# Calculation of the remaining period of use of your LIFTKET electric chain hoist

Blog Post | February 2022

The annual calculation & documentation of the remaining period of use of your LIFTKET electric chain hoist is extremely important. After the theoretical service life of your electric chain hoist has been reached, a general overhaul or replacement of the electric chain hoist is necessary. Other inspections must be carried out after 3 months or even daily. You can find out which inspections these are in the LIFTKET operating instructions under point 7.1.

To help you understand the calculation of the remaining period of use, we use the following example:

A LIFTEKT electric chain hoist, type 071/55, with an operating hours counter has been used for two years, 3 days a week for 4 hours each. The electric chain hoist works half of the time under full load (2h), a quarter with only ¼ load (1h) and the other quarter (1h) without load.

#### Calculation of the remaining useful lifetime

In the first step, the load collective factor **kmi **must be determined and calculated completely. For this purpose, a table (see fig. 1) is available in the inspection book of your electric chain hoist.

With the help of this table, the corresponding values can be read quite easily. The values for our example, i.e. at 50% full load and 25% ¼ load, are marked in yellow in the table. *Note: Lifts without load have no affect on theremaining period of use. For this reason, no load collective factor needs to be entered.*

For the final calculation of the kmi value, simply use the table provided (see Fig. 2), which you will also find in the inspection book of your electric chain hoist.

The next step is to determine the total consumed portion of the theoretical useful life in the determination period (Si). Usually, this determination period is always a whole year. However, this depends above all on the individual type of use of the electric chain hoist. For the determination, the kmi, the effective working time per day **(T)**, the working days and the surcharge factor are entered into the formula provided (Inspection book) (see Fig. 3).

You can determine the additional factor using the table, which you can also find in the inspection book. Since in our case the chain hoist has an operating hours counter, the additional factor = **1.1** (see Fig. 4).

Furthermore, it is necessary to determine the total consumed portion of the theoretical useful lifetime (S). To do this, the value just determined (Si) is added to the sum of all previous periods. In our example, another **346 **hours are added, because the electric chain hoist was used under the same conditions for the whole two years (see Fig. 5).

As the proportion of already used theoretical service lifetime (S) is now known, the remaining theoretical service lifetime can be determined now. To do this, we need to know the drive group of our chain hoist. In this example we use a LIFTKET electric chain hoist, type 071/55, which has a duty group of 2m. With the help of the table below, which can also be found in the inspection book, the theoretical service lifetime (D) can be read off quite simply. In our case this would be 1600 full load hours (h). (see Fig. 6)

Finally, the ratio of actual use (S) to theoretical use (D) must be calculated on the basis of the values determined. If this is **>=1**, your electric chain hoist must be checked again or even overhauled. You can calculate this ratio using the formula below (see Fig. 7).

In our case example, the ratio is less than **1**, so the chain hoist can still remain in use. The remaining usage time in hours would be 908h.

Of course, such a calculation always involves a little effort and care. We wouldn’t be LIFTKET if we hadn’t developed a solution for this long ago. With our STAR LIFTKET VFD, such a calculation no longer needs to be carried out. Because its integrated “Lifetime Display” makes it easy to read off the remaining period of use of the electric chain hoist, among other things.

If you have any questions regarding the calculation of the remaining period of use, please do not hesitate to contact our technical colleagues. Would you prefer the STAR LIFTKET VFD? Then simply contact our sales team. We will be happy to advise you.