The selection of rotary joints must not be based solely on interface dimensions; rather, it requires a comprehensive assessment of the actual operating conditions inherent to the continuous casting process. Continuous casting cooling systems are characterized by continuous operation, fluctuating water quality, and limited spatial availability; therefore, the selection process must prioritize the following factors:

• Material Compatibility: Since the internal sealing components of the rotary joint remain immersed in cooling water for extended periods, material selection must strike a balance between corrosion resistance and wear resistance. The stationary sealing ring should ideally be fabricated from silicon carbide or cemented carbide, while the rotating ring is best constructed from stainless steel exhibiting superior fatigue resistance. The use of high-quality materials can significantly retard the aging of sealing surfaces and extend the service life—and thus the replacement cycle—of the components.
• Structural Suitability: The cooling channels within continuous casting rollers typically feature a dual-passage design; consequently, the rotary joint must be selected with a specific distinction between single-flow and dual-flow structures. Dual-flow rotary joints facilitate the separation of incoming supply water from outgoing return water, thereby preventing any decline in heat exchange efficiency. For guide rollers where installation space is restricted, a compact design should be selected to minimize axial spatial requirements.
• Selection of Sealing Mechanism: Depending on the cooling water pressure and rotational speed, one may choose between a balanced or an unbalanced mechanical seal configuration. In a balanced seal, the specific pressure exerted on the sealing faces is less susceptible to fluctuations in media pressure; this makes it particularly suitable for operating conditions involving significant pressure variations, offering superior sealing stability.

Installation quality serves as the fundamental prerequisite for the long-term, stable operation of a rotary joint. The following points require careful attention during on-site installation:

• Coaxial Alignment: The coaxial alignment between the rotary joint and the roller shaft must be maintained within a tolerance of 0.1 mm. Any deviation exceeding this tolerance will induce radial runout in the sealing pair, thereby accelerating the uneven wear of the sealing components. During installation, a dial indicator should be utilized to verify alignment; where necessary, a flexible coupling should be installed to compensate for any residual misalignment.
• Piping Support Configuration: The cooling water piping connected to the rotary joint must be equipped with independent supports to prevent the weight of the piping or operational vibrations from being transmitted to the joint housing. Improper piping support can subject the joint to excessive bending moments, thereby compromising the integrity of the sealing surfaces.
• Implementation of Anti-Loosening Measures: Since rotary joints typically operate under vibrating conditions for extended periods, anti-loosening measures—such as the use of lock washers or the application of thread-locking adhesives—must be applied to the connection threads to prevent leaks caused by loosening.

Maintenance management following commissioning has a decisive impact on the service life of a rotary joint:

• Water Quality Control: Suspended solids and water hardness in the continuous casting cooling water are the primary causes of wear on sealing components. Water quality should be monitored regularly to ensure that the suspended solids content does not exceed 50 mg/L and total hardness remains below 300 mg/L (expressed as CaCO₃). For turbid circulating water systems, installing additional filters can effectively capture large particulate impurities, thereby reducing abrasive wear.
• Leak Prediction and Remediation: Initial leakage in a rotary joint typically manifests as minor seepage. At this stage, the condition of the sealing surfaces should be inspected immediately to prevent the leak from escalating. Regular monitoring of flow rates in the return water line is recommended; if an abnormal drop in flow is detected, the sealing surfaces should be examined to determine whether flow capacity has been reduced due to scaling or wear.
• Periodic Replacement Mechanism: Even in the absence of visible leaks, the internal sealing components of a rotary joint undergo a natural cycle of fatigue and aging. It is recommended to establish a preventive replacement schedule based on production cycles—typically involving disassembly, inspection, or replacement every 12 to 18 months—to prevent sudden leaks from disrupting continuous production.

During the actual operation of rotary joints, equipment management personnel frequently encounter three typical types of anomalies. It is essential to accurately diagnose the underlying cause based on the observed symptoms and take prompt corrective action.

• Water dripping at the joint is the most common operational fault, typically caused by wear on the sealing surfaces or the entrapment of foreign objects. After prolonged operation, the working surfaces of the sealing rings may develop microscopic scratches due to friction, or hard particles present in the cooling water may become lodged within the sealing gap, thereby compromising the integrity of the seal. To resolve this issue, the joint should be disassembled immediately; the sealing components should be thoroughly cleaned, and the sealing surfaces carefully inspected for any visible scratches or localized spalling. If the sealing surface sustains only minor damage, it can be restored through lapping; however, if wear is severe or through-cracks have developed, the sealing components must be replaced entirely.
• Excessive heating of the housing often indicates the presence of abnormal internal resistance. Common causes include insufficient cooling water flow—leading to poor heat dissipation—or internal bearing issues such as seizing or lubrication failure. To address this, one should first verify that the water supply lines are unobstructed, clear any impurities from the filters, and confirm that the inlet pressure meets the equipment's specifications. If the flow rate is normal yet the housing continues to overheat, a further inspection of the bearing condition is required; if necessary, the unit should be disassembled to replace the bearings and replenish the appropriate amount of lubricant.
• Rotational binding manifests as a significant increase in the rotational resistance of the rotary joint, or even intermittent stalling. This is typically associated with excessively tight sealing clearances or severe scale accumulation. When the cooling water possesses high hardness, prolonged operation can lead to the formation of limescale on the sealing faces and the inner walls of the flow channels, thereby constricting the sealing clearance. Additionally, improper adjustment of the seal compression during installation can also result in an overly tight fit. To resolve this, one should first verify the cooling water quality parameters; if the hardness is found to be excessive, water treatment measures must be enhanced. After disassembling the joint, remove the scale deposits from the surfaces of all components, verify that the sealing ring clearances fall within the design specifications, and readjust the assembly parameters accordingly.