Often not given consideration required during the selection process and sometimes even ignored, but can have, and it must be said not immediate consequences but future possible serious problems. So to make the correct choice of material from which your Nexus anchor produced will overcome any future areas of concern.
If we consider that anchors in the main will be used either, internally or, externally, this way the process of understanding the environment and its effects on the installed fixing can be better understood and therefore the material and or plating from which the final fixing can be produced determined to deal with the local conditions.
External applications will more often than not require the use of perhaps stainless steel. If you are unsure about levels of pollution in certain areas, date concerning relating to this can be obtained from organizations such as the World Bank.
The table to the right issued in 1998 records pollution levels in various locations around the world and indicates the extent of pollution in the respective city.
Again the locations where a product will be used can be further defined as Rural, Urban, and Industrial.
| CITY | Suspended Particulate ug/m3 | Sulfar Dioxide ug/m3 |
|---|---|---|
| Beijing | 377 | 90 |
| Calcutta | 375 | 49 |
| Helsinki | 40 | 4 |
| Los Angeles | 46 | 9 |
| Moscow | 100 | 109 |
| New York | 23 | 26 |
| Paris | 14 | 14 |
| Rio de Janerio | 139 | 129 |
| Sydney | 54 | 28 |
| Tokyo | 49 | 18 |
| Toronto | 36 | 17 |
Rural or suburban areas will normally have low population with light industry that does not produce high levels of corrosion. However, the prevailing winds may alter this and should be considered when making a specification.
Urban areas that include residential, commercial and light industry with low levels of traffic, producing some pollution. The levels of pollution can increase due to no pollution controls being present or local conditions being such that they create the environment for corrosion to take place.
Typical results of high levels of corrosion found in industrial areas are sulphur and nitrogen oxide found in chemical and processing plants. Air bound soot from fuel or iron oxides are also typical of highly polluted atmospheres in areas were no controls are in place to combat the problem and therefore worsen the situation.
Further corrosion of architectural and structural metals including some stainless steels can be found in areas with little or no air pollution controls.
Rural or suburban areas will normally have low population with light industry that does not produce high levels of corrosion. However, the prevailing winds may alter this and should be considered when making a specification.
Urban areas that include residential, commercial and light industry with low levels of traffic, producing some pollution. The levels of pollution can increase due to no pollution controls being present or local conditions being such that they create the environment for corrosion to take place.
Typical results of high levels of corrosion found in industrial areas are sulphur and nitrogen oxide found in chemical and processing plants. Air bound soot from fuel or iron oxides are also typical of highly polluted atmospheres in areas were no controls are in place to combat the problem and therefore worsen the situation.
Further corrosion of architectural and structural metals including some stainless steels can be found in areas with little or no air pollution controls.
With modern building design, considerations of how suitable preventional measures may be taken early on in the design process to combat fires if, and when they take place, can and does have a major influence in selecting the correct materials that will prevent either the onslaught or stop completely the spread of fires.
It must however be said that at the moment there are no regulations that govern the design of either fixings and anchors in situations where fire may occur. A major influence in understanding the requirement is not just how does the product behave in its own right in a fire? But, rather how does the attachment and the anchor or fixing perform together when tested in a fire.
In general, all fire tests that have been conducted have been done mainly into concrete, whereas there are a vast number of fixings that have been and will be installed into either masonry, stone and not forget panel materials such as plasterboard.
One of many solutions is to apply one of a numerous number of coatings that can be applied to the fixing or anchor, which at the same time is being applied to the attachment. The type and coating thickness will also effect the overall performance of the whole application and therefore should be considered in its own right. It may be possible that with the suitable protective coating that the application may last for as much as 30 times longer. As a guide the protective material must be applied to the area against which the attachment will sit, equivalent to that of 2 times the fixing embedment depth in the substrate. In addition, there are currently at the moment no common procedures for testing anchors and fixings in fire situations. Therefore, in most areas
unless the application is repetitive to such an extent that a high number of the applications are the same, and unless a test from a commercial point of view is deemed to be economical. Fire tests on a whole have been carried out in isolation.
The real bench mark for fire is at 500 C where the steel yield strength is reduced by half and at slightly higher temperatures, the tread of the anchor will fail before the anchor actually fails. Bearing in mind that not only the steel is affected by the temperature, but also that of the concrete, both compressive and tensile strengths may again be reduced by as much as half. It should also be bourn in mind that in an application the applied load may be not only in tension but also shear or a combination of both forces. Therefore, once again the problem in a given fire situation is very difficult to establish without the need of a specific test for a specific situation.
By selecting a suitable stainless steel the overall performance compared to a carbon steel may be twice as high. In the past resin anchors have been considered to be unsuitable for fire rated applications. However, testing has shown that the performance is only slightly reduced. As already discussed the nut may well fail (temp. Causes thread striping) before the anchor.
In each case, either the local or national standards that relate to fired and prevention must be observed.