New Actuator for Hazardous Locations

August 21, 2020
Explosion Proof Actuator with Supervision
Supervised Actuator for Hazardous Locations

Supervised latching solenoid actuators are some of the primary releasing devices used on gaseous extinguishing systems in the market today. These actuators are usually attached to the suppressant’s discharge valve and electrically connected to the fire alarm control panel (FACP). When the actuator receives the release signal, it causes the discharge valve(s) to open and dispense the extinguishing agent into the suppression system. Anytime the actuator is removed from the discharge valve (for maintenance, etc.), the FACP registers an audible and visual alarm to indicate that the actuator is disconnected. The actuator’s integrated supervisory feature is critical because the fire suppression system cannot operate unless the actuator is properly installed. The alarm ensures that the actuator is not accidentally left disconnected after maintenance of the system. The alarm is deactivated only when the actuator is properly installed on the discharge valve.

While supervised latching solenoid actuators meet the actuation needs of most gaseous fire suppression systems, there are additional specifications and challenges that need to be considered when designing a solution for hazardous location applications that are suitable for the global market. Utilizing design features from supervised actuation devices that meet UL 2166 and NFPA 2001 standards, a new actuator for hazardous locations has been developed to meet the growing need for these types of suppression systems.

During development of this hazardous location actuator, consideration was made to ensure that the actuator would be suitable for different types of systems. Depending on the application and fire suppression system requirements, agents and pressures can vary. The hazardous location actuator and enclosure design allows for internal components to be matched specifically to the operating system pressure. Whether the operating pressure is 25 bar or 300 bar, the actuator needs to meet specific force requirements to open the discharge valve. By customizing the internal components to properly affect the force output, system manufacturers can be assured that the hazardous location actuator will meet the correct force over stroke requirements for their specific system. This ensures that the actuator will open the valve quickly and without damage.

This new hazardous location actuator also reduces the number of potential leak points in the system. Many hazardous location approved systems use solenoid valves in an electric and pneumatic actuation combination. This creates a number of potential leak points as the discharge pressure is routed through the system past multiple connection points. As a top-mounting linear actuator design, this new hazardous location actuator does not act as a pressure vessel on the discharge valve. This means that the only potential leak point is within the top of the discharge valve at the discharge valve pin, ultimately providing a more reliable fire suppression system.

The components of this hazardous location actuator also second as an enclosure in difficult to meet conditions, such as acetylene, through specific design features and material grade selection. Due to the strict controls on plating inside flame paths (per CSA C22.2 No. 30) and harsh testing requirements of UL50E to meet a 4X enclosure rating, all enclosure components and flame paths are produced from passivated 304SS.

This hazardous location actuator does not use brass, bronze, or copper in exterior components (UL 1203 8.2), including the swivel designed for easy rotation during installation. Adhering to this UL requirement allows for the actuator to meet Class 1, Group A location standards, which do not allow copper and copper alloys to be used for an enclosure of a device containing acetylene unless the actuator has been coated with the approved list of coatings. Additionally, to meet the Class 1, Group A location standards, CSA C22.2 No. 30 requires cylindrical gaps to be a minimum of 31.75 mm in length with a diametral gap no greater than .09906 mm. This requires tight control of bore and rod diameters (fire pin, manual override, and switch pin) in the hazardous location actuator.

Additional requirements for UL 1203 have been met in this new hazardous location actuator, which requires all parallel ISO threads to be no finer than 1.27 mm and have a class fit of 6g/6H with at least six full threads of engagement. Within the flame path of the actuator enclosure, a 2 mm pitch with eight minimum full threads of engagement have been used for increased protection. This will ensure the greatest resistance to highly corrosive environments and provide the proper flame path features. Environmental gaseous materials that could potentially ignite materials in the atmosphere are thereby prevented from propagating in the actuator.

To meet several global hazardous location certifications, the hazardous location actuator has been designed to achieve the basic rating labels with the most encompassing options. Testing is scheduled to be completed by the end of 2020. These ratings include the following:

  • UL & cUL: Class I Division 1 Groups A, B, C, and D
  • UL, cUL, IECEx, ATEX: Class I Zone 1 AEx db IIC T_, II 2 G Ex db IIC T_Gb, Ex db IIC T_Gb (Temperature ratings will be confirmed once UL testing is completed)
  • The above ratings were based on the following design specifications:
  • UL 1203
  • UL 60079-0 & 1
  • IEC 60079-0 & 1
  • CENELEC EN 60079-0 & 1
  • CSA C22.2 No. 30-M1986, 60079-0:19 & 60079-1

This hazardous location actuator meets a broad range of hazardous location certifications. The actuator utilizes integrated installation supervision technology to meet UL and NFPA requirements, and its force output can be matched to the operating pressure of any given fire suppression system. Additionally, the unique design of the hazardous location actuator greatly reduces leak points, enhancing the system’s reliability. The actuator also incorporates design features and materials enabling it to withstand highly corrosive environments and ensure a proper flame path. All of these features combine to make this actuator ideal for the global hazardous location market.

This article was originally published by Gulf Fire Magazine in July 2020