In technological processes of modern enterprises of oil and gas production flammable and explosive substances turn, which, combined with a wide range of changes and extreme values of technological parameters - temperature, pressure, flow rate, corrosivity, causes high rates of accidents risk. Pipe heating furnaces are among the most dangerous objects of oil and gas production, more than 10% of all accidents occur on them. Cause most of these accidents is leakage of pipe coil and the ingress of the process medium into the combustion space of the pipe heater. During operation, irreversible damage accumulates in the pipe coil metal, there is an uneven stress-strain state due to thermal force loading, there is a carbon deposition on the inner surface. This article discusses the process of carbon-producing in the pipe heaters on the example of a pipe heater box type using a computer predictive model of the production process. According to the results of the study, a new evaluation criterion for the level of coking of the pipe coil – the rate of carbon-producing is proposed and its value corresponding to the maximum permissible level of coking is determined. Calculation of the rate of carbon-producing is carried out by virtual quality analyzers using the process parameters of the carbon-producing.