Disable Windows Server 2012 automatic log off

I have been searching for a while, but I don't find a solution for this anywhere... I'm in a factory and they have Windows Server 2012 with an HMI (HumanMachineInterface) on it. They have computers that they can log on the server to access the HMI. However every 15 minutes they are logged off of their session automatically. This is really annoying because they have to do it 50 times a day.

How can I disable that feature?

Quoting from Technet:

To specify timeout and reconnection settings for a remote session:

On the RD Session Host server, open Remote Desktop Session Host Configuration. To open Remote Desktop Session Host Configuration, click Start, point to Administrative Tools, point to Remote Desktop Services, and then click Remote Desktop Session Host Configuration.

Under Connections, right-click the name of the connection, and then click Properties.

In the Properties dialog box for the connection, on the Sessions tab, select the following options as necessary:

Select the Override user settings check box, and then set timeout settings for End a disconnected session, Active session limit, and Idle session limit.

Select the Override user settings check box, and then select one of the following reconnection settings: Disconnect from session or End session.

Click OK.

Changes to timeout and reconnection settings are not applied to sessions that are connected when the change is made. The changes will take effect the next time the user establishes a new connection to the RD Session Host server.

You can also configure timeout and reconnection settings by applying the following Group Policy settings:

• Set time limit for disconnected sessions
• Set time limit for active but idle Remote Desktop Services sessions
• Set time limit for active Remote Desktop Services sessions
• Terminate session when time limits are reached

These Group Policy settings are located in the following locations:

Computer Configuration\Policies\Administrative Templates\Windows Components\Remote Desktop Services\Remote Desktop Session Host\Session Time Limits

User Configuration\Policies\Administrative Templates\Windows Components\Remote Desktop Services\Remote Desktop Session Host\Session Time Limits

These Group Policy settings can be configured by using either the Local Group Policy Editor or the Group Policy Management Console (GPMC).

On Windows Server 2012 R2:

Local Security Policy -> Local Policies\Security Options

Microsoft Network server: Amount of idle time required before suspending session

15 minutes is default.