Remote temperature indication should be provided, as follows, on most process equipment and piping:
• Columns. All inlet and outlet lines
• Vessels. All inlet and outlet lines expected to have different temperatures
• Fired heaters. Inlet line and outlets from each pass, header pass points from the convection to the radiant section, on the tube wall as recommended by the furnace supplier (a minimum of three per pass), and on the stack just ahead of the damper
• Process stream junctions. Downstream of the junction point of all important process streams
• Coolers. All liquid product inlets and outlets
• Temperature controllers and transmitters. These instruments should have an additional thermocouple and thermowell separate from the controller or transmitter. Instruments on high pressure piping and reactors may use a common thermowell
• Orifice flow meters. For heavy hydrocarbons. Used to estimate viscosity and make flow corrections from fluid temperature changes
• Parallel piping lines. Temperature transmitter thermowells should be installed in both lines, and the sensing bulb for the transmitter in one line. The installation should permit transfer of the sensing bulb to the other well
• Process compressors or blowers. Inlet and outlet lines. One point is required on the combined inlet and one on the combined outlet of compressors or blowers in parallel on the same service
