1. What,/.is,/.HTHA?:,/.It,/.is,/.exposure,/.of,/.Steels,/.to,/.Hydrogen,/.gas,/.at,/.high,/.temperature.,/.Temperature,/.>,/.204,/.
Deg,/.C,/.(400,/.Deg,/.F).
2. When,/.is,/.the,/.Surface,/.Decarburization,/.happens,/.in,/.HTHA?:,/.At,/.High,/.Temperature,/.and,/.L
ow,/.H2,/.pressure.
3. When,/.is,/.the,/.internal,/.HTHA,/.attack,/.heppens?:,/.Internal,/.HTHA,/.attack,/.happens,/.at,/.High,/.temp
,/.(>204,/.Deg,/.C),/.and,/.high,/.H2,/.partial,/.pressure.,/.hydrogen,/.penetrates,/.into,/.steel,/.and,/.joins,/.with,/.carbon,/.present,/.in
,/.steel,/.to,/.form,/.CH4.,/.CH4,/.gets,/.trapped,/.within,/.the,/.grain,/.and,/.pressure,/.is,/.built,/.up.,/.Internal,/.pressure,/.of,/.CH4,/.sta
rts,/.forming,/.cavities,,/.then,/.micro,/.fissures,,/.and,/.finally,/.these,/.micro,/.fissures,/.combines,/.to,/.from,/.cracks.
4. Which,/. can,/. damage,/. more,,/. surface,/. or,/. Internal,/. decarburization?:,/. Internal,/.HTHA
attack,/.leads,/.to,/.cracking,/.and,/.leads,/.to,/.equipment,/.failure.
5. What,/.happens,/.at,/.high,/.temperature,/.and,/.high,/.H2,/.partial,/.pressure?:,/.Both,/.surf
ace,/.and,/.Internal,/.carburization,/.happen.
6. What,/.is,/.the,/.effective,/.Temperature,/.for,/.HTHA?:,/.204,/.Deg,/.C,/.(400,/.Deg,/.F)
7. Which,/.material,/.works,/.well,/.with,/.HTHA?:,/.5Cr,,/.9Cr,,/.12C
r,/.300,/.Series,/.SS
are,/.not,/.susceptible,/.to,/.HTHA,/.at,/.conditions,/.normally,/.seen,/.at,/.Refinery.
8. How,/.Cr-Mo,/.helps,/.in,/.preventing,/.HTHA?:,/.Cr-
Mo,/.increases,/.Carbide,/.stability,/.and,/.less,/.C,/.is,/.available,/.to,/.from,/.CH4,/.thus,/.minimising,/.formation,/.of,/.CH4,/.
and,/.otter,/.resistance,/.to,/.HTHA.
9. What,/.is,/.common,/.design,/.practice,/.against,/.HTHA?:,/.Common,/.design,/.practice,/.is,/.to,/.
use,/.15,/.-,/.30,/.Deg,/.C,/.margin
170,/.Kpa,/.-,/.345,/.Kpa,/.(25-50,/.psi)
Safety,/.factor,/.approach,/.when,/.using,/.API-941,/.curves.
10. How,/.stress,/.relief,/.helps,/.against,/.HTHA?:,/.Non-
stress,/.relieved,/.CS,/.welds,/.have,/.shown,/.a,/.higher,/.susceptibility,/.to,/.HTHA,/.compared,/.to,/.stress-
relieved,/.welds,/.and,/.non-welded,/.components.
11. Which,/.weld,/.overlay,/.is,/.used,/.against,/.HTHA?:,/.300,/.series,/.weld,/.overlay,/.or,/.bond,/.cladding,/.is,/.u
sed,/.for,/.HTHA,/.when,/.the,/.base,/.material,/.does,/.not,/.have,/.adequate,/.high-temperature,/.H2,/.resistance.
12. In,/.cladded,/.vessels,,/.which,/.are,/.the,/.most,/.vulnerable,/.locations?:,/.Where,/c. ladding,/h . ave,/.c
racked,/.and,/.become,/.dis-bonded.
