UL - 121303 BULLETIN
UL Standard for Safety for the Guide for Use of Detectors for Flammable Gases
|Publication Date:||5 June 2020|
The intent of this document is to provide recommendation for use of detectors for flammable gases, which includes fixed, portable and transportable equipment types, to provide protection from explosion or fires by minimizing the possibility of an accumulation of flammable gases reaching ignitable levels and initiating mitigative actions based upon defined gas concentration limits. There are three independent applications for use of gas detection equipment within hazardous locations: personnel and property protection, classified area surveillance, and supplemental protection for the use of otherwise unsuitable equipment.
Detectors for flammable gases for personnel and property protection provides ability to work in hazardous (classified) locations, alert user to unsafe conditions, and take mitigative actions as appropriate. It is the intent of this document to compile and provide techniques for proper use of this equipment to achieve personnel and property protection.
Area monitoring gas detection equipment provides surveillance of a hazardous (classified) location to demonstrate that levels of flammable gases are below the accepted levels of ignitable concentrations. When exposure limits are exceeded, alarm and notif ication are initiated to prompt evacuation of personnel from the affected location. Also, when exposure limi ts are exceeded and ventilation techniques are not effective, then repair of equipment is warranted, or a shutdown action will be required. This prevents further loss of containment for the affected process and that the electrical equipment not suitable for use in the flammable atmosphere be de-energized. It is the intent of this document to compile and provide techniques for the use of detectors for flammable gases to monitor and control sources of flammable gas release as a means of process safety management.
In addition, supplemental area protection is provided by use of gas detection equipment to allow the use of otherwise unsuitable electrical equipment within hazardous (classified) locations. Criteria are developed to establish flammable gas levels to initiate alarms, initiate increase in ventilation rates and to initiate shutdown of processes to shut off the flow of flammable gas that has breached containment and to de-energize all unsuitable electrical equipment. It is the intent of this document to compile and provide techniques for the use of flammable gas equipment to monitor and control sources of flammable gas release into the atmosphere within designated spaces. It is also the intent that these products and techniques be adapted by industries and used with processes that have historically not employed flammable gas detection.
Detectors for flammable gases as described in this document may be applied as stand-alone sensor/controllers or may be incorporated with or into another system such as, Basic Process and Control System (BPCS), Safety Instrumented System (SIS) or Fire and Gas System that may be employed in an industrial facil ity. When ventilation rates are to be controlled by the various responses of the flammable gas detection and control devices, there may also be interaction with the HVAC control system or devices.
NOTE 1: Applicable Detectors for flammable gases performance standards include FM 60079-29-1/UL 60079-29-1 and FM 60079-29-4/UL 60079-29-4.
For the purpose of this document flammable gases include flammable gases and vapors.
This document provides guidance on personnel and property protection by the use of detectors for flammable gases as defined within the following specified documents.
• ANSI/NFPA 72 for all installations.
• Title 29 Code of Federal Regulations 1910.119(k) OSHA regulations to support the hot work permit.
This document provides guidance on the use of a flammable gas detection system as a means of protection in industrial establishments with restricted public access and where the conditions of maintenance and supervision allow only qualified persons service the installation as defined within the following specified documents:
• ANSI/NFPA 70 (NEC) where for specific applications, electrical equipment that would not otherwise be permitted in the hazardous (classified) location may be used in conjunction with detectors for flammable gases;
• API RP 500 and API RP 505 for the determination of ventilation required to provide adequate dilution of the detected flammable gas to prevent the possibility of ignition;
• API RP 14F and API RP 14FZ also provide guidance on the use of gas detection as a protection technique.
Documents other than API RP 500 and RP 505 that describe area classification techniques ar e ANSI/NFPA 497 and ANSI/ISA 60079-10-1. Application of flammable gas detection and control as described in this document can provide additional protection from fire and explosion over typical electrical protection techniques by risk reduction methods . Industries that use these and other area classification documents can benefit by application of the techniques and cri teria presented in this document.
NOTE 2: Where mandatory text is provided in this Technical Report, the basis of the mandatory text is derived directly from referenced standards.
This document provides guidance on the use of flammable gas detection as a supplement to other explosion protection in adequately ventilated spaces.
This document provides guidance on the use of detectors for flammable gases for monitoring classified areas for low LFL level of flammable gas to initiate maintenance actions to locate and repair leaks in addition to providing alarm to notify personnel for evacuation.