Could you please advive me an issue: about hydrogen detectors for hydrogen leakage detection in the refineries?
Does it really needed? Any of hydrogen detectors installed at which refineries as examples please?

Flame Detection
Any hydrogen risk on the site shall have potential fire locations monitored by Ultra-violet flame detectors (not Infra-red units). Target and location of "Hydrogen fire detection" shall be as follows:
High temperature (above 220 deg C) and high pressure (more than 42 barg)
Large pipe size (larger than 8 inch flanges).
The coverage of hydrogen detection shall be max. 30 m.

An internet source says:
"Hydrogen leak detection systems may be required by the Authority Having Jurisdiction (AHJ) or may be installed as a means for enhancing safety. Leak detection can be achieved by providing hydrogen (or flammable gas) detectors in a room or enclosure, or by monitoring the internal piping pressures and/or flow rates for changes that would suggest a leak is present in the system. Other methods include providing detectors in close proximity to the exterior piping or locating hydrogen piping within another pipe and monitoring the annulus for leaks."