A seawater electrolyser stream is a hydraulic system and as such can be subject to media leakage. Any leakage will be infrequent and of short duration and dependent on the position of a leak within that stream a varying quantity of Hydrogen will then be released from entrainment in the leaked media.
There are varying schools of thought within the industry regarding the hazardous area assessment relating to an electrolyser stream, varying from unclassified (safe) to Zone II.
With an essentially multi flanged piping assembly it is however difficult to argue against Zone II C due to the potential for infrequent leakage of a hazardous gas (Hydrogen) for short periods in an electrolyser area. Typically a media leakage will have entrained Hydrogen of varying percentage content depending on the location of the leak within the Electrolyser Stream, however where interstage degassing is incorporated any leakage in the degas line will be of significantly higher percentage,
<=100% H2.
This suggests that the installation should be subject to a hazardous area assessment, e.g. to EN 60079-10, the extent of the hazardous zone defined and the installation designed, installed and inspected to comply with the applicable standard by a Notified Body or approved inspection agency, e.g. ATEX directive.
The installation of a Hydrogen detection system above electrolyser streams is near universal. The usual argument for this device is to protect against some catastrophic failure that leads to a massive hydrogen release from the media, this is not a requirement for a hazardous area survey as these do not address catastrophic failures.
It is of importance for those responsible for the preparation of equipment requisitions and specifications to satisfy themselves in this respect as there are different schools of thought amongst suppliers.
It should be noted that EN 60079 is not a prerequisite standard for ATEX and is considered a conservative standard based on air changes per second. Therefore separate Electrolyser rooms are preferable to maintain ventilation and hazardous area limits to a reasonable level as Vz becomes a function of air changes per second.
