Cementing trucks use swivel joints to connect high-pressure discharge lines while allowing limited rotation and layout adjustment. The union connection at the swivel joint must withstand high pressure, vibration, repeated assembly, and abrasive cement slurry.
An improved union connection structure focuses on the sealing interface, thread engagement, and shoulder support. A more stable metal-to-metal locating surface helps the seal ring maintain compression under pulsating pressure, while the union nut provides fast field assembly and disassembly.
The structure should avoid stress concentration at the thread root and sealing shoulder. Correct heat treatment, accurate machining of the sealing groove, and controlled surface finish are important for extending service life.
During field use, the connection should be inspected for thread damage, seal wear, galling, and impact deformation. Damaged union nuts, seal rings, and mating subs must be replaced before the assembly is returned to pressure service.
