PFS Calculator

Calculation of the useful life of lifting equipment: PFS and % SWP

This website is designed especially for those who want to quickly and easily understand how to calculate the safe working capacity (SWP) of a crane, without needing to be an expert in technical terms. Here we will briefly explain what you need to know in a clear and accessible way.

In our work environment, cranes play a crucial role in construction and moving heavy loads. However, it is essential to understand safe life limits to avoid costly accidents and damage.

The calculator is a simulator to be able to see as an example how the value varies according to the data entered, and should not be used as a certified tool. The results obtained may not correspond to reality, contact us if you have any doubts or if you wish to have a more exact calculation.

Calculation of useful life during inspections: As indicated by the different standards ISO 12482:2014, FEM 9755 and its counterpart UNE 58919:1995, it is necessary to calculate the period of safe operation during inspections. We quote literally: “Many elements of the kinematic chain of a standard lifting device are not visible and therefore cannot be regularly checked during the prescribed checks. Therefore, it may not be possible to detect a break or an incipient fault.

Over time, when the theoretical potential of use, for which the mechanism has been sized, has been achieved, a danger may appear with increasing probability.

Thus, the theoretical utilization potential, in hours of life for which the machine has been designed, makes it possible to determine, by comparing it with the actual demands of the device in hours, the Safe Operating Periods (PFS) for each lifting mechanism of the machine. crane.

When the theoretical service usage is reached or exceeded, a general inspection must be carried out to continue using the appliance or it must be replaced with a new one. This general review must be carried out no later than 10 years from the first commissioning of the crane and subsequently, a maximum of 10 years after each general review.

The manufacturer or the company performing the overhaul must determine the theoretical utilization value and the new deadline for the next overhaul. During maintenance, only original parts or parts specifically admitted in writing by the crane manufacturer will be used.

The period of safe operation can be indicated in two ways:

  • According to the ISO standard: where the percentage of remaining useful life is indicated, the initial value being 100%, and the final value being 0%.
% SWP = (
D – S / D
) x 100
  • According to UNE 58919:1995 as a relative indicator hours of use/hours of design, where the PFS index refers to the life consumed.
S / D

When the theoretical service utilization D is reached or exceeded, that is, when S/D ≥ 1 or %SWP is 0, it must be dismantled and a general inspection carried out in order to continue using the device.

Where D are the design hours of the equipment according to the manufacturer and the FEM standard, and S are the estimated loads of the crane accumulated during its entire time of use.

The calculation of S must be calculated from commissioning, and must be calculated by accumulating the S value of the last service with that of the current interval using the previous crane log books. If it does not exist, S must be calculated from the beginning.

Links of interest for more information:

Simulador %SWP y PFS

Step 1: Technic Features

Step 2: Calculate the motor operating hours (running hours) per inspection in inverval

Step 3: Calculate the load spectrum factor per inspection inverval

Load % Lifting time %
100 %
80 %
60 %
40 %
20 %

X Ti Kmi Si

% SWP entre intervenciones: % | PFS entre intervenciones:

%SWP total= %SWP entre intervenciones - %SWP anterior

%SWP total: % | PFS total:

Se ha agotado la vida útil de tu equipo.

La vida útil de tu equipo se está agotando.

Tu equipo dispone de buena vida útil.