Rajasekaran,
Preventive Maintenance Duration was not computed by SAP standard reports. for this reason, one of the very first Infoset Queries I made was this.
See this report (I named it as ZIW28)
For this computation (Prev Mnt Dur) I used a FM (in the Infoset code section) as shown below
You can develop this report with VIQMEL and CRHD tables (join CRHD-ARBPL to VIQMEL-OBJID) . CRHD table in case you need Work Center field. Otherwise only VIQMEL table will do it.
Jogeswara Rao K