Conduit preheating control

A system for controlling preheating of a conduit, the system comprising:

• a steam supply fluidly coupled to the conduit;
• at least one control valve in the conduit;
• at least one steam drain valve configured to drain steam from the conduit upstream of the at least one control valve;
• at least one upstream thermocouple disposed upstream of the at least one control valve and the at least one steam drain valve;
• and
• a controller configured to:
• preheat the conduit by flowing the steam from the steam supply through the conduit with the at least one control valve closed to prevent downstream steam flow and the at least one steam drain valve open;
• determine an initial temperature and an initial pressure of the steam upstream of the at least one control valve and the at least one steam drain valve using the at least one thermocouple;
• calculate a predicted exit temperature of the steam downstream of the at least one steam drain valve using a linear regression model based on the initial temperature, the initial pressure, and a Joule-Thompson cooling effect analysis of the steam at the at least one steam drain valve;
• in response to the predicted exit temperature of the steam downstream of the at least one steam drain valve being greater than or equal to a required exit temperature of the steam at the at least one steam drain valve, close the at least one steam drain valve and open the at least one control valve to allow steam to flow downstream in the conduit;
• and
• in response to the predicted exit temperature being less than the required exit temperature of the steam at the at least one steam drain valve, continue the preheating.

A system for controlling preheating of a conduit, the system comprising:

• a steam supply fluidly coupled to the conduit, wherein a gas backfills the conduit from a downstream gas source;
• a first control valve in the conduit;
• a first steam drain valve configured to drain steam from the conduit upstream of the first control valve;
• a second control valve in the conduit downstream of the first control valve;
• a second steam drain valve configured to drain steam from the conduit downstream of the first control valve and upstream of the second control valve;
• at least one gas drain valve in the conduit downstream of the second control valve;
• at least one sensor upstream of the first and second control valves and the first and second steam drain valves to provide an initial temperature and an initial pressure of the steam entering the conduit;
• and
• a controller configured to:
• preheat the conduit by flowing the steam through the conduit with the first control valve closed to prevent downstream steam flow and the first steam drain valve open;
• in response to a predicted exit temperature of the steam downstream of the first steam drain valve being less than the required exit temperature of the steam at the first drain valve, continue the preheating;
• in response to the predicted exit temperature of the steam downstream of the first steam drain valve being greater than or equal to the required exit temperature of the steam at the first steam drain valve, close the first steam drain valve and open the first control valve to allow steam to flow downstream in the conduit, and subsequently:
• stop the preheating by closing the second steam drain valve and opening the second control valve in response to a predicted exit temperature of the steam downstream of the second steam drain valve being greater than the required exit temperature of the steam at the second steam drain valve, and a predicted exit temperature of the gas downstream of the at least one gas drain valve being greater than a required exit temperature of the gas at the at least one gas drain valve, and
• wherein each predicted exit temperature of the steam or the gas downstream of a respective drain valve is calculated using a linear regression model based on the initial temperature, the initial pressure and a Joule-Thompson cooling effect analysis of the steam or the gas at the respective drain valve.