13. What,/.is,/.the,/.HTHA,/.curve,/.called?:,/.It,/.is,/.called,/.as,/.Nelson,/.Curve,/.under,/.API-941.
,/. ,/.
Deg,/.C,/.(400,/.Deg,/.F).
2. When,/.is,/.the,/.Surface,/.Decarburization,/.happens,/.in,/.HTHA?:,/.At,/.High,/.Temperature,/.and,/.L
ow,/.H2,/.pressure.
3. When,/.is,/.the,/.internal,/.HTHA,/.attack,/.heppens?:,/.Internal,/.HTHA,/.attack,/.happens,/.at,/.High,/.temp
,/.(>204,/.Deg,/.C),/.and,/.high,/.H2,/.partial,/.pressure.,/.hydrogen,/.penetrates,/.into,/.steel,/.and,/.joins,/.with,/.carbon,/.present,/.in
,/.steel,/.to,/.form,/.CH4.,/.CH4,/.gets,/.trapped,/.within,/.the,/.grain,/.and,/.pressure,/.is,/.built,/.up.,/.Internal,/.pressure,/.of,/.CH4,/.sta
rts,/.forming,/.cavities,,/.then,/.micro,/.fissures,,/.and,/.finally,/.these,/.micro,/.fissures,/.combines,/.to,/.from,/.cracks.
4. Which,/. can,/. damage,/. more,,/. surface,/. or,/. Internal,/. decarburization?:,/. Internal,/.HTHA
attack,/.leads,/.to,/.cracking,/.and,/.leads,/.to,/.equipment,/.failure.
5. What,/.happens,/.at,/.high,/.temperature,/.and,/.high,/.H2,/.partial,/.pressure?:,/.Both,/.surf
ace,/.and,/.Internal,/.carburization,/.happen.
6. What,/.is,/.the,/.effective,/.Temperature,/.for,/.HTHA?:,/.204,/.Deg,/.C,/.(400,/.Deg,/.F)
7. Which,/.material,/.works,/.well,/.with,/.HTHA?:,/.5Cr,,/.9Cr,,/.12C
r,/.300,/.Series,/.SS
are,/.not,/.susceptible,/.to,/.HTHA,/.at,/.conditions,/.normally,/.seen,/.at,/.Refinery.
8. How,/.Cr-Mo,/.helps,/.in,/.preventing,/.HTHA?:,/.Cr-
Mo,/.increases,/.Carbide,/.stability,/.and,/.less,/.C,/.is,/.available,/.to,/.from,/.CH4,/.thus,/.minimising,/.formation,/.of,/.CH4,/.
and,/.otter,/.resistance,/.to,/.HTHA.
9. What,/.is,/.common,/.design,/.practice,/.against,/.HTHA?:,/.Common,/.design,/.practice,/.is,/.to,/.
use,/.15,/.-,/.30,/.Deg,/.C,/.margin
170,/.Kpa,/.-,/.345,/.Kpa,/.(25-50,/.psi)
Safety,/.factor,/.approach,/.when,/.using,/.API-941,/.curves.
10. How,/.stress,/.relief,/.helps,/.against,/.HTHA?:,/.Non-
stress,/.relieved,/.CS,/.welds,/.have,/.shown,/.a,/.higher,/.susceptibility,/.to,/.HTHA,/.compared,/.to,/.stress-
relieved,/.welds,/.and,/.non-welded,/.components.
11. Which,/.weld,/.overlay,/.is,/.used,/.against,/.HTHA?:,/.300,/.series,/.weld,/.overlay,/.or,/.bond,/.cladding,/.is,/.u
sed,/.for,/.HTHA,/.when,/.the,/.base,/.material,/.does,/.not,/.have,/.adequate,/.high-temperature,/.H2,/.resistance.
12. In,/.cladded,/.vessels,,/.which,/.are,/.the,/.most,/.vulnerable,/.locations?:,/.Where,/c. ladding,/h . ave,/.c
racked,/.and,/.become,/.dis-bonded.
13. What,/.is,/.the,/.HTHA,/.curve,/.called?:,/.It,/.is,/.called,/.as,/.Nelson,/.Curve,/.under,/.API-941.
,/. ,/.
