Monthly Archives: March 2015

Miniature-scale fire testing aims to lower product development costs

tests

A new means of small-scale fire testing may yield significant benefits for companies that develop new products, as it will enable them to perform multiple tests in a single development cycle. First, however, it is up to DBI to crack the code and pinpoint a well-defined correlation between results derived from small-scale and full-scale testing.

Full-scale fire testing is both time-consuming and costly. As a new tool, DBI is therefore underway in developing a new means of miniature-scale fire resistance testing, which will hopefully lay the groundwork for an effective and less costly method of fire-testing components used in construction, shipbuilding and other industries.

Initially, miniature-scale fire testing may prove helpful to innovative companies that develop new products. If DBI can uncover the key to ‘translating’ such test results to full-scale testing, the faster and much cheaper method may, among other things, indicate whether the development project is on the right track.

– A miniature test will most likely be carried out in just a few hours, which would make it feasible to test several product types at once. It is our goal to be able to use results obtained through small-scale testing as we would those obtained from full-scale testing. This would constitute a significant advantage in connection with development work and when planning the final, full-scale approval test, says DBI civil engineer Trine Dalsgaard Jensen, who continues:

– Valid results from miniature-scale fire testing will give manufacturers greater flexibility in their development work, as testing costs will be considerably lower. For example, manufacturers would be able to test various wall thicknesses to find the optimal dimensions, which would otherwise be far too costly with full-scale testing.

Testing in miniature furnaces
The hypothesis behind the new development project is that several fire safety parameters are the same in small and large-scale testing environments – or, at the very least, that there is a documented correlation between the two.

To test this hypothesis, DBI is working with a miniature furnace in which the test pieces measure just 25 x 25 cm. The initial attempts at controlling the furnace’s temperature, output and oxygen content precisely enough to carry out a test that can be repeated, has yielded promising results. The same is true of tests conducted using mid-sized pieces of 1.5 x 1.5 metres.

The next step in the project is to determine whether small and medium-scale fire resistance testing yields results that are comparable to those obtained from full-scale testing methods. By doing so, DBI will learn more about how to compare results from fire tests carried out in different scales, increase testing reliability and minimise the uncertainty of small-scale testing.

– Over time, I believe we’ll see a sharp reduction in the overall number of full-scale tests. Instead, manufacturers will test materials in miniature scale and use the results as input for a computer model of the complete product, which can then be used as official documentation. As a result, full-scale testing will then be used for model validation. If it works, we’re talking about a whole new generation of fire testing. For this to happen, though, the method must ultimately be incorporated into European testing standards, explains Jensen, who emphasises that this type of small-scale testing is still years away from being adopted.

Comprehensive full-scale testing
Currently, full-scale fire testing is the preferred method and involves mounting pieces such as doors, windows or panels in large test furnaces. The test piece is then subjected to a well-defined ‘fire’ that follows a standardised testing curve. Meanwhile, the piece is observed at a series of temperature points in order to determine whether it is capable of withstanding the fire for the required period of time.

Temperature curves and methods are established in European standards and, as mentioned above, this means of conducting fire tests can be a costly affair. It often takes several days just to set up a testing environment, and one or more test pieces are destroyed throughout the process.

Furthermore, the results of a full-scale test are only valid for the specific product, which means there are limited options in terms of variation. For example, a fire door manufacturer that wishes to sell several variations of the same product type must therefore conduct several such fire tests.

Significant challenges
There are still a number of considerable challenges in this area. Among other things, it is important to understand what testing in multiple scales means for edge effects, mechanical reactions and similar variables.

For example, how does one go about ‘translating’ the formation of cracks in a gypsum board from one scale to another? Does the formation of a tiny crack during a miniature-scale test become larger, smaller or identical during a full-scale test?

DBI currently has test furnaces in three different sizes: two full-scale furnaces for 3 x 3 metre pieces, one model furnace for 1.5 x 1.5 metre pieces and a new miniature furnace for 25 x 25 cm pieces. The model furnace has been used for years in mid-scale testing – but always with reservations with respect to the correlation of the results with full-scale tests.

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DBI’s development project…
Is being carried out as part of the research and development project, ‘MAT – Risk Assessment of New Materials,’ which is co-financed by The Danish Council for Technology and Innovation. The development project is a classic example DBI’s efforts as a GTS institute to strengthen the innovative force and competitiveness of small and medium-sized companies.

NEW GUIDELINES EMERGENCY EXIT DOORS IN NON RESIDENTIAL PREMISIS

GuidelineSecurityNew

It is natural to assume that it might be impossible to overcome the conflict between providing an easy and rapid means of escape in an emergency and the prevention of intrusion by criminals. Consequently, it is common for compromises to be made that seriously undermine security.  Obviously, life safety interests are of the highest importance but, as this guide explains, safe escape and security can be brought into balance with informed planning and knowledge of suitable methods and security products. You find the Guideline here.

Both opportunities and challenges exist in scaled fire tests

Martin Sørensen IDA

Fire tests in e.g. scale 1:5 for can certainly tell us a lot about the tested structures, but there are also differences in relation to full scale tests. This was shown at a technical meeting at IDA Brandteknik (The Danish Society of Engineers, Fire Engineering) in October 2014.

