The RMG and RMK series are heavy-duty, metal-shell circular underwater connectors designed specifically for commercial diving equipment, ROV-mounted cameras and lights, subsea instruments, and applications requiring robust mechanical protection combined with reliable seawater sealing. This guide covers the design features, specifications, available configurations, and typical application scenarios for the RMG/RMK series.
The RMG (Robust Metal Glanding) series features a full 316L stainless steel outer shell with a glanding-style cable entry. The metal shell provides mechanical protection against impact, abrasion from coral and rock surfaces, and compression loading from trawl gear or umbilical crossovers. The glanding cable entry provides a secure, strain-relieved seal on a wide range of cable diameters without the need for a separate back-shell accessory.
The RMK (Robust Metal Knurled) series is dimensionally similar to the RMG but features a knurled outer locking ring for improved grip in cold-water glove operations and when manipulator-mated on ROV systems. The knurled surface provides tactile feedback confirming full engagement without requiring visual verification.
Unlike polymer-body connectors, the RMG/RMK series provides a continuous metal enclosure from cable entry to mating face. This gives the connector significantly higher resistance to:
The coupling ring uses a multi-start thread for rapid engagement — typically 1.5 turns from contact to full lock — combined with a spring-loaded detent for vibration-resistant locking. This prevents accidental disconnection in dynamic environments such as ROV umbilical systems subject to wave-induced motion.
Standard RMG/RMK connectors are rated to 200 bar (2,000 m depth). Enhanced versions with upgraded O-ring geometry and tighter manufacturing tolerances on the mating face are available rated to 400 bar (4,000 m).
316L stainless steel housing provides excellent corrosion resistance in standard seawater conditions. For long-term fixed installations in warm tropical seawater (where galvanic corrosion risk from dissimilar metal structures is elevated), titanium housing variants are available on request.
| Model | Contacts | Max Current/Contact | Max Voltage | Depth Rating |
|---|---|---|---|---|
| RMG-3 / RMK-3 | 3 | 20 A | 500 VAC | 2,000 m |
| RMG-4 / RMK-4 | 4 | 15 A | 500 VAC | 2,000 m |
| RMG-6 / RMK-6 | 6 | 10 A | 300 VAC | 2,000 m |
| RMG-8 / RMK-8 | 8 | 7 A | 300 VAC | 2,000 m |
| RMG-12 / RMK-12 | 12 | 5 A | 300 VAC | 2,000 m |
The RMK-4 and RMK-6 are widely used for helmet-to-umbilical connections, carrying communications audio, video, and hot-water suit heating supply. The knurled ring is critical here — divers wearing thick gloves in cold water must be able to confirm connection by feel alone.
ROV-mounted LED lights require high-current, low-contact-resistance connections. The RMG-3 provides 3-contact power (typically supply, return, and dimmer signal) with 20 A capacity per contact — sufficient for high-wattage LED arrays up to 3 kW.
Camera housings for ROV and fixed observatory applications use RMG-8 or RMG-12 connectors, combining power, sync trigger, RS-232 control, and video or Ethernet data in a single interface. The metal shell provides EMI screening for video signal quality.
Fixed monitoring stations and seafloor landers use RMG connectors for their instrument interfaces due to the combination of corrosion resistance, mechanical robustness, and ability to remain mated for extended deployment periods (6–24 months between service visits).
