Thermowell Insertion Lengths

Either of two methods can be used to provide for thermowells in the des of process piping. In 

The other advantage of this method is that it will also reduce the number of types of thermowells that have to be ordered. The types that must be carried in stock for future maintenance work are kept to a minimum. When the piping designer knows in advance the thermowell insertion lengths preferred, he will be in a better position to provide for their installation in the process piping. Time will be saved and he will be able to complete his drawing sooner. 

When the thermowell is installed perpendicular or at a 45° angle to the pipe wall, the thermowell tip should be at or near the centerline of the pipe. Thermowells and their connections should point counter to the flow in the process line whether installed on pipe elbows or on a 45° angle. The well perpendicular to the pipe will naturally be in the turbulent flow section of the pipe. Such an arrangement will not always be possible because of the piping arrangement and direction of the process flow. 

Because the accessories attached to the thermowell may protrude, they must be so instaUed on the piping that they will be parallel with walkways and platforms. If not, a workman carrying tools on his shoulder could accidently knock off the head of a dial thermometer. An operator in an emergency rush could be injured by a T/C head 

7-95—1-in., 6000 lb. elbow adapter installed on 2H to 12 welding pipe elbow for thermowell 

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Mount probes and flow meters in vertical lines to prevent soUds accumulation. Provide insertion lengths at least ten times the diameter for thermowells. 

Local measurements of wet chlorine temperature use tantalum-sheathed flanged thermowells with bimetallic dial thermometers. The insertion length should be selected to place the tip about one third of the diameter into the piping or into an elbow. 

The temperatures and conversions were measured either before or after the radio-active tracer experiments. Intermediate samples were taken from nozzles at one quarter, at half and at three quarters of the kiln length. The latter two nozzles were also used for measurement of the gas and solids temperatures with a specially constructed thermowell, which could be quickly inserted or removed during rotation of the kiln. Samples were also taken from the solids feed and from the cooler. Samples were analysed for LOI and boehmite conversion using X-ray diffractometry. 

For a thermocouple to read correctly, it should be fully inserted in a thermowell and the thermowell itself should extend several inches into the process liquid. If the process stream is a vapor, which has poorer heat-transfer properties than do liquids, the thermowell, especially if the external insulation is poor, should extend more than 6 in into the process flow. To check the length of the thermowell, unscrew the thermocouple assembly and pull it out, then simply measure the length of the thermocouple. This is also a good opportunity to verify the control-room reading with a portable temperature probe or a glass thermometer inserted in the thermowell. 

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