What is a NH Fire Hose Coupling?

The NH Fire Hose Coupling is a vital piece of equipment in the US firefighting and industrial sectors. It is a highly efficient, standardized connector designed to connect fire hoses, hydrants, nozzles, and other firefighting equipment.

NH: National Hose Thread

NH stands for "National Hose." In the US, it is used interchangeably with NST (National Standard Thread) to refer to the same thread standard. This standard defines the thread size, number of threads per inch, and thread shape for fire hose couplings, ensuring seamless connection between equipment from different manufacturers.

How NH Fire Hose Couplings Work

NH fire hose couplings consist of two main parts:

• Male coupling: This has external threads and is typically connected to one end of the hose or equipment.
• Female coupling: This has internal threads and a built-in gasket and is typically connected to the other end of the hose or equipment.
  
  

When connecting, the male coupling screws into the female coupling, and the threads secure and connect. The gasket inside the female connector performs a crucial sealing function, ensuring no leakage even under high-pressure water flow. This design makes NH fire hose connectors highly reliable and essential for firefighters to quickly deploy firefighting equipment.

Why are NH threads straight?

NH fire hose connectors utilize straight threads. Unlike common tapered threads (such as NPT), straight threads do not rely on a tight fit within the threads themselves to seal, relying entirely on the gasket within the female connector. This design offers several significant advantages:

• Quick Connection: Straight threads can be quickly threaded in and out, saving valuable time for rapid emergency response.
  
  
• Reusable: Since the threads themselves do not perform the sealing function, repeated connection and disconnection do not wear the threads, extending the life of the connector.
  
  
• Safe and Reliable: The gasket provides a strong seal, effectively preventing leaks under high pressure, which is crucial for fire safety.
  
  

Differences Between NH, NPSH, and NPT Threads

A common point of confusion when selecting and using NH fire hose couplings is the difference between them and other thread standards, such as NPSH and NPT.

• NH/NST: Designed specifically for fire hose, it has a straight thread and uses a gasket for sealing.
  
  
• NPSH (National Pipe Straight Hose): Also a straight thread, but with the same thread pitch as NPT. This allows NPSH female connectors to be connected to NPT male connectors, but not vice versa.
  
  
• NPT (National Pipe Taper): A tapered thread, where the thread itself acts as a seal. It's primarily used in plumbing systems, not fire hose, and requires thread sealing tape for additional sealing.
  
  

Understanding these differences can help you select the correct NH fire hose connector and corresponding adapters, ensuring compatibility across all your equipment.