Materials Performance Supplements

CORTEC 2018

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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corporate maintenance and repair costs. The promising results of the first injec- tion in a sour water tank (Figure 3), along with positive feedback from tank operators (Middle East and the United States) and technical papers, the company manage- ment gave the go-ahead for the project. For the first phase, 21 tanks were selected. The exact location of chemical injec- tion and the number of ER probes were determined during the engineering study. The ER probes were installed in a polyvinyl chloride (PVC) pipe under the tank f loor with a sensing element completely embed- ded in the sand pad (Figure 4). Data were regularly collected for all tanks before and after corrosion inhibitor application. The design scope of work included the following general steps: 1. Installation of monitoring device: This included installation of a number of ER monitoring probes at numerous locations under the tank floor. A minimum of two months prior to VCI injection, ER probe readings were collected. The number of monitoring probes depended on the size of the tank. The ER probe readings revealed the corrosiveness level of the under tank environment without VCI. 2. Installation of VCI injection pipes: The VCI was applied into the interstitial space for effective distribution. Injec- tion tubes were installed by core drill- ing into th e bitum en/concret e ring foundation . VCI slurr y was injected through distributed perforated injec- tion pipes. The pipes were embedded within the sand pad to ensure effec- tive and even distribution of the slurry, such that once applied and migrated, the entire bottom plate was controlled (Figure 4). The application system was configured for future online replenish- ment. The annular plate was sealed to avoid escaping of the VCI or air and moisture ingress into the tank bottom during breathing out. 3. Collection of ER probe data: ER probe readings were collected and the effi- cacy of VCI was evaluated by differen- tiating results between ER probe read- ings prior to VCI injection and after. Online Injection of Vapor Phase Corrosion Inhibitors to Extend Storage Tank Floor Life FIGURE 5 Metal loss monitoring graph for ER probes in TK-02. FIGURE 6 Metal loss monitoring graph for ER probes in TK-03. Results Significant reduction in corrosion rate is now clearly identifiable across the major- ity of ER probes. It is expected that as time progresses the outliers shall also reinforce the success of the project. ER probe data showed a significant reduction in corrosion rate after injection of the VCI slurry, with the average percentage reduction for all probes to be 70%. Sample ER probe metal loss charts and three-period rolling average corrosion rate charts for two tanks are displayed in Fig- ures 5 and 6. The pre-and-post injection trend lines are clearly separated with a ver- tical dotted line. The decline in corrosion rate trends con- firms the functionality of the ER probes. The corrosion rate data were treated by using a three-day moving average as shown in Fig- ures 7 and 8. Data after injection of VCI illustrate a reduction in the corrosion rate and ended up to a common corrosion rate. Table 1 clearly defines the efficacy of the 7 CORTEC SUPPLEMENT TO MP MATERIALS PERFORMANCE JUNE 2018

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