You might notice that sometimes the Welcome page is presented for you to sign in again, even though you did not sign out. This is a security measure.
The system automatically signs you out when there is no on-screen activity for a specified period of time. This reduces the risk, for example, of someone requisitioning materials from your PC, under your sign-in name, while you are away from your desk.
The default automatic sign-out period is 30 minutes. The period of inactivity before automatic sign-out can be revised by your system administrator.