Yet another small piece of the large puzzle known as scaling down of fire tests was described at a meeting of IDA Brandteknik in Copenhagen on October 7, 2014.

Here, civil engineer Martin Sørensen from If P&C Insurance told about his Master’s thesis from the Technical University of Denmark on scaled experiments with sandwich panels. The thesis was completed in cooperation with the insurance company that has great interest in more knowledge about whether scaled down experiments can provide results which can be used in connection with insurance work.

Several fires where sandwich panels with combustible insulation were involved have formed the background of the project. The fires cost If a large amount, and the company therefore decided to examine the fire properties of the sandwich panels in more detail.

– My project is only a small part of the effort. I am building upon a series of full-scale experiments with sandwich panels to see if one can achieve the same results with scaled down fire tests, said Martin Sørensen at the meeting.

Save on costly full-scale tests
The interest in scaled tests is due to the fact that full-scale tests require large test facilities and are expensive to conduct. If the same results can be achieved through significantly smaller tests, then there will be a lot of money to be saved.

And the principle of scaled fire tests is simple. By making everything smaller, both the structures that are to be tested, as well as the fire effect, the temperature sequence and the development of the fire ought in principle to be the same as with a full-scale test in principle. In practice, however, this is not the case in all areas, as Martin Sørensen’s project shows.

The full-scale tests were performed in compliance with the ISO 13784-1 standard Reaction-to-fire tests for sandwich panel building systems, which affects a constructed room of panels with 100 kW for 10 min., 300 kW for 10 min. and 0 kW (burner off) for 10 minutes. However, the standard was extended by the following three “additions” in order to get closer to the situation in reality:

  • The tested structures were built by craftsmen and not by fire technicians.
  • After the first 20 minutes, the output was increased to 600 kW per minute in order to correspond better to the heavy fire load which is often found in companies.
  • The panels were given various major and minor damages to assess the significance of these.

The scaled-down tests were conducted in a corresponding room built up of panels one-fifth of the length and width. Tests were conducted with two types of panels with rock wool and PIR insulation (polyisocyanurate) respectively, which isolates significantly better than rock wool, but is a combustible cellular plastic. In both cases, the insulation was enclosed between two steel plates.

– The 1:5 scaling-down of the test room did not, however, include the thickness of the panels, which is 100 mm. It has a significant influence on the results, says Martin Sørensen.

The gas burner was also physical scaled down to 1:5, but the fire affect must be significantly reduced if it is to correspond to the full-scale experiments. In fact, the effect must only be 1.8 kW in the first period, 5.4 kW in the second period and 10.7 kW in the last period, instead of 100 kW, 300 kW and 600 kW. Nor are the periods 10 minutes long in the scaled experiments, but 4.5 minutes. The measurements included temperature and loss of mass.

Both similarities and differences
- The results clearly show that the thickness of the panels is important for the results in the scaled experiments. The panels absorb more of the heat, so the temperature increases more slowly. However, the final temperature is about the same, said Martin Sørensen.

At the same time, the scaled experiments confirmed a result from the full-scale experiments, which showed that minor damages to the panels such as screw holes do not have a significant impact in the event of fire. The loss of mass of the panels does not increase when the panels have minor damages, so the insulation does not contribute additionally to the fire. This consistency between large and small scales can perhaps pave the way for scaled experiments to assess damaged panels and any repairs.

– However, here it is important to emphasize that the influence of minor damages may not be as significant in relation to the total size of the fire, but on the contrary very important in relation to how a fire can occur, and how quickly it can develop, said Martin Sørensen.

He ended his presentation by concluding that, in general, there is good consistency between full-scale experiments and scaled experiments with regards fire development and temperatures in the room, but that there are differences when it comes to the temperature development in the core of the panel and heat transfer through the panel. In this way, heating­inertia does not follow the scaling.

Scaled tests are good with development work
Fire safety adviser Anders Dragsted from DBI found the presentation interesting, in the light of the fact that DBI also works with scaling fire tests.

– Scaling is an interesting possibility, which we would like to find out how we can use. For example, it would be a good idea to use scaled tests in connection with development work so that our customers can find out if their ideas work before they invest in a full-scale test for approval, he says.

DBI is currently investigating the possibilities for scaling in the project ‘MAT – risk assessment of new materials’.

Memorandum of Understanding

MoUCFPA Europe is proud to announce that two Memorandums of Understanding have been signed: one with the Federation of the European Union Fire Officer Associations (FEU) and another one with the International Association of Fire and Rescue Services (CTIF).

Both documents state that there is a common mission of advancing fire related issues through the exchange of experience and information and the intention to work together to jointly promote the adoption of global best practices in the areas of fire prevention and all-hazards response and mitigation and related fire and life safety initiatives and services. Whenever possible, the respective presidents and executive directors / secretaries attend and actively participate in each organization’s conferences and meetings and to cooperatively advance the goals and objectives of each organization through jointly agreed upon projects and programs.