the entry level machines. Drilling machines are usually set up before the sawing machines, which models were described previously.

Beam marking V704
Relatively speaking, beam marking is a new development. Voortman also offers a standalone beam marking machine which would be used in conjunction with older model drills or for increased capacity.

Marking on all four sides is possible with milling heads, offering full or partial contour marking which is still visible after shot blasting.

Beam cambering V2000 For those of us who have operated in the multi-storey steel framed structures arena, we know that beam cambering is an essential requirement to enable (pre-) cambering floor beams so that when all dead load has been applied the
(composite) concrete floor will be level.

I have seen many variations in the past of the basic concept of a horizontal hydraulic ram and two movable anvils with the settings for pre-cambering dimensions per beam size. These dimensions were totally dependent upon the hit or miss efforts in the past to create historical records of the settings required. Sadly of course these historical records were usually stored in the brains of the machine operators, and were lost on retirement or disappearance of the said operator.

Voortman has come up with two models (based on the capacity of the hydraulic ram) for 200 and 400 tons. But in this instance the historical records are replaced with a PLC control which has the option of a remote control. The machines have motor driven rolls for feeding the beams into the machines (no crane necessary – much lower handling costs).

Plate drilling and cutting
We previously looked at stand-alone plate cutting (V304) and drilling (V200) as well as a combined plate drilling and cutting (V320) machines. In the case of the latter machine the machine had one gantry with cutting in front of the girder and drilling at the back of the girder.

The ‘one-step-above’ machine with increased through-put capacity has two gantries with one for cutting (plasma and oxy fuel) and the second gantry for the drilling head. Optional extras include automatic plate handling with lifting magnets and marking by plasma or milling.

Punching and shearing 

There is a specialist model, the V505, for those fabricators who specialise in tower manufacturing which comes in two models – one for angles up to 160 x 160, and the second for angles up to 250 x 250. I am sure some of our designers could do wonders for their designs if these big angles were available in SA!

The machines have optional punching heads and or drilling heads (for those angles too thick to punch) with high speed carbide drills. Thread tapping and countersinking are available as well as a shearing head. The machines have automatic in-feeds and use feeder truck measuring systems. Numbering systems built in or stand alone are possible (V70).

The exciting new stuff

Flat and angle storage (V3100). No, this is not a machine, well I guess it is of sorts, but it is a great concept for storage and easy access of 6 metre lengths of flat bars and angles.

One of my earliest recollections of an accident at the fabrication works that I witnessed occurred when loading angle irons into a ‘Christmas tree-like’ storage rack system. Labourers were pushing small angles into the storage rack which had a series of arms to support the angles. One of the labourers was at the end of the angle pushing it in when the angle snagged and he thumped his stomach on the angle.

That is definitely not a danger in Voortman’s V3100 storage system.

It consists of a series (7) of bins each 6300 long x 2320 wide internally allowing for small piles of flats to be stacked next to each other. The draws are opened using electro motors and the flats are removed by electro magnets suspended from the cranes. What another great and simple concept idea.

In the last article I commented “there does not seem to be a one off machine “does it all” solution available from Voortman”. In fact, there is at least one that cuts holes and shapes in three dimensions.

It is euphemistically called…

Beam coping
Do you want one machine that is capable of cutting every 3D shape possible and put in the holing, prep for welding etc. into beams, angles, plates and other shape?

Well as long as your profile fits into a 500 x 1 250 mm range then you must have a close look at the Voortman V808 coping machine. The description coping really does not do justice to the machines capability.

This eight-axis, industrial robot with a plasma head will do the notches at the ends of floor beams; it will cut the beam to length; shape and put in all the holes (both holes for bolts and any other reasons), will mark using plasma for attachments and numbering. It comes with a roller feed measuring system.

What a fascinating machine to see in action!

The pièce de résistance
Yes, this most definitely is the future: Robots to do all the work of assemblers and welders.

Assembling and welding – The
Fabricator
Much to my disappointment I had to leave just when this machine of the future was about to be displayed.Just imagine it, a machine
1. which has an inbuilt shuttle and beam rotator;
2. that has a series of robots to handle plates up to 75 kg each;
3. hydraulic presses to position the plates accurately and three robots with welding heads that automatically feeds material in and out using an automated crane built into the system;
4. processes all four sides of a beam;
5. handles plates automatically;
6. tacks and fully welds and even automatically cleans the welding torch…

…and if that is not enough it can be integrated into a saw cutting, drilling, plate cutting, holing and any other Voortman machine you use or need to make a totally automatically assembler and welder of beams.

