In Jboss 7 session timeout is not working as expected.

Hi ,

We are recently migrated from jboss5 to jboss7.
We have the session timeout configuration of 15 minutes configured.
But the session timeout is not working and the session are being live for unlimited times.
As these sessions are not getting timed out, session objects are filling out the Heap memory.
Can you please let us know why these session objects are not getting timed out.
I am attaching the xml file which we are using it.

Regards
Suresh