Seems like you already negating that something wrong with (pure?) graphite and Inconel wire against Ammonia.
For us to better understand the issue, suggest to elaborate the story more.
PS: Graphite (alone) and Inconel are relatively inert against most medium; plus graphite by default is already brittle, hence IMO these two materials may not be the issue.
Please elaborate:
- type of valve, how many packing used, what sort of packing from packing 1 to packing 5?
- is there any carbon bushing (usually at the bottom) and/or lipseal?
- you were saying repacking: did you use exact similar (type and dimension) as original packing?
- dimension of spindle OD, ID housing, and OD-ID of the packing
- protocol of installing the packing? did you pre-compressed it one by one with certain torque upon inserting each packing, and then final torque after the last packing inserted. Or did you do it in one go (shuffle all in first) and just do one time final torque?
- after above (packing torqued), did you operate the valve and re-torque?
- composition of packing? Please note that graphite may not be pure (industrial standard can be 93-95% purity, seldom 99-100%), and remaining can be considered as impurities and/or bonding agent such as but not limited to Mercury, Sulfur, Boron, Bromine, Fluorine, Chlorine and PTFE. Of which some of them might be reactive against Ammonia.
some high pressure graphite such as HAMAR Eriks, certain brand of James Walker or other brands might do the trick. but that's from material point of view only. if not adhering the protocol of gland packing installation and/or quality check (e.g. tolerance between spindle vs packing vs housing), then classic issues such as relaxation borne to happen.
It is quite common to see (more) brittle and porous on old packing.
High pressure application stress the necessity of sufficient radial sealing stress on each packing ring. often can only be achieved by proper installation (including pre-compress the packing and re-torque the gland housing after several open/close)
Regards
D
