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We use two block valves with one blind for isolation at boundary limit of each process unit in our refinery. Gate valve is selected for block valve mainly. For hydrogen system, we select one ball valve (Orbit Valve) installed at main header side, and one gate valve at process side for block valve service. Would you please advice if Rising Stem Ball Valve is better for hydrogen system, and what condition should be used?
13/12/2011 A: keith bowers, B and B Consulting, kebowers47@gmail.com
'Orbit' valves have provided excellent ultra-low stem leak service in sour LPG, H2S, services (where even miniscule leaks create odor problems.) A 'gate' valve, unless specifically specified and supplied 'bubble tight or better' should not be considered suitable for blocking high pressure hydrogen service. If used, it should be installed with stem down to keep all debris out of the sealing groove. 'Edwards Y-pattern' valves are specified by many refineries for absolute no-leak reliability in high pressure service. They will usually provide 'commercially tight' seal, although some organizations do require a 'drop-out spool' and deflector for absolute safety before entry into a vessel with such a connection.