High performance elevator shaft fire doors.
Passive fire protection for lifts – Microtherm® insulation for lift doors.
The design of any building to effectively contain a serious fire and its effects is one of the most technically complex challenges of fire protection. When a fire starts in a high rise building the challenge is not simply confinement to a room or small area, but also prevention of the spread of the fire and its effects between floors. Elevators are natural chimneys so the provision of fire stopping elevator shaft access doors is an obvious priority.
The overriding objective is the safe evacuation of any occupants of the building.
A fire is a chemical reaction of a fuel source with oxygen accompanied by the creation of heat, flame, and smoke. In fire protection, all three of these need to be guarded against. The testing of fire rated products for buildings such as doors, reflects these needs and follows the same general principles all around the world. The product to be tested is first clamped onto a special furnace and then exposed to a controlled fire for a predetermined period of time. Performance is assessed against a standard for both the insulation performance – the thermal resistance against the transfer of heat from the exposed side to the unexposed side, and also the integrity – the ability to stay whole and functional and block the passage of smoke and flame. Based on these criteria, a successfully tested product will be granted a rating such as A60 which indicates to an architect or fire officer that it is suitable for use as a 60 minute rated component of an overall fire / evacuation strategy for a building.
Infra-red photo of lift doors during fire test at the Microtherm in-house fire test facility.
Performance testing is normally carried out at approved test centres that are recognised by the Classification Societies. Microtherm operates an in-house test facility in their specialised test laboratory at their HQ in Sint-Niklaas in Belgium. A brochure outlining capabilities is available in the Downloads section of this web site.
The category of fire for most building fires is defined as "A" class, sometimes known as a cellulosic fire. The test furnace will be controlled to match the known profile of this fire, monitoring the relationship of temperature with elapsed time. Temperature increase at the start of the fire is rapid – over 540 °C (1000 °F) in less than 5 minutes. To put this in perspective, aluminium melts around 660 °C (1220 °F) which is reached in under 10 minutes. After one hour the temperature is up around 945 °C (over 1700 °F) and exposed steel is glowing red hot.
In the European countries, performance testing of lift shaft access fire doors has been mainly to European Standards DIN EN 1363-1 and DIN EN 1364-1 which cover fire resistance testing of non-load bearing building elements. The testing also conforms to the EN 81-58:2003 Standard which is the current European regulation, published in January 2004. This specifies the method of test for determining the fire resistance of elevator landing doors which may be exposed to a fire from the landing side in accordance with the Lift Directive 95/16 EU. This method has been designed to measure the Integrity and, if required, full thermal insulation performance of the elevator landing doors. The insulation component of the door controls the temperature of the unexposed face of the door to within prescribed limits. Quite obviously, the longer the insulation performance requirement, the thicker the door becomes unless an extremely efficient thermal insulation layer is incorporated.
In America and Canada any fire performance testing may also include the application of a specified standard fire hose stream after the final stages of the fire exposure in accordance with Practice E2226. This is an additional test of the integrity of a door under conditions created to simulate an actual building fire.
Designing large, multi-leaf elevator shaft landing access doors with fire ratings up to 2 hours is very difficult. Architects are constantly striving to reduce door thicknesses to make them as light and slimline as possible. The challenge arises because of the multiple layers necessary in the design to fully meet the structural and also the fire barrier requirements. To keep a door as slim as possible, the best possible thermal insulation material must be used.
The design must allow for the large expansion of the exposed face of the door, and the resultant bow that occurs when the unexposed face remains at just slightly higher than ambient temperatures. This flexing of the door during exposure to fire means that rigid insulation materials such as calcium silicate board are unable to cope with the distortion from a fire. They fracture and create a weakness in the insulation protection through which heat will escape.
The most efficient thermal insulation for passive fire protection applications is a microporous insulation such as Microtherm®. Microtherm® is a lightweight material made from “nano technology” sized particles. It is 90% air. However, the air is contained in minute pockets which are smaller in size than the mean free path of an air molecule which effectively eliminates heat transfer by gaseous conduction.
Microtherm® out performs conventional insulation materials by a factor of at least 3 or 4 at high temperatures, even as high as
1200 °C (2192 °F). It contains a fine particle opacifier material that enables it to block the movement of infra red radiation almost completely.
This material structure effectively minimises all the forms of heat transfer to a level that is close to the lowest theoretically possible and helps to make a microporous insulation a more efficient thermal barrier even than still air over its full working temperature range.
Microtherm® Slim&Light panel
In order to be effective, any insulation should ideally be fitted as a complete sheet to match the door size. Partial sheets of insulation need to be fitted with overlapping joints to cater for expansion movement of door components. This in turn increases both thickness and weight. By making the insulation panel large enough to cover the full area of a door leaf it is possible to achieve long duration fire protection with just a single layer.
The thermal efficiency achieved using Microtherm® microporous insulation, together with the simplified design possible from full size Microtherm® Slim&Light panels, has enabled full two hour fire protection to be possible from doors as thin as 25mm overall.
Most lift access doors are sliding doors but using Microtherm® Slim&Light panels, an Italian customer has recently achieved a rating of EI 120 on one and two panel swing doors after testing to EN 81-58:2003, the standard fire resistance test for lift landing doors. This rating confirms compliance for a full two hours on the integrity and the insulation performance of the door systems.
For passive fire protection solutions Microtherm has the answer.