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51 NACE INTERNATIONAL: VOL. 56, NO. 4 MATERIALS PERFORMANCE APRIL 2017 tained at 98.5% to achieve a dew point of 0 °C (32 °F). The dew point data of the in- coming and outgoing gas, however, var y between <–5 to >15 °C during the winter and summer months (December/January and May/July, respectively) as depicted in Table 1, which also illustrates the dew point variations during particular winter and summer months. The high dew point in the outlet gas illustrates the relative in- efficiency of the glycol absorber in keeping the outlet gas moisture free. Corrosion in Export Gas Lines The dehydrated H 2 S and CO 2 -contain- ing gas is transported to a common mani- fold. From there, it goes through a common pipeline equipped with bottom-of-the-line mass-loss corrosion coupons on its way to the acid gas removal plant for sweetening. Coupon monitoring 2 provides information on general and pitting corrosion, deposits, and sessile bacteria in the accumulated condensed water or carryover water/glycol mixture. Corrosion coupon retrieval and re- placements are carried out at 90-day inter- vals. Figure 1 illustrates the trend of general and pitting corrosion rates from 2011 to 2015. The incidents of high and severe pit- TABLE 1. DEW POINT VARIATION DURING SUMMER AND WINTER Dew Point (°C) Dew Point During Winter Months Dew Point During Summer Months December 2014 January 2015 May 2015 July 2015 GC-27 Dehydration Unit GC-28 Dehydration Unit GC-27 Dehydration Unit GC-28 Dehydration Unit GC-27 Dehydration Unit GC-28 Dehydration Unit GC-27 Dehydration Unit GC-28 Dehydration Unit Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet Inlet Outlet < –5 3 3 3 3 3 4 2 3 — — — — — 1 — — –4.99 to –0.01 2 4 — 1 4 3 2 4 1 2 1 1 1 — — 1 0 to 4.99 4 10 — 9 2 5 5 6 1 10 1 11 — 12 1 12 5 to 9.99 9 11 9 5 2 4 3 3 9 2 11 3 12 2 11 2 10 to 14.99 10 2 6 8 7 2 6 3 6 4 5 3 2 — 3 — >15 2 — 12 5 1 1 3 2 1 — 1 — — — — — Total no. of days (A) 30 30 30 31 19 19 21 21 18 18 19 18 15 15 15 15 (A) The dew point values are not available every day of the month FIGURE 1 High/severe general pitting corrosion rates vs. exposure period for four monitoring locations. ting indicate the presence of high corrosion activity in the gas export pipeline. In an ear- lier study of a crude oil handling system, 3 it was established that the trend of increasing pitting corrosion rates vs. time paralleled the corresponding trend of water separa- tion/accumulation as well as bacteria pop- ulation density. The observation was in line with another article, 4 which concluded that bacteria population is the key performance indicator for corrosion in the KOC Water Handling Systems. For these reasons, the observed inci- dents of high and severe pitting suggest the presence of unacceptable levels of bacteria population density, albeit there was no ses- sile bacteria sampling in the export gas line during the period from 2011 to 2013. How-