Hi sudharshanan:

It seems to me that nobody knows the answers to your questions. I belong to that group; however, I´ll make some comments that, I hope, will help you.

One reliable and widely used method of automatically detecting fires on an offshore platform fires is a pneumatic line containing strategically located fusible elements.

Fusible elements normally are metallic plugs that melt at designed temperature or a section of fusible synthetic tubing. So they are fixed temperature fire detectors.

Fire plugs may be installed in the various pneumatic line of the safety system if the signal generated initiates the proper shuting functions except for equipment required to control the fire. And another use for fire plugs is activating fire control/extinguishing systems.

Regarding your questions:

  • What is the maximum distance a fusible loop can be?
  • What are the limitations regarding the response time and length of the fusible loops?


I would say that the limitations (distance, response time) are imposed by the constraints of the ESD system.

Now, let´s see your questions in terms of fire control/extinguishing systems:

  • What is the maximum distance a fusible loop can be?
  • What are the limitations regarding the response time and length of the fusible loops?
  • Is there any standard specifying the length, response time and deluge actuation through fusible loop pressure?


NFPA 15 (2007) states in Chapter 10 "System Acceptance", 10.4.2.1 "Under test conditions, the heat detection system, where exposed to a heat source or pilot sprinkler line test valve opened, shall operate the system actuation valve within 40 seconds." So this requirement will have an impact on the length of the fusible loops. Think of the most remote (in hydraulic terms) fire plug being activated.

Most deluge systems provided at process facilities are activated by a heat detection system. Fusible plugs are the simplest, most reliable, and least expensive fire detection and shutdown system commonly used. If you need a faster opening of the deluge valve, you should consider another type of detection such as Ultraviolet and Infrared Flame Detection.

Regards