lub ric ated ▁or ▁non - lub ric ated ; ▁for ▁high ▁pressure ▁( 3 5 0 ▁- ▁ 7 0 0 ▁bar ), ▁non - lub ric ated ▁compress ors ▁are ▁preferred ▁to ▁avoid ▁oil ▁cont am ination ▁of ▁the ▁hydro gen . ▁ ▁Ex pert ▁know - how ▁on ▁p ist on ▁se aling ▁and ▁pack ing ▁rings ▁can ▁ensure ▁that ▁reci proc ating ▁compress ors ▁out perform ▁the ▁compet ing ▁techn ologies ▁in ▁terms ▁of ▁M T BO ▁( Me an ▁Time ▁Between ▁Over ha ul ). ▁ ▁I onic ▁liquid ▁p ist on ▁compress or ▁ ▁An ▁ion ic ▁liquid ▁p ist on ▁compress or ▁is ▁a ▁hydro gen ▁compress or ▁based ▁on ▁an ▁ion ic ▁liquid ▁p ist on ▁instead ▁of ▁a ▁metal ▁p ist on ▁as ▁in ▁a ▁p ist on - met al ▁dia ph rag m ▁compress or . ▁ ▁Elect ro chem ical ▁hydro gen ▁compress or ▁A ▁multi - stage ▁electro chem ical ▁hydro gen ▁compress or ▁incorpor ates ▁a ▁series ▁of ▁memb rane - elect ro de - ass emb lies ▁( ME As ), ▁similar ▁to ▁those ▁used ▁in ▁pro ton ▁exchange ▁memb rane ▁fuel ▁cells ; ▁this ▁type ▁of ▁compress or ▁has ▁no ▁moving ▁parts ▁and ▁is ▁compact . ▁The ▁electro chem ical ▁compress or ▁works ▁similar ▁to ▁a ▁fuel ▁cell , ▁a ▁voltage ▁is ▁applied ▁to ▁the ▁memb rane ▁and ▁the ▁resulting ▁electric ▁current ▁pull s ▁hydro gen ▁through ▁the ▁memb rane . ▁With ▁electro chem ical ▁compression ▁of