A fluid transfer system for transferring urea or urea derivatives from a reservoir to a nozzle, the fluid transfer system comprising • a through flow device adapted to receive the urea or urea derivatives from the reservoir and transfer the urea or urea derivatives through the system and/or measuring the amount of the urea or urea derivatives being transferred from the reservoir to the nozzle, • a controllable shut-off valve arranged upstream of the nozzle and downstream of the through flow device, and • a controlling unit controlling at least the state of the shut-off valve, wherein the through flow device comprises a dosing pump, wherein the nozzle is adapted to atomize the transferred urea or urea derivatives without mixing it with pressurized air, wherein the controlling unit is adapted to control the state of the shut-off valve, so that the pressure of the urea or urea derivatives being fed to the nozzle is above a first pre-selected pressure limit (P min) being a level at which it can be assured that the urea or urea derivatives fed to the nozzle is atomized by the nozzle, wherein the controlling unit turns the shut-off valve into its open state when the pressure upstream of the shut-off valve is above a second pre-selected pressure limit (P max), wherein the controlling unit turns the shut-off valve into its closed state when the pressure upstream of the shut-off valve is decreased to the first pre-selected pressure limit (P min) so that a pressure build up is initiated again, and wherein the system further comprises a fluid connection extending from the shut-off valve to the nozzle, the fluid connection is a line made of stainless steel and being stiff so as to avoid expansion of the fluid connection which would cause uncontrollable flow through the connection due to contraction of the connection when the shut-off valve is closed. • a through flow device adapted to receive the urea or urea derivatives from the reservoir and transfer the urea or urea derivatives through the system and/or measuring the amount of the urea or urea derivatives being transferred from the reservoir to the nozzle, • a controllable shut-off valve arranged upstream of the nozzle and downstream of the through flow device, and • a controlling unit controlling at least the state of the shut-off valve, wherein the through flow device comprises a dosing pump, wherein the nozzle is adapted to atomize the transferred urea or urea derivatives without mixing it with pressurized air, wherein the controlling unit is adapted to control the state of the shut-off valve, so that the pressure of the urea or urea derivatives being fed to the nozzle is above a first pre-selected pressure limit (P min) being a level at which it can be assured that the urea or urea derivatives fed to the nozzle is atomized by the nozzle, wherein the controlling unit turns the shut-off valve into its open state when the pressure upstream of the shut-off valve is above a second pre-selected pressure limit (P max), wherein the controlling unit turns the shut-off valve into its closed state when the pressure upstream of the shut-off valve is decreased to the first pre-selected pressure limit (P min) so that a pressure build up is initiated again, and wherein the system further comprises a fluid connection extending from the shut-off valve to the nozzle, the fluid connection is a line made of stainless steel and being stiff so as to avoid expansion of the fluid connection which would cause uncontrollable flow through the connection due to contraction of the connection when the shut-off valve is closed. wherein the through flow device comprises a dosing pump, wherein the nozzle is adapted to atomize the transferred urea or urea derivatives without mixing it with pressurized air, wherein the controlling unit is adapted to control the state of the shut-off valve, so that the pressure of the urea or urea derivatives being fed to the nozzle is above a first pre-selected pressure limit (P min) being a level at which it can be assured that the urea or urea derivatives fed to the nozzle is atomized by the nozzle, wherein the controlling unit turns the shut-off valve into its open state when the pressure upstream of the shut-off valve is above a second pre-selected pressure limit (P max), wherein the controlling unit turns the shut-off valve into its closed state when the pressure upstream of the shut-off valve is decreased to the first pre-selected pressure limit (P min) so that a pressure build up is initiated again, and wherein the system further comprises a fluid connection extending from the shut-off valve to the nozzle, the fluid connection is a line made of stainless steel and being stiff so as to avoid expansion of the fluid connection which would cause uncontrollable flow through the connection due to contraction of the connection when the shut-off valve is closed.