A mobile system 70 for cleaning a vessel 12, said vessel 12 preferably being a tank or a pipeline, said system comprising: a first trolley 56 comprising an internal reservoir for accommodating between 50 litres and 1000 litres of cleaning fluid, and a fluid connector for connecting to said internal reservoir from the outside of said first trolley 56, said first trolley further comprising a heating system 64 for heating said cleaning fluid within said internal reservoir, a second trolley 30 comprising a conduit between a fluid inlet having an inlet valve and being connectable to said fluid connector of said first trolley and a fluid outlet having an outlet valve and being connectable to said vessel, said conduit comprising a pump 40 connected to said fluid inlet for pumping cleaning fluid from said internal reservoir of said first trolley 56 via said fluid inlet and fluid outlet to said vessel, said second trolley 30 further comprising a relief valve for relieving said conduit of any excessive pressures, a pressure measurement device 46 for measuring the pressure within said conduit, a temperature measurement device 48 for measuring the temperature within said conduit, a flow measurement device 50 for measuring the flow of cleaning fluid through said conduit, and a processing unit for receiving said measured pressure, temperature and flow, said first trolley 56 and said second trolley 30 each having at least 2 wheels 34, preferably at least 3 wheels 34, more preferably at least 4 wheels 34, and each having a height and a width being less than the height and width of a standard residential door, said first trolley 56 further comprising inlet 60 having a valve for being connected to an opening 74 of said vessel 12, hereby suitable for arranging a closed circuit between the system 70 and the vessel 12, such that said pump 40 generates a transport of cleaning fluid from said vessel 12. a first trolley 56 comprising an internal reservoir for accommodating between 50 litres and 1000 litres of cleaning fluid, and a fluid connector for connecting to said internal reservoir from the outside of said first trolley 56, said first trolley further comprising a heating system 64 for heating said cleaning fluid within said internal reservoir, a second trolley 30 comprising a conduit between a fluid inlet having an inlet valve and being connectable to said fluid connector of said first trolley and a fluid outlet having an outlet valve and being connectable to said vessel, said conduit comprising a pump 40 connected to said fluid inlet for pumping cleaning fluid from said internal reservoir of said first trolley 56 via said fluid inlet and fluid outlet to said vessel, said second trolley 30 further comprising a relief valve for relieving said conduit of any excessive pressures, a pressure measurement device 46 for measuring the pressure within said conduit, a temperature measurement device 48 for measuring the temperature within said conduit, a flow measurement device 50 for measuring the flow of cleaning fluid through said conduit, and a processing unit for receiving said measured pressure, temperature and flow, said first trolley 56 and said second trolley 30 each having at least 2 wheels 34, preferably at least 3 wheels 34, more preferably at least 4 wheels 34, and each having a height and a width being less than the height and width of a standard residential door, said first trolley 56 further comprising inlet 60 having a valve for being connected to an opening 74 of said vessel 12, hereby suitable for arranging a closed circuit between the system 70 and the vessel 12, such that said pump 40 generates a transport of cleaning fluid from said vessel 12. <EOS>