In short , for Pm the BOM is used for the tracking of spare parts.
The main functionality of BOM is to get the list of spare parts at the time of creation of maintenance order so that you can save your extra time for searching the proper spare part and its required quant.
There are three types of BOM
Function location BOM
you can also create maintenance assembly or IBU assembly. That is not presented physically in the plant but you can assign them to BOM as non stock item.
BOM is nothing but the spare wise division of the equipment .As naveen specified we can use BOM to save our time in searching spares while creating order .
Also we can use Assembly .the difference between assembly and BOM is that for Assembly we don not maintain stock .they are mainly used to represent the equipment graphically .
Also against a specific assembly we can create order but against BOM we cann't .
Hope this wil help
Thanks for your valuable replies, from this it is very clear what BOM is used for in PM, now the other question comes to my mind is, they say that:
"Bills of material are used to describe the structure of a technical object and to allocate spare parts for maintenance purposes."
can anyone explain me how Bills of Material are used to allocate spare parts for maintenance purposes?
Thanks once again
Go to IB01, create BoM for equipment.
Now go to IW31, create one Maintenance Order for same equipment. Go to components tab. There in the bottom, you should find List button. Click that, it will list the components which are allocated to Equipment in BoM. If you select any component, that will be filled up in the order with assigned qty.