Technical Articles & Selection Guides

Why NACE Sour Service Swivel Joints Must Be Specified Separately

Explains material, hardness, seal and documentation requirements for swivel joints used in H₂S service.

Swivel Joint selection should be treated as part of the complete high-pressure flowline system, not as an isolated replacement item. For this topic, the practical confirmation work starts with the rated pressure, bore size, Fig connection system, end arrangement, service condition and documentation requirements. These details determine whether the product can be installed safely and whether it will match the rest of the equipment on site.

The main technical check points are raceways, balls, seals, elbow body, end connections and rotation plane. In field service, these areas are exposed to pressure pulsation, vibration, repeated make-up and break-out, abrasive fluid or sour-service requirements. When any of these details are overlooked, the likely consequences include stiff rotation, seal leakage, raceway wear, wrong end orientation or service-condition mismatch.

Selection and ordering information

For new projects, customers should provide the operating pressure, working medium, temperature range, line layout and mating equipment. For replacement jobs, old-part photos, body markings, end-connection photos and installation position are very helpful. If the product is required for NACE sour service, low-temperature service, third-party inspection or special documentation, the requirement should be stated before production.

  • Confirm size, Fig rating and pressure rating as one complete specification.
  • Confirm end connections and installation direction before ordering.
  • Confirm whether standard service, NACE sour service or low-temperature service is required.
  • Confirm required documents such as MTC, pressure test report, NDT report or third-party inspection.

Field use and inspection

Swivel Joint should be inspected before installation and after high-frequency service. Sealing faces must be protected from impact damage. Threads, union ends and mating faces should be clean before make-up. The product should not be forced into alignment by hammering, pulling or side-loading the connected flowline.

When the product is used together with hose loops, pup joints, plug valves and hammer unions, the complete line should be checked as a system. A single component may be correctly manufactured, but the assembly can still fail to fit if the adjacent components use a different connection direction, pressure rating or service specification.

Technical feedback

If leakage, abnormal operation, difficult make-up, stiff movement or pressure-test instability occurs, useful feedback should include the model, pressure, medium, service condition, installation photos and close-up photos of the affected area. This allows our sales and technical team to distinguish between a component issue, an installation issue, a wear-part issue or a specification mismatch.