This burners use current control system that is independent viscosity changing.Fuel pump is a type of fixed convection that transfer fixed rate of volume valve.This fuel come into a cage that has two series of holes and almost half of them all always clogged up by a circulator gate. When gate rotate half of holes become opened and half of them become closed.Some of holes guide fuel toward burner and some of them guide it to line of return. In fact fixed rate of entrance volume valve is divided according to necessity.Pressure variation in back of valve has effect on flow in holes and this effect is neutralized by equalizer piston hat always balance pressure on back off holes.When the pump is working and electrician valves are closed (for example when weighed fuel is separated under common temperature) relief valve is opened for rotate the warm fuel to become again warmer.There is back pressure valve circuit to assure that there is resistance against flow that guarantees correct performance.