Full Description

High Temperature Hydrogen Attack (HTHA) has plagued the oil and gas industry for decades, causing many equipment failures and, in some cases, loss of life. The so-called Nelson Curves that currently appear in API RP 941 were first developed in 1949 as a simple means of avoiding HTHA. These material-specific curves represent limiting combinations of temperature and hydrogen partial pressure for acceptable operation; operating below these curves is generally regarded as acceptable (not susceptible to HTHA), while operating above is not. They were derived solely from industrial experience (reported failures).