The analysis of torque required for sealing of threaded brass flare fittings

Irving, Jonathan (2022) The analysis of torque required for sealing of threaded brass flare fittings. [USQ Project]

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Flare fittings seal by the application of clamp force between the flare face of the fitting, flared tube and flare face of the nut. For real world use the required clamp force is translated into torque requirements as this is easier to measure on site. The hypothesis is that a seal will occur between the yield strength of the tube material at the lower end, and at the upper end either the ultimate strength of the tube material, or the yield strength of the nut material. It seems that in brass flare fittings to be used with copper tubing the appropriate torque has not been empirically identified; rather a ratio between the tensile strength of brass and carbon steel is applied to empirically tested data for carbon steel to give an estimation.

This study theoretically calculated the minimum and maximum clamp force, thus torque for the fittings at extremes of tolerances, i.e. a female flare nut at the largest ID tolerance with a male flare plug at the smallest OD tolerance, and vice versa. Empirical torque and pressure testing was then carried out to determine an optimal working torque range for each size and type of flare fitting connection.

The empirical results are compared to the theoretical limits found as validation, torque windows and the linked ‘number of turns from hand tight’ were recorded.

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Item Type: USQ Project
Item Status: Live Archive
Faculty/School / Institute/Centre: Current – Faculty of Health, Engineering and Sciences - School of Engineering (1 Jan 2022 -)
Supervisors: Senadeera, Wijitha; Jackson Shaun
Qualification: Bachelor of Engineering (Honours) (Mechanical)
Date Deposited: 19 Jun 2023 23:47
Last Modified: 20 Jun 2023 01:16
Uncontrolled Keywords: Threaded flare fittings; Torque; Brass; Clamp Force; Pressure

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