As Featured in Glass Times - 03/18
Phil Brown, European regulatory marketing manager at Pilkington United Kingdom Limited, explains how a European Standard changes the best practice approach to specifying glass in lifts.
Glass lifts can create an eye-catching focal point in modern building designs. As well as providing a panoramic view, they must, of course, meet essential functional demands such as safety and loadbearing capability. A new British and European Standard sets out requirements for the use of glass in lifts and those in our industry supplying into this sector need to be aware of them.
A new standard
BS EN 81-20: 2014: Safety rules for the construction and installation of lifts – Lifts for the transport of persons and goods – Part 20: Passenger and goods passenger lifts specifies the rules for permanently installed new passenger or goods lifts, with traction, positive or hydraulic drive.
Although it was originally amended in 2015, several of the standards that BS EN 81-20 replaces were only withdrawn in August 2017. It defines safety rules that apply to lifts to safeguard people and objects against risk of accidents during use, maintenance and emergency operation.
Designing lifts for strength
There are requirements for landing doors on each floor and also lift-car doors with glass panels. The glass specified needs to have withstood soft and hard pendulum impacts at various striking points during testing. The key objective here is that no cracks should be recorded after pendulum impact.
The standard also advises that any exposed glass edges should be ground down in order not to cause injury.
A key requirement for lifts under the new standard is the ability to withstand loadings and limit both permanent and elastic deformation of the glass. It dictates that glass panels used in the lift well, car walls and doors must be made of laminated glass, which typically comprises of two panes of glass that are bonded together with polyvinylbutyral (PVB) interlayer under heat and pressure. Should the glass break, then the interlayer tends to hold the pieces together. If suitably constructed, laminated glass can be designed to withstand bullet or blast resistance as well as repeated blows from heavy objects.
The method of breakage and, in particular its resistance to penetration breakage, makes laminated glass the obvious choice for protecting people in glass lifts.
Avoiding extra tests
For lift car walls made wholly or partly of glass, physical tests aren’t necessary if they meet the 'deemed-to-satisfy' conditions of the standard. These conditions apply to flat glass panels framed on all sides. The thickness of the glass used has to increase as the panel’s length and breadth increases. For a laminated toughened glass panel, in which both panes are toughened glass, the minimum thickness is 8.8 mm if its inscribed circle does not exceed 1 metre in diameter. For the same panel of laminated annealed glass, however, the minimum thickness is 10.8 mm. Thicker glass is required to satisfy the same conditions for larger panels.
Additionally, car walls with glass less than 1,100 mm from the floor require the installation of a handrail, which must be fixed independently from the glass at a height between 900 mm and 1,100 mm.
Installers should always provide clients with certificates and test reports for the glass, where applicable, in technical compliance documentation. Glass also needs to be marked in accordance with the standard, i.e. the type of product used and its thickness and configuration, with the name of the supplier and their trademark.
The standard isn’t overly complex and shouldn’t lead barriers in the use of glass lifts. By understanding the requirements for compliance, architects, specifiers and installers can be confident in designing and delivering glass lifts.