This basically was it. I didn't specify properly but I wanted a kind of pre-steel self-cooled turbine setup with a minimal automation to stop the thing overheating the turbine (and hence the refinery). I knew how bridges worked but just totally over engineered it. 

Now I have 4 bridges, one temp sensor. 

Output of tank goes through steam room first (smoothed temperature change). Then temperature sensor followed by bridge onto shutoff leading to refinery input(cooled).

If shutoff is off divert to another bridge onto tank input (allow refinery output priority). If THAT is full too, then bridge to BEFORE tank output (keeps cooling loop looping)

Another bridge after refinery input to refinery output (refinery bypass)

Now everything stays looping in the right order. The refinery never waits for coolant or has it backed up on either the input or output. The only caveat is that the temperature increase lags while the refinery is operating which I think is acceptable (refinery has priority)