Does putting that paper on top of the heatsinks really help airflow that much?  What are the temp differences with and without that you are seeing?

i'm also add second fun (12cm to 5v pins, low noise), without paper it is a ~50-54 after adding - ~42-45.
Paper is the most important to the most distant from the fan chips. Without it, the end of the radiator can be burned my finger when i touching.

There are may PSU claim to be a big strong one, but please select a brand name quality PSU for the Ant.  

1 Rail +12V is not enough but you can use 1 rail PCI-E and lines from CPU Power lines. 

That one was Chieftec . Now I have FSP 650 aurum and  FSP 750 aurum they both are holding 11.6V while asic works. And still I get xxx sometimes. Will go buy better PSU's right now.  

Thank you sir...

Why should it get in flames - heatsink? According to this - autoignition point for paper is at 218-246 'C  - I kinda doubt it that you will reach it with antminer. As for a better material - perhaps you can use a metal plate, but again there is a risk that it will melt at 1538 'C 

Personally, I have 1 machine running on a 600W Corsair, which claims 560W on a single 12V rail. It is happily operating a 400MHz antminer (from the second batch) and seems problem-free around 48/50 degrees, 2 fans and some paper overtop (the paper does help) using 1 4-pin ATX per board (wires are barely warm).

That said, not all PSUs (or electronics in general) meet the specs. some can handle more then rated and some struggle to come close, even in the same brand or batch. Even if you have more than the required (~500W?) available on your 12V rail the PSU may not be capable of providing the limit 24/7.

ALSO: make sure that if you have 2 or more rails each board has a seperate rail with enough amperage. I have a 730W PSU with roughly 325W available on 2 rails. 1 rail is used via the 2x4pin ATX cable, and the other via the PCI-e cable.

My AntMiner starts to beep after a short time and stops mining.
Does anyone know what the problem could be or how I can debug this?

I use a 650W PSU without OC so it should have enough W.
The environment temperature is 14 degrees C.

Thanks!

I run 2x 200GH AntMiner on Seasonic X-series 1050W Gold and they take 830W from the wall.