The thought is mind boggling; the fact is it is now a reality.

My wildest imagination and dreams have come true!

Cladding vs. the weather

By Dennis White, Director SAMCRA

Leaking pierce-fixed roofs following hailstorms Over this summer SAMCRA received a number of requests for assistance from
property owners whose mainly pierce-fixed roofs have leaked following hailstorms where fine hail has accumulated on the roof up to a depth of 40/50mm. On the Highveld this type of storm is not uncommon over a period of ten years or so. The root cause of
the leaks is that the hail reduces the water carrying capacity of the cladding thereby causing a buildup of water at the interface
between the melting hail and cladding which results in the development of a capillary siphon at the side-laps between adjacent sheets. The flatter the roof the more prevalent the leaks – a roof inclined at 10° has a drainage capacity 36% greater than one inclined at 5°.

The solution is to insert a butyl based sealer strip, preferably one with a reinforcing string, on the weather side of the fasteners along the entire length of the lap joint. In order to ensure the development of a continuous weatherproof seal we recommend that
stitching screws be installed, at no more than 600mm centres, between the fasteners anchoring the cladding to the supporting structure.

An area often overlooked is the top section of a curved roof which is effectively flat – the larger the radius the greater the extent of the ‘flat’ section. It is strongly recommended, as an absolute minimum, that a sealer strip be fitted in the side-laps from the crest to the point where the slope of the cladding is equal to the minimum slope for the respective profiles.

Weatherproofing of in-plane rooflights
SAMCRA also received enquiries pertaining to the weatherproofing of inplane rooflights and in particular those comprising polycarbonate material.

In-plane rooflights are those where the translucent material is made to the same profile as the roof cladding material and effectively replace a section of the cladding at the point where a rooflight is required as opposed to out-of-plane rooflights where the translucent component is fixed to a supporting frame, etc. which projects above the plane of the roof. In-plane rooflights are by far the preferred form of rooflight used in South Africa.

The most common in-plane rooflight configurations are:
• Chequer board
• Ridge to eaves
• Mid slope (a hybrid of chequerboard) and
• Ridge to eaves with portions of metal cladding at the ridge and eaves.

Whilst the chequerboard configuration is considered to provide the most even distribution of light it is the most difficult to weatherproof. A ridge to eaves configuration eliminates the problem of upslope metal to translucent lap joints but exposes the translucent cladding to the high wind loading at the eaves and to a lesser extent at the ridge. As translucent cladding is in the main non-trafficable the ridge to eaves configuration will inhibit access across a roof. Of the three configurations the mid slope is the most practical.

The two main factors that make it so difficult to weatherproof in-plane rooflights are differential thermal expansion and thickness of the translucent materials.

GRP (Glass Reinforced Plastic) and polycarbonate cladding have longitudinal coefficients of expansion of 2.5 and 5.6 six times respectively of that of steel. Surface temperature on a roof is considerably higher than ambient temperature. Surface temperatures of 60°C are common during the summer months. Heated through 60°C a 3.6m long metal sheet will expand 2.6mm
whereas a GRP sheet will expand 6.5mm and a polycarbonate sheet 14.6mm.

Assuming an operational range from 0° to 60°C and the cladding is installed at a temperature of 15°C the steel will expand/contract 1.9/0.6mm, the GRP 4.9/1.6mm and polycarbonate 10.9/3.6mm. The differential movement at the ends will be +1.5 –0.5mm for GRP and +4.5 –1.5mm for polycarbonate. GRP cladding will require a hole 3mm larger in diameter than the fastener and polycarbonate a 10mm slot. If the differential is not provided for, the translucent cladding will buckle between fasteners or may even crack. It is important to remember that the weatherproof seal on the underside of the metal washer of the primary fastener also has to accommodate this differential movement as does the sealer strip inserted in the end laps. With sealants transfers movement is directly related to thickness. A bead of sealant squashed to 2/3mm simply won’t cope. Based on this data we recommend that the lengths of GRP and polycarbonate profiled cladding be limited to 8.0m and 3.6m respectively.

Profiled translucent cladding is designed to fit over metal cladding, not under it.

This is the reason it is almost impossible to weatherproof a metal over translucent end lap. A more practical solution is to fix the translucent cladding over the metal cladding on all four sides and then back flash the upslope lap to the ridge.