Abstract: An experimental test rig for simulating and analyzing the fouling behavior of petrochemicals when heated within a pipe or other such conduit, the rig comprising: a supply of petrochemical product; an annulus test section arranged to receive petrochemical product from the said supply, the annulus test section comprising an inner tube and an outer tube with the petrochemical product passing therebetween; a tubular test section arranged to receive petrochemical product from the said supply; a pipe circuit connecting the supply of petrochemical product to the test sections; means for heating a region of the annulus test section; means for heating a region of the tubular test section; and means for controlling and measuring the flow of the petrochemical product from the supply to the test sections; wherein the pipe circuit is configured such that the petrochemical product can be simultaneously supplied to the annulus and tubular test sections while they are heated.