1. This notice highlights the problems that can occur where fire and gas detection information is routed to the control point via a communications network node eg local area network (LAN) rather than by direct hard wire from field sensor to central control point.
2. Fire and gas detection information has been lost during an emergency incident where such nodes have been de-energised due to detection gas releases in the areas which they cover
3. A gas release in a process module resulted in emergency shutdown (ESD) and blowdown. Gas was detected at a local equipment room (LER) heating ventilation and air conditioning (HVAC) duct inlet located just outside the module's hazardous zone. All electrical equipment within the LER (designated a safe area), including the fire and gas system network node, was isolated in accordance with the ESD philosophy.
4. The module's process control system node located within the LER was also de-energised. As a result ESD and blowdown valve status was lost. A failure of the blowdown valve for the process segment involving the release source was not detected.
5. The impact of loss of these nodes was as follows:
6. Where a fire and gas system network node is located in an LER in or near hazardous areas, duty holders should review the LER HVAC design and shutdown philosophy. It should be ensured that, as far as is reasonably practicable, fire and gas detection system information will not be lost following gas release incidents within the areas covered by the node.
7. Where:
internal gas concentrations should be monitored effectively, ie internal gas detectors should be located to ensure, as far as is reasonably practicable, detection of flammable gas.
8. Where an LER containing a fire and gas system network node is vulnerable to impairment from gas release incidents, the duty holder should carry out an exercise to determine (or otherwise establish and ameliorate) the likely impact on their emergency response arrangements. These arrangements should include procedures for recovery of injured personnel, incident recovery and safely gas freeing the LER before re-energising equipment.
9. The relevant legal requirements are:
The following publication is also recommended:
Prevention of fire and explosion and emergency response on offshore installations. Offshore Installations (Prevention of Fire and Explosion and Emergency Response) Regulations 1995. Approved Code of Practice and guidance L65 HSE Books 1997 ISBN 0 7176 1386 0
Any queries relating to this safety notice should be addressed to:
Health and Safety ExecutiveThis guidance is issued by the Health and Safety Executive. Following the guidance is not compulsory and you are free to take other action. But if you do follow the guidance you will normally be doing enough to comply with the law. Health and safety inspectors seek to secure compliance with the law and may refer to this guidance as illustrating good practice.