Measuring temperature of a fluid in pipe and vessels is achieved by installing local temperature gauges or by temperature transmitter which send their output to process control room.
Temperature gauges consists of a metallic probe which is inserted into the pipe or vessel through a nozzle arrangement. Dial connected to probe shows temperature on a circular scale. Head of the guage is either fixed or swivel headed for various readout angles.
Then temperature must be read remotely, thermocouple type of temperature transmitters are used. They have a metallic probe same as gauge indicators, but instead of a dial attached to other end, they have a terminal head which houses electronics circuit which transmit temperature signal to process control room for process control and display on screen.
Both gauge indicators and thermocouples are generally flanged or screwed, and their pipe and vessel connetions sizes range from 1/2in to 2 in. Minimum pipe size usually required is 4″. If pipe is of smaller size, it is locally increased to 4″ NPD with the use of two reducers.
On a distilation tower, temperature instrument must be located in liquid space. A ladder access is usually sufficient for temperature guages and transmitters.
Temperature Guage
Temperature Transmitter