Testing stuff

Heath Robinson's rope test
Heath Robinson’s rope test

Got a week of testing coming up next week in Scotland, which I’m looking forwards to, good crew to spend time with, in the Highlands, which is always beautiful – and let’s not talk about the weather forecast. I’ll be writing about it on the blog as we progress…

Thinking about this got me pondering testing.

Testing implies something that is complex and somehow mysterious. It’s not – or at least it needn’t be. As a kid I loved Heath Robinson’s drawings (see above) – still do, come to that – where he would develop a solution to a seemingly easy task by means of some ridiculously complex contraption held together by bits of string, nails and springs (I suppose the modern-day equivalent to that would be zip-ties and Duck tape). This is one way to do you testing, but there is a different approach, which – as in any systems design – is to keep it as simple as possible.

First off you want to decide what you want to find out about: maybe it was a question that came up during a lunch break and that lead to a heated debate. One way to resolve this is to define a test set- up and to run some tests. An example? One year I finished off a presentation with a slide with a picture of a compact steel karabiner choked onto a lanyard. The discussion that year had been on configuration of connectors and one of the summaries was a suggestion or a question whether it might be an idea to use a compact steel connector in certain applications. Thinking about this, observing my own use of karabiners and discussing it with Chris raised further questions, so we decided to do some testing on choked karabiners.

We defined a test methodology, met in our yard on a Saturday, set up and got going… The test set-up involved a mechanical advantage system, three steel drums of different diameters to simulate a range of branch diameters, a load cell and a Dyneema line.

Test set-up
Test set-up

We defined a three minute 15kN pull on three different diameters of “branch” and documented each sample. This resulted either in a pass or fail. The summary was that all karabiners struggled on the small diameter, with one complete failure (karabiner broke), whilst on the larger diameters, the shorter the karabiner, the better it handled this unusual loading – unusual in the sense that the connectors are not designed for this. No manufacturer would ok this kind of loading, the design merely foresees loads along major and minor axis and with the gate open. Still, we felt this was a configuration used fairly frequently in tree care and we weren’t able to find any answers to our questions, so by doing this testing we improved our knowledge – and were actually able to back up a gut feeling with facts.

The other testing I mentioned in a post a while ago was the continuous long descents testing. For this we went to the Musical Theatre here in Basel, as that offered a height of 20m plus, sufficient to do the testing in. Next problem was measuring the descent speed, 1, 2 and 3m/second. The way we sorted this was by building a rig consisting of a wooden base that we could load with weights and a small 20″ kid’s bike wheel with a speedometer on it. The line ran round this and gave us the speed km/ h speed that we converted into m/ sec. Obviously not super-accurate, but good enough to get the descent speeds roughly right.

Not brilliant quality image, sorry about that, lighting left something to be desired… still, gets the point across. Actually looks quite Heath Robinson-ish, come to think of it.

The point I’m getting to here is that if you have a question about a technical issue, go beyond a web search on Wikipedia, Youtube and the forums, get together with some friends, work out a replicable test methodology and go for it. Don’t let yourself be intimidated, testing is not something reserved for boffins in labs in white coats, it can be hands-on, exciting and can expand your comprehension of tools and systems you are working with.

It doesn’t even have to look very sexy, as long as it does the trick! Just look at the Russian space program – basically tractors sitting atop big rockets, but they get the job done.

We Are Arborists

Fantastic videos by Florim Ajda, we were treated to a sneak preview of the whole thing today after Climbers’ Forum set up in Augsburg… Florim manages to capture a lot of the soul and spirit of what it means to work in trees – and of the people who do so.

Thank you for your hard work, Florim.

Certification of PPE

This is a huge topic and I would never claim to understand all details and aspects, however I would like to highlight one specific angle that we have discussed over the years.

In Europe, the placing of Personal Protective Equipment (PPE) of class three on the market is regulated by directive  89/686/EEC, the PPE directive. This is a very comprehensive piece of legislation that defines parameters for the manufacturing, quality control and  certification, but also basic ergonomic and health and safety requirements that manufactures have to consider when designing and producing equipment. The compliance with this directive is indicated by the CE mark on the product and the declaration of conformity in the technical manual. Further central elements of the directive are traceability during the manufacturing process and third party testing, whereby the manufacturer has a notified body verify type certification, quality assurance – and ultimately compliance with the directive. The notified body is indicated on the technical label by the four digit number behind the CE sign. 

Example for a manufacturer standard product marking
Example for a manufacturer standard product marking

One of the reasons for this post is to share a drawing I made last year for a presentation Chris and I made last year at the Climbers’ Forum at the Tree Care days in Augsburg. This asked the question whether certification ensures that a product is fit to perform the foreseen purpose. The image depicts the two routes that can be followed to achieve conformity:

Often as not, manufacturers will certify according to existing EN standards. These define the scope, the pre-conditioning of samples, test parameters and set up of testing. This is all very well for a product that fits one of these boxes, such as a pulley, a sling or a karabiner. This first route is indicated by the top path in the drawing: pre-defined EN standard hurdles that a device must successfully pass to achieve conformity with the directive. 

Certified = fit for purpose?
Certified = fit for purpose?

However, for a piece of equipment that doesn’t fit one of the standards, that is innovative, new, or just plain different, things may be a bit less straightforward  One route a manufacturer  then may choose to follow is simply to look for a standard which they know their device will pass and to certify according to this. This is true to the letter of the PPE directive, but in my eyes not to the spirit.

For cases like this there is a different route a manufacturer can choose to take by writing a manufacturer standard. In this case, you define your own criteria for testing. This is indicated in the drawing by the lower route, the adventure obstacle course. The obstacles are set by the manufacturer, but critically, both routes lead to conformity to the PPE directive. In my eyes this is the more honest route to take: by doing so the foreseen use can be more clearly  indicated to the end user and the testing corresponds more accurately with the purpose the device was designed for, rather than just ticking boxes of a standard that has very little to do with the actual use of the piece of equipment.

If the manufacturer decides to take the lower route and to create a manufacturer standard the conformity will be indicated on the device and in the technical manual, however there will be no EN standards indicated, for obvious reasons. The manufacturer does however need to supply the end user with information in regards to how the testing was done, so that the end user can in turn decide, based on his or her risk assessment whether the testing corresponds with the intended use.

So ultimately the prime target is to achieve conformity with the PPE directive. To do so there are two routes: the EN standard route or the manufacturer standard route, both are equally valid. In a sense the EN standards are nothing other than a form of shorthand, interchangeable modules used to express requirements.

The final point that the drawing makes is that certification is in itself not guarantee that a device is fit for purpose. The fit for purpose party tent may be just behind the conformity finishing line, in which case things are fairly straight forward. However, there may be a bit of a walk between the finishing line and the tent. In this case the end user needs to identify this and to take extra measures to ensure that the device is not only certified but is also fit for the intended purpose.

In my opinion the whole certification process should be viewed like a dialogue between the designer and manufacturer of a piece of PPE and the end user. The designer/ manufacturer uses this process to ensure they have done their due diligence and to explain the rationale behind the device. The end user aims to understand this thought process and to use the device in the way intended. In this respect the declaration of conformity is a legal agreement between the manufacturer and the end user, whereby both parties agree to obligations and responsibilities.

This may all sound a little dry and theoretical, but it does have very real implications for a person working a height. In this respect I would encourage you to meet up with manufacturers whose equipment you use, to discuss issues with them and to get a feeling of what the ideas and concepts behind the devices are. One great occasion to do so is at the Tree Care Days in Augsburg, beginning of May, as there are many brands and manufacturers represented there at the trade show…