First of all I have no experience of working with IPCs and don't have any technical information about it. I have only worked with PLCs, HMIs and PC based HMI systems (WinCC) before. So I came across this new machine which has a SIMATIC IPC627D (6AG4131-2GA30-0BX1), An S7 1500 PLC and a B&R HMI. There's also a monitor connected with the IPC. Now I have a few questions:

1. What do you guys think the purpose and role of the IPC there? PLC is there as the brain of the control system, HMI is there to visualize the control system. What's IPC for? I googled but don't seem to understand the basic purpose.

2. If the IPC fails and we need to replace it what is the procedure? Just remove the HDD and install the HDD in the new IPC and it will just work fine just like a desktop PC with windows OS or are there any steps? For example when replacing a PLC CPU we need to remove the MMC from the old CPU and insert in the new one and sometimes also need to redownload the program. When replacing HMIs we need to redownload the program in the new HMI. How is it for IPCs?  

Thank you