▁and ▁m ating ▁must ▁accommod ate ▁secondary ▁se aling ▁elements . ▁ ▁In ▁some ▁designs , ▁various ▁retain ers , ▁sle e ves ▁and ▁other ▁components ▁may ▁also ▁include ▁secondary ▁se aling ▁elements . ▁ ▁Where as ▁a ▁simple ▁O - ring ▁might ▁require ▁only ▁a ▁gro ove ▁for ▁fitting , ▁some ▁secondary ▁se aling ▁elements ▁( for ▁example , ▁pack ing ) ▁might ▁require ▁mechanical ▁compression . ▁ ▁Although ▁O - r ings ▁are ▁available ▁in ▁many ▁el ast om ers , ▁sometimes ▁an ▁el ast omer ▁might ▁not ▁be ▁compatible ▁with ▁the ▁fluid ▁being ▁se aled ▁or ▁might ▁be ▁considered ▁too ▁expensive . ▁ ▁In ▁such ▁cases , ▁a ▁secondary ▁se aling ▁element ▁might ▁be ▁manufact ured ▁from ▁per flu oro el ast omer ▁and ▁sh aped ▁in ▁the ▁form ▁of ▁a ▁w edge , ▁V ▁or ▁U . ▁ ▁Config ur ations ▁ ▁Although ▁all ▁end - face ▁mechanical ▁se als ▁must ▁contain ▁the ▁five ▁elements ▁described ▁above , ▁those ▁functional ▁elements ▁may ▁be ▁arranged ▁or ▁orient ed ▁in ▁many ▁different ▁ways . ▁Several ▁dimensional ▁and ▁functional ▁standards ▁exist , ▁such ▁as ▁API ▁Standard ▁ 6 8 2 ▁- ▁Sh aft ▁Se aling ▁Systems ▁for ▁Cent rif ug al ▁and ▁Rot ary ▁P umps , ▁which ▁describes ▁the ▁configurations ▁for ▁used ▁in ▁O il ▁& ▁Gas ▁applications . ▁ ▁Even ▁though ▁the ▁scope ▁of ▁API ▁ 6 8 2 ▁is ▁somewhat ▁limited , ▁it ▁may ▁be ▁extended ▁to ▁describe ▁end - face ▁mechanical ▁se als ▁in ▁general . ▁Configuration ▁refers