Manufacturing Processes of Loading Arm Swivel Joints
In previous articles, we discussed the importance of loading arm swivel joints in the petrochemical industry. Today, we will focus on their manufacturing processes, which mainly include three types: hot rolling, cold drawing, and hot expansion. Let's briefly understand these three processes:
According to different production methods, they can be divided into hot-rolled pipes, cold-rolled pipes, cold-drawn pipes, extruded pipes, etc.
Hot-rolled loading arm swivel joints
These are generally produced on automatic pipe rolling mills. Solid billets are inspected to remove surface defects, cut to the required length, and centered on the end face of the billet's piercing end. They are then sent to a heating furnace for heating and pierced on a piercing machine. During piercing, the billet continuously rotates and advances. Under the action of the rolls and the plug, a cavity gradually forms inside the billet, known as a "hollow billet." The hollow billet is then sent to an automatic pipe rolling mill for further rolling, followed by wall thickness equalization on a sizing mill and final sizing on a reducing mill to meet the specified dimensions. Using a continuous pipe rolling mill to produce hot-rolled seamless steel pipes is a relatively sophisticated method.
Cold-rolled and cold-drawn loading arm swivel joints
To obtain swivel joints with smaller dimensions and better quality, cold rolling, cold drawing, or a combination of both methods must be used. Cold rolling is usually performed on a two-high rolling mill, where the steel pipe is rolled in an annular pass consisting of a variable-section circular groove and a fixed conical plug. Cold drawing is typically carried out on single-chain or double-chain cold drawing machines with a capacity of 0.5–100 tons.
Extruded loading arm swivel joints
The extrusion method involves placing a heated billet in a closed extrusion cylinder. A piercing rod and an extrusion stem move together to force the extruded part out through a smaller die hole. This method can produce steel pipes with smaller diameters.
Due to their different manufacturing methods, loading arm swivel joints require appropriate usage practices. This not only extends their service life but also ensures their smooth operation.
