For cover of fire valves.Brass Nakajima couplings are rigid, interlocking quick-connect fittings primarily used in marine firefighting and industrial applications. Constructed from durable brass, these couplings are engineered to resist corrosion from saltwater, oxidation, and abrasion, making them standard equipment for commercial vessels, yachts, and port facilities.
Key Performance Features
- Quick Connection: The Nakajima design uses a quarter-turn locking mechanism with external lugs that engage notches on a corresponding fitting, allowing for rapid deployment in emergencies without the need for tools.
- Hermaphrodite Design: Features identical interlocking halves, enabling any two Nakajima ends of the same size to connect securely.
- Spark Resistance: Inherent brass properties make these couplings spark-resistant, which is critical for safety in flammable marine or industrial environments.
- Pressure Reliability: They are typically rated for working pressures between 12 to 20 bar (up to 290 psi) and are tested to maintain a leak-proof seal under high-pressure conditions.
Standard Sizes and Specifications
Nakajima couplings are categorized by their Japanese Industrial Standard (JIS) sizing, often matching common fire hose diameters:
| JIS Size | Nominal Size (Inches) | Lug Size (mm) | Common Hose Tail |
|---|
| 40A | 1.5″ | 61 mm | 38 mm |
| 50A | 2.0″ | 71 mm or 72 mm | 50 mm or 52 mm |
| 65A | 2.5″ | 91 mm or 92 mm | 64 mm or 65 mm |
Common Configurations and Adapters
Because fire mains and equipment may use different threading standards, Nakajima fittings are available in several formats:
- Hose Shanks/Tails: Feature deep serrations to provide a powerful grip when clamped to a lay-flat fire hose.
- Threaded Adapters: Available with BSP (British Standard Pipe) or NST (National Standard Thread) male and female threads to connect Nakajima hoses to hydrants or nozzles from different regions.
- Blind Caps: Used to seal off hydrants or hose ends to prevent blockages from debris or pests while not in use.
