Lift system calculations in EN 81-50

Nick Mellor

Thursday 25th September 2014

Lift engineers responsible for the design of lift systems conforming to EN 81-1 should be conversant with the equations for guide rails, rope traction and rope factor of safety in that standard. The new EN 81-20 references EN 81-50 which now includes such equations, with some minor changes, and some additional helpful guidance. Despite the apparent complexity of these equations, making calculations need not be a daunting prospect. The use of manual or spreadsheet methods are valuable in gaining an engineering appreciation for these calculations. Such an appreciation is important in interpreting the results obtained from software packages and might not be gained simply by “plugging in” numbers. The use of such software packages (which might not be infallible or which might incorporate assumptions not clear to the user) should be subject to verification; one method is comparison with manual calculations. This paper looks at the main changes in the calculations for guide rails, rope traction and rope factor of safety and through examples provides a means to assess the implications of these changes. The paper also reflects on some underlying assumptions in these equations and some engineering implications from their use. Implications for conformity with the new standards will be touched-on. Future directions for the development of the standards will be mentioned